2 August 1999

Contents

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Plant breeding

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The International Rice Research Notes (IRRN) expedites communication among scientists concerned with the development of improvedtechnology for rice and rice-based systems. The IRRN is a mechanism to help scientists keep each other informed of current rice researchfindings. The concise scientific notes are meant to encourage rice scientists to communicate with one another to obtain details on theresearch reported. The IRRN is published three times a year in April, August, and December by the International Rice Research Institute.

24.2/1999

Pest science & management

Economics of direct seeding in Asia:patterns of adoption and research prioritiesS. Pandey and L. Velasco

Electronic information: newopportunities for rice scientistsI. Wallace

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EDITORS’ NOTE

RESEARCH NOTES

KHRS26 (KHP5) for upland direct-seeded conditionsY.G. Shadakshari, H.M. Chandrappa, A. Manjunath,and S.C. Chandrasekharaiah

Grain quality characteristics of aromaticand nonaromatic rice cultivarsM. Sakila, S.M. Ibrahim, C.R. Anandakumar,S. Backiyarani, and D. Bastian

Feeding effects of rice leaffolder on flag leafgas exchange of rice plants at floweringT. Watanabe

Effects of Heterodera sacchari population densityon establishment and development of upland ricecv. IDSA6 under field and pot conditionsD.L. Coyne and R.A. Plowright

International Rice Research InstituteIRRI home page: http://www.cgiar.org/irri

Riceweb: http://www.riceweb.orgRiceworld: http://www.riceworld.org

IRRI Library: http://ricelib.irri.cgiar.orgIRRN: http://irriwww/IRRIHome/irrn.htm

http://www.cgiar.org/irri/irrn.htm

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International Rice Reasearch Notes

Performance of prototype rice lines from ideotypebreedingA. Kumar, R.K.S. Tiwari, S.S. Parihar, K.S. Pandya,and M.P. Janoria

VL Dhan 61, a new rice variety for the northwesternHimalayan regionR.K. Sarma, V.S. Chauhan, J.C. Bhatt, K.D. Koranne,and P. Singh

Usefulness of blast resistance genes and theircombinations in different blast-endemic locationsin IndiaR. Sridhar, U.D. Singh, P.K. Agrawal, J.N. Reddy,S.S. Chandrawanshi, R.B.S. Sanger, J.C. Bhatt,Y. Rathaiah, and K.V.S.R.K. Row

Usefulness of combinations of bacterial blightresistance genes at Cuttack, Orissa, IndiaR. Sridhar, J.N. Reddy, U.D. Singh, and P.K. Agrawal

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MINI REVIEWS

About the cover A farmer direct seedingrice in Los Baños, PhilippinesCover photo: Lingkod Sayo

3IRRN 24.2

Soil, nutrient, & water management

Crop management & physiology

NOTES FROM THE FIELD

RESEARCH HIGHLIGHTS

NEWS

INSTRUCTIONS TO CONTRIBUTORS

Nitrogen responsiveness of lowland rice varietiesunder irrigated conditions in West AfricaK.L. Sahrawat, S. Diatta, and B.N. Singh

Relative efficiency of different N fertilizers appliedto rice at medium elevationD. Jena

Alleviating zinc deficiency in transplanted floodedrice grown in alkaline soils of PakistanA. Rashid, M.A. Kausar, F. Hussain, and M. Tahir

Biochemical studies on rice seedlingsunder salt stressM.P. Mandal, R.A. Singh, and J.K. Handoo

Chemical clearing of irrigation channels–a comparative evaluationK. Joseph

Allelopathic effects of weeds on germinationand seedling vigor of hybrid riceP. Oudhia, N. Pandey, and R.S. Tripathi

Equilibrium moisture content for sorption ofwater vapor by milled riceJ.P. Pandey

Weed meal from a rice plot for broiler chicksN.M. Anigbogu

Socioeconomics

Editorial BoardMichael Cohen (pest science and management), Editor-in-ChiefDarshan Brar (plant breeding; molecular and cell biology)David Dawe (socioeconomics; agricultural engineering)Achim Dobermann (soil, nutrient, and water management; environment)Bao-Rong Lu (genetic resources)Len Wade (crop management and physiology)

Plant population requirement of hybrid ricein the Tarai region of Uttar Pradesh, IndiaP.S. Bisht, P.C. Pandey, and P. Lal

Promising medium-duration varieties fordouble-cropped areas of AssamK.K. Sharma, P.K. Pathak, T. Ahmed, S. Hussain,D.K. Bora, S. Ali, H.C. Bhattacharyya, and A.K. Pathak

Further testing of a yield loss simulation modelfor rice in different production situationsI. Focus on rice-wheat system environmentsL. Willocquet, L. Fernandez, H.M. Singh,R.K. Srivastava, S.M.A. Rizvi, and S. Savary

Further testing of a yield loss simulation modelfor rice in different production situationsII. Focus on water-stressed environmentsL. Willocquet, L. Fernandez, and S. Savary

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Production TeamKatherine Lopez, Managing EditorEditorialBill Hardy and Tess RolaDesign and layoutThe CPS Creative Services Team:Albert Borrero, Grant Leceta, Erlie Putungan,Juan Lazaro, Emmanuel PanisalesWord processingArleen Rivera

Thrips infestation in relation to panicle stage in riceS. Chander

4 August 1999

EDITORS’ NOTE

A year ago, the newly constituted IRRNeditorial board and IRRI’s Communi-

cation and Publications Services (CPS) de-cided to undertake a readership survey togather concrete information about IRRNaudience needs and preferences.

The survey aimed to determinereaders’ perceptions about the contentand layout of IRRN. Results were used totransform the publication into a more dy-namic and relevant scientific medium ofcommunication among rice scientiststhroughout the world. The pretested ques-tionnaire looked at three aspects: thesociodemographic characteristics of read-ers; distribution and subscription; and ac-ceptability and readability of the journal.

Questionnaires were distributed bypost or e-mail to 4,000 individuals and in-stitutions on the IRRN mailing list, ran-domly selected IRRI internationally and na-tionally recruited staff, and national agri-cultural research systems (NARS) collabo-rators. The survey questionnaire was alsoposted on the IRRI Web site to reach re-spondents who have access to the Web andto encourage online responses.

Some 989 completed question-naires, or 22% of the total sample, werereturned to IRRN Central. Most were re-turned by post, and a handful via e-mail orthe IRRI Web site. The results of the sur-vey were compiled, collated, and analyzed.

Early this year, the IRRN team de-signed a new look for IRRN. Specific de-sign considerations; inputs from varioussources such as the editorial board, IRRNeditors, and CPS creative services team;and feedback from readers have helpedshape this new look for the publication.Readers will note that many changes haveoccurred, beginning with the first issue ofthe year, not only in the appearance ofIRRN, but also in the organization andscope of the publication. Survey resultsvalidated most of the decisions taken bythe IRRN editorial board and its team ofeditors and designers in the make-over ofIRRN. Results are summarized as follows.

Who reads IRRN?Of 989 respondents, about a third describethemselves as primarily professors orteachers and one-fourth as scientists orresearchers. Only 15% of the respondentsare women. More than 60% of respondentsare 40–59 years old, and three-fourths haveadvanced degrees (53% PhD and 22%master’s). Two-fifths work at academic in-stitutions and one-fifth each are from re-search organizations or government agen-cies. About one-fourth each of the totalrespondents were from the Philippinesand India.

Thus, the average IRRN reader is amale researcher or professor, about 50years old or less, with a PhD, and involvedin rice research and development.

Distribution and subscriptionEighty-seven percent of the respondentsare on the mailing list so they get copiesof IRRN by subscription. Half (51%) havebeen subscribing to IRRN from 6 to 15years. They usually pass on copies of thepublication to their colleagues. Respon-dents read IRRN mainly for information onlatest developments in rice research (61%)and for news about IRRI and its activities

The typical IRRN reader• Male professor or researcher• 50 years old• with a PhD• Works in an academic or

research institution• Specializes in agriculture,

genetics/breeding, or plantpathology and entomology

(34%). Of the 25% who have published inIRRN, about half have published one tothree times. Thirty-six readers (4%) reporthaving published 7–10 times!

Sixty-four percent of the respon-dents prefer a quarterly IRRN rather than athree issues-a-year publication (19%); 62%prefer to receive printed copies over elec-tronic copies (via the Web, by diskette, orCD-ROM), and 88% say that they would liketo continue receiving a printed copy eventhough IRRN is now available on the Web.About 40% of the respondents have accessto the Internet. In addition, readers wantfree copies of the publication because theythink that the subscription fee of US$24for developed countries or $19 for devel-oping countries is expensive (61%).

IRRN covers 1976-1999 ▼

5IRRN 24.2

Readers’ evaluation of the qualityof IRRN

Content 1* 2 3 4 5•Readable 560 266 110 19 5•Understand– able 491 345 102 13 6•Citable 488 307 130 22 8•Credible 389 301 181 58 17•Useful 570 270 94 14 8•Accurate 403 372 134 21 6•Timely 343 336 199 45 20•Relevant 491 312 116 19 7

Layout•Attractiveness 286 406 184 32 11•Organization 405 371 119 21 5

*Note: 1 is the highest score, 5 is the lowest.

How do the readers perceiveIRRN’s content and layout?

Content. Most of the IRRN reader-respon-dents (80%) perceive IRRN as a credible,readable, understandable, “citable,” useful,accurate, timely, and relevant publication.More than half (57%) think that it is com-parable with other peer-reviewed journals,but about a third think that it is not com-parable because of its format and the brev-ity of the notes.

Readers find notes on the followingtopics featured in IRRN very useful: cropmanagement; resistance to variousstresses; integrated pest management; andsoil, nutrient, and water management.They suggest including items such as ab-stracts or summaries of important newpapers, news about IRRI, new publications,training and scholarship announcements,and book reviews.

To further improve the content ofIRRN, respondents recommend that IRRNbroaden its scope of coverage, includemore details in the notes, and better orga-nize the presentation of information.

Layout. Most of the readers (72%) like thepre-1999 look of IRRN. They consider thelayout and format as attractive, organized,and suitable for a scientific journal. They

think the publication is organized, com-prehensive, and meets the standard of ascientific journal. Those who did not likethe pre-1999 format suggest that the IRRNlook be improved by using more visualcues and graphics, better and bigger pho-tographs, more organized page layouts,more readable type, and more attractivecolors. Although many readers (64%) likethe regular cover used by the journal, somesuggest using a different photograph forthe cover for each issue.

Based on these results and com-ments, the IRRN team decided to intro-duce major changes in IRRN’s substanceand look. These included the inclusion ofnew departments or sections such as Minireviews, Notes from the field, and Re-search highlights; addition of more refer-ences for research notes–from two to five;and the use of more visual cues–icons forthe various topics, more attractive andmore readable type, color enhancements,and more visually appealing graphics orphotographs.

Discovering what IRRN readers hadto say about the publication has greatlyhelped us in the transformation of IRRN.The IRRN team thanks all those who com-pleted the survey. We will continue to re-fer to the survey results as we fine-tune the

new IRRN and consider new features toadd. We welcome feedback from IRRNreaders on an ongoing basis and hope thatwe can continue to provide a rice sciencejournal that you–the readers–want.

The Editors

Since the inception of IRRN in 1976,its mission has been to expedite

communication among scientists work-ing on rice and rice-based systems. Indesigning the new IRRN masthead, weattempted to capture the breadth of riceresearch that is reported in the journal. This research is farwider than what can be represented by rice seeds, the some-what overpopularized stand-alone icon that was the center-piece of the previous IRRN cover.

Each color in the new logo (one for each letter) repre-sents a component of the rice ecosystem: blue for water, yel-low for sun, brown for the earth or soil, and green for the

plant. A rice seed icon sits on thecounter of the R for rice.

In designing the typeface of thelogo, we considered the multiculturalnature of IRRN readers and their vari-able reactions to type use. The chal-

lenge for the design team was to develop a type that is simpleand easily recognizable, and yet distinctive to IRRN.

A third design concern was the versatility of use in di-verse media, e.g., printed pages and Web pages. The whitespaces and choice of colors help make the logo an attractivepresence wherever it is placed.

A note about the IRRN masthead and logo

6 August 1999

MINI REVIEWS

Economics of direct seedingin Asia: patterns of adoptionand research prioritiesS. Pandey and L. Velasco, Social Sciences Division, IRRI

Background

Although transplanting has been a major traditional method of rice establishment in Asia, economic factorsand recent changes in rice production technology have improved the desirability of direct-seeding methods.

The rising labor cost and the need to intensify rice production through double and triple cropping provided theeconomic incentives for a switch to direct seeding. Simultaneously, the availability of high-yielding, short-dura-tion varieties and chemical weed control methods made such a switch technically viable. As the rice productionsystems of Asia undergo adjustments in response to the rising scarcity of land, water, and labor, a major adjust-ment can be expected in the method of rice establishment. This paper provides a brief overview of the patternsof changes in crop establishment methods that have taken place in Asia and their impact and implications forresearch and technology development.

There are three principal methods of rice establishment: dry seeding, wet seeding, and transplanting.Although these methods vary, each is characterized by distinct salient features. Dry seeding consists of sowingdry seeds on dry (unsaturated) soils. Seeds can be broadcast, drilled, or dibbled. Wet seeding involves sowingpregerminated seeds in wet (saturated) puddled soils. Transplanting involves replanting of rice seedlings grownin nurseries to puddled soils. Because the seeds are sown directly, the dry- and wet-seeding methods are oftenjointly referred to as direct seeding.

Dry seeding is probably the oldest method of crop establishment. Historical accounts of rice cultivation inAsia indicate that, during its early period of domestication, rice used to be dry sown in a mixture with other cropsthat were established under the shifting cultivation system (Grigg 1974). This extensive system of land use gaveway to more intensive rice systems, especially in river valleys, as the population pressure on land increased with

7IRRN 24.2

Japan

Java

South Korea

Lower Myanmar

Bangladesh

Thailand

Philippines

Malaysia

Mekong Delta

Sri Lanka

1009080706050403020100

19951950

% area transplanted

Fig. 1. Changes in rice establishment methods in Asia.

population growth. Transplanting, weeding, fertilization, andelaborate water management systems evolved over time. The in-creased labor supply resulting from population growth made theuse of labor-intensive methods of rice production possible. Bythe 1950s, transplanting had become the dominant method ofcrop establishment in most of Asia. Dry seeding was practicedonly in those areas where low population density and/or severeclimatic/hydrological constraints prevented intensification of ricesystems.

Accurate data on the proportion of rice area establishedby different methods are scanty. Published agricultural statisticsin most countries do not include such data. As a result, informa-tion on this has to be culled from several data sources. Table 1presents rough estimates for major rice-growing areas. The di-rect-seeded area in Asia is about 29 million ha, which is approxi-mately 21% of the total rice area in the region. This estimate alsoincludes upland and submergence-prone environments whereopportunities for transplanting are limited. If only the rainfedlowland and irrigated rice ecosystems are considered, the totaldirect-seeded area is about 15 million ha. Compared with the1950s, the importance of direct seeding in irrigated and rainfedlowlands increased during the past three decades mainly in Ma-laysia, Thailand, and the Mekong Delta (Fig. 1).

Determinants of adoption of alternativecrop establishment methodsGenerally, water availability and the opportunity cost of labor arethe major determinants of crop establishment methods (Fig. 2).

Wateravailability

Low

Wage rate

Low High

High TP WS/TP

DS/TP DRS

Fig. 2. Hypothesized effects of wage rate and water availability on thechoice of crop establishment methods. TP=transplanting, DS=directseeding, WS=wet seeding, DRS=dry seeding.

Table 1. Direct-seeded rice area (million ha) in various Asian countries by ecosystem.a

Flood-prone + Irrigated + Irrigated + Area direct Total rice Total direct % of total upland rice rainfed rainfed lowland seeded (as a % areab seeded area direct

areab lowland area direct of irrigated + seededareab seeded rainfed lowland

area)

South Asia 8.4 47.8 6.3 13.0 56.2 14.9 26.0 Bangladesh 1.9 8.8 0.1 1.0 10.7 2.0 19.0 India 6.5 36.0 5.5 15.0 42.5 12.0 28.0 Pakistan 2.1 2.1 Sri Lanka 0.9 0.7 78.0 0.9 0.7 77.0Southeast Asia 4.0 68.2 8.3–10.3 11–14 72.2 12.3–14.3 17–20 Cambodia 0.2 1.7 1.9 0.2 10.0 China 0.5 31.6 1–2.5 3–8 32.1 1.5–3 5–9 Indonesia 1.2 9.8 0.8 8.0 11.0 2.0 18.0 Lao PDR 0.2 0.4 0.6 0.2 33.0 Malaysia 0.1 0.6 0.4 67.0 0.7 0.5 71.0 Myanmar 0.6 5.7 6.3 0.6 9.0 Philippines 0.2 3.4 1.3 38.0 3.6 1.5 42.0 Thailand 0.5 9.1 2.8 31.0 9.6 3.3 34.0 Vietnam 0.5 5.9 2–2.5 34–42 6.4 2.5–3 39–47East Asia 3.2 0.1 3.0 3.2 0.1 3.0 Japan 2.1 2.1 Korea 1.1 0.1 9.0 1.1 0.1 9.0 Total 12.4 119.2 14.7–16.7 12–14 131.6 27.3–29.3 21–22

aSources of information on direct-seeded area: Bangladesh - Huke and Huke (1997), S. Bhuiyan, pers. commun.; India - Palaniappan and Purushothaman (1991); Sri Lanka - Pathinayake etal (1991); Cambodia - Helmers (1997); China - Lu Ping, pers. commun.; Indonesia - Huke and Huke (1997) and H. Pane, pers. commun.; Malaysia - Huke and Huke (1997) and own estimate;Myanmar - Huke and Huke (1997) and own estimate; Philippines - PhilRice-BAS (1995) and own estimate; Thailand - Dr. Booribon Somrith, pers. commun. and data from AgriculturalExtension Office, Khon Kaen; Japan - Yujiro Hayami, pers. commun.; Vietnam - T.P. Tuong, pers. commun. and Agricultural Statistics of Vietnam (1998); Korea - Kim (1995); bHuke and Huke(1997).

Region/country

8 August 1999

A low wage rate and adequate water supply favor transplanting.When the water supply is plentiful and the wage rate is high, theparticular method adopted depends partly on the cost of weedcontrol. Economic incentives are likely to be higher for wet seed-ing when the cost of weed control is low. On the other hand,transplanting may be economically more profitable. Farm-levelstudies have shown that transplanting tends to be the dominantmethod in bottom lands where water accumulates from neigh-boring fields while direct seeding is practiced in higher fields(Pandey and Velasco 1999). Similarly, farmers with smaller fami-lies in relation to the size of the farm they manage prefer directseeding to deal with the labor shortage (Erguiza et al 1990, Pandeyet al 1995).

The transplanting method, although cost-effective in con-trolling weeds, may not be feasible when water availability is lowor uncertain. The traditional system of direct seeding such asgogorancah in Indonesia and aus and beushani in Bangladeshevolved mainly in response to rainfall uncertainty.

Economic incentives for direct seeding increase when la-bor scarcity and wage rates are high. Much of the recent spreadof direct seeding in Southeast Asian countries has been in re-sponse to the rising wage rate. Even though a switch to directseeding may have lowered rice yield slightly compared with trans-planted rice, farmers have found such a change economicallyprofitable.

Labor scarcity and shifts in crop establishmentmethodsHistorically, two major adjustments in crop establishment meth-ods have been made to deal with rising labor costs. In temperateAsian countries and territories such as Japan, Korea, and Taiwan,the farm labor shortage led to a change from manual to mechani-cal transplanting (Fig. 3). On the other hand, in tropical coun-tries such as Malaysia and Thailand, the labor shortage induced ashift to direct seeding.

Several factors explain this difference in the way the twogroups of countries have responded to labor shortages. Smallfarm size, a long history of transplanting culture, and a very in-tensive rice production system in Japan favored the continuationof this practice. In addition, high rice prices that farmers were

able to obtain in Japan reinforced the incentive to continue withthe transplanting method because a switch to direct seeding mayhave resulted in income losses due to lower yields. Transplant-ing may have also helped farmers deal with the low temperaturethat can adversely affect the performance of direct-seeded rice athigher altitudes. In contrast, Thailand and Malaysia have a muchmore recent history of transplanting culture. In addition, pro-duction in these countries is characterized by a relatively land-extensive agriculture, absence of a temperature constraint fordirect seeding, and lower overall average yield and net returns torice production. Thus, savings in labor cost from direct seedingoutweighed the potential loss in income from rice and favored ashift to direct seeding.

In addition to mechanical transplanting, farmers have usedother types of labor-saving methods for transplanting. Farmersin irrigated areas of Laguna, Philippines, use the dapog methodof seedbed preparation. In this method, seeds are sown on a raisedseedbed that is covered with banana leaves, empty bags, or plas-tic sheets. The covering prevents the roots from coming in con-tact with the soil. Labor is saved as seedlings transplanted areyounger (2 wk old), do not need to be uprooted, and are easilyseparated during transplanting. Similarly, farmers in some partsof China throw a bunch of 2-wk-old seedlings in the air so thatthey land scattered on puddled fields. This method can saveabout 25% on labor cost compared with normal transplanting(Table 2).

Potential advantages and disadvantagesof direct seedingDirect-seeding methods have several advantages over transplant-ing. First, direct seeding saves on labor (Table 2). Depending onthe nature of the production system, direct seeding can reducethe labor requirement by as much as 50%. Second, in situations

Mechanical transplanting[Japan; Taiwan; Korea; part of China]

Dry seeding[Rainfed area: northeast Thailand;

Central Luzon, Philippines]

Wet seeding[Irrigated area: Suphanburi, Thailand;

Muda, Malaysia]

Manual transplanting

Fig. 3. Alternative patterns of changes in crop establishment methods.

Table 2. Preharvest labor use (person-d ha-1) in different countriesby crop establishment method.

Country/province Dry Wet Transplanting Dapog Seedlingseeding seeding throwing

Philippines Iloiloa 40 30 53 Pangasinanb 22 49 Lagunac 37India Uttar Pradeshd 72 66 112 Bihare 75 152 Orissaf 141 152 Tamil Nadug 93 29Myanmarf 19 60Vietnam Long Anh 38 38 68Indonesia Central Java 129f–240g 75g

Thailandi 15 29

aPandey and Velasco (1998). bPandey et al (1995). cHayami and Kikuchi (2000). dPandey et al(1998). eSingh et al (1994). fFujisaka et al (1993). gSuyamto and Anwari (1995). hFarm surveydata. iIsvilanonda (1990).

9IRRN 24.2

Table 4. Cost of crop establishment and weed control ($ ha-1), Iloilo,Philippines.

Item Dry seeding Wet seeding Transplanting

Weed control 71 40 24 Labor 51 20 10 Herbicide 20 20 14Crop establishment Labor 17 16 70

Table 5. Economic returns ($ ha-1) of different crop establishmentmethods in the wet season.

Site Dry Wet Transplanting %seeding seeding difference

Suphan Buri, Thailanda

Cash costb 152 148 3Gross returnsc 505 476 6Gross margind 353 328 8Net returnse 168 132 27

Pangasinan, Philippinesf

Cash cost 230 273 -16Gross returns 608 666 -9Gross margin 378 393 -4Net returns 288 247 17

Iloilo (double-cropped),Philippinesg

Cash cost 736 441 67Gross returns 1,627 904 80Gross margin 891 464 92Net returns 695 382 82

aSource: Isvilanonda (1990). All values converted to US$ using the exchange rate $1 =B20. bCost of all purchased inputs. cGross value of output. dGross value of output minusthe cost of purchased inputs. eGross value of output minus the cost of purchased andfamily-owned inputs. fPandey et al (1995). gPandey and Velasco (1998). Comparison be-tween two crops of wet-seeded rice vs only one crop of transplanted rice.

where no substantial reduction in labor requirement occurs, di-rect seeding can still be beneficial because the demand for laboris spread out over a longer time than with transplanting, whichneeds to be completed within a short time. The traditional dry-seeding system (beushani) in rainfed areas of eastern India is agood example. Land preparation, laddering, and weeding opera-tions in this system are spread over several months, thus allow-ing farmers to make full use of family labor and to avoid laborbottlenecks (Singh et al 1994).

Third, when rainfall at planting time is highly variable, di-rect seeding may help reduce the production risk. The traditionalsystem of direct (dry) seeding in some rainfed tracts of easternIndia evolved partly in response to rainfall uncertainty (Fujisaka

et al 1993, Singh et al 1994). Direct seeding can also reduce therisk by avoiding terminal drought that lowers the yield of trans-planted rice, especially if the latter is established late due to de-layed rainfall. Fourth, direct seeding can facilitate crop intensifi-cation. In Iloilo, Philippines, the spread of direct seeding in thelate 1970s led to double-rice cropping in areas where farmersgrew only one crop of transplanted rice (Pandey and Velasco1998). Similarly, in the Mekong Delta, cropping intensity increasedrapidly over the past decade as farmers switched to direct-seed-ing methods. Finally, irrigation water use can be reduced if di-rect-seeded (especially dry-seeded) rice can be established ear-lier by using premonsoon showers. In the Muda Irrigation Areaof Malaysia, farmers have been able to establish successful ricecrops by dry seeding when the irrigation water supply was low(Ho 1994). Similarly, water use in wet-seeded rice in the Philip-pines has been substantially lower than in transplanted rice(Bhuiyan et al 1995).

Direct seeding, however, also has several potential disad-vantages. The yield of direct-seeded rice under farmers’ field con-ditions tends to be lower than that of transplanted rice (Table 3).Poor and uneven establishment and inadequate weed control arethe major reasons for its poor performance (De Datta 1986,Moody 1982). Farmers may end up using most of the labor savedby direct seeding to control weeds. In addition, the chemical costof weed control tends to be higher than that of transplanted rice.Farm survey data from Iloilo indicated that the weed control costfor direct-seeded rice can be as high as 20% of the total preharvestcost (Table 4). More use of chemical weed control methods indirect-seeded rice can also be potentially damaging to humanhealth and the environment. Other major problems with direct-seeded rice include difficulties in controlling snails and qualitydeterioration resulting from harvest that may occur during therainy season.

Impact of the shift to direct seedingAlthough the direct-seeding method has both advantages anddisadvantages, its rapid spread in various parts of Asia indicatesthat the net economic benefit has been positive. Despite a loweraverage yield, direct-seeded rice has a higher net profit, with thesavings in labor cost outweighing the value of loss in output(Table 5). This has occurred especially in areas where labor costhas risen rapidly in relation to the rice price. In addition, totalfarm income has increased because direct seeding facilitateddouble cropping of rice in areas where only one crop of trans-planted rice would have been grown otherwise. For example, inIloilo, farmers’ income almost doubled as a result of the dou-bling in cropping intensity made possible by direct seeding. To-tal labor employment also increased because of crop intensifica-tion even though the amount of labor used per crop declined.

The likely future patternDespite the rapid spread of direct seeding in several SoutheastAsian countries, transplanting remains the dominant method of

Table 3. Average rice yield (t ha-1) by crop establishment method.

Site Dry seeding Wet seeding Transplanting

Nueva Ecija, Philippinesa 4.1 4.3Iloilo, Philippinesb 3.7 (1.0) 2.7 (0.9) 3.3 (0.9)Pangasinan, Philippinesc 2.7 (1.1) 2.9 (1.2)Faizabad, eastern Indiad 1.3 (3.7) 1.3 (1.3) 1.6 (0.7)Long An, Vietnam 4.9 (0.9) 5.0 (0.5) 5.0 (0.3)

Sources: aErguiza et al (1990). bPandey and Velasco (1998). cPandey et al (1995). dPandeyet al (1998).

10 August 1999

crop establishment. Because of differences in rice productionsystems and economic conditions, it is convenient to examinethe likely scenario for East, Southeast, and South Asia separately.

In East Asia, where rice production systems are input-in-tensive, a major shift to direct seeding in response to a furtherescalation of the wage rate is unlikely to occur. Compared withother Asian countries, these countries are more industrializedand have higher per capita incomes. Farm incomes are maintainedat a higher level through policies that keep the rice price highcompared with the international market price. Under this situa-tion, the potential threat to farmer income because of a wageincrease is likely to be addressed by policy changes that compen-sate farmers for a loss in profits rather than by changes in cropestablishment method.

Direct seeding is likely to expand further in Southeast Asiancountries with low population densities, especially in areas wherethe labor cost is escalating. Mechanization of land preparation,harvesting, and threshing along with a shift from transplanting todirect seeding are likely to be increasingly adopted. An expan-sion of irrigation and drainage would further reinforce a shift to-ward direct (wet) seeding. This type of wage-induced shift, how-ever, is a function of the growth rate of the economy. The recenteconomic crisis in the region may have slowed down the growthin rural wages and, to a certain degree, may result in some shiftback to transplanting. In very densely populated areas such asJava, western China, and the Red River Delta of Vietnam, trans-planting is likely to remain the dominant culture.

In South Asia, where population density is high and over-all economic growth is slow, economic incentives for a shift todirect seeding are likely to remain weak. The adoption pattern ofdirect seeding in Southeast Asia shows that it is first adopted inthe dry season probably because of better water control than inthe wet season. In South Asia, dry-season rice accounts for onlyabout 12% of the total rice area compared with 22% in SoutheastAsia. In addition, the overall proportion of rainfed rice area inSouth Asia is higher. These features of rice systems may contrib-ute to the slower adoption of direct seeding in South Asia. Evenwhen wage rates rise high enough, drainage constraints in rainfedareas may encourage a shift toward mechanical transplanting in-stead of direct seeding.

Research implicationsThe primary economic motives for a shift to direct seeding arethe savings in labor cost and the possibility of crop intensifica-tion. The priority research issue depends on which of the twomotives is likely to play a more important role in a particularecoregion. If the main driving force for the transition to directseeding is the rapidly rising wage rate, research to generate la-bor-saving technological innovations would have a high priority.These include mechanical tillage and labor-saving weed controlmethods. Where drought and early submergence impede theadoption of direct seeding, research to develop varieties and cropmanagement practices to relax these constraints is also needed.

If crop intensification is the major reason for direct seed-ing, however, research to facilitate early establishment and earlyharvest of the direct-seeded crop would have a higher prioritybecause this will permit timely planting of the subsequent crop.Developing short-duration varieties would be important in thiscase. Even though the cost of labor may be low initially in theseareas, intensification of land use may lead to labor shortages be-cause of the peak labor demand during the previous crop’s har-vest and establishment of the succeeding crop within a shortperiod. Suitable mechanical devices for land preparation that canreduce turnaround time between crops could help achieve ahigher and more stable yield of the second crop.

The high costs of weed control could be a major constraintto the widespread adoption of direct-seeding methods, especiallydry seeding. The key to the success of direct-seeded rice is theavailability of efficient weed control techniques. Varieties withearly seedling vigor and crop management technologies that helpreduce the competitive effects of weeds on crops are needed. Itis essential, however, to evaluate the environmental and healthconsequences of potential technologies that are based on chemi-cal means of weed control.

Empirical analyses have indicated that the technical effi-ciency of rice production is lower and more variable for direct-seeded rice than for transplanted rice (Pandey and Velasco 1999).This suggests the existence of a higher “yield gap” between the“best practice” farmer and the average farmer when rice is direct-seeded. A greater variability in the technical efficiency of direct-seeded rice could be partly due to the use of varieties that wereoriginally developed for transplanted culture. Varieties that arespecifically targeted for direct-seeded methods could help reducesuch yield gaps. Better crop management practices, especiallythose that facilitate early and more uniform establishment, canbe similarly helpful.

Precise water management is a critical factor for high pro-ductivity of wet-seeded rice (De Datta and Nantasomsaran 1991).Greater control of water flow on irrigated fields is hence desir-able. Most irrigation systems in Asia, however, have been designedto supply water to transplanted rice for which precision in watermanagement is not as critical. Suitable modifications of irrigationinfrastructure may not only ensure high yield of direct-seededrice but also improve water use efficiency. In addition, appropri-ate mechanical systems of field leveling that ensure uniformity infield-water level are needed.

In dry-seeded rice, land preparation under dry conditionsmay require mechanical power, especially for hard clayey soils.Large four-wheeled tractors have been used extensively in largeflat tracts of northeast Thailand and the Mekong Delta. It is es-sential to identify the conditions that led to the evolution of rentalmarkets for tractors in these areas so that appropriate policies todevelop such markets in other similar areas could be made. Smalldevices such as power tillers may be more suitable in rainfed ar-eas where fields are too small for effective operations with largetractors.

11IRRN 24.2

Although direct seeding is likely to be more widely adoptedin the future, transplanting will probably continue to be used,especially in poorly drained rainfed areas. As labor costs rise, farm-ers would seek labor-saving methods for establishing rice in thesepoorly drained areas. Without these labor-saving transplantingmethods (or heavy investments in drainage), these areas may stopproducing rice as labor costs keep rising. Mechanical transplant-ing could play an important role in these environments, but it iscurrently not popular in South and Southeast Asian countries.

Research to develop cost-efficient mechanical transplant-ers that would be more suitable to the farming conditions of Southand Southeast Asia could have high payoffs. In addition, othermethods of transplanting such as the dapog method practiced inirrigated areas of the Philippines and seedling throwing practicedin some parts of China could have high potential returns.

Available evidence indicates that a shift to direct seedinghas had a favorable impact on farmer income because it has helpedreduce the cost of labor. Where farmers have been able to growmore than one rice crop as a result of direct seeding, the benefitshave been even more pronounced. The incomes of landless andmarginal farmers, however, could be adversely affected becausethey are the major sources of hired labor for farm activities in-cluding transplanting. If direct seeding leads to an increase incropping intensity, the net effect on labor demand tends to bepositive, as indicated by experiences in Iloilo, Philippines, andthe Mekong Delta. If cropping intensity does not increase ad-equately to fully absorb the displaced labor, or if other nonfarmemployment opportunities are not available, direct seeding canhave an unfavorable impact on income distribution. Rural indus-trialization and other policies that help generate additional em-ployment in rural areas may be needed to counteract any nega-tive distributional consequences that may result from a shift todirect seeding.

ReferencesBhuiyan SI, Sattar MA, Tabbal DF. 1995. Wet-seeded rice: water use efficiency,

productivity and constraints to wider adoption. In: Moody K, editor.Constraints, opportunities, and innovations for wet-seeded rice. IRRIDiscuss. Pap. Ser. 10.

De Datta SK. 1986. Technology development and the spread of direct seededrice in Southeast Asia. Exp. Agric. 22:417–426.

De Datta, Nantasomsaran P. 1991. Status and prospects of direct-seededflooded rice in tropical Asia. In: Direct-seeded flooded rice in thetropics: selected papers from the International Rice ResearchConference. Manila (Philippines): International Rice Research Institute.

Erguiza A, Duff B, Khan C. 1990. Choice of rice crop establishment technique:transplanting vs wet seeding. IRRI Res. Pap. Ser. 139.

Fujisaka JS, Moody K, Ingram K. 1993. A descriptive study of farming practicesfor dry-seeded rainfed lowland rice in India, Indonesia and Myanmar.Agric. Ecosyst. Environ. 45:115–128.

Grigg DE. 1974. The agricultural systems of the world: an evolutionaryapproach. Cambridge (UK): Cambridge University Press.

Hayami Y, Kikuchi M. 2000. A rice village saga: the three decades of GreenRevolution in the Philippines. Makati City (Philippines): InternationalRice Research Institute. (in press)

Helmers K. 1997. Rice in the Cambodian economy: past and present. In:Nesbitt HJ, editor. Rice production in Cambodia. Manila (Philippines):International Rice Research Institute.

Ho NK. 1994. Management innovation and technical transfer in wet-seededrice: a case study of the Muda Irrigation Scheme, Malaysia. In:International Workshop on Constraints, Opportunities and Innovationfor Wet-Seeded Rice, Bangkok, Thailand.

Huke RE, Huke EH. 1997. Rice area by type of culture: South, Southeast andEast Asia. Manila (Philippines): International Rice Research Institute.

Isvilanonda S. 1990. Effects of pregerminated direct seeding technique onfactor use and the economic performance of rice farming: a case studyin an irrigated area of Suphan Buri. In: Fujimoto A, editor. Thai ricefarming in transition. Tokyo: World Planning Commission.

Kim SC. 1995. Weed control technology of direct seeded rice in Korea. Paperpresented at the International Symposium on Weed Control underDirect Seeded Rice, 31 Jul 1995, Omagari, Akita, Japan.

Moody K. 1982. Weed control in dry-seeded rice. In: Report on Workshop onCropping Systems Research in Asia. Manila (Philippines): InternationalRice Research Institute.

Palaniappan SP, Purushothaman S. 1991. Rainfed lowland rice farming systemin Tamil Nadu (India): status and future thrust. In: Proceedings of theRainfed Lowland Rice Farming Systems Research Planning Meeting,Myanmar, August 1991. Manila (Philippines): International RiceResearch Institute.

Pandey S, Velasco L, Masicat P, Gagalac F. 1995. An economic analysis of riceestablishment methods in Pangasinan, Central Luzon. Social SciencesDivision. Manila (Philippines): International Rice Research Institute.

Pandey S, Velasco LE. 1998. Economics of direct-seeded rice in Iloilo: lessonsfrom nearly two decades of adoption. Social Sciences DivisionDiscussion Paper. Manila (Philippines): International Rice ResearchInstitute.

Pandey S, Velasco LE. 1999. Economics of alternative rice establishmentmethods in Asia: a strategic analysis. Social Sciences Division DiscussionPaper. Makati City (Philippines): International Rice Research Institute.

Pandey S, Singh HN, Villano RA. 1998. Rainfed rice and risk-coping strategies:some micro-economic evidences from Uttar Pradesh. Paper presentedat the Workshop on Risk Analysis and Management in Rainfed RiceSystems, 21–23 Sep 1998, New Delhi, India.

Pathinayake BD, Nugaliyadde L, Sandanayake CA. 1991. Direct seedingpractices for rice. In: Sri Lanka in direct-seeded flooded rice in thetropics. Manila (Philippines): International Rice Research Institute.

PhilRice-Bureau of Agricultural Statistics. 1995. Provincial rice statistics.Muñoz, Nueva Ecija: Philippine Rice Research Institute.

Singh RK, Singh VP, Singh CV. 1994. Agronomic assessment of beushening inrainfed lowland rice cultivation, Bihar, India. Agric. Ecosyst. Environ.51:271–280.

Suyamto AM, Anwari. 1995. Improvement of gogorancah rice productionsystems and introduction of dry-seedbed nursery system on rainfedlowlands. In: Fragile lives in fragile ecosystems. Proceedings of theInternational Rice Research Conference. Manila (Philippines):International Rice Research Institute. p 407–420.

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12 August 1999

Scientists are now offered a vast array of new, electronicpossibilities, most of which fall under the general heading

of ICTs (information and communication technologies). Basi-cally, what this means is that information is increasingly beingpackaged in new electronic formats that make storage, re-trieval, and transfer far easier than in the case of paper. Somesay that the arrival of these ICTs is the most important ad-vance in information dissemination since the invention of theprinting press more than five centuries earlier. Let’s reviewsome of the exciting new options now available to scientists,starting with libraries.

Virtual librariesLibraries are gradually being transformed from quasi-ware-houses of books and journals, where the emphasis was onownership of information, to electronic clearinghouses thatfocus on access to information. It is important to note thatthese new “virtual libraries” have not abandoned informationin the traditional formats. Books and journals will not disap-pear overnight,1 in fact, they will endure for a long time tocome. Nonetheless, they are being supplemented by online,electronic resources, which are not “acquired” in the tradi-tional sense. Instead, computer links are established to theseelectronic resources, making them locally available, even whenthe host computer site may be located on the other side ofthe planet.

Electronic information:new opportunities for rice scientistsI. Wallace, Information Center, IRRI

1At an international conference in Singapore, in March 1998, Brian Land, director of the British Library, stated that “if the book were to be invented today, it would be proclaimed asa marvel of ingenuity and practicality.” 2http://ricelib.irri.cgiar.org

Dr. Oryza, chief scientist of the National Rice Institute, is ina dilemma. The Global Bank is after him again for a reportabout how the special grant of $25,000 had been spent.The money was to have paid for attendance at interna-tional conferences by senior research staff. But not a singledollar has been spent and the financial year is drawing to aclose. Of course, the last thing he wants is to return thegrant unspent, but he has no idea about upcomingconferences and meetings, and by the time announce-ments of such meetings usually reach him, the conferenceis often already over.

In addition, the International Subscriptions Agency hasjust sent him a bill for next year’s subscriptions to fiveinternational journals and his tiny operating budget wouldbe slashed again. He has no recourse but to cut these lastfew international subscriptions and rely on national

journals only. He would surely incur the wrath of hisfellow scientists who would be bitterly angered by thiscutback in subscriptions.

To top it all, Dr. Sativa, the fiercest critic of theInstitute library which Dr. Oryza also manages, has beencomplaining about the lack of information resources inthe library, which makes it problematic for him to workon collaborative projects with other national programscientists in other countries. Dr. Oryza would just have tosee what could be done about strengthening the library.

Many scientists in the national programs have thiscommon problem: lack of ready access to currentscientific information. What can be done about it? Thisreview enumerates the various options available tonational program scientists who have access to theInternet.

In 1996, the IRRI Library launched its Web site2 and, forthe first time, users could consult many of the resources ofthe Library without having to travel to Los Baños. Formerly, touse the card catalogue, users would have to actually be physi-cally present in the library building. For access, this change isnothing short of revolutionary and the Library is now regu-larly “visited” by clients based in such far-away countries asCuba, India, and Mozambique. Distance, always a barrier toinformation access, has thus been at least partially eliminated.

New computer technology has brought many other advan-tages to the library world. For example, complicated literaturesearches are now far easier to perform. Consider this hypotheti-cal library search:

Subject: weed control in riceExclusion: chemical herbicidesDates: 1995 onwardsLanguages: English or JapaneseType of document: books only

Such a search would take a long time in a traditional cardcatalogue but can be performed in seconds in an electronic cata-logue, even in one located thousands of kilometers away. Fur-thermore, references can be saved for later use or even sent toan e-mail address. Thus, scientists are no longer obliged to writedown references of interest; they can be saved electronically, evenseveral hundred at a time.

DR. ORYZA’S DILEMMA

13IRRN 24.2

How does one access an e-journal? In the case of commer-cial journals, a fee of one kind or another must be paid beforeaccess is possible and, usually, this fee is about the same as thecost of a print subscription, except in the case of pay per view(PPV), where a smaller amount is paid to read a single article orjournal issue. Of course, most scientists would prefer free accessand this may indeed come to pass, but probably not very soon.Virtually all of the major scientific journals now offer electronicaccess.

Many noncommercial journals are also available throughthe Internet and access is free. Increasingly, libraries such as IRRI’soffer their readers a selection of online journals, in addition totheir traditional print subscriptions. Listed below are a few ex-amples of noncommercial e-journals of possible interest to ricescientists:

Electronic Journal of Biotechnology12

Farm Journal Today13

Food Outlook14

Integrated Crop Management15

International Rice Research Notes16

New Agriculturalist17

Rice Journal18

Weeds World19

The advantages of e-journals are so many that, increasingly,scientists will be reading them on a computer screen, rather thanawaiting the arrival of a paper journal from New York, Amsterdam,or Bangkok.

E-journals also offer new possibilities to scientists, manyof who are unable to publish in traditional journals because ofhigh page charges and a preference by some of the leading jour-nals for established authors from advanced countries. With thearrival of e-journals, the old power structure may find its hold onscientific publishing somewhat weakened if only because unpub-lished scientists now have new alternatives. They can publish theirarticles in an e-journal or even start one of their own! Given thevery low cost of electronic publishing, launching a new journal isnot such a daunting task as it would have been a few years ago.

Meanwhile, major newspapers have also taken the plungeand are offering free electronic access to their readers. Somepopular Asian titles are:

Bangladesh The Daily Star20

China South China Morning Post21

India The Times of India22

Korea Korea Times23

Philippines Manila Bulletin24

Vietnam Saigon Times Daily25

Thailand Bangkok Post26

3http://www.lights.com/webcats 4http://library.ust.hk 5http://www.tulips.tsukuba.ac.jp/welcome.english.html 6http://www.infomal.com.my/library/virtua/index.html 7http://www.cmu.ac.th 8http://www.library.uq.edu.au/iad/mainmenu.html 9http://www.agralin.nl/desktop 10http://olc1.ohiolink.edu 11A good overview of electronic journals and their future isprovided by Thomas J. Walker, “The future of scientific journals: free access or pay for view?,” American Entomologist, Fall 1998, p 135-138. A much longer Web-published article by thesame author features illustrations and abundant hyperlinks to relevant literature and examples. Titled “The electronic future of scientific journals,” this article can be viewed at thefollowing Web address: http://csssrvr.entnem.ufl.edu/~walker/fewww/aedraft.htm 12http://www.ejb.org 13http://www.FarmJournal.com 14http://www.fao.org/waicent/faoinfo/economic/giews/english/fo/fotoc.htm 15http://www.ipm.iastate.edu/ipm/icm 16http://www.cgiar.org/irri/irrn.htm 17http://www.new-agri.co.uk 18http://www.ricejournal.com 19http://nasc.nott.ac.uk:8300/home.html 20http://www.dailystarnews.com 21http://www.scmp.com 22http://www.timesofindia.com 23http://www.koreatimes.co.kr 24http://www.mb.com.ph25http://www.saigon-news.com 26http://www.bangkokpost.net

Today, there are more than 6,000 electronic libraries ac-cessible from scientists’ computers, and most of these are acces-sible through a central Internet-based service, WebCats,3 whichis maintained in Canada. Users can connect to WebCats and thensearch for libraries by country/city or by type of library, e.g., “spe-cial” or “university.” Libraries offering electronic access includethe Hong Kong University of Science and Technology,4 the Uni-versity of Tsukuba (Japan),5 the National Library of Malaysia,6 andthe University of Chiang Mai,7 in Thailand. Not surprisingly, mostelectronic libraries are in developed countries. Three good agri-cultural libraries are the University of Queensland,8 in Australia,the Wageningen Agricultural University,9 in the Netherlands, andOhioLink,10 in the United States, which is a consortium of 18 largelibraries, including that of Ohio State University. Anyone with anInternet connection can “visit” these libraries and see what hasbeen published recently about rice or other subjects.

Electronic journalsAs the century ends, a revolution is taking place in journal pub-lishing: more and more journals are appearing in electronic for-mat.11 These e-journals, as they are known, have several advan-tages over traditional paper journals: (1) production costs arevery low, there being no significant paper or delivery expenses;(2) they are available almost instantly through the Internet,whereas, with print journals, subscribers have to wait for deliveryin the mail; (3) text and figures can be modified or augmented atany time; (4) content is electronically searchable—even manyyears’ issues in a single search; and (5) issues do not need to bebound or shelved, nor are they ever lost or mutilated. Undoubt-edly, e-journals will become increasingly important in the com-ing years.

14 August 1999

Similarly, newspapers published in other parts of the worldare also available on the World Wide Web.

Electronic document deliveryOne difficulty faced by most scientists in developing countries ishow to obtain print copies of journal articles that cannot be foundonline or where electronic access to them is expensive. This isno longer so daunting an undertaking as before and libraries suchas IRRI’s offer fast and inexpensive document delivery services totheir clients. Under optimum conditions, a scientist could easilyreceive a copy of a requested article in less than an hour, even ifshe or he happened to live thousands of kilometers away fromthe IRRI Library. Here is an example of how this works:1. A scientist in New Delhi searches IRRI’s online Rice Bibliog-

raphy,27 selects references of interest, and sends them toher local e-mail account

2. The scientist then sends the saved references back to theIRRI Library by e-mail28

3. The IRRI Library sends the complete article to the scientistin New Delhi, using Ariel software

A new software package designed to deliver short textsover the Internet, Ariel29 works quickly and inexpensively. Texttransmitted by Ariel is very clear and, of course, there are no faxor mail charges. Best of all, texts can be sent in a few seconds,either across the street or to the other side of the world, to any-one with an Internet connection. Once again, distance is becom-ing less of an obstacle to fast access to information.

The IRRI Library will provide copies of articles about rice,but what about other subjects? Here, too, there are some goodelectronic possibilities. One of the most interesting is UnCover,30

which stands out in what is becoming a very competitive field.31

UnCover is based in the United States and offers online access tothe tables of contents of more than 17,000 journals covering mostsubject areas. Anyone can connect to UnCover and search byauthor, subject, journal title, and so on. Thus, a search by authorwould retrieve articles written by a particular author and pub-lished in one or more journals. Users can search for as long asthey like with no charges being imposed by UnCover. Obviously,this is quite advantageous for scientists, but, not unsurprisingly,UnCover needs to make money and it does this mainly throughits document delivery service. Here is how it works. After a userhas identified articles of interest, these are marked for overnightdelivery by fax. Costs are quite high, unfortunately, usually morethan $15 for a single article, but the service is quick and easy touse, not to mention far less expensive than subscribing to costlyjournals. A companion service, UnCover Reveal, will send to any

e-mail address the tables of contents of up to 50 journals, as theyare published, for an annual charge of only $25.

Although very popular with some users, commercial ser-vices such as UnCover are usually too expensive for scientists indeveloping countries where, in any case, more affordable localalternatives are often available. A good example is the IndianNational Scientific Documentation Service (INSDOC),32 whichroutinely provides photocopies of articles from Indian journals.An equivalent service in China is offered by the National Libraryof China,33 while in Pakistan, inquiries should be addressed tothe National Agricultural Research Centre in Islamabad.34 Manyother Asian countries offer similar services, although electronicaccess is not always available.

Electronic bibliographic databasesIn earlier times, scientists looking for articles on a particular sub-ject usually had to wade through stacks of journals or abstractbulletins. Happily, this time-consuming task is now mostly in thepast, thanks to electronic bibliographic databases such as IRRI’sRice Bibliography, a file containing about 180,000 references onrice and fully searchable online. Larger, more general agriculturaldatabases can also be searched electronically, e.g., AGRICOLA,which is produced by the U.S. National Agricultural Library and isfreely available on the Web.35

Two other electronic databases also provide good cover-age of agriculture: AGRIS, produced by FAO, and CAB Abstracts,from CAB International in the United Kingdom. Both are avail-able on CD-ROM from SilverPlatter Information, Inc.36 and onother platforms as well by arrangement with each vendor. At theIRRI Library, for example, AGRICOLA, AGRIS, and CAB Abstractsare all mounted in CD-ROM towers that provide instant networkaccess to these databases to about 900 networked computers atthe Institute. IRRI scientists can thus search these vast files with-out even having to leave their office or laboratory, 24 hours a dayif need be.

Meanwhile, a popular option with scientists these days isto set up their own electronic databases with a product such asProCite.37 With this software, scientists can build up personal bib-liographies by either typing in references themselves or by elec-tronically importing them from other databases, such as the IRRIRice Bibliography or CAB Abstracts. This is an ideal way to keeptrack of office reprint collections.

Other electronic possibilitiesAlmost limitless amounts of electronic information can now beaccessed by anyone with an Internet connection. Examples are:

27http://ricelib.irri.cgiar.org 28E-mail address: c.austria@cgiar.org 29For more information about Ariel, visit this Web site: http://www.rlg.org/ariel.html 30Web address: http://uncweb.carl.org 31The Document Solution is another well-known service. It is offered by the publishers of Current Contents and the Web address is http://ids.isinet.com 32Contact Mrs.Alicja Shrivastava. E-mail: mcs@sirnetd.ernet.in 33Contact Mrs. Wu Jingsheng. E-mail: dcjyb@public.nlc.gov.cn 34Contact Shahnaz Zuberi, Sr. Information Officer, NARC. E-mail:SIU@DSI-NARC.sdnpk.undp.org 35http://www.nal.usda.gov/ag98 36http://www.silverplatter.com 37http://www.risinc.com

15IRRN 24.2

Institutes, organizations, universities. Most of these nowhave their own Web sites that offer visitors vast amounts of infor-mation about personnel, programs, services, and the like. A se-lected list is available at the IRRI Library Web site and includesone such as CAB International,38 FAO,39 IRRI,40 the M.S.Swaminathan Research Foundation,41 and the Chinese Agricul-tural University.42

Meteorological information. Is it hot or cool inKathmandu? Will it rain in Nairobi? CNN43 and other organiza-tions have the answers at their Web sites.

Cultural visits. More and more museums are establishingelectronic sites and IRRI’s Riceworld Museum and Learning Cen-ter is one of them.44 A related Web site, known as Riceweb,45 linksvisitors to dozens of rice-related sites worldwide.

Books and publishing. A phenomenon of the late 1990s isthe electronic bookstore, which offers customers a huge selec-tion of books at very competitive prices. Thus, a rice scientist inHyderabad or Jakarta can now buy the latest books without leav-ing home. Two well-established e-bookstores are Amazon46 in theUnited States and Waterstones47 in the United Kingdom. Simi-larly, all the major international publishers have now posted theircomplete catalogues on the Web.

Reference information. Virtually any subject can now beexplored on the Internet, from airline timetables to software prod-ucts. Many universities have assembled on their Web sites wide-

38http://www.cabi.org 39http://www.fao.org 40http://www.cgiar.org/irri 41http://www.mssrf.org 42http://www.cau.edu.cn 43http://www.cnn.com/WEATHER 44http://www.riceworld.org45http://www.riceweb.org 46http://www.amazon.com 47http://www.waterstones.co.uk 48http://thorplus.lib.purdue.edu/reference/index.html 49http://www.agbioforum.missouri.edu50http://agrinet.tamu.edu 51http://www.agry.purdue.edu/agronomy/links

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ranging selections of electronic reference information, and oneof the best is offered by Purdue University48 in the United States.

Web sites with an agricultural focus. There are many ofthese and a small selection can be found at the IRRI Library Website, such as AgBioForum,49 AgriNet,50 and Agronomic Links acrossthe Globe.51 These handy sites are open 24 hours a day and arefree to users.

The importance of information “Without information, there can be no development.” This ad-age has been around for decades and it is as true today as it hasever been. Rice scientists understand all too well the importanceof information as no research project can go very far without theappropriate facts and figures. Experimental data are vital in theresearch process, whether they come from the scientist’s ownfield and laboratory investigations or whether they appear in jour-nals, reports, and books.

Until very recently, however, information has often beendifficult to acquire, especially for scientists in developing coun-tries where really good science libraries are few and far between.We have seen, though, that new electronic technologies arechanging the world fast and scientists who formerly suffered froma paucity of information may soon be complaining of “informa-tion overload!” This can only bode well for rice research in devel-oping countries.

About IRRI’s Library andDocumentation Service

Did you know...

...that IRRI has the world’s biggest rice library?

...that it provides a free photocopy service1 to ricescientist everywhere?...that its catalogue and rice bibliography are avail-able on the World Wide Web for searching, 24hours a day2?...that IRRI Library staff are waiting right now toreceive your requests3?

We hope to be of service to you soon!

1Maximum of 50 pages per request2Web address: http://ricelib.irri.cgiar.org3Write to Carmelita Austria at this address:Library and Documentation Service,International Rice Research Institute,MCPO Box 3127, Makati City 1271, Philippines.E-mail address: c.austria@cgiar.org

16 August 1999

Plant breeding

KHRS26 (KHP5) for upland direct-seeded conditionsY.G. Shadakshari, H.M. Chandrappa, A. Manjunath, and S.C. Chandrasekharaiah, Regional ResearchStation (RRS), Mudigere 577132, Karnataka, India

Table 1. Performance of KHRS26 in upland rice variety trial (direct-seeded) at the RegionalResearch Station, Mudigere, 1991-96.

Grain yield (t ha-1) % Straw %Entry increase yield increase

over check (t ha-1)b over check1991 1992 1993 1994 1995

KHRS26 1.3 3.9 3.6 4.8 2.6 3.2 4.3G318a 1.0 2.6 1.6 3.7 2.8 2.4 27 3.8 13Karnaa 1.2 2.6 1.9 3.7 2.4 2.4 27 3.7 13Jayaa 1.3 2.8 2.8 3.4 3.1 2.7 17 3.6 14 Mean 1.3 3.5 2.5 3.6 2.8 3.7 CD (5%) 0.17 0.82 0.36 0.62 0.45 0.40 CV (%) 6 14 9 10 10 7

aRecommended varieties used as checks. b1996 data.

Rainfed kharif rice is the major field cropin the hill zone of Karnataka (11°56' and15°46' N latitude and 74°31' and 76°4' Elongitude). Rainfall in the zone ranges from1,363 to 3,426 mm, with an average of 2,173mm. Rice is grown as a drill-sown crop inthe uplands and, to some extent, in themidlands, where rainfall is medium to low;it is mostly a transplanted crop in the low-lands. Crop area in the zone is 284,700 ha,with an annual production of 723,000 t. Itrepresents nearly 23% of the rice area inthe state. The average production in thezone is lower (2.5 t ha-1) than that of thestate (3 t ha-1).

Jaya, G318, and Karna are the threevarieties recommended for direct sowingin the hill zone. Attempts were made atthe RRS during the mid-1980s to identify asuitable variety for the region. Of the se-lections obtained from the cross Intan/IET7191, KHRS26 was the most promisingin station trials. It was further tested in farmtrials for 3 yr. Based on its superior perfor-mance, the variety was released for com-mercial cultivation in 1998.

Farmers usually prefer semitall vari-eties with medium bold grain for drill-sownsituations in the uplands. KHRS26 wasreadily accepted because it yielded 17–27% more grain and 13–14% more fodderin the station (Table 1) compared with thechecks, in addition to meeting farmers’preferences for plant height and grainquality.

KHRS26 is suitable for upland direct-seeded situations, having an optimum du-ration of 150–155 d (Table 2). Early ma-turing varieties are usually harvestable dur-ing the rainy season and are also more at-tractive to birds.

The variety had an 11% higher yieldthan the checks (Table 3) in farmers’ fields(tested in 19 locations across 4 districts).

Table 2. Comparison of KHRS26 with check varieties for yield attributes in upland rice vari-ety trial (direct-seeded), 1991-96.

Days Plant Panicles m-2 Panicle Grain 1,000-Entry to height (no.) length type grain

flowering (cm) (cm) weight(g)

KHRS26 125 85–90 260 19.1 Medium bold 27.6G318a 110 60–65 265 17.7 Long bold 26.2Karnaa 115 65–70 260 18.2 Medium bold 25.0Jayaa 115 65–70 265 18.1 Medium bold 27.5

aRecommended varieties used as checks.

Table 3. Performance of KHRS26 in farm trials (direct-seeded), 1994-96.

Grain yield (t ha-1)

1994 1995 1996 Av % increase(5)a (8) (6) (19) over check

KHRS26 3.9 4.2 5.3 4.5Checkb 3.2 3.9 4.9 4.0 11

aNumbers in parentheses represent number of test locations. bRecommended varieties used as checks.

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International Workshop on Characterizing andUnderstanding Rainfed Rice Environmentsscheduled for December 1999

IRRI, in partnership with national agricultural research systems in several Asian countries, has been carry-ing out studies to understand rainfed rice environments as well as evaluate cropping practices to translateresearch into appropriate technological interventions. This research ranges from broad, regional-scale char-acterization to detailed farm-level studies. Studies have been and are being carried out in different geo-graphical areas by different institutions. Different methodologies have been tested, and several cross-cut-ting issues have emerged. These and other findings and conclusions will be discussed in the Rainfed Low-land Rice Research Consortium (RLRRC) workshop to be held on 6-10 December 1999 at Bali, Indonesia.The workshop aims to bring together researchers involved in characterizing rainfed rice environments, toreview the progress in research related to characterization of the rainfed rice environment, including workcarried out at RLRRC sites, and identify needs and opportunities for using characterization work for re-search prioritization and planning of the Consortium’s future research activities. Characterization was cho-sen as the theme for this year’s workshop.

For more information, contact Dr. T.P. Tuong, IRRI, (e-mail: t.tuong@cgiar.org)

Av

17IRRN 24.2

Grain quality characteristics of aromaticand nonaromatic rice cultivarsM. Sakila, S.M. Ibrahim, C.R. Anandakumar, S. Backiyarani, and D. Bastian, Department of Agricultural Botany,Agricultural College and Research Institute, Madurai 625104, India

Milled rice is judged by its appearance,which depends on grain size and shape,whiteness, and translucency. Broken andunattractive grains diminish the economicvalue of rice that is consumed as wholegrain. Rice consumers want products withthe best qualities. Selection for qualitycharacters therefore leads to varieties morereadily accepted by farmers and consum-

ers. We therefore aimed to develop high-yielding varieties with these grain qualitycharacteristics—long slender or medium-long slender translucent grain with highmilling recovery, intermediate gelatiniza-tion temperature (GT), and very goodgrain elongation. Grain elongation is a spe-cial characteristic of several high-grain-quality varieties such as Basmati 370 and

Nga Kywe. This polygenically controlledtrait is difficult to transfer.

In the wet season (June to Septem-ber), we evaluated 12 high-yielding variet-ies, 11 IET (Initial Evaluation Trial) lines,and scented rice for hulling, milling, headrice recovery, and quality parameters suchas amylose content (AC) and gel consis-tency (GC) (see table). Each genotype was

Grain quality characteristics of aromatic and nonaromatic cultivars.

% total Head rice Kernel Kernel Length/ Linear Alkali Gelati- Amylose Grainmilled recovery length width breadth elongation spreading nization content yieldrice (%) (mm) (mm) ratio ratio value temp.a (%) (t ha-1)

High-yielding varietiesADT36 64.4 44.2 6.7 1.9 3.5 1.8 3.3 I 28.4 Hard 5.0ADT42 73.2 44.3 6.6 1.9 3.5 1.8 3.7 I 27.3 Hard 6.0ADT43 62.7 44.7 5.7 2.3 2.4 1.6 6.8 L 26.2 Hard 5.9ADRH1 69.5 36.6 6.8 2.2 3.1 1.7 3.8 I 24.3 Hard 6.4CORH1 72.2 43.0 5.6 2.3 2.4 1.6 7.0 L 25.1 Hard 6.0ASD16 70.7 44.5 5.2 2.7 1.9 1.5 7.0 L 24.3 Hard 5.6ASD17 70.6 48.1 5.4 2.8 1.9 1.4 6.9 L 28.1 Hard 5.4ASD20 64.6 50.5 6.8 2.0 3.4 1.7 3.8 I 27.3 Hard 6.7TKM9 71.9 45.4 5.7 2.6 2.2 1.2 6.6 L 30.4 Hard 6.0MDU5 72.6 49.1 5.8 2.5 2.4 1.5 7.0 L 26.3 Hard 4.9IR50 72.5 51.1 6.7 2.0 3.5 1.7 3.2 I 23.1 Hard 6.0IR64 68.9 42.5 6.8 1.9 3.6 1.8 3.6 I 21.3 Hard 5.8IET linesb

JGL496 68.6 46.4 5.5 1.6 3.4 1.4 6.0 L 21.3 Hard 6.0CB96073 72.5 44.6 5.6 1.5 3.6 1.3 6.0 L 26.4 Hard 6.2CB(DH)95299 66.0 42.7 5.0 1.3 3.8 1.6 7.0 L 24.7 Hard 5.4MTU1029 74.2 51.3 5.6 1.6 3.5 1.6 6.4 L 23.1 Hard 5.2HKR95-219 70.6 44.6 6.7 2.0 3.4 1.7 3.5 I 22.3 Hard 5.6CSR27 70.7 50.4 6.6 3.3 2.0 1.4 6.4 L 21.8 Hard 5.3NWGR9 72.3 46.0 6.8 2.0 3.4 1.7 3.6 I 24.4 Hard 5.2NWGR13 71.0 43.8 6.8 2.0 3.4 1.7 3.9 I 20.0 Hard 5.7RR380-10-3 75.6 32.1 6.6 3.6 1.8 1.6 3.6 I 24.3 Hard 5.6RR389-8-2 68.6 36.6 6.6 1.9 3.4 1.5 7.0 L 26.1 Hard 5.3RNRM 22 62.3 33.9 6.8 3.3 2.0 1.3 3.5 I 23.7 Hard 5.8Basmati 370c 60.3 49.6 7.0 2.1 3.2 1.8 3.3 I 19.2 Medium 3.9Basmati 385c 64.5 31.1 6.8 2.2 3.1 1.5 3.7 I 19.3 Medium 4.0Pusa Basmat 1c 62.4 44.4 7.0 2.1 3.2 1.8 3.2 I 19.6 Medium 4.3Kasturic 63.4 38.9 5.7 2.4 2.3 1.5 7.0 L 19.9 Medium 4.2Pak. Basmatic 61.2 46.6 6.9 2.3 2.8 1.5 3.4 I 21.3 Medium 4.1Har. Basmatic 58.7 36.6 6.7 2.1 3.1 1.7 3.2 I 20.4 Medium 4.0Meenambur Local 77.1 39.9 4.1 1.5 2.6 1.4 7.0 L 22.3 Hard 3.0Jeeragasamba 67.4 45.5 4.2 1.5 2.7 1.4 6.8 L 24.1 Hard 3.9Nepaljeeragas 63.4 32.3 4.0 1.5 2.6 1.4 6.7 L 23.1 Hard 3.7AmbaWhite ponni 63.2 48.8 5.7 2.4 2.3 0.4 7.0 L 22.4 Hard 5.0TM95005 72.1 49.9 5.7 2.2 2.5 1.5 7.2 L 26.5 Hard 5.4ACM 95132 70.2 34.5 5.6 2.3 2.3 1.5 7.0 L 28.1 Hard 5.9 Mean 68.3 43.2 5.8 2.2 2.9 1.5 5.3 23.9 5.2 SE 3.76 4.88 0.75 0.43 0.51 0.07 1.57 1.5 0.77

aL = low, I = intermediate. bIET = Initial Evaluation Trial. cAromatic rice.

Genotype Type

18 August 1999

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transplanted in a randomized block designwith three replications at 20 × 15-cm spac-ing. Observations from 10 randomly se-lected plants per replication in each geno-type were recorded. Aroma was deter-mined by using chopped leaves collectedat 50% flowering stage.

GT is a measure of cooking ease andis indexed by the alkali digestibility test(Little et al 1958). It is measured by thealkali spreading value (ASV) of individualmilled rice soaked in 1.7% KOH solutionfor 23 h at 30 °C using a 1–7 scale. A highrating indicates more disintegration and isclassified under low GT. Rice varieties withintermediate GT (ASV of 3–5) are usuallypreferred over those with low GT (ASV of6–7). The AC determines cooking behav-ior and eating quality of cooked rice. Thiswas estimated and classified using a modi-

fication of Shen’s method (1990), whichwas developed at the Cuttack Rice Re-search Institute (Swain and Nagaraju 1997).The GC test is a reliable index for cookedrice texture. A method modified byCagampang (1973) was used to analyze theGC of 35 varieties. Length is classified ashard (6–10 mm), medium (11–20 mm),and soft (>20 mm).

Milled rice percentage was high forADT42 (high-yielding variety RR380-10-3(IET line), and Meenambur Local (scentedrice). Percent head rice recovery was high-est in IR50, TM95005, (MTU1029), andCSR27. ADT36 had the highest linear elon-gation among all genotypes. All scentedvarieties had intermediate (17–22%) ACand medium (11–20 mm) GC (data notshown), while the high-yielding,nonscented, and IET lines recorded higher

(>22%) AC and hard (6–10 mm) GC (datanot shown). ADT36, ADRH1, HKR95-219,NWGR9, and NWGR13 showed normalmilled rice percentage and head rice re-covery, long slender grains, intermediateGT, hard GC, and high AC.

ReferencesCagampang GB, Perez CM, Juliano BO. 1973. A gel

consistency test for eating quality of rice. J.Sci. Food Agric. 24:1589–1594.

Little RR, Hilder GB, Dawson EH. 1958.Differential effect of dilute alkali on 25varieties of milled white rice. Cereal Chem.35:111–126.

Shen YZ. 1990. Genetical studies on amylosecontent of rice grain and modification of thedetermination method. Sci. Agric. Sin.23(1):60–68. (in Chinese).

Swain BR, Nagaraju M. 1997. Modified method fordetermination of amylose content using asingle rice kernel. Int. Rice Res. Notes22(1):48.

Performance of prototype rice lines from ideotype breedingA. Kumar, R.K.S. Tiwari, S.S. Parihar, K.S. Pandya, Indira Gandhi Agricultural University, Regional Agricultural ResearchStation (RARS), Bilaspur, Madhya Pradesh 495001; and M.P. Janoria, Department of Plant Breeding and Genetics,Jawaharlal Nehru Agricultural University (JNAU), Jabalpur, Madhya Pradesh 482004, India

Several new plant type (NPT) rice breed-ing lines for the irrigated ecosystem havebeen developed at JNAU from crossesIR47705-AC5/ChIR87-3-1//Kranti (the 57Kseries), IR47705-AC5/IR32307-75-1-3-1//Kranti (the 63K series), and IR47705-AC5/IR28211-45-1-1-2//Kranti (the 72K series).These were based on a basic ideotype ofrice (Janoria 1989).

We evaluated 16 NPT lines withthree checks—MW10, IR36, and Kranti—during the 1996-97 dry (December-May)and wet (June-November) seasons atRARS. The two field experiments were laidout in a randomized block design withthree replications, 6 × 1.2-m net plot size,and 20 × 20-cm spacing, and with 100-60-40 kg NPK ha-1.

Five plants were randomly sampledper plot for plant height, panicle number

plant-1, and grain number panicle-1. Grainyield (t ha-1) was estimated from net plotsof 7.2 m2 and days to maturity and 1,000-grain weight on a plot basis.

The top-yielding NPT lines in theearly and medium maturity groups—NPT63K-1-20 and NPT63K-12-51, respec-tively—significantly (P = 0.05) outyieldedthe respective checks (see table) in bothseasons. NPT57K-3-6 (very early) had ayield similar to its check MW10 during thewet season. NPT lines generally had a muchhigher grain number panicle-1, lowerpanicle number plant-1, and greater plantheight than the semidwarf checks in ac-cordance with the ideotype design.

The top-yielding NPT line (NPT63K-12-51) was resistant to bacterial leaf blight(caused by Xanthomonas oryzae pv.oryzae) and sheath blight (caused by

Rhizoctonia solani f. sp. sasakii), the twomajor constraints to yield in MadhyaPradesh under artificial inoculation.

The longer duration of experimen-tal entries in the dry season was due tolower temperatures during December andJanuary, which slowed seedling growth inthe nursery. Hence, seedling age at trans-planting was 50 d in the dry season com-pared with 21 d in the wet season. Simi-larly, higher photothermal regimes duringthe postplanting phase reduced plantheight and increased yields in the dry sea-son.

ReferenceJanoria MP. 1989. A basic plant ideotype for rice.

Int. Rice Res. Notes 14:12–13.

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19IRRN 24.2

VL Dhan 61, a new rice variety for the northwesternHimalayan regionR.K. Sarma, V.S. Chauhan, J.C. Bhatt, K.D. Koranne, and P. Singh, Vivekananda Parvatiya Krishi Anusandhan Sansthan, IndianCouncil of Agricultural Research, Almora 263601, Uttar Pradesh, India

A new rice variety, VL Dhan 61, was re-leased by the Central Varietal Release Com-mittee in 1997 for cultivation under irri-gated transplanted conditions of hilly andvalley areas (up to 1,150 m) of UttarPradesh and Himachal Pradesh. VL Dhan61 was developed to combine high yieldand blast resistance from the cross Jaya/Ta-poo-cho-z, using the pedigree method.Eighty-two desirable plants were selectedin the F

2 generation in 1986. Further se-

lection was made until uniformity wasachieved.

VL Dhan (IET13485) was tested inthe 1992-95 All-India Coordinated Trials atdifferent hill sites. It yielded an average of4.9 t ha-1—16% higher than zonal checkHimdhan, 22% higher than the state/localcheck, and 6% higher than the high-yield-ing test genotype (Table 1). It is anonlodging, semitall (110 cm) variety with130-135 d duration. It has compact, well-exserted long panicles with good spikeletfertility and long bold grains (length/breadth, 2.65). It has also shown resistanceto/tolerance for prevailing biotic stresses(leaf and neck blast, stem borer) and tol-erance for abiotic constraints (low tem-perature) (Table 2).

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Performance of top new plant type breeding lines of very early, early, and medium maturity groups, RARS, Bilaspur, India, 1996 wet season(WS) and dry season (DS).

Days to Plant height Panicles Grains panicle-1 1,000-grain Grain yieldmaturity (cm) plant-1 (no.) (no.) weight (g) (t ha-1)

WS DS WS DS WS DS WS DS WS WS DS

Very earlyNPT57K-3-6 107 137 114 85 6.7 8.7 163 207 25.1 6.4 7.7MW10 (check) 105 138 92 79 9.3 10.0 111 121 22.7 5.2 5.6EarlyNPT63K-1-20 118 143 107 86 6.7 7.3 205 260 28.2 7.4 8.2IR36 (check) 116 142 82 72 10.0 11.0 126 139 22.8 5.7 7.2MediumNPT63K-12-51 127 152 117 100 9.3 9.3 228 271 28.6 9.2 9.9Kranti 128 146 106 86 11.3 11.3 129 164 28.1 6.5 7.5 LSD (0.05) – – 8.6 6.5 2.0 2.3 40.4 46.1 – 1.5 1.6

Entry

Table 1. Grain yield (t ha-1) of VL Dhan 61, All-India Coordinated Trials, hill zone, 1992-95.

Genotype 1992 1993 1994 1995 Mean Gain (%)

VL Dhan 61 4.8 3.6 5.0 6.2 4.9 – (IET13485)Himdhan 4.2 3.2 2.7 4.8 4.2 16 (zonal check)State check 3.7 2.9 4.1 5.3 4.0 22VL 89-1167 4.1 3.2 4.8 5.6 4.4 11 (IET13483)VL 89-1177 4.6 3.4 5.0 5.5 5.6 6 (IET13484)

Table 2. Comparison of newly released variety VL Dhan 61 with its parents.

Parents

Jaya Ta-poo-cho-z

Days to 50% flowering 103–105 100 109Days to maturity 130–135 131 140Plant height (cm) 110 85 90Panicle type Compact Compact CompactPanicle length (cm) 25.5 25.2 22.0Awn Tip awned Awnless AwnPanicle exsertion Well Well WellThreshability Easy Moderate Hard1,000-grain weight (g) 23.4 25.0 23.0Milling (%) 65.8 74.0 60.3Kernel length (mm) 6.68 6.27 5.14Kernel breadth (mm) 2.52 2.54 2.69L/B (length/breadth) 2.65 2.47 1.91Grain shape Long bold Long bold Short boldAlkali digestion value 5.2 7.0 –Disease and insect score (0–9 score)a

Leaf blast 4 – 2 Neck blast 3 5 3 False smut 3 – – Stem borer 3 – – Leaffolder 5 – –aMaximum score recorded using Standard evaluation system for rice.

Character VL Dhan 61

20 August 1999

Pest science and management

Feeding effects of rice leaffolder on flag leafgas exchange of rice plants at floweringT. Watanabe, Kyushu National Agricultural Experiment Station, Nishigoshi, Kumamoto, 8611192 JapanEmail: tomoya@narc.affrc.go.jp

The rice leaffolder (LF) Cnaphalocrocismedinalis (Gueneé) folds leaves andscrapes off the green tissues. LF infesta-tions are apparent after flowering. Thefolding of leaves and tissue removal resultin a loss of effective leaf area for photo-synthesis. The relationship between in-fested leaf area and photosynthetic activ-ity is not yet fully understood (de Jong1992, Yamamoto et al 1997). Leaf gas ex-change of infested flag leaves was mea-sured to quantify this relationship, whichis important for simulating changes in as-similate production and yield.

The study was conducted from 30Aug to 16 Sep 1995 on an experimentalfield subjected to standard cropping man-agement at the Kyushu National Agricul-tural Experiment Station, Kumamoto, Ja-pan (32°51' N, 130°44' E). Two japonicacultivars (Hinohikari and Reiho) and oneindica cultivar (IR24) were used in thisstudy. Net photosynthesis and stomatalconductance were measured after flower-ing by using a LI-COR 6200 portable pho-tosynthesis system with a 0.25-L chamber.Flag leaves folded by LF were unfolded andlarvae were removed before measurement.A portion of the flag leaf blade that in-cluded the injured part was inserted intothe chamber. Measurements were carriedout under clear sky conditions (1450–1950µmol PAR m-2 s-1). The leaf blades weremeasured and cut, and then the leaf areawas measured by gas exchange with a LI-COR 3100 leaf area meter. Infested leaf areawas traced with black ink onto a transpar-ency film and measured with a leaf areameter. The photosynthetic rate of healthyflag leaves in the same plant with infestedleaves was measured as the control.

No differences were observed in thereduction pattern of net photosynthesisand stomatal conductance among culti-

vars. There was a negative linear relation-ship between net photosynthesis and leafarea infested by LF (Fig. 1). The regressioncoefficients were significantly lower than0 (P<0.0001). A 10% loss in leaf area re-sulted in a 14–19% reduction in net pho-tosynthesis. These values suggested thatthe effect of LF injury caused by the reduc-tion in photosynthetic rate was larger thanthe effect of LF injury caused by reductionin leaf area.

The greater effect of LF injury on netphotosynthesis was probably caused by acombination of factors such as an increasein dark respiration, a reduction in stomatalaperture, and a reduction in photosyn-thetic activity in the mesophyll tissue.There was a negative linear relationshipbetween stomatal conductance and leafarea infested by LF (Fig. 2). The reduction

rate in stomatal conductance, however,was nearly the same as the reduction ratein leaf area consumed by LF. The leaf tem-perature of infested leaves was 0.6–1.0 °Chigher than that of the control. The linearrelationship between leaf area infested byLF and an increase in leaf temperature (r2

= 0.22 to 0.36, P<0.01) suggest an increasein dark respiration.

On an infested leaf, LF feeding re-duces the leaf area and photosyntheticactivity of undamaged tissues. LF feedingeffects on leaf photosynthesis at floweringhave not yet been introduced in simula-tion models to evaluate LF infestation(Benigno et al 1988, de Jong and Daamen1992, Graf et al 1992). The effects of leafremoval by LF on total canopy photosyn-thesis and total assimilate productionshould be investigated.

Fig. 1. Relationship between percentage of leaf area infested by leaffolder larvae and netphotosynthesis of flag leaf.

30

25

20

15

10

5

050403020100

Infested leaf area (arcsine-transformed)

Net photosynthesis (µ mol m-2 s-1)

IR24 Y=25.2-0.32X (r2=0.55)Reiho Y=23.2-0.38X (r2=0.68)Hinohikari Y=23.4-0.39X (r2=0.79)

21IRRN 24.2

ReferencesBenigno EA, Shepard BM, Rubia EG, Arida GS,

Penning de Vries FWT, Bandong JP. 1988.Simulation of rice leaffolder populationdynamics in lowland rice. IRRI Res. Pap. Ser.135, 8 p.

de Jong PD. 1992. Effects of folding and feedingby Cnaphalocrocis medinalis onphotosynthesis and transpiration of riceleaves. Entomol. Exp. Appl. 63:101–102.

de Jong PD, Daamen RA. 1992. Simulation of yieldloss by the rice leaffolder Cnaphalocrocismedinalis under different growingconditions. J. Plant Prot. Trop. 9:117–123.

Graf B, Lamb R, Heong KL, Fabellar L. 1992. Asimulation model for the populationdynamics of rice leaffolders (Lepidoptera:Pyralidae) and their interactions with rice. J.Appl. Ecol. 29:558–570.

Yamamoto H, Honda Y, Hayakawa S, Ohgata Y.1997. Photosynthetic and respiration ratesof leaves damaged by rice leaffolderCnaphalocrocis medinalis Gueneé. Jpn. J.Appl. Entomol. Zool. 41:115–119.

Fig. 2. Relationship between percentage of leaf area infested by leaffolder larvae and stomatalconductance of flag leaf.

IR24 Y=1.21-0.013X (r2=0.29)Reiho Y=0.88-0.009X (r2=0.29)Hinohikari Y=1.27-0.014X (r2=0.26)

2.0

1.5

1.0

0.5

0.00 10 20 30 40 50

Infested leaf area (arcsine-transformed)

Stomatal conductance (mol m-2 s-1)

Effects of Heterodera sacchari population density onestablishment and development of upland rice cv. IDSA6under field and pot conditionsD.L. Coyne, Natural Resources Institute, Chatham Maritime, Kent ME4 4TB; R.A. Plowright, CABI Bioscience, BakehamLane, Egham, Surrey TW20 9TY, UK Email: dannycoyne@compuserve.com

In West Africa, the cyst nematodeHeterodera sacchari is known to causestunting and chlorosis of upland rice. Stud-ies have also demonstrated its high patho-genicity on susceptible cultivars (Babatola1983, Coyne and Plowright 1998).

We studied the effect of the nema-tode on rice (cv. IDSA6) development in anaturally infested field site at the West Af-rica Rice Development Association(WARDA), Cote d’ Ivoire, and in 100-mLpots in the screenhouse.

In the field, rice was sown at 5 seedshill-1, spaced 25 cm apart, on 60 m2 of sandysoil (10% clay, 27% silt, and 63% sand) inJune 1997. The area had been sown to ricecv. IDSA6 the previous year and was knownto be infested with H. sacchari. Becauseof the heterogeneity of nematode occur-rence, a range of infection densities overthe area was expected. Other nematodes

present were Pratylenchus zeae,Meloidogyne incognita, Helicotylenchusdihystera, and Mesocriconema tescorum.Cyst-infested soil from rice cultures wasalso incorporated evenly into the soil sur-face. Fertilizer was applied at 60 kg NPKha-1 (10:18:18) at sowing and 40 kg ureaha-1 at 56 d after sowing (DAS). The experi-ment was maintained weed-free. At 90DAS, 189 single hills were randomly se-lected and height and tiller number wererecorded. Root and leaf fresh weights weremeasured and nematode population den-sities were determined from 5 g of roottissue + 100 mL of soil.

In a pot experiment replicated 10times, seeds were sown singly into 100 mLof steam-sterilized sandy soil. Freshlyhatched H. sacchari juveniles were inocu-lated in a water suspension at nine densi-ties (see table) at sowing. Plant height was

recorded at 7 and 14 DAS and fresh rootand leaf weight at 40 DAS.

In the field, H. sacchari reduced thegrowth of IDSA6. There was a negativecorrelation between leaf weight and H.sacchari juvenile population density at 90DAS (see figure) (r = 0.4; P<0.001). Nega-tive correlations were also observed withroot weight (r = 0.27; P<0.05) and tillernumber (r = -0.23; P<0.05). There was norelationship between nematode popula-tion density and plant height.

In pots, very low inoculation densi-ties appeared to have an initial stimulatoryeffect on plant development, but densitiesof 8 juveniles mL-1 of soil at sowing sup-pressed the development of emergingseedlings. Hatching H. sacchari juveniles,however, emerge from their protectivecysts over an extended period (Ibrahim etal 1993). Seeds germinating in the pres-

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22 August 1999

ence of cysts will therefore likely be con-tinually exposed to invading juveniles.

The suppression of emerging seed-lings and reduced leaf weight, root weight,and tiller number of susceptible uplandrice in the presence of H. sacchari wouldlikely affect the crop’s ability to cope withadditional stresses such as weeds anddrought, thereby exacerbating potentiallosses.

AcknowledgmentsThis paper is an output from a projectfunded by the UK Department for Inter-national Development (DFID) (Project No.R6658, Crop Protection Programme) forthe benefit of developing countries. Theviews expressed are not necessarily thoseof DFID.

ReferencesBabatola JO. 1983. Rice cultivars and Heterodera

sacchari. Nematol. Mediterr. 11:103–105.Coyne DL, Plowright RA. 1998. The cyst nematode

Heterodera sacchari in rainfed riceproduction in West Africa: distribution, croploss assessment, and management. Paperpresented at the European Society ofNematologists meeting, 4–8 Aug 1998, St.Andrews, Scotland.

Ibrahim SK, Perry RN, Plowright RA, Rowe J. 1993.Hatching behavior of the rice cystnematodes Heterodera sacchari and H.oryzicola in relation to age of host plant.Fund. Appl. Nematol. 16:23–29.

Relationship between fresh leaf weight of IDSA6 at 90 d after sowing and H. sacchari populationdensity under field conditions in sandy soil.

Usefulness of blast resistance genes and their combinationsin different blast-endemic locations in IndiaR. Sridhar, U.D. Singh, P.K. Agrawal, and J.N. Reddy, Molecular Plant Pathology Laboratory, Central Rice Research Institute,Cuttack 753006; S.S. Chandrawanshi, Zonal Agricultural Research Station (ZARS), Indira Gandhi Agricultural University(IGAU), Jagadalpur 494005; R.B.S. Sanger, ZARS, IGAU, Ambikapur 497001; J.C. Bhatt, Vivekananda Parvatiya KrishiAnusandhan Sansthan, Almora 263601; Y. Rathaiah, Assam Agricultural University, Jorhat 785013; and K.V.S.R.K. Row,J.S.S. Krishi Vigyan Kendra, Suttur 571129, India Email: rsridhar@crri.ori.nic.in

Identification of functional blast (causedby Pyricularia grisea) resistance genes fora particular region is a prerequisite for theirmeaningful deployment. In a mini-networkprogram, we evaluated some blast resis-tance genes in six blast-endemic locations

spread over five different states in India(Cuttack in Orissa, Jagadalpur andAmbikapur in Madhya Pradesh, Almora inUttar Pradesh, Jorhat in Assam, and Sutturin Karnataka). Plants were raised fromseeds sown thickly (650–700 seeds m-2)

under Uniform Blast Nursery conditionsduring the 1998 wet season.

Local susceptible cultivars—Karuna(Cuttack), HR12 (Jagadalpur, Ambikapur,Almora and Suttur), and Mahsuri (Jorhat)—were used in spreader rows. A single row

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00 2500 5000 7500 10000 12500

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Effect of H. sacchari inoculation density at sowing on mean height of rice cv. IDSA6 at 7 and14 d after sowing (DAS), and root and leaf fresh weights at 40 DAS.

Initial Height (mm) Fresh weight (g)inoculationdensity seed-1 7 DAS 14 DAS Root Leaf

0 40.6 175 0.25 0.36 10 51.0 220 0.35 0.51 20 46.9 212 0.35 0.48 40 50.4 210 0.27 0.43 80 38.9 187 0.28 0.43100 43.8 214 0.28 0.41200 44.2 180 0.26 0.33400 41.0 185 0.25 0.36800 27.9 132 0.14 0.22LSD (P<0.05) 10.7 37.8 ns 0.16 (P<0.01) 14.3 50.3 - ns (P<0.001) ns 65.4 - -

23IRRN 24.2

of the susceptible check was planted alter-nately between two rows of the test entry,providing a spreader row on either side ofeach test entry in addition to two spreaderrows around the bed. The rows were notreplicated because the plant population ineach row was very high for a qualitativeassessment of the disease.

Uniform incidence of leaf blast oc-curred in all test locations at the seedlingstage. Leaf blast reaction was recorded at30 and 45 d after sowing (DAS). Results inthe table are those from the second ob-servation, when the disease was at its peak.The disease was scored using a 0–5 scale(0 = no visual symptoms; 1 = brownspecks smaller than 0.5 mm in diameter; 2= brown specks about 0.5–1 mm in diam-eter; 3 = roundish to elliptical lesions

about 1–3 mm in diameter with gray cen-ters and brown margins; 4 = typicalspindle-shaped blast lesions, 3 mm orlonger with little or no coalescence of le-sions; 5 = same as 4 but half of one moreleaf killed by coalescence of lesions)(Mackill and Bonman 1992). Plants rated1–3 were considered resistant, and thoserated 4–5 were considered susceptible.

The susceptible checks—Karuna,HR12, and Mahsuri—and the two recurrentparents—Kalinga III and Vandana (beingused at CRRI for improving blast resis-tance)—were highly susceptible to blast inall locations (see table). Another suscep-tible cultivar, Co 39, carrying resistancegene Pi-a, (Co 39 gene) in whose back-ground the near-isogenic lines with blastresistance genes have been developed,

succumbed to the disease in all test loca-tions except at Jorhat, where it was resis-tant.

The effectiveness of individual re-sistance genes varied between locations.Pi 1(t) was effective in Jorhat, Ambikapur,and Suttur and Pi 2(t) in Jorhat, while Pi3(t), Pi 4a(t), and Pi 4b(t) were generallynot effective in all test locations. The re-sistance of F-124-1, presumably carryingPi 4a(t), however, varied in different loca-tions. In all probability, this line might carrysome additional resistance genes. CultivarMoroberekan, which possesses many re-sistance genes, was resistant in five of sixlocations. Among recombinant inbred lines(RILs) derived from Moroberekan andCo39, however, RIL 10 [Pi 12(t)] showedresistance only in Suttur and RIL 29 [Pi

Cultivar/line Known resistance gene

Reaction (0–5 scale) of a set of cultivars/lines possessing known genes with resistance to blast at six different locations in India.a

Locations

Cuttack Jagadalpur Ambikapur Almora Jorhat Suttur

Kalinga III nd 5 4 5 5 2 4Vandana nd 5 4 5 5 3 5Co 39 Pi-a(Co 39 gene) 5 5 5 5 2 5Moroberekan Pi 5(t), Pi 7(t), 2 2 2 4 1 1

Pi 10(t), Pi 12(t), Pi 157(t)O. minuta derivative Pi 9(t) 1 3 1 4 1 4 (WHD-IS-75-1-127)C101LAC Pi 1(t) 5 2 1 5 1 1C101A51 Pi 2(t) 5 3 2 4 3 4C101PKT Pi 4a(t) [Pi-ta] 5 5 5 4 4 5C102PKT Pi 4a(t) [Pi-ta] 4 4 5 5 3 4C104PKT Pi 3(t) 5 5 5 5 5 5C105-TTP-4-L23 Pi 4b(t) 5 5 5 5 5 3C103TTP nd 4 3 5 5 2 2C104LAC nd 3 3 5 5 2 4C101TTP-1 nd 4 5 5 4 4 4Li-jiang-xin-tuan hei-gu nd 5 5 5 5 5 5F-80-1 Pi k 5 5 5 5 5 1F-98-7 Pi km 5 4 5 5 3 1F-124-1 Pi-ta 5 3 3 5 1 1F-128-1 Pi-ta2 5 4 4 3 1 5F-129-1 Pi kp 5 5 4 5 4 3F-145-2 Pi b 5 4 4 5 3 1RIL 10 Pi 12(t) 4 5 4 5 5 1RIL 29 Pi 7(t) 4 5 ng 5 5 5RIL 45 Pi 5(t) 1 3 4 5 1 5RIL 77 Pi 5(t) 5 5 5 5 5 5RIL 249 Pi 5(t) 3 4 2 3 1 1BL 122 Pi 1(t), Pi 2(t) 1 3 1 2 1 4BL 142 Pi 1(t), Pi 4(t) 2 5 1 4 5 1BL 245 Pi 2(t), Pi 4(t) 1 2 1 1 3 1IR64 Pi ta2, Pi 20(t) 1 nt nt nt nt 5Karuna nd 5 5 5 5 3 5HR12 nd 5 nt 5 5 nt ntMahsuri nd 5 nt nt nt 5 nt

and = not detected, nt = not tested, ng = not germinated. Note: See text for rating scale.

24 August 1999

Usefulness of combinations of bacterial blight resistancegenes at Cuttack, Orissa, IndiaR. Sridhar, J.N. Reddy, U.D. Singh, and P.K. Agrawal, Molecular Plant Pathology Laboratory, Central Rice Research Institute,Cuttack 753006, India Email: rsridhar@crri.ori.nic.in

Although 19 bacterial blight resistancegenes have been identified so far(Kinoshita 1991), precise information ontheir compatibility or incompatibility withlocal pathogen populations is essential fordesigning breeding programs for resistantvarieties. We evaluated the effectiveness ofknown bacterial blight resistance genessingly and in combination under field con-ditions against local populations of thepathogen in a trap nursery under irrigatedconditions during the 1998 wet season.

Twenty near-isogenic lines in theIR24 background, 11 of them carryingsingle known resistance genes and the re-maining nine possessing various combina-tions of these genes, along with an Oryzaminuta derivative line (WHD-IS-78-1-5)and Malagkit Sungsong were tested (seetable). IR24 and Karuna (Co 33) were in-cluded as susceptible checks. For eachentry, 44 hills were planted per row, with20-cm spacing between plants and rows.Two replications were maintained in acompletely randomized design. Each rep-lication consisting of four rows of the testentries was flanked on either side with asingle row of the local susceptible checkKaruna. Fertilizer was applied to supply 80kg N ha-1, half basally and half at thepretillering stage. No pesticide was ap-plied. The fields were kept clean by hand-weeding twice.

Plants were exposed to natural in-fection by bacterial blight. Bacterial blightstarted to appear at tillering and contin-ued to spread vertically until the crop head-ing stage. Both the intensity of vertical sus-ceptibility (denoted by multiples of S [seetable] and quantitative reactions to bacte-

rial blight (based on the 0–9 scale of theStandard evaluation system for rice, SES,IRRI 1996) were recorded at the milk stage.Levels 1–5 covering 1–25% of leaf bladeinfection are considered resistant, whilelevels 7–9 are considered susceptible.

7(t)] succumbed to the disease in all testlocations. RIL 45 and 249, presumably car-rying Pi 5(t), showed differential reactionsto pathogen populations at Jorhat andSuttur, while RIL 77 was susceptible at alltest sites, suggesting that this RIL may nothave the Pi 5(t) gene. LTH (Li-jiang-xin-tuan-hei-gu) near-isogenic lines that weresusceptible at Cuttack varied in their reac-

tions at other locations, particularly in theeastern (Jorhat) and southern (Suttur) re-gions.

Of the four gene combinationsevaluated, the one with Pi 1(t) and Pi 4(t)was susceptible to blast at Jagadalpur,Almora, and Jorhat. The combination withPi 1(t) and Pi 2(t) was resistant in all loca-tions except Suttur, while that with Pi 2(t)

and Pi 4(t) was effective in all six test loca-tions. Our results clearly showed the use-fulness of resistance genes in different lo-cations.

ReferenceMackill DJ, Bonman JM. 1992. Inheritance of blast

resistance in near-isogenic lines of rice.Phytopathology 82:746–749.

Reaction of near-isogenic lines carrying bacterial blight resistance genes singly and in com-bination, Cuttack, Orissa, India.

Bacterial blight reaction

Vertical 0–9 SESsusceptibilitya scaleb

Karuna (local susceptible check) ndc SSSS 9IR24 (susceptible check) Xa18 SSS 9WHD-IS-78-1-5 Xa23 R 5WHD-IS-78-1-5 Xa23 R 5(O. minuta derivative)Malagkit Sungsong Xa3 R 5IRBB1 Xa1 SSS 7IRBB3 Xa3 SSS 7IRBB4 Xa4 SSS 7IRBB5 xa5 R 5IRBB7 Xa7 SSS 7IRBB8 xa8 R 3IRBB10 Xa10 SSS 7IRBB11 Xa11 SSS 7IRBB13 xa13 R 5IRBB14 Xa14 SSS 7IRBB21 Xa21 R 1AY4 + 5-2 Xa4 + xa5 R 3NH8-15-1-5 Xa4 + xa13 R 3NH9-52-1-4 Xa4 + Xa21 R 1NH11-21-1-3 xa5 + xa13 R 1NH12-17-2-4 xa5 + Xa21 R 1NH15-51-1-3 xa13 + Xa21 R 1NH21-37-1-1 Xa4 + xa5 + xa13 R 3NH24-10-1-3 Xa4 + xa5 + Xa21 R 1NH56-1-44-4 Xa4 + xa5 + xa13 + Xa21 R 1

aDenotes intensity of vertical susceptibility of plants (susceptible reaction of 7 restricted to 1/4 (S), 1/2 (SS), 3/4 (SSS),almost all leaves infected (SSSS); reactions of less than 7 are considered as resistant (R). b0–9 scale (SES) for field test,lesion area: 1, 1–5%; 3, 6–12%; 5, 13–25%; 7, 26–50%; 9, 51–100% (reactions of 1–5 are considered as resistant, while 7 andabove are susceptible). cnd = not detected.

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Variety/line Resistancegene

25IRRN 24.2

Bacterial blight incidence was uni-form in the fields. The susceptible checksshowed a disease rating of 9 in the SES.The vertical spread of the disease withinhills, however, was maximum in Karunawhen compared with IR24. Interestingly,Malagkit Sungsong and the O. minuta de-rivative exhibited a susceptible rating of 5,despite their being resistant in earlieryears. IRBB5 and IRBB13, carrying xa5 andxa13, respectively, also showed a similardegree of susceptibility. Lines possessingXa1, Xa3, Xa4, Xa7, Xa10, Xa11, and Xa14individually were all distinctly susceptibleto the disease. On the other hand, genesxa8 and Xa21 were singly effective in re-sisting bacterial blight, exhibiting a scoreof 1. All the gene combinations (see table)were resistant, presumably because of in-

teraction or quantitative complementationbetween resistance genes (Yoshimura etal 1995, Huang et al 1997). This studypoints out that, even though a particulargene is ineffective singly against bacterialblight (for example, Xa4, XA5, and xa13),its combination with another resistancegene (Xa4 + xa5, Xa4 + xa13, xa5 + xa13,Xa4 + xa5 + xa13) conferred resistance.The combination xa5 and xa13 was rela-tively superior to the other combinations(Huang et al 1997). All combinations car-rying Xa21 were also resistant. In this case,resistance may be attributed to the pres-ence of Xa21, which individually conferredresistance. Deploying multiple genes to-gether may lessen the possibility of rapidpathogen adaptation to cultivars carryingsingle resistance genes.

ReferencesHuang N, Angeles ER, Domingo J, Magpantay G,

Singh S, Zhang G, Kumaravadivel N, BennettJ, Khush GS. 1997. Pyramiding of bacterialblight resistance genes in rice: marker-assisted selection using RFLP and PCR.Theor. Appl. Genet. 95:313–320.

Kinoshita T. 1991. Report of Committee on genesymbolization, nomenclature and linkagegroups. Rice Genet. Newsl. 8:2–25.

International Rice Research Institute (IRRI). 1996.Standard evaluation system for rice. INGER,Genetic Resources Center. Manila(Philippines): IRRI.

Yoshimura SY, Yoshimura A, Iwata N, McCouchSR, Abenes LL, Baraoidan MR, Mew TW,Nelson RJ. 1995. Tagging and combiningbacterial blight resistance genes in rice usingRAPD and RFLP markers. Mol. Breed.1:375–387.

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Thrips infestation in relation to panicle stage in rice

Thrips incidence at the panicle stage in ricewas investigated because such informationwould be useful in (a) timing plant pro-tection measures and (b) getting correctsamples to estimate the thrips populationon the crop. The infestation of paniclethrips, Haplothrips ganglbaueri Schmutz,was studied in variety Pusa 169 grown un-

S. Chander, Division of Entomology, Indian Agricultural Research Institute, New Delhi 110012, India

der transplanted and irrigated conditionsduring kharif (monsoon) in 1997 and 1998(see table).

One-month-old seedlings weretransplanted in the main field in the sec-ond week of July each year. Thrips inci-dence was observed in panicles of differ-ent ages—(a) emerging panicles with their

basal portion still in the leaf sheath, (b)freshly emerged panicles, and (c) paniclesin the milky stage. In each category, 25panicles were observed for thrips popula-tion counts. The panicle was enclosed in apolythene bag and shaken gently to dis-lodge the thrips. Sampling was done oncein 1997 and three times in 1998 at 5-d in-

Incidence of Haplothrips ganglbaueri Schmutz on panicles of different ages in variety Pusa 169, New Delhi, India, 1997-98.

Season

1997 kharif 1998 kharifPanicle stage

1st sampling 1st sampling 2nd sampling 3rd sampling(70 DAT)a (65 DAT) (70 DAT) (75 DAT)

Population Population Population Population Population Population Population Populationpanicle-1 range panicle-1 range panicle-1 range panicle-1 range

Emerging panicle 2.10 0–5 0.40 0–2 3.15 0–10 1.95 0–8(1.22)b (0.27) (1.56) (1.11)

Freshly emerged 5.00 2–9 1.20 0–3 6.00 0–12 4.2 0–10 panicle (2.03) (0.98) (2.28) (1.94)Panicle in milky 0.40 0–2 0.25 0–2 0.45 0–2 0.05 0–1 stage (0.36) (0.22) (0.39) (0.05) SE± (0.24) (0.16) (0.23) (0.20) CD (5%) (0.48) (0.33) (0.46) (0.42) CD (1%) (0.65) (0.44) (0.62) (0.56)

aDAT = days after transplanting. bNumbers in parentheses are square root-transformed values of original thrips counts.

26 August 1999

Further testing of a yield loss simulation model for ricein different production situationsI. FOCUS ON RICE-WHEAT SYSTEM ENVIRONMENTS

A synthetic yield loss simulation model forrice pests was developed recently(Willocquet et al 1998) as a tool for settingresearch priorities and improving pestmanagement. This model is productionsituation (PS)-specific and addresses sev-eral rice pests. It has been tested in sev-eral Asian PSs (e.g., in the Philippines andVietnam), where it simulates attainable ricecrop growth adequately as well as lossescaused by various pests (diseases, insects,and weeds) (Willocquet et al 1998).

This work aimed at further testingof the model under a wider range of PS.The PSs and injuries addressed here weredefined based on characterization of riceinjury profiles and PSs across tropical Asia(Savary et al 1998). The first PS, PS2, is areference used in all experiments. Twoother PSs (PS8 and PS9) represent thoseprevailing in Uttar Pradesh (Savary et al1997).

An experiment was done at NDUATin the 1998 kharif season. In each PS, in-jury-free plots and rice plots injured bypests (alone or in combination) were es-tablished. Crop growth, environmental fac-tors, and pest injuries were monitoredthroughout the growing season. In a given

PS, data from injury-free plots were usedto calibrate parameters to simulate attain-able yield. Data from injured plots wereused to test simulations of yield losses.Three PSs were addressed: PS2 (IR72transplanted with young seedlings, 110 kgN ha-1, irrigated rice), PS8 (Sita transplantedwith old seedlings, 100 kg N ha-1, rainfedcrop), and PS9 (direct-seeded NDR80, 80kg N ha-1, rainfed crop). Five injury treat-ments common in South Asia (Savary et al1997) were established in each PS: sheathblight (SHB), deadhearts and whiteheads(DWH), brown spot (BS), the combinationof the four injuries (COMBI), and thenoninjured (CTRL) treatment. The injurytreatments were randomized with threereplications in each PS. Individual plotswere 2.8 × 2.8 m and included four zonesfrom the outer to the inner part of the plot:a border row, 20 cm wide; a sampling zone,20 cm wide, to monitor crop growth (de-structive samplings) and injuries; a secondborder row, 20 cm wide; and the centralharvest area.

The simulation of attainable growth(leaf, stem, root, and panicle dry weight;and tiller population) and of final yield wasclose to observed values (see figure) in the

three PSs considered. In all PSs, the samepatterns were observed: an increase in leafweight until flowering, then a decline (leafsenescence); an increase in root weightuntil flowering, remaining stable after-wards; an increase in stem weight untilflowering, then a decline (translocation ofstored starch from stems to panicles); andan increase in panicle weight from flower-ing to maturity. Tillering occurred until 30to 40 d after crop establishment (DACE).Tiller number declined afterwards becauseof tiller death and remained constant afterflowering. The dry weights of leaves andpanicles were very sensitive to varying PSs:the maximum values were highest in PS2and lowest in PS8 and PS9 (shortage ofwater and/or N). Final yield varied between151 g m-2 (PS8) and 666 g m-2 (PS2). Tillernumber was higher in PS2 than in PS8 andPS9, mainly because of crop establishmentmethod (young seedlings in PS2, olderones in PS8 and PS9).

The table shows the simulated andobserved grain yields for the 15 (PS × in-jury) combinations addressed in the ex-periment. An acceptance interval of ± 10%of the observed grain yield was defined toassess the simulated yield outputs. The

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tervals. In the second year, sampling wasdone in different parts of the field. Thethrips counts were transformed by squareroot transformation and single-factor analy-sis of variance (ANOVA) was undertaken,considering panicles as replicates. SeparateANOVA were done for each sampling dateduring 1998.

The thrips population differed sig-nificantly among the three categories ofpanicles (see table). Freshly emerged

panicles harbored the most thrips, fol-lowed by emerging panicles and paniclesin the milky stage. The panicle stage thusinfluenced thrips incidence. The study re-vealed that panicle thrips in rice first at-tacked the emerging panicles, continuinguntil the milky stage. Therefore, to preventcrop loss from thrips, control measuresshould be applied at the panicle initiationstage. Control measures at the milky stagewould be useless because, at this stage, the

thrips population has almost disappearedand the crop has already been damaged.

The study also showed that freshlyemerged panicles had the highest numberof thrips among the three stages of paniclegrowth. Therefore, to correctly estimatethe thrips population in rice, freshlyemerged panicles should be sampled. Sam-pling on emerging panicles or panicles inthe milky stage would underestimate thethrips population.

L.Willocquet, IRRI-ORSTOM Project on Rice Pest Characterization, IRRI; L. Fernandez, Entomology and Plant PathologyDivision, IRRI; H.M. Singh, R.K. Srivastava, S.M.A. Rizvi, Narendra Deva University of Agriculture and Technology(NDUAT), Narendra Nagar, PO Kumarganj, Faizabad 224229, Uttar Pradesh, India; and S. Savary, IRRI-ORSTOM Projecton Rice Pest Characterization, IRRI Email: laetitia.willocquet@mpl.ird.fr

27IRRN 24.2

model simulated yields within this accep-tance interval in the SHB treatment and inthe COMBI treatment (except in PS9). In-jury because of whiteheads and deadheartswas underestimated by the model. Threeareas for further improvement ofdeadheart injury modeling are (a) alter-ation of the dynamics of tillers: because ofcompensation mechanisms, more tillersare produced than in an uninjured crop;(b) most of these tillers that are producedat a late development stage remain veg-

could be recalibrated using data from thisexperiment and tested in another indepen-dent experiment.

Although further improvements inthis simulation model are necessary, it isflexible enough to account for diverse PSsand has the potential to reflect reasonablywell the damage mechanisms due to vari-ous rice pests.

ReferencesSavary S, Srivastava RK, Singh HM, Elazegui FA.

1997. A characterization of rice pests andquantification of yield losses in the rice-wheat system of India. Crop Prot. 16:387–398.

Savary S, Elazegui FA, Willocquet L, Teng PS. 1998.Changing production situations in rice andimplications for plant pathology. Paperpresented at the International Conferenceof Plant Pathology, 9–16 Aug 1998,Edinburgh.

Willocquet L, Savary S, Fernandez L, Elazegui FA,Teng PS. 1998. Simulation of yield lossescaused by rice diseases, insects, and weedsin tropical Asia. IRRI Discuss. Pap. Ser. 34.

Simulated and observed grain yields (g m-2), NDUAT, 1998.

PS2b PS8b PS9b

Observed Simulatedc Observed Simulated Observed Simulated

CTRL 583 586 83 83 113 113DWH 400 531c 26 41c 74 93c

SHB 478 518 59 55 83 91BS 544 469c 66 51c 81 68c

COMBI 397 411 27 25 70 55c

aCTRL = control, DWH = deadhearts and whiteheads, SHB = sheath blight, BS = brown spot, and COMBI = combinationof the four injuries. bPS2 = reference production situation, PS8 and PS9 = production situations that prevail in UttarPradesh. cSimulated grain yield is outside the acceptance interval (± 10% of observed grain yield).

Treatmenta

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etative and compete with the reproductiveones for assimilate partitioning, leading toa decrease in grain filling; (c) in “poor” PSs,such as PS8 and PS9, compensation mecha-nisms in terms of dry weight of organs arelimited due to the unfavorable environ-ment for rice growth. Yield losses from BSwere slightly overestimated (see table).The damage mechanism function for BSwas represented as a reduction in photo-synthesis in the area surrounding the le-sion. This area might be overestimated and

Attainable rice growth in three production systems (PS): observed (dots) ± SEM and simulated (plain line) dry weight (g m-2) of roots (ROOTW),dry weight of leaves (LEAFW), dry weight of stems (STEMW), dry weight of panicles (PANW), and number (m-2) of tillers (TOTIL). Observeddata were collected from control plots in the experiment done at NDUAT in 1998 (A:PS2, B:PS8, C:PS9) (see text for details).

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28 August 1999

Further testing of a yield loss simulation model for ricein different production situationsII. FOCUS ON WATER-STRESSED ENVIRONMENTS

A recently developed yield loss simulationmodel for rice pests was tested under thedifferent production situations (PSs) ofSouth Asia and Southeast (Willocquet etal 1998, 1999). The work reported hereaimed at testing this model under a refer-ence PS (PS2) used in experiments doneat different sites, and under a second PS(PS4) not yet addressed in previous work,where the crop experiences high waterstress. Deadhearts and whiteheads causedby stem borers and weeds were consideredas common rice pests that can cause yieldlosses in tropical Asia (Savary et al 1998).

An experiment was done at IRRIduring the 1998 dry season. The approachused to calibrate and test the model, theexperimental layout, and the field proce-dures applied were the same as those de-scribed in Willocquet et al (1999 p 25, thisvolume). Two PSs were addressed: PS2

(IR72 transplanted with young seedlings,110 kg N ha-1, irrigated rice) and PS4 (IR64transplanted with young seedlings, 110 kgN ha-1, rainfed crop). Five injury treatmentswere addressed in each PS: weed infesta-tion (WD), deadhearts (DH), whiteheads(WH), the combination of the three inju-ries (COMBI), and the noninjured treat-ment (CTRL).

The simulation of attainable organgrowth, tiller dynamics, and final yield wasclose to the actual observation (see figure)in the two PSs considered. The dry weightsof leaves and panicles were very sensitiveto varying PSs: the maximum values werehighest in PS2 and lowest in PS4 (shortageof water and/or N). Final panicle yieldwas150 g m-2 in PS4 and 800 g m-2 in PS2.

The table gives simulated and ob-served grain yields for the 10 (PS × injury)combinations addressed in the experi-

ment. An acceptance interval of ± 10% inthe observed yield was defined to assesssimulated yield outputs. The model simu-lated yields within this acceptance inter-val in all but two cases (PS2, WEED andCOMBI treatments). The model overesti-mated yield losses caused by weeds in PS2.

The model simulated attainablegrowth and yield adequately under thesetwo contrasting PSs. This modeling ap-proach thus enables us to simulate dam-age mechanisms in contrasting PSs. In gen-eral, the yield-reducing effects of the dif-ferent pests addressed are well accountedfor by the model (see table).

ReferencesSavary S, Elazegui FA, Willocquet L, Teng PS. 1998.

Changing production situations in rice andimplications for plant pathology. Paperpresented at the International Conferenceof Plant Pathology, 9–16 Aug 1998, Edinburgh.

Attainable rice growth in two PSs: observed (dots) ±SEM and simulated (plain line) dry weight (g m-2) of roots (ROOTW), dry weight of leaves(LEAFW), dry weight of stems (STEMW), dry weight of panicles (PANW), and number (m-2) of tillers (TOTIL). Observed data were collectedfrom control plots in the experiment done at IRRI in 1998 (A:PS2, B:PS4) (see text for details).

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LEAFWleaf OROOTWroot O

1200

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00 20 40 60 80 100 120

TOTILtotil O

400

300

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00 20 40 60 80 100 120

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Weight (g m-2) Weight (g m-2) Tillers (no m-2)

L. Willocquet, IRRI-ORSTOM Project on Rice Pest Characterization, IRRI; L. Fernandez, Entomology and Plant PathologyDivision, IRRI; and S. Savary, IRRI-ORSTOM Project on Rice Pest Characterization, IRRI

29IRRN 24.2

Simulated and observed grain yields (g m-2), IRRI, 1998.

PS2b PS4Treatmenta

Observed Simulated Observed Simulated

CTRL 704 696 94 91DH 686 676 90 93WH 637 621 100 90WEED 571 470c 61 59COMBI 525 413c 52 57

aCTRL = control, DH = deadhearts, WH = whiteheads, WEED = weed infestation, COMBI = combination of the threeinjuries. bPS2 = reference production situation, PS4 = production situation with high water stress. cSimulated grain yieldoutside the acceptance interval (± 10% of observed grain yield).

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Willocquet L, Savary S, Fernandez L, Elazegui F,Teng PS. 1998. Simulation of yield lossescaused by rice diseases, insects, and weedsin tropical Asia. IRRI Discuss. Pap. Ser. 34.

Willocquet L, Fernandez L, Singh HM, SrivastavaRK, Rizvi SMA, Savary S. 1999. Furthertesting of a yield loss simulation model forrice in different production situations. 1.Focus on rice-wheat system environments.Int. Rice Res. Notes 24(2):25-27.

4th International Rice GeneticsSymposium set for October2000

The Fourth International Rice Genetics Symposium (IRGS) will beheld at IRRI on 22-27 October 2000. The first IRGS was held in 1985.It led to the birth of the Rice Genetics Cooperative (RGC), whichaimed to promote international cooperation in rice genetics. Thesame year, the Rockefeller Foundation organized the InternationalProgram on Rice Biotechnology, which has played a major role inadvancing the frontiers of rice science, international collaboration,and human resource development in rice. During the second IRGS(held in 1990), a unified numbering system for rice chromosomesand linkage groups was established. More than 500 scientists from31 countries participated in the third IRGS (held in 1995). Correctorientation of classical and molecular linkage maps was one of thesymposium highlights.

Major advances in the genetics and molecular biology of ricehave become apparent during the past 15 years. A high-density mo-lecular genetic map of more than 2,300 DNA markers has been de-veloped and several genes of economic importance as well as quan-titative trait loci (QTL) have been tagged with molecular markers.Synteny relationships between genomes of rice and several othercereals have been established. Molecular marker-aided selection isbeing used to move genes from one varietal background to anotherand to pyramid genes. Scientists have developed BAC and YAC li-braries and are using them in the physical mapping of the rice ge-nome. A map-based cloning strategy has been used to isolate agro-nomically important genes. Regeneration from protoplasts of manyindica and japonica varieties has allowed researchers to introducenovel genes into elite germplasm through transformation. More re-cently, biolistic and Agrobacterium-mediated transformation proce-dures have become available. International programs on rice genomesequencing and functional genomics have been established. Thesedevelopments have opened new frontiers in rice molecular biology,particularly for understanding the genetic architecture of traits andtheir manipulation, modifying gene expression, genome sequenc-ing, functional genomics, and gene discovery. Researchers are usingthese breakthroughs to develop rice varieties with higher yield po-tential and yield stability for feeding 50% more rice consumers by2025.

The fourth IRGS will feature plenary sessions, oral presenta-tions, and poster sessions. Participants will discuss the latest develop-ments in rice systematics and evolution, cytogenetics, classical genet-ics, tissue and cell culture, molecular markers, genetic engineering,and genomics. The proceedings will be published.

Scientists interested in attending the symposium should senda registration form indicating their name, academic title, address(phone, fax, email), and tentative presentation title to Dr. G.S. Khushat IRRI, MCPO Box 3127, Makati City 1271, Philippines (fax: 0063-2-761-2404; email: g.khush@cgiar.org or to Dr. T. Kinoshita, Faculty ofAgriculture, Hokkaido University, Kita 9, Nishi 9, Sapporo 060, Japan(fax: 0081-11-706-4934; email: Takamure@abs.agr.hokudai.ac.jp).

Important dates31 October 1999 - Deadline for submission of registration

forms1 April 2000 - Deadline for abstracts30 June 2000 - Deadline for full papers

The members of the organizing committee are J. Bennett, D.S. Brar,S.K. Datta, B. Hardy, M.T. Jackson, G.S. Khush, H. Leung, and Z. Li.

For more information, contactD.S. BrarChair, Organizing Committee4th International Rice Genetics SymposiumInternational Rice Research InstituteMCPO Box 3127, Makati City 1271, PhilippinesTel.: (63-2) 845-0563 ext. 709Fax: (63-2) 891-1292, 761-2406, 845-0606E-mail: d.brar@cgiar.orgIRRI Web site: http://www.cgiar.org/irri

30 August 1999

Soil, nutrient, and water management

Nitrogen responsiveness of lowland rice varietiesunder irrigated conditions in West AfricaK.L. Sahrawat, S. Diatta, and B.N. Singh, West Africa Rice Development Association (WARDA),01 BP 2551 Bouaké 01, Côte d’Ivoire

We studied the response to N inputs ofsome of the most popular lowland ricevarieties bred in Africa and compared itwith that of local check Bouake 189. Fieldexperiments were conducted at the MbeValley in central Cote d’Ivoire during the1994 wet (August-December) (WS) and1995 dry (February-June) (DS) seasonsunder irrigated conditions.

Soil at the site was an Alfisol (pH 5.9,organic C 18.5 g kg-1 soil, 0.825 g total Nkg-1 soil, and 6.8 mg Bray 1 P kg-1 soil) witha sandy clay-loam texture. Test varietieswere ITA212, ITA306, ITA402, and Bouaké.Four N application rates (0, 30, 60, and 90kg N ha-1 as urea) were used in three splitsat planting, tillering, and flowering in a ran-domized complete block design with fourreplications.

Three-week-old rice seedlings, atthree seedlings hill-1, were transplanted at15 × 15-cm spacing in 15-m2 plots. All plotsreceived uniform basal applications of P(50 kg P ha-1 as triple superphosphate) andK (80 kg K ha-1 as KCl). Yield data werecorrected to 14% moisture level.

Results showed that grain yieldswere higher in the DS than in the WS by1.0-1.5 t ha-1 (see table). The highest yieldswere obtained by ITA212 and ITA306 forboth seasons. Yield differences were dueto the greater number of panicles m-2 inthe DS than in the WS (see table). Theharvest index of the varieties varied from56% to 59% in the WS and from 53% to56% in the DS, and was generally not af-fected (P<0.05) by N application (data notshown).

Agronomic N-use efficiency (NUE)was generally high, varying between 20 and57 kg grain kg-1 N in the DS and between25 and 50 in the WS. Nitrogen level signifi-cantly affected grain yield, straw yield,height, tiller number, and panicle number.

Yield leveled off at 90 kg N ha-1. The re-sults of regression analyses between N leveland each of the response variables are sum-marized below:

Regression analyses between N level and yield and yield components1994 wet seasonGrain yield = 0.2061* x2 + 40.133** x + 4,206 R2 = 0.5218**Straw = 12.349** x + 4,059.2 r = 0.4427**Panicle no. = 0.5044**x + 18.16 r = 0.4756**Tiller no. = 0.5206** x + 210.78 r = 0.4809**Height = 0.0758** x + 91.212 r = 0.4353**1995 dry seasonGrain yield = -0.2403**x2 + 40.894**x + 3,360.3 R2 = 0.5921**Straw = -0.1653*x2 + 29.251**x + 2,556.7 R2 = 0.4593**Panicle no. = 0.34**x + 142.23 r = 0.5141**Tiller no. = 0.1975*x + 149.14 r = 0.2771**Height = -0.0017**x2 + 93.166 R2 = 0.1544**

compared with local improved checkBouake 189. It is not known whether thehigher yields may have been due to betteruse of solar radiation rather than to betterresponse to N fertilizer. ITA402 and ITA306had more panicles m-2 than Bouake189 inboth seasons (see table).

Only ITA212 and ITA306 signifi-cantly (P<0.05) outyielded Bouake 189 inthe DS, but all ITA varieties outyieldedBouake 189 in the WS. The higher yieldpotential of the ITA varieties was not ex-pressed under conditions of lower solarradiation. The high yield stability of ITA306was confirmed by its consistently superioryields in the Sahel during the WS on both

farmers’ and researchers’ plots, resultingin its release in Senegal in 1994.

We conclude that ITA212, ITA306,and ITA402 have superior yield potential

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Mean yield and yield components of different varieties, 1994 wet season and 1995 dry sea-son.

Variety Grain yield Straw yield Tillers Panicles Height (kg ha-1) (kg ha-1) (no. m-2) (no. m-2) (cm)

1994 wet seasonBouaké 189 5,410 4,000 147.6 147.9 107.88ITA402 5,590 4,000 162.1 160.5 91.12ITA306 6,010 4,670 168.8 166.4 94.94ITA212 5,940 4,100 153.6 155.4 100.12 SE (N = 16) 120.6 124.7 5.6 3.9 1.0 5% LSD (45 df) 343.6 355.1 15.9 11.2 3.01995 dry seasonBouaké 189 5,980 5,380 229.2 194.7 96.26ITA402 6,930 5,360 246.8 216.6 90.92ITA306 7,470 6,200 247.8 233.8 93.93ITA212 7,010 6,150 212.9 198.4 97.39 SE (N = 16) 373.0 156.0 6.9 5.8 1.2 5% LSD (45 df) 1301.0 444.4 19.8 16.4 3.5

SE = standard error, df = degrees of freedom.

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31IRRN 24.2

Relative efficiency of different N fertilizers applied to riceat medium elevationD. Jena, Dryland Agriculture Research Project Orissa University of Agriculture and Technology (OUAT), Phulbani 762001,Orissa, India

A field experiment was laid out during1994-95 rabi and 1995 kharif in a medium-elevation land site of the Central ResearchStation, OUAT, Bhubaneswar, Orissa, tocompare the efficiency of ureasupergranules (USG) with that of othernitrogenous fertilizers. The experimentalsite had sandy loam soil (member of mixedhyperthermic family of Haplaquepts) witha bulk density of 1.6 g cm-3. The steadystate infiltration rate was 0.67 cm h-1. SoilpH is neutral (6.8). The soil has low or-ganic C (0.31%) and alkaline KMnO

4-N (240

kg ha-1) but high Olsen P (12 kg ha-1) andNH

4OAc extractable K (200 kg ha-1). Soil

CEC is 5.00 C mol (P+) kg-1.The experiment was laid out in a

randomized block design with five repli-cations. Plot size was 4 × 5 m. Each plotwas enclosed with galvanized iron sheetup to a depth of 30 cm to stop sidewardseepage. The treatments were T

1 = no N

(control); T2 = 76 kg N ha-1 as prilled urea

(PU); T3 = 76 kg N ha-1 as NH

4Cl; T

4 = 76

kg N ha-1 as (NH4)

2SO

4; T

5 = 76 kg N ha-1 as

CAN (calcium ammonium nitrate); T6 = 76

kg N ha-1 as USG.Thirty-day-old rice seedlings (cv.

Lalat, 120 d) were transplanted. Single su-perphosphate at 22 kg P ha-1 and muriateof potash at 41.5 kg K ha-1 were appliedbasally during both seasons. PU, NH

4Cl,

(NH4)

2SO

4, and CAN were applied at a ra-

tio of 1:2:1 at transplanting, tillering, andpanicle initiation. A full dose of USG (at 76kg N ha-1) was placed at a 5-cm depth inbetween four hills of alternate rows at 7 dafter transplanting (DAT). All other inter-cultural and plant protection measureswere followed when necessary.

Grain yield was recorded at 14%moisture content. Straw weight was re-corded after sun-drying for 6 d. The tableshows grain yield, straw yield, and N-useefficiency (NUE) data for 1994-95 rabi and1995 kharif. Grain yield during 1994-95 rabiranged from 3.3 to 6.1 t ha-1. The highest

yield was noted in the USG treatment,which is statistically superior to the PUtreatment but on a par with NH

4Cl (5.7 t

ha-1), (NH4)

2SO

4 (5.7 t ha-1), and CAN (5.8 t

ha-1). The lowest yield of 4.7 t ha-1 was re-corded in the standard PU treatment foran equal dose of N. Mean straw yieldranged from 4.5 to 9.1 t ha-1. The higheststraw yield was recorded in the USG treat-ment, which is statistically superior to allother treatments. Harvest index values var-ied from 0.40 to 0.49. The lowest harvestindex (USG treatment) indicated that a fulldose of N (76 kg ha-1) applied at 7 DATinduced more biomass production at theearly stages and could have exhausted thefertilizer N before grain filling, leading tomore sterile grains (22%) compared withthe other treatments.

Mean grain yield recorded during1995 kharif ranged from 3.0 to 4.4 t ha-1

(see table). USG had the highest yield,which is statistically superior to PU andNH

4Cl but on a par with (NH

4)

2SO

4 and

CAN. Straw yield during kharif ranged from2.2 to 4.0 t ha-1. The highest straw yield of4 t ha-1 was recorded in the NH

4Cl and

(NH4)

2SO

4 treatments. Harvest index val-

ues and percent sterile grain in the USGtreatment were higher, probably becauseof the application of an entire amount ofN at 7 DAT that led to higher early biomassproduction with more primary as well assecondary tillers. In all treatments, yieldsrecorded during the rabi season werehigher than those during kharif becauseof better management of irrigation waterand fertilizer. About 80% of rainfall (1,200mm) received during kharif induced pooryield, and NUE was reduced, probably bythe higher percolation rates. The agro-nomic efficiency of the different treatmentsranged from 18.42 to 36.96 for rabi andfrom 9.08 to 18.02 for kharif. The USGtreatment had the highest agronomic effi-ciency and relative efficiency. Based on thebenefit-cost ratio, relative efficiency, andNUE, USG is a better source of N fertilizerfor the rabi season. Although its benefit-cost ratio was much lower than that of PUduring the kharif season, USG can also berecommended because of the higher NUEand higher yield associated with it.

Effect of different forms of N on rice yield, 1994-95 rabi and 1995 kharif, Orissa, India.

Grain Straw Agronomic Relative Harvest Sterility Benefit-Treatment yield yield efficiency efficiency index (%) costb

(t ha-1) (t ha-1) (NUE)a (%)

1994-95 rabiT1: Control 3.3 4.5 – – 0.42 12.3 –T2: PU 4.7 6.3 18.42 100 0.43 17.1 8.60T3: NH4Cl 5.7 6.3 30.84 167 0.47 11.2 8.15T4: (NH4)2SO4 5.7 7.1 31.36 170 0.45 12.0 6.83T5: CAN 5.8 6.1 32.62 177 0.49 12.8 4.48T6: USG 6.1 9.1 36.96 200 0.40 22.0 9.31 CD (0.05) 1.05 1.42 – – – – –1995 kharifT1: Control 3.0 2.2 – – 0.58 10.2 –T2: PU 3.9 3.9 12.23 100 0.50 16.9 6.04T3: NH4Cl 3.6 4.0 9.08 74 0.48 10.8 2.89T4: (NH4)2SO4 4.0 4.0 13.82 113 0.50 11.5 3.32T5: CAN 4.1 3.8 14.60 119 0.52 12.0 2.18T6: USG 4.4 3.6 18.02 151 0.55 20.5 4.35 CD (0.05) 0.46 0.48 – – – – –

aNUE = N-use efficiency, PU = prilled urea, CAN = calcium ammonium nitrate, USG = urea supergranule. bGrain price:US$117 t-1, straw: $14 t-1, and USG: 0.153 kg-1 (Rupee 36=US$1).

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32 August 1999

Alleviating zinc deficiency in transplanted flooded ricegrown in alkaline soils of PakistanA. Rashid, Land Resources Research Institute, National Agricultural Research Center, Islamabad 45500; M.A. Kausar,F. Hussain, and M. Tahir, Nuclear Institute for Agriculture and Biology, Faisalabad, PakistanEmail: rashid@sfs-narc.sdnpk.undp.org

Zinc (Zn) deficiency, a widespread micro-nutrient disorder constraining rice produc-tion worldwide (Shorrocks 1992), is effec-tively controlled by field application of zincsulfate (ZnSO

4) (Takkar and Walker 1993).

A more convenient and economicalmethod of alleviating the deficiency, how-ever, is desired. In greenhouse and fieldexperiments, we studied the comparativeeffectiveness of various management prac-tices in alleviating Zn deficiency in trans-planted flooded rice grown in the alkalinesoils of Punjab Province, Pakistan.

The greenhouse study used surfacesoils (0–15 cm) of Miranpur (AquicUstochrepts) and Eminabad series (TypicHaplorthids) with pH 7.8–8.0, EC 1.0–2.1dS m-1, CaCO

3 equivalent 1.1–2.6%, organic

matter 1.4–1.7%, and DTPA Zn 0.5–1.0 mgkg-1. Pots containing 4.5–kg soil portionswere arranged in a randomized completeblock design (RCBD) with three replica-tions (see table for treatments). Basal fer-tilization included 75 mg N soil-1, 16.4 mgP soil-1, and 23 mg K kg soil-1. Dry matteryield, Zn concentration, and total Zn up-take were recorded after harvest (cv. IR6)of whole shoots at 50 d after transplanting(DAT).

All the management practices usedincreased rice biomass over that of thecontrol (1.33 g dry matter plant-1, P<0.05),ranging from 25% (for foliar spray of 1%ZnSO

4 solution) to 79% (for Zn-enriched

seedlings obtained by applying 5 mg Znkg-1 silica sand from a nursery bed) (seetable). Various treatments, except for theZn-enriched nursery, also enhanced the Znconcentration of whole shoots at 50 DATfrom 16.2 mg kg-1 (control plants) to 34.3mg kg-1 (foliar Zn spray). Weir andCresswell (1994) have shown that mostpractices that increase plant tissue Znconcentration beyond the critical range of15–18 mg Zn kg-1 in whole shoots of IRRI

rice cultivars at the preflowering growthstage also increase plant growth. The sub-stantial increase in Zn uptake of the treat-ments also showed that improved Zn nu-trition enhanced yield (see table).

Subsequently, five field experimentswere carried out using IR6 at Mangtanwala,Nankana District (Miranpur soil series[Aquic Ustochrepts]), Muridke,Sheikhupura District (Satghara series[Typic Haplorthids]), and Gujranwala(Gujranwala series [Udic Haplustalfs]). Thesoils were alkaline (pH, 7.8–8.4), calcare-ous (CaCO

3 equivalent, 1.0–4.1%), and

nonsaline (EC, 1.0–3.9 dS m-1), with 1.4–2.1%organic matter, 5.2–22.2 mg Olsen P kg-1, and0.5–0.9 mg DTPA Zn kg-1. Experimentswere laid out in an RCBD with four repli-cations. Basal fertilization consisted of 100kg N ha-1 (urea) and 26.2 kg P ha-1 (singlesuperphosphate). The mean yield increaseover that of the control (3.0 t ha-1) rangedfrom 23% (for foliar ZnSO

4 spray) to 41%

(nursery root dipping in 1% ZnSO4 solu-

tion for 5 min) (P<0.05; see figure). Theyield increase in other treatments was

greater than the increase in the treatmentusing a conventional field broadcast ofZnSO

4 (27% over that of the control). The

use of Zn-enriched rice seedlings obtainedby applying 20 kg Zn ha-1 to the nurserybed resulted in more yield increase (mean31%) than with 10 kg Zn ha-1 field-broad-cast (see figure) in a variety of soils withvariable native Zn status. Thus, contrary toprevious findings (Takkar and Walker1993), the use of Zn-enriched seedlingsproved effective in correcting the defi-ciency even in severely Zn-deficient soils.In addition to seedling enrichment, high-Zn soil particles on the seedling roots mayhave contributed to Zn supply enhance-ment. Although nursery root dipping in 1%ZnSO

4 solution (41% increase) or in 1%

ZnO slurry for 1 min (31% increase) alsoproved very effective, these practices arenot adaptable at the farm level because oftheir high labor requirements. Nurseryroot dipping in ZnO slurry, despite beinginexpensive (uses ~ 0.8 kg Zn ha-1) andcomparable in effectiveness to ZnSO

4 field

application (Yoshida et al 1970), was not

Effect of Zn management practices on rice biomass production at 50 d after transplantingand on plant Zn content in a pot culture studya.

Dry Zn concentration in Zn uptakeTreatment matter whole shoots (µg plant-1)

yield (mg kg-1)(g plant-1)

Control 1.3 a 16.2 a 21.6 aFoliar spray of 1% ZnSO4 solution 1.7 a 34.3 c 56.9 fPeriodic drainage of floodwater 2.1 ab 17.5 a 36.1 bNursery roots dipped in 1% ZnO slurry 2.1 ab 18.5 a 38.3 bc5 mg Zn kg-1 as ZnSO4, mixed with whole soil volume 2.1 ab 23.5 b 49.4 dNursery roots dipped in 2.5% ZnSO4 solution 2.1 ab 17.6 a 37.1 b5 mg Zn kg-1 as ZnSO4, soil surface broadcast 2.2 ab 24.0 b 51.6 eZn-enriched seedlings, 5 mg Zn kg-1, nursery bed 2.4 c 15.6 a 37.1 b LSD (0.05) 0.6 3.4 1.9

aValues followed by different letters are significantly different at P<0.05.

33IRRN 24.2

adopted as a routine practice because ofits high labor requirement and erratic ef-fectiveness (Takkar and Walker 1993).Similarly, drainage of flood water (result-ing in a 20% yield increase; data not shown)

is hardly practicable at the desired growthstage because “flood-like situations” arenot uncommon in the Punjab rice-grow-ing areas due to heavy monsoon rains inJuly-August. Thus, considering effective-

ness, economics, and adaptability at thefarm level, the only viable alternative to theZnSO

4 application method is seedling en-

richment or application of ZnSO4 to nurs-

ery beds. This practice is also economicalfor managing Zn deficiency using a mat-type nursery in mechanical transplanters.

ReferencesShorrocks VM. 1992. Micronutrients—require-

ments, use and recent developments. In:Portch S, editor. Proceedings of theInternational Symposium on the Role ofSulfur, Magnesium, and Micronutrients inBalanced Plant Nutrition. Washington, DC:The Sulfur Institute. p 391–412.

Takkar PN, Walker CD. 1993. The distribution andcorrection of zinc deficiency. In: Robson AD,editor. Zinc in soils and plants. London:Kluwer Academic Publishers. p 151–165.

Weir RG, Cresswell GC. 1994. Plant nutrientdisorders. 4. Pastures and field crops.Inkata, Melbourne, Australia.

Yoshida S, McLean GW, Shafi M, Mueller KE. 1970.Effect of different methods of Zn applicationon growth and yield of rice in a calcareoussoil, West Pakistan. Soil Sci. Plant Nutr.16:147–149.

Biochemical studies on rice seedlings under salt stressM.P. Mandal, R.A. Singh, and J.K. Handoo, Department of Botany and Plant Physiology, Rajendra Agricultural University,Pusa 848125, Samastipur, Bihar, India

We estimated the amylase, peroxidase, andprotease enzyme activity in four rice geno-types that have different degrees of salttolerance. Pusa 2-21 and Saket 4 are salt-tolerant and Kamini and Sugandha are sus-ceptible varieties. The enzymes were stud-ied because salinity effects on seedlinggrowth have been attributed to variationin activities of key hydrolytic enzymes suchas L-amylase and protease (Dubey 1982,Kumar et al 1996). Similarly, peroxidaseactivity is related to the maintenance of cellmembrane integrity through its involve-ment in detoxifying H

2O

2 to water (Levitt

1980), thus modifying the effect of freeradicals under stress.

Seeds of four genotypes were ger-minated in control and salt solutions

(NaCl:CaCl2:Na

2SO

4 in the ratio of 7:2:1; EC

12.0; and 16.0 dS m-1) in sterilized germi-nating boxes lined with blotting papers andkept at 25 ± 2 °C in an incubator undercontrolled conditions with three replica-tions. The embryonic axis of 7-d-old seed-lings was observed to estimate enzymeactivity using a standard procedure.

Amylase and peroxidase activitiessignificantly decreased but protease activ-ity increased under salt stress in all geno-types (see table). A decrease in activity ofthe hydrolyzing enzyme L-amylase causedby a decrease in water uptake has beenreported by Dubey (1983). The decline inthe free energy of water caused by the pres-ence of salts in the medium limited amy-lase activity by reducing water uptake. In

contrast, protease activity increased undersalinization in this study, confirming thefindings of Reddy and Vora (1986) andSheoran and Garg (1978). Salt-tolerantgenotypes (Pusa 2-21 and Saket 4) showeda reduction of 18% and 20% at 12.0 dS m-1

and 33% and 36% at 16.0 dS m-1 for amy-lase, and 10% and 17% at 12.0 dS m-1 and15% and 16% at 16.0 dS m-1 for peroxidaseactivity, respectively. In comparison, thedecrease in activity of amylase (31% and32% at 12.0 dS m-1 and 46% and 48% at16.0 dS m-1) and peroxidase (15% and 15%at 12.0 dS m-1 and 24% and 24% at 16.0 dSm-1) in susceptible genotypes (Kamini andSugandha, respectively), was relativelymore. A decrease in the scavenging en-zyme—peroxidase—under stress with rela-

Effect of management practices on rice yield and leaf Zn concentration (mean of 5 fieldexperiments).

○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Control

Zn foliar spray

ZnSO4 broadcast

ZnO root dip

Zn-enriched nursery

ZnSO4 root dip

0 1 2 3 4 5

3025201510530

Leaf Zn concentration (mg kg–1)

Yield (t ha-1)

Yield

Leaf Zn concentration

34 August 1999

tively less inhibition in tolerant varietiesthan in susceptible genotypes would pre-vent degradation of cell membrane integ-rity against free radicals formed under saltstress. Protease activity, on the other hand,increased by 45%, and 111% in tolerantgenotypes, and by 90% and 202% in sus-ceptible varieties. The differences betweenthe tolerant and susceptible varietiesacross salinity stress levels were highly sig-nificant (see table).

Results indicated that the lower pro-tease activity and higher peroxidase activ-ity in the embryonic axis favor tolerancefor stress by reducing the catabolic break-down of proteins and membranes. Differ-ences in salt tolerance measured via theactivity of these three enzymes at the earlygrowth stage are useful in assessing vari-etal tolerance.

ReferencesDubey RS. 1982. Biochemical changes in

germinating rice seeds under saline stress.Biochem. Physiol. Pflanz. 177:523–535.

Dubey RS. 1983. Hydrolytic enzymes of rice seedsdiffering in salt tolerance. Plant Physiol.Biochem. 10(5):168–175.

Kumar SA, Muthukumarasamy M, Panneerselvam,R. 1996. Nitrogen metabolism in blackgramunder NaCl stress. J. Indian Bot. Soc. 75:69–71.

Chemical clearing of irrigation channels—a comparative evaluationK. Joseph, Center for Water Resources Development and Management, Kunnamangalam, Kozhikode 67357, Kerala, India

Irrigation channels below the sub-distributory level up to the command areaare usually earthen (unlined) and dry dur-ing the nonirrigation months, i.e., fromJune to November. The conducive environ-ment in the channels favors the growth ofmany weeds. To improve water flow, farm-ers clear the channels by scraping the soilwith a spade before the start of irrigation.This practice is labor-intensive, increasesthe channel cross-section through soil loss,

and accelerates sedimentation down-stream. The best option is to use concreteor polythene lining, but it is costly.

Under these circumstances, an ex-periment was undertaken in the fields ofthe Ichannur subdistributory of theKuttiadi Irrigation Project in Kerala to op-timize water flow by clearing the channelsof weeds using Paraquat, a nonselectiveherbicide. This experiment was done in1994-95, 1995-96, and 1996-97. A 3.5-km-

long channel was used for the experiment.Three sections of 250 m each were identi-fied for the different treatments. One sec-tion was lined with concrete, the othersection was cleared with Paraquat, and thethird section was cleared by spade scrap-ing (i.e., farmers’ practice). Paraquat wasapplied at a concentration of 0.15% 2 wkbefore water release. One week afterParaquat application, the dried plant partswere burned and the area smoothed. Ve-

Levitt J. 1980. Responses of plants to environ-mental stresses, II. Water, radiation, salt andother stresses. New York: Academic Press.p 489–553.

Reddy MP, Vora AB. 1986. Salinity inducedchanges in pigment composition and

chlorophyllase activity of wheat. J. PlantPhysiol. 29:331–334.

Sheoran IS, Garg OP. 1978. Effect of salinity on theactivities and early growth of mungbean.Physiol. Plant. 44:171–174.

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Influence of salinity on some enzyme variables in rice seedlings.

Amylase Peroxidase Proteaseactivity activity activity

Tolerant 114.3 162.7 25.9Susceptible 105.4 146.9 31.1 F 1,866.29** 23,987.41** 3,443.91**VarietyPusa 2-21 115.4 163.5 25.6Saket 4 113.2 161.8 26.2Kamini 105.6 147.3 31.1Sugandha 105.2 146.6 31.0 SE 0.278 0.059 0.010 CD 0.811** 0.172** 0.030**StressControl 140.8 173.4 16.412.0 dS m-1 105.0 151.2 27.916.0 dS m-1 83.6 139.8 41.2 SE 0.241 0.051 0.009 CD 0.703** 0.149** 0.026**Pusa 2-21 at 0.0 dS m-1 139.4 178.4 17.2Pusa 2-21 at 12.0 dS m-1 113.2 160.0 25.0Pusa 2-21 at 16.0 dS m-1 93.7 152.1 34.7Saket 4 at 0.0 dS m-1 138.8 177.7 17.1Saket 4 at 12.0 dS m-1 111.4 157.9 25.4Saket 4 at 16.0 dS m-1 89.4 150.0 36.1Kamini at 0.0 dS m-1 142.1 168.7 15.8Kamini at 12.0 dS m-1 98.2 144.2 30.0Kamini at 16.0 dS m-1 76.3 129.1 47.6Sugandha at 0.0 dS m-1 143.0 168.8 15.5Sugandha at 12.0 dS m-1 97.3 143.0 31.2Sugandha at 16.0 dS m-1 75.1 127.9 46.3 SE 0.481 0.102 0.018 CD 1.405** 0.298** 0.053**

**Significant at 1% level.

35IRRN 24.2

Average flow velocity through irrigation channel (m s-1), Kerala, India, 1994-97.

Treatment 1994-95 1995-96 1996-97 Av

Chemical clearing 0.24 0.28 0.31 0.28Concrete lining 0.31 0.21 0.34 0.29Farmers’ practice 0.13 0.13 0.18 0.15

locity of water flow was measured after ir-rigation water flow was established in thefull length of the channel, at 0.2 and 0.8 mwater depth. Soil in the area is lateriticloam.

Weeds were completely eliminatedafter 3 yr as a result of Paraquat applica-tion. The table presents the average val-ues of water velocity. Chemical clearingachieved a flow velocity almost equal tothat of concrete lining. Cutting the sidesand clearing (farmers’ practice) reduced

the flow rate considerably, to almost 50%.This may be due to the greater penetra-tion of water through the pores createdby scraping. Irrigation water flowingthrough the herbicide-treated canal did

not have any adverse effect on seedlinggrowth in the rice nursery as well as in themain field where the water was used. Chan-nel clearing through herbicide applicationis more effective.

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Rice research for food security and poverty alleviation is thetheme of the International Rice Research Conference (IRRC)2000 to be held at IRRI headquarters, 31 March—3 April 2000.To assure food security and to continue the advance againstpoverty in rice-consuming countries of the world, farmerswill have to produce 40% to 50% more rice with improvedqualities to meet consumer demand in 2025. This additionalrice will have to be produced on less land with less water,less labor, and fewer chemicals. To meet this challenge ofincreasing rice production during the first quarter of the 21stcentury, scientists must develop rice varieties with higheryield potential, durable resistance to diseases and insects,and tolerance for abiotic stresses. Recent breakthroughs inmolecular biology have provided greater opportunities forrice scientists to develop a new generation of rice varieties.Increases in rice production can also be achieved by closingthe yield gap and improving yield stability through knowl-edge-intensive crop and natural resource management.

The 1995 IRRC focused on less-favored and fragileenvironments—the rainfed lowland, upland, and flood-pronerice ecosystems. IRRC 2000, as part of IRRI’s 40th anniver-sary celebration, will focus on the irrigated ecosystem andprovide a forum for rice scientists to present research resultsand exchange ideas. The topics for the seven sessions of theIRRC 2000 are: “Increasing yield potential in irrigated rice:breaking the barrier, Exploitation and utilization of heterosisin rice, Breeding for abiotic stress tolerance, Durable host-plant resistance, Integrated nutrient and pest management,Water and weed management in direct-seeded rice, and Im-pact of technologies on food security and poverty alleviation.”

Selected full papers from oral presentations will bepublished in the Conference proceedings. Selected posterabstracts will be published in future installments of the In-ternational Rice Research Notes (IRRN).

International Rice Research Conference set for31 March—3 April 2000

Important dates1 October 1999 Deadline for submission of abstracts1 December 1999 Mailing of invitations to selected

participants and detailedinstructions to authors.

1 March 2000 Submission of full papers to theorganizing committee

31 March—3 April 2000 Conference at IRRI headquarters,Los Baños, Philippines

The members of the organizing committee are DarshanS. Brar, Michael B. Cohen, Eugene P. Hettel, MahabubHossain, Gurdev S. Khush, Hei Leung, Shaobing Peng, andTo Phuc Tuong.

For more information, contact:

Shaobing PengChair, Organizing CommitteeInternational Rice Research Conference 2000International Rice Research Institute (IRRI)P.O. Box 3127, Makati City 1271, PhilippinesTel: (63-2) 845-0563, ext. 767Fax: 63-2-891-1292, 761-2406, 845-0606E-mail: s.peng@cgiar.orgIRRI Website: http://www.cgiar.org/irri

2000

IRRC

2000

36 August 1999

Crop management and physiology

Allelopathic effects of weeds on germinationand seedling vigor of hybrid riceP. Oudhia, N. Pandey, and R.S. Tripathi, Department of Agronomy, Indira Gandhi Agricultural University(IGAU), Raipur, Madhya Pradesh, India Email: pankajoudhia@usa.net

Parthenium hysterophorus and Lantanacamara are common weeds in theChhattisgarh region of India, where thearea under high-yielding rice varieties isincreasing rapidly. The allelopathic effectsof Parthenium and Lantana have beenreported on many crops but not on hybridrice (Narwal 1994, Oudhia and Tripathi1999). To discover the allelopathic poten-tial of Parthenium and Lantana leaves andParthenium flowers on germination andseedling vigor of hybrid rice var. Proagro6111, a pot experiment was carried out atthe IGAU.

To prepare extracts, leaves ofParthenium (PL) and Lantana (LL) andflowers of Parthenium (PF) were collectedrandomly from fields. The crushed leavesand flowers were allowed to stand for 24 hin distilled water in the ratio of 1:5 (20%),1:10 (10%), 1:15 (6.7%), and 1:20 (5%)[1:10 (5%) for PF and LL] of weed materialand water, respectively. Extracts were de-cayed at room temperature (28 + 1 °C).After decaying, extraction was done with a2-mm mesh sieve. A bioassay was done inearthen pots filled with neutral clay loamsoil and uniformly fertilized with 16, 18,and 12 ppm of urea, diammonium phos-phate, and muriate of potash, respectively.Rice seeds were soaked in the differentextracts or distilled water (control) for 24 h.After soaking, 20 rice seeds were sown ineach pot. The experiment was laid out in arandomized complete block design withtwo replicates and was repeated twice.Germination was recorded at 5, 7, 9, and11 d after sowing (DAS) and root and shootlengths and dry matter accumulation at 11DAS.

The different aqueous extracts ofParthenium and Lantana produced nega-tive and positive allelopathic effects on ger-mination and seedling vigor of rice seeds(see table). At 5 DAS, the aqueous extractof PL (5%) produced a significantly higher

germination than the rest of the treatmentcombinations except PL (10%) and PF(10%). At 11 DAS, the highest germinationwas noted in the control and PL (5%), andthe lowest in PL (6.7%) and PF (10%). PL(5%) had the longest root and LL (10%)the shortest root. PL (20%) and PL (6.7%)resulted in maximum and minimum shootlength, respectively. PL (5%) had a shootlength comparable with that of PL (20%).PL (20%) and PF (10%) produced the high-est and lowest dry root weight, respec-tively, whereas PL (5%) and PF (10%)showed the highest and lowest dry shootweight, respectively.

The negative (stimulatory) allelo-pathic effects of different aqueous extractsof PL on field crops have been reported(Oudhia and Tripathi 1999). Manyallelochemicals—e.g., parthenin, p-coumaric acid, caffeic acid, coronopillin,and sesquiterpene lactones—from theaqueous extracts of Parthenium respon-sible for positive (inhibitory) allelopathiceffects have also been reported (Narwal1994). In this experiment, the effects ofthese allelochemicals were significant upto 6.7% concentration. At lower concen-tration (i.e., 5%), the phytotoxic effects ofthese allelochemicals were not observed.

Some growth-promoting substances suchas glucose, galactose, and potassium chlo-ride in the diluted aqueous extracts of PLhave also been reported (Rastogi andMehrotra 1991). This is probably why theaqueous extract of PL (5%) generally pro-duced germination comparable with thatof the control, and higher root and shootelongation and dry matter accumulation.

The study indicated the possibilityof using the aqueous extract of PL at lowerconcentrations (e.g., 5%) to promote earlygermination and vigor of rice seeds andseedlings in place of water alone throughsoaking treatments. The effects of thispromising extract on ultimate crop produc-tion are under study. Repetition of thiswork using different hybrid rice varietiesand different concentrations would pro-vide a better understanding of allelopathy.

ReferencesNarwal SS. 1994. Allelopathy in crop production.

Jodhpur (India): Scientific Publishers. 288 p.Oudhia P, Tripathi RS. 1999. Allelopathic effect of

Lantana camara L. on germination ofKodo (Paspalum scrobiculatum L.). WeedNews (in press).

Rastogi RP, Mehrotra BN. 1991. Compendium ofIndian medicinal plants. Vol. II. CentralDrug Research Institute. New Delhi:Lucknow and P&I Directorate. 832 p.

Allelopathic effect of weeds on rice seedlings.

Germination (%) Root Shoot Root ShootTreatment length length weight weight

5 DASa 7 DAS 9 DAS 11 DAS (cm plant-1)(cm plant-1) (mg plant-1) (mg plant-1)

T1 = Parthenium 66.7 83.3 86.7 86.7 5.95 9.40 33.25 9.33 leaves (20%)T2 = Parthenium 73.3 80.0 83.3 86.7 6.58 7.52 25.17 5.89 leaves (10%)T3 = Parthenium 63.3 70.0 73.3 76.7 7.06 5.98 20.55 6.33 leaves (6.7%)T4 = Parthenium 86.7 93.3 93.3 93.3 8.06 8.35 32.61 12.61 leaves (5%)T5 = Parthenium 76.7 83.3 76.7 76.7 5.80 6.85 18.75 4.17 flowers (10%)T6 = Lantana 53.3 73.3 80.0 80.0 5.73 7.00 21.64 6.15 leaves (10%)T7 = Control 50.0 80.0 93.3 96.7 7.84 6.63 24.22 5.40(soaked in water) LSD (0.05) 20.7 ns ns 8.1 1.62 2.17 7.28 3.65

aDAS = days after sowing.

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37IRRN 24.2

Equilibrium moisture content for sorptionof water vapor by milled riceJ.P. Pandey, Department of Post Harvest Process and Food Engineering, G.B. Pant University of Agriculture andTechnology, Pantnagar 263145, Udham Singh Nagar, India

Hygroscopicity is a fundamental character-istic of biological materials that influencesvirtually every aspect of handling, storage,manufacturing, and consumption of foodproducts. When such materials are ex-posed to the atmosphere, they tend to loseor gain moisture, depending on tempera-ture and relative humidity. The process bywhich hygroscopic materials lose or gainmoisture is called sorption, and the mois-ture content at equilibrium is known asequilibrium moisture content (EMC).

EMC data are directly applicable tothe analysis of mass transfer phenomenain storage and drying processes. Milledrice, like other grains, is hygroscopic innature—it loses or gains moisture when thevapor pressure of water surrounding thegrain is different from that inside the grain.Basic EMC data on milled rice with differ-ent milling degrees in relation to tempera-ture and relative humidity of the storageatmosphere are necessary for analyzing themoisture exchange process during storage.This study was undertaken to establish theEMC of rice with different milling degreesunder relative humidities ranging from 0.1to 0.9 and temperatures of 20, 30, and 40 °C.

The experiments were conductedusing a recently released hybrid rice vari-ety (Pant Sankar Dhan-1). Sorption char-acteristics of milled rice with different de-grees of milling (0%, 3.8%, 6.6%, 10.3%)were studied at prespecified temperaturesand relative humidity under adsorptionand desorption using the static method.In the static method, the material wasplaced in a desiccator containing a satu-rated salt solution or sulfuric acid solutionthat gives a certain specific relative humid-ity. The grain was allowed to equilibriatein still, moist air. Aqueous sulfuric acid andhydrochloric acid solutions of various con-centrations was used to control the rela-tive humidity of moist air between 0% and

100%. The vapor pressure above an acidsolution depends on the chemical, concen-tration, and temperature.

The EMC values for milled rice of3.8%, 6.6%, and 10.3% degree of polishranged from 6.9% to 24.2% (adsorption)and 7.6% to 26.2% (desorption); 6.6% to26.2%, and 8.0% to 27.0%; and 6.0% to24.0% and 8.0% to 25.0%, respectively. For0% milled rice (brown rice), the minimumand maximum EMC values during adsorp-tion were 7.0% and 24.2%, and those fordesorption were 7.6% and 25.6% (seetable). One-way analysis of variance(ANOVA) indicated that the effect of de-gree of milling on EMC of adsorption anddesorption was significant at 5% and 0.5%levels of significance.

EMC values for desorption werehigher for milled rice than for unmilled rice(8.6% at 20 °C and 0.11 relative humidity).The EMC generally decreased with an in-crease in temperature and generally in-creased with a rise in relative humidity forboth adsorption and desorption processes.Differences varied with level of relative hu-midity and temperature. At constant rela-tive humidity, hysteresis was higher atlower temperature. For example, at a rela-tive humidity of 0.11, the difference be-tween desorption and adsorption EMC for3.8% milled rice was 2.1%, 1.1%, and 0.4%,at temperatures of 20, 30, and 40 °C re-spectively. Similar effects were also ob-served for other relative humidities.

Equilibrium moisture content of milled rice at different temperatures and relative humidities.Pantnagar India.

Adsorption DesorptionTemperature Relative (°C) humidity 0.0 3.8a 6.6a 10.3a 0.0 3.8a 6.6a 10.3a

20 0.11 8.0 7.3 7.6 7.6 8.6 9.4 9.0 9.20.34 12.4 12.4 12.6 13.6 14.3 14.4 15.2 15.80.44 14.2 14.4 14.4 14.8 16.0 16.2 16.6 17.00.59 16.8 17.3 17.0 16.9 18.6 18.6 18.6 19.10.76 19.8 20.4 20.2 20.0 21.4 21.8 22.0 21.80.80 20.6 21.2 21.4 21.2 22.2 22.8 23.0 22.80.91 24.2 24.2 25.3 b 25.6 26.2 26.0 b

30 0.11 7.4 6.9 6.8 6.7 8.2 8.0 8.3 8.60.33 13.4 11.8 12.2 13.0 14.6 13.2 14.2 15.60.44 15.0 14.0 14.0 14.5 16.2 15.3 16.2 16.40.63 17.6 17.0 18.6 18.8 18.4 18.2 20.0 20.70.76 20.1 19.2 20.6 20.1 20.8 20.6 21.8 22.20.80 21.0 21.0 21.4 21.0 21.8 22.4 22.8 22.40.96 b b 26.2 b b b 27.0 b

40 0.11 7.0 7.2 6.6 6.0 7.6 7.6 8.0 8.00.32 12.1 11.8 11.8 12.2 13.0 12.6 13.4 13.20.43 14.4 13.6 13.8 13.4 14.8 14.4 15.2 14.50.63 17.8 16.8 18.2 17.4 18.6 18.0 19.0 18.40.75 20.4 19.6 20.4 19.8 20.8 20.9 21.4 20.90.80 21.0 20.6 21.4 20.6 21.6 21.2 22.2 21.80.91 23.0 23.4 24.6 24.0 23.6 24.6 24.8 25.0

aDegree of milling (%). bNo observations due to mold growth.

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38 August 1999

Plant population requirement of hybrid rice in theTarai region of Uttar Pradesh, IndiaP.S. Bisht, P.C. Pandey, and P. Lal, Agronomy Department, G.B. Pant University of Agriculture and Technology (GBPUAT),Pantnagar 263145, Uttar Pradesh, India

We conducted field experiments to evalu-ate the effect of plant density on yield ofhybrid rice during the 1996-97 wet seasonsat the GBPUAT Crop Research Centre. Asplit-plot design, with 20 × 20 cm and 15× 15-cm spacing in the main plot and 1, 2,and 3 seedlings hill-1 in the subplot, wasused with four replications. Promising hy-brid variety PRH1 (128 d) (1996) and re-cently released Pant Sankar Dhan-1 (118d) (1997) were used.

Nurseries were sown on 12 June andtransplanting began on 12 July in bothyears. The crop was fertilized with 175 -26.4 - 33 kg NPK ha-1. Half of the N and thefull P and K were applied basally before

transplanting. The remaining N wastopdressed, at tillering and at panicle ini-tiation. The crop was sprayed with 0.5%ZnSO

4 + 0.25% slaked lime in water, twice

(10 and 20 d after transplanting, [DAT]) inthe nursery and once in the main field (15DAT). The soil was silt loam (AquicHapludoll) with pH 8.0, 1.1% organic C,20 kg available P ha-1, and cation exchangecapacity of 20 meq 100 g-1 soil.

Dense transplanting at 15 × 15-cmspacing was superior to normal spacing (20× 20 cm), but the difference in yield wassignificant only in 1996. The higher yields(8.3% in 1996 and 7.4% in 1997) underclose spacing were associated with signifi-

cantly increased panicle numbers and to-tal spikelets m-2 (see table).

The recommended 2 seedlings hill-1

for inbred rice varieties was optimum evenfor these hybrids. Transplanting with 2 or3 seedlings hill-1 increased the number ofpanicles and total spikelets. This increasewas significant in both years, except fortotal spikelets in 1997.

Results showed no indication of re-duced plant density under experimentalconditions. A yield advantage of 0.5 t ha-1

for close transplanting at 15 × 15 cm maycompensate for the high seed cost of hy-brid rice.

Effect of seedling number and spacing on grain yield, harvest index, and yield components of hybrid rice, GBPUAT, Pantnagar, India, 1996-97.

PRH1 (1996) Pant Sankar Dhan-1(1997)

Grain Harvest Panicles m-2 1,000- Grain Harvest Panicles m-2 1,000-yield index (no.) Spikelets grain yield index (no.) grain

(t ha-1) wt (g) (t ha-1) wt (g)Total m-2 Filled Unfilled Total m-2 Filled Unfilled

(no. × 1,000 ) panicles (%) (no. × 1,000 ) panicles (%)(no.) (no.)

Plant spacing20 × 20 cm 6.0 0.52 246 29.1 98 18 24.8 5.4 0.48 245 35.3 105 28 24.315 × 15 cm 6.5 0.52 301 35.0 97 19 24.8 5.8 0.49 270 40.2 108 28 23.9 SE± 0.1 0.002 6 0.8 5 1 0.1 0.1 0.002 5 0.6 4 1 0.2 LSD (5%) 0.3 nsa 26 3.6 ns ns ns ns ns 22 2.7 ns ns ns CV (5%) 4.0 1.33 7 9.0 16 11 1.0 7.0 1.56 7 5.5 12 9 3Seedling number hill-1

1 5.9 0.53 229 30.7 109 19 24.7 5.4 0.49 241 36.5 111 27 24.42 6.4 0.52 286 31.5 96 17 24.7 5.7 0.49 261 37.9 106 26 24.03 6.5 0.52 1 33.9 88 19 24.8 5.8 1.49 271 38.9 101 29 24.0 SE± 0.1 0.004 10 7.5 4 1 0.1 0.1 0.003 6 0.6 3 1 0.2 LSD (5%) 0.4 ns 30 1.6 13 ns ns 0.3 ns 18 ns ns ns ns CV (%) 6.0 2.17 10 5.0 11 16 11 5.0 2.01 6 5.0 9 11 2

ans = not significant.

Spikelets

Promising medium-duration varieties for double-croppedareas of AssamK.K. Sharma, P.K. Pathak, T. Ahmed, S. Hussain, D.K. Bora, S. Ali, H.C. Bhattacharyya, and A.K. Pathak, Regional AgriculturalResearch Station (RARS), Titabar 785630, Assam, India

Most rice-growing areas in Assam, India,are monocropped. Farmers grow long-duration varieties (140–160 d) in areas

where land becomes unsuitable to take uprabi (wet season) crops because of mois-ture stress and cold environmental condi-

tions after rice harvest. This is why mostcultivable land remains fallow after sali(June/July-November/December) rice.

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Treatment

39IRRN 24.2

Rice cultivars with medium duration (130 d)are needed to grow rabi crops after fallowand thus increase cropping intensity.

Using pedigree selection methods,we developed two medium-duration vari-eties, Satya and Basundhara, from crossesIET9711/IET11162 and IET9711/IET11161,respectively. They can be sown in June andharvested in October. Both varieties takeabout 130 d from seed to seed so that ricefields are cleared by October to facilitateearly tillage operations for the timely sow-ing of rabi crops. Table 1 shows the salientfeatures of the two varieties.

Satya and Basundhara were resistantand moderately resistant to several insectpests and diseases, except bacterial leafblight (BLB) and sheath blight of rice. Theyshould not be planted in BLB-endemic ar-eas. No other popular variety, however, isresistant to sheath blight in the state. Satyaand Basundhara can replace existing vari-eties as a follow up rabi crop.

The varieties were tested at four lo-cations in 1994 and in farmers’ fields inAssam in 1997. They were also includedunder the All-India Testing and FrontlineBlock Demonstration Programme inAssam. Table 2 shows the performancedata on these varieties at various locations.Although yields of Satya and Basundharawere not exceptionally higher than thoseof popular long-duration varieties, theirshorter growth duration makes them idealfor growing before the rabi season.

Table 1. Salient features of Satya and Basundhara at RARS, Titabar, Assam, India.

Feature Satya Basundhara Control (Mahsuri)

Cross IET9711/IET11162 IET9711/IET11161 (Mayong Ebos 80/Taichung 65)//Mayong Ebos 80

Designation TTB148-169-2-1-1 TTB149-121-5-1-1 CheckDays to 50% flowering 100 100 115Plant height (cm) 113 107 140Flag leaf size (cm) 36 × 1.5 33 × 1.6 43.5 × 2.0Leaf collar Green Green Light greenTillers plant-1 (no.) 8–10 8–10 8–10Panicle type Compact Compact CompactPanicle length (cm) 21 23 26Grains panicle-1 (no.) 160 170 284Threshability Intermediate Intermediate ShatteringKernel length (mm) 4.76 4.78 5.70Kernel breadth (mm) 1.64 2.04 2.20Length/breadth (L/B) 2.90 2.34 2.591,000-grain wt (g) 19.6 24.0 16.2Endosperm type Nonglutinous Nonglutinous NonglutinousKernel color White White WhiteAbdominal white Absent Trace AbsentHulling (%) 78 75 75Milling (%) 64 62 62Head rice recovery (%) 63 60 60Seed dormancy Nondormant Nondormant NondormantPhotoperiod sensitivity Insensitive Insensitive InsensitiveDisease reactiona

Blast MR MR S Bacterial leaf blight S S MR Sheath blight S S SInsect reactiona

Stem borer MR MR MR Gall midge R R MS Brown planthopper R R S Whitebacked planthopper R R S Leaffolder MR MR MR

aMR = moderately resistant, R = resistant, MS = moderately susceptible, S = susceptible.

Table 2. Mean yield (t ha-1) of Satya and Basundhara under various trials, India, 1994-97a.

CheckLocation

Satya Basundhara Jaya Mahsuri Ratna LSD 5%

Within state (1994) RARS, Titabar 4.6 5.2 3.9 3.6 0.5 FTS, Nagaon 4.9 5.2 4.3 4.3 0.8 FTS, Sukliboria 4.2 4.2 3.9 4.0 0.8 FTS, Gerua 2.7 2.3 2.3 2.7 0.4 Mean 4.1 4.2 3.6 3.6 –Farmers’ fields (1997) Mohimabari (Jorhat) 5.1 5.0 3.0 Bherbheri (Nagaon) 5.0 4.8 3.5 Dalgaon (Darrang) 4.2 4.0 3.1 Dhekiajuli (Sonitpur) 3.9 3.8 2.9 Mean 4.5 4.4 3.1All India trials (1996) Bhubaneswar 3.6 5.5 3.3 4.8 0.8 Joypur 5.9 4.9 3.6 4.8 0.9 Ciplima 4.4 5.4 4.3 3.3 0.6 Patna 5.6 4.5 5.4 5.2 0.8 Chinsurah 4.0 3.0 3.0 3.5 0.6 Pusa 3.5 4.3 4.3 3.5 ns Masodha 3.4 6.0 5.5 3.6 1.2 Jagdalpur 2.9 3.6 3.4 – 0.7 Raipur 4.1 3.7 3.5 3.7 0.6 Mean 4.2 4.5 4.0 4.0 –

aRARS = Regional Agricultural Research Station, ns = not significant.

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Scholarships for 2000IRRI is pleased to announce the availabilityof scholarships to be awarded during 2000to support highly qualified scientists fromrice-growing developing countries inter-ested in pursuing a graduate degree in ar-eas related to rice science. These scholar-ships include those provided by IRRI (PhDscholarships only) as well as scholarshipfunds which IRRI administers for other agen-cies, primarily the Asian Development Bank(ADB)-Japan scholarship fund (MS and PhDscholarships).

Write to: The Office of the Scholars AffairsInternational Rice Research InstituteMCPO Box 3127, Makati City 1271, PhilippinesTel : (63-2) 845-0563; 844-3351 to 53Fax : (63-2) 891-1292; 845-0606E-mail: Postmaster@irri.cgiar.org; URL: www.cgiar.org/irri

40 August 1999

Socioeconomics

Weed meal from a rice plot for broiler chicks

N.M. Anigbogu, Department of Animal Nutrition and Feed Milling Technology, Federal University ofAgriculture, Umudike, P.M.B. 7267, Umuahia, Abia State, Nigeria

Weeding contributes to the high cost ofrice production in southern Nigeria. Manyfarmers cut and then burn weeds to con-trol them. The biochemistry, economics ofweed processing, and supplemental use ofweed meal from rice (WMR) as broiler feedwere evaluated as an integral part of thefarming system.

A total of 354 kg of weeds were gath-ered from the farm plot, chopped, driedunder shade 10–13 d before being ex-posed to slight sunlight on the 14th day,and then milled into ground particles withgreen coloration. Woody stems were re-moved before and during drying. The nu-trient composition of both fresh and pro-cessed weed (weed meal) was determinedfollowing methods recommended by theAssociation of Official Analytical Chemists(AOAC 1984). The weed population con-sisted of 71% grasses, 23% sedges, and 6%broadleaf weeds. Dominant weeds wereEchinochloa colona, E. crus-galli,Commelina benghalensis, Cyperusdifformis, C. iria, and Eclipta prostrata.

Feed combinations for straight-runbroiler chicks were (a) pure commercialfeed mash (CFM), (b) CFM + 5% WMR,(c) CFM + 10% WMR, and (d) CRM + 15%WMR. One hundred and sixty commercialstraight-run broiler chicks composed of 10per plot (four replications) were fed for 8wk. Response criteria (weight, feed con-sumption, mortality, breast-fleshing ability,feathering rate, pigmentation of skin andshanks, and incidence of cannibalism)were recorded and statistically analyzedusing a complete randomized design.

The nutrient composition data in-dicated that weeds were rich in protein,ash, carbohydrate, fat, calcium, andphosphorus when processed into meal(Table 1). A total of 118 kg of fresh weedswas processed in this study. The cost of

the finished product was N1.39 kg-1, whichincluded costs of 0.94N kg-1 for freshweeds, 0.3N kg-1 for drying, and 0.15N kg-1

for milling (US$1= N85).In all measures, the CFM + 5% WMR

diet performed as well as the CFM diet(Table 2). The two diets with higher levelsof WMR did not perform as well, as indi-cated by lower values of final weight, feedconversion efficiency, and breast-fleshing

ability. No effect of WMR on mortality wasnoted, even at the 15% level in the diet.All birds in the lots were fully feathered at8 wk and their pigmentation was gener-ally the same light yellow.

ReferenceAOAC (Association of Official Analytical Chemists).

1984. Official methods of analysis. 14th ed.Washington, D.C.

○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Item

Table 1. Nutrient composition of fresh and processed weed from rice farm plot.

Nutrient composition (mg 100 g-1)

Fresh Processed

Proximate composition (N = 3)a

Moisture 75.78 ± 0.14 bb 12.33 ± 0.07 aDry matter 24.22 ± 3.42 a 87.67 ± 0.95 bAsh 2.26 ± 0.05 a 9.00 ± 0.34 bCrude protein 2.15 ± 0.21 a 10.59 ± 0.94 bCrude fat 0.68 ± 0.02 a 1.53 ± 0.22 bCrude fiber 8.96 ± 0.11 a 34.49 ± 0.43 bNitrogen-free extract 10.17 ± 0.32 a 32.06 ± 1.03 bCalorific value (kcal 100 g-1) 91.24 a 322.33 bMineral content (N = 3)a

Calcium 0.24 ± 0.04 a 0.92 ± 0.07 bPhosphorus 0.10 ± 0.01 a 0.40 ± 0.04 b

aValues are means ± standard deviations of triplicate determinations. bMeans in the same row with different letters differat the 1% level of significance.

Table 2. Average production performance of straight-run broiler chicks.a

Item CFMb CFM + CFM + CFM +5% WMRc 10% WMR 15% WMR

Initial weight (g) 48.95 48.95 48.95 48.95Final weight (g) 1,417.30 a 1,454.30 a 1,303.00 b 1,280.30 bTotal weight gain (g) 1,368.35 a 1,405.35 a 1,254.05 b 1,231.35 bDaily weight gain (g) 24.43 a 25.10 a 22.39 b 21.99 bTotal feed consumption (g)d 3,509.80 3,618.50 3,662.20 3,563.60Feed conversion efficiency 2.5 a 2.5 a 2.8 b 2.8 bBroiler chicks at start of trial (no.) 40 40 40 40Mortality (no.) 1 0 0 1Breast-fleshing ability (%) 67.2 a 69.6 a 49.8 b 48.6 b

aMeans in the same row with different letters differ at the 5% significance level. bCFM = commercial feed mash. cWMR =weed meal from rice. dAnalysis of variance showed no significance at the 5% level.

41IRRN 24.2

NOTES FROM THE FIELD

In situIn situIn situIn situIn situ conservation of conservation of conservation of conservation of conservation of OryzaOryzaOryzaOryzaOryzarufipogonrufipogonrufipogonrufipogonrufipogonB.R. Lu, Genetic Resources Center, IRRI

Oryza rufipogon Griff. is one of three na-tive wild rice species found in southernChina that have contributed greatly to thecountry’s rice breeding programs. The di-rect use of O. rufipogon in a rice breedingprogram through wide hybridization inGuangdong Province was recently re-ported. Professor Haidong Song of theZhengchen Agricultural Bureau crossedindividuals from one O. rufipogon popu-lation near Yangtian Bridge, ZhengchenCity, with an improved Chinese rice vari-ety, Guicao No. 2. After several years ofevaluation and selection, a series of ricevarieties—Guiye Zhan No. 2, No. 3, and No.10; Guiye Wanzhan No. 1 and No. 2; YeaoSimiao; and Guiao Simiao—were bred.These wide cross-derived new rice variet-

Occurrence of Occurrence of Occurrence of Occurrence of Occurrence of FusariumFusariumFusariumFusariumFusarium sheath sheath sheath sheath sheathrot in West Bengalrot in West Bengalrot in West Bengalrot in West Bengalrot in West BengalA. Biswas, Rice Research Station, Chinsurah712102, West Bengal, India

During the 1996 wet season (June-Octo-ber), sheath rot (ShR) was first observedin cytoplasmic male sterile (CMS) lineIR62829A in hybrid rice seed productionplots at the District Seed Farm, Susunia,Bankura, West Bengal. Since then, it hasbeen observed in different CMS lines un-der natural field and pot conditions at theRice Research Station, Bankura andChinsurah, West Bengal. Critical observa-tion showed that symptoms on CMS linesalmost resembled those produced bySarocladium oryzae.

In 1998, the causal fungus was iso-lated on potato dextrose agar (PDA) me-dium from infected leaf sheaths of CMSlines IR62829A and IR58025A at Chinsurah.The culture was pale violet. Both micro-and macroconidia were abundant, with nochlamydospore. Microconidia in chainsformed under optimum growing condi-tions. They were 0-septate and fusiform toclavate with a slightly flattened base mea-suring 5–12 × 1.5–2.5 µm. Macroconidiawere equilaterally fusoid, delicate, thin-walled with an elongated often sharplycurved apical cell and pedicellate basal cell,and mostly 3-septate, measuring 25–36 ×2.5–3.5 µm. These cultural and morpho-logical features confirmed that the funguswas Fusarium moniliforme Sheld.

Pathogenicity tests were performedto confirm fungus association with ShR.Plants were inoculated by inserting myce-lial bits grown on PDA medium into theboot leaf sheath before panicle emergence.Typical ShR symptoms appeared, lesionsdeveloped within a week, and the sheathcompletely rotted in a month. The patho-genicity test also confirmed the suscepti-bility of cultivars such as TN1, Vikramarya,Bennibhog, and IR20 to fusarium sheathrot. This is the first report of fusariumsheath rot in West Bengal.

Rice scientists fromthe South ChinaAgriculturalUniversity andZhengchenAgricultural Bureaucollect wild ricefrom the in situconservation site.

Prof. Song Donghai (left) at the in situ conservation site of the Zhengchen AgriculturalBureau, Guangdong Province, China, and Dr. B.R. Lu (right) of Genetic Resources Center,IRRI. Prof. Song received several awards from the Chinese government for his successfuluse of wild rice in breeding.

ies are characterized by high yield, excel-lent eating quality, and good resistance torice blast, bacterial blight, bacterial leafstreak, and brown planthopper. These va-rieties are grown on about 950,000 ha in13 provinces.

Because O. rufipogon from theZhengchen area has played such an impor-tant role in the rice breeding program, thelocal agricultural authority has focused onconserving these wild rice populations. Butthe fast development of the rural economyand rapid change in farming styles haveseriously threatened the survival of wildrice populations. To protect these dimin-ishing but valuable populations, the localgovernment established the first in situconservation site near Yangtian Bridge forO. rufipogon. This will guarantee long-term availability of O. rufipogon popula-tions for use as genetic resources in ricebreeding programs.

42 August 1999

RESEARCH HIGHLIGHTS

Kronzücker HJ, Siddiqi MY,Glass ADM, Kirk GJD. 1999.Nitrate-ammonium synergism inNitrate-ammonium synergism inNitrate-ammonium synergism inNitrate-ammonium synergism inNitrate-ammonium synergism inrice: a subcellular flux analysis.rice: a subcellular flux analysis.rice: a subcellular flux analysis.rice: a subcellular flux analysis.rice: a subcellular flux analysis.Plant Physiol. 119:1041-1045.

This paper shows that hydroponic lowlandrice is exceptionally efficient in absorbingnitrate (NO

3–) and that synergy occurs be-

tween NO3– uptake and ammonium (NH

4+)

uptake. This is important because (a) itmeans that rice may efficiently captureNO

3– formed in the rhizosphere but oth-

erwise lost through denitrification, and (b)plant growth and yield are generally im-proved when plants absorb their N as amixture of NO

3– and NH

4+ compared with

either NO3– or NH

4+ alone.

The evidence is as follows. First,measurements of the change in NO

3– in-

flux over time following its resupply toplants deprived of NO

3– showed exception-

ally rapid induction of NO3

–. Peak rates ofinflux occurred within 2 h of resupply. Forcomparison, in white spruce, which is notwell adapted to using NO

3–, full induction

takes several days, and, in barley, which isconsidered one of the most efficient NO

3–

users among higher plants, full inductiontakes up to 24 h.

Second, in plants grown on 100 µMNO

3– or NH

4+, steady-state influx of NO

3-

and NH4

+ into roots followed Michaelis-Menten kinetics over the relevant concen-tration range, and V

max for NO

3– was about

40% bigger than that for NH4

+ and 50%smaller for K

m.

Third, although concentrations ofNO

3– in the cytoplasm were almost twice

the NH4+ concentrations, half-lives of cel-

lular exchange—indicating the intensity ofnegative feedback of internal N accumula-tion on uptake—were similar. Half-lives forNO

3– were substantially larger than those

observed in other plant species. Whilesimilar proportions of incoming NH

4+ and

NO3

– were channeled into assimilation andto root cell vacuoles, more than twice asmuch N was made available to the shoot

with NO3– nutrition and nearly half as much

incoming N was lost through efflux backinto the solution bathing the roots.

When NO3

– and NH4

+ were pro-vided together in the nutrient solution atthe same total N concentration (100 µM,i.e., [NO

3–] = [NH

4+] = 50 µM), plasma

membrane fluxes of NH4+, cytosolic NH

4+

accumulation, and NH4+ assimilation were

larger than with sole NH4

+ at–µM, andNH

4+ efflux was smaller. Conversely, NO

3–

influx, accumulation, and metabolism wererepressed by NH

4+. Net N acquisition and

N translocation to the shoot were muchlarger, however, than when NO

3– or NH

4+

was provided alone (29% and 83% larger,and 83% and 299% larger, respectively).Because very little free NH

4+ is translocated

to the shoot, the enhanced translocationof N to the shoot in the presence of NO

3–

indicates that NH4+ assimilation is stimu-

lated by NO3

–.

Welch RM, Graham RD. 1999.A new paradigm for worldA new paradigm for worldA new paradigm for worldA new paradigm for worldA new paradigm for worldagriculture: meeting humanagriculture: meeting humanagriculture: meeting humanagriculture: meeting humanagriculture: meeting humanneeds. Productive, sustainable,needs. Productive, sustainable,needs. Productive, sustainable,needs. Productive, sustainable,needs. Productive, sustainable,nutritious. nutritious. nutritious. nutritious. nutritious. Field Crops Res.60:1-10.

The authors argue that a new paradigm foragriculture is needed. After an agriculturefocused on increasing production (the pro-duction paradigm during the Green Revo-lution) and an agriculture centered onsustainability (the sustainability paradigm),it is now time for an agriculture that fo-cuses on nutritional quality (the food sys-tems paradigm). Micronutrient malnutri-tion (“hidden hunger”) now afflicts morethan 2 billion people worldwide, resultingin poor health, low worker productivity,high rates of mortality and morbidity, in-creased rates of chronic diseases (coronaryheart disease, cancer, stroke, and diabe-tes), and permanent impairment of cogni-tive abilities of infants born to micronutri-

ent-deficient mothers. An overview of mi-cronutrient malnutrition is given, indicat-ing that an estimated 2.15 billion peoplesuffer from iron deficiency, most of whomare women and children from the devel-oping world. It is estimated that iron defi-ciency costs India and Bangladesh about5% and 11%, respectively, of their grossnational product. Iodine, vitamin A, andzinc deficiency are also major nutritionalproblems.

In South Asia, the production ofcereal crops has increased tremendouslyduring the Green Revolution, whereas theproduction of pulses has actually declinedby 20% since 1970. The consequences offood system failures include lethargic na-tional development efforts, continued highpopulation growth rates, and a viciouscycle of poverty for massive numbers ofunderprivileged people in all nations. Theworld’s food systems are failing globally bynot providing enough balanced nutrientoutput to meet all the nutritional needs ofevery person, especially resource-poorwomen, infants, and children in develop-ing countries. Agriculture is partly respon-sible because it has never held nutrientoutput as an explicit goal of its productionsystems. Indeed, many agricultural policieshave fostered a decline in nutrition anddiet diversity for the poor in many coun-tries. Nutrition and health communities arealso partly responsible because they havenever considered using agriculture as aprimary tool in their programs directed atalleviating poor nutrition and ill health glo-bally. Therefore, ways must be consideredin which agriculture can contribute to find-ing sustainable solutions to food systemfailures through holistic food-based systemapproaches, thereby closely linking agri-cultural production to improving humanhealth, livelihood, and well-being.

Note: Field Crops Research has published a special issue(vol. 60, no. 1-2, p 1-188) on “Sustainable field crop systemsfor enhancing human health: agricultural approaches tobalanced micronutrient nutrition.”

43IRRN 24.2

Xiao J, Grandillo S, Ahn SA,McCouch SR, Tanskley SD, Li J,Yuan L. 1996. Genes from wild Genes from wild Genes from wild Genes from wild Genes from wildrice improve yield. rice improve yield. rice improve yield. rice improve yield. rice improve yield. Nature384:223-224.

Wild species are often inferior to commer-cial cultivars because of several agronomi-cally undesirable features such as low yield,heavy seed shattering, poor plant type, andphotoperiod sensitivity. However, they arean important reservoir of useful genes forresistance to major diseases and insects,tolerance for abiotic stresses, cytoplasmicmale sterility, and improved quality traits.In the past, plant breeders have used thegenetic variability of wild species tobroaden the gene pool of crop plants fordeveloping disease- and insect-resistantcultivars. Notable examples include rustresistance in wheat and grassy stunt virusresistance and cytoplasmic male sterility inrice. Wild species have rarely been used,however, for the genetic enhancement ofquantitative traits such as yield. This is be-cause superior traits of interest are diffi-cult to identify phenotypically in wild spe-cies. Moreover, in such germplasm, favor-able genes are present in low frequencyand are often masked by effects of delete-rious genes. Molecular markers providethe opportunity to identify favorable quan-titative trait loci (QTLs) from wild speciesand to monitor introgression of these fa-vorable alleles into cultivated germplasmto improve grain yield.

Dr. K.J. Frey of Iowa State Univer-sity, USA, did pioneering work in cereals,demonstrating that wild and weedy spe-cies can increase grain in oats and barley.More recently, Xiao et al have identifiedQTLs in a wild species (Oryza rufipogon,AA, 2n = 24) for enhancing grain yield ofcultivated rice. In these studies, O.rufipogon alleles at two QTLs on chromo-somes 1 and 2 were associated with an 18%and 17% increase in grain yield per plant,respectively. These findings offer new op-portunities to exploit wild speciesgermplasm in combination with molecu-lar marker technology to enhance grainyield of crops.

Waterhouse PM, Graham MW,Wang M-B. 1998. Virus resis-. Virus resis-. Virus resis-. Virus resis-. Virus resis-tance and gene silencing intance and gene silencing intance and gene silencing intance and gene silencing intance and gene silencing inplants can be induced by simul-plants can be induced by simul-plants can be induced by simul-plants can be induced by simul-plants can be induced by simul-taneous expression of sensetaneous expression of sensetaneous expression of sensetaneous expression of sensetaneous expression of senseand antisense RNA.and antisense RNA.and antisense RNA.and antisense RNA.and antisense RNA. Proc. Natl.Acad. Sci. USA 95:13959-13964.

Since the origin of the concept of patho-gen-derived resistance in 1985, severalcrops have been genetically engineeredwith the coat protein genes of plant virusesto achieve viral resistance. Initially, thistype of resistance required the expressionof protein. Later reports, however, showedthat resistance can occur even if RNA istranscribed but not translated. Constructswith untranslatable coat protein or repli-case genes conferred resistance, and thissecond type of resistance has been calledRNA-mediated resistance. The transcrip-tion of sense and antisense RNA intransgenic plants can be downregulated byposttranscriptional gene silencing. Howdoes this downregulation occur in theplant cell? Researchers have proposed thata plant-encoded RNA-dependent RNApolymerase could make a complementarystrand of the transgene mRNA and that thisaction could either trigger specific RNAdegradation or an arrest in the translationof the target RNA.

Waterhouse et al decided to testwhether the simultaneous expression ofsense and antisense RNAs, which are ca-pable of forming a duplex, would induceor suppress the posttranscriptional genesilencing phenomenon. The authorsshowed that sense and antisense con-structs derived from the protease gene ofpotato virus Y can confer immunity to thevirus in tobacco plants and that immunityis independent of the transgene proteinexpression. They also demonstrated thatthe immunity is mediated by a sequence-specific degradation of protease RNAwithin the genome of the virus used in in-oculation. Coexpressing the sense andantisense mRNA in the same construct orcrossing the plants with the sense genewith those containing the antisense gene

Van Beem J, Smith ME, ZobelRW. 1998. Estimating root Estimating root Estimating root Estimating root Estimating rootmass in maize using portablemass in maize using portablemass in maize using portablemass in maize using portablemass in maize using portablecapacitance meter. capacitance meter. capacitance meter. capacitance meter. capacitance meter. Agron. J.90:566-570.

Time and expense are major constraintsto detecting genotypic differences in thelength, structure, and growth rate of rootsystems in soil. The recent developmentof a hand-held capacitance meter couldfacilitate the routine quantification of rootmass. This study determined the accuracywith which a BK Precision 810A capaci-tance meter can estimate root fresh massin maize (Zea mays L.) using a techniquethat allows a rapid and noninvasive capaci-tance reading. The capacitance meter mea-sured root capacitance of maize grownunder greenhouse (8 genotypes) and field(6 genotypes) conditions. After the capaci-tance readings, 14 plants per genotypewere uprooted, roots were washed thor-oughly, and root fresh mass was obtained.The statistical relationship between capaci-tance and root fresh mass in greenhouseexperiments was significant early in thegrowth season for all genotypes (r2 = 0.73,P>0.001) and significant only late in thegrowth season for inbreds (r2 = 0.56,P<0.001). In conclusion, capacitancemeters equipped with a clamp for rapidattachment to the plant may facilitate thenondestructive identification of genotypeswith root characteristics that confer adap-tation to various environments. Conditionsfor accurate capacitance measurementsincluded a moist medium around theplant’s root system and a consistent place-ment of the electrode at 6 cm above thecrown.

is more effective at inducing the immunityresponse than transforming plants withonly one of the constructs. Because thedelivery of RNAs with the potential to formduplexes is effective at inducing immunityto plant viruses and affecting gene silenc-ing in plants, this strategy can now be ex-ploited further in an attempt to confer re-sistance to other pathogens and insects.

44 August 1999

Goto F, Yoshihara T, ShigemotoN, Toki S, Takaiwa F. 1999. Iron. Iron. Iron. Iron. Ironfortification of rice seed by thefortification of rice seed by thefortification of rice seed by thefortification of rice seed by thefortification of rice seed by thesoybean ferritin genesoybean ferritin genesoybean ferritin genesoybean ferritin genesoybean ferritin gene. NatureBiotechnology 17:282-286.

Iron deficiency is a serious nutritionalproblem affecting about 30% of the worldpopulation, especially where vegetable-based diets prevail. Ferritin is an iron-stor-age protein found in animals, plants, andbacteria. The ferritin gene has been iso-lated and sequenced in plants such as soy-bean, maize, and pea. Both plants and ani-mals use ferritin as the storage form of iron.Increasing the ferritin content of cerealsby genetic engineering could overcomethe problem of iron deficiency. Goto et al(1999) introduced the soybean ferritingene into rice variety Kita-ake byAgrobacterium-mediated transformation.The ferritin gene was expressed under thecontrol of a rice seed-storage protein glu-telin promoter, Glub-1. Stable accumula-tion of the ferritin subunit in the rice seedwas demonstrated by western blot analy-sis and its specific accumulation in theendosperm by immunologic tissue print-ing. The transgenic rice seeds stored threetimes more iron (38.1 + 4.5 µg g-1 dryweight) than the (untransformed) normalseeds (11.2 + 0.9 µg g-1 dry weight).

Losey JE, Rayor LS, Carter ME.1999. Transgenic pollen harmsTransgenic pollen harmsTransgenic pollen harmsTransgenic pollen harmsTransgenic pollen harmsmonarch larvaemonarch larvaemonarch larvaemonarch larvaemonarch larvae. Nature399:214.

The pollen of many genetically engineeredcrop plants contains the protein encodedby the “transgene,” or foreign gene intro-duced into the plant. In this paper, theauthors studied pollen from a commer-cially released maize variety that is geneti-cally engineered with a gene from Bacil-lus thuringiensis (Bt). This gene encodesan insecticidal protein that confers resis-tance to caterpillar pests. The pollen wasapplied to leaves of milkweed (Asclepiascurassavica) and fed to larvae of the mon-arch butterfly Danaus plexippus. The

monarch is an attractive butterfly that oc-curs widely in North America. It feeds onlyon milkweed species, and its most abun-dant host, A. syiaca, commonly grows inor around maize fields. Monarch larvae fedmilkweed leaves dusted with Bt maize pol-len had significantly higher mortality andconsumed significantly less food than lar-vae fed untreated milkweed leaves or milk-weed leaves dusted with pollen fromnontransgenic maize.

This is a small and preliminary study,and much followup research is needed todetermine whether pollen from Bt maizewill have a measurable impact on popula-tions of the monarch or other nontargetmoths and butterflies that feed on plantsin the vicinity of crop fields. It serves as animportant reminder, however, that scien-tists and regulators may not foresee allpotential risks associated with a new tech-nology. The results are also of particularrelevance to silk-producing areas in Asia,where mulberry plants (the only food ofsilkworm larvae) may be grown near Btcrops.

Cohen MB, Jackson MT, Lu BR,Morin SR, Mortimer AM, PhamJL, Wade LJ. 1999. PredictingPredictingPredictingPredictingPredictingthe environmental impact ofthe environmental impact ofthe environmental impact ofthe environmental impact ofthe environmental impact oftransgene outcrossing to wildtransgene outcrossing to wildtransgene outcrossing to wildtransgene outcrossing to wildtransgene outcrossing to wildand weedy rices in Asia.and weedy rices in Asia.and weedy rices in Asia.and weedy rices in Asia.and weedy rices in Asia. In:Gene flow and agriculture:relevance for transgenic crops.BCPC Symposium Proceedingsno. 72. Brighton: British CropProtection Council. p 151-156.

The outcrossing of foreign genes fromtransgenic crops to wild and weedy croprelatives is one of the most significant con-cerns regarding the possible environmen-tal impact of genetically engineered crops.This issue is particularly important fortransgenic rice in Asia, because Asia is thecenter of origin of Oryza sativa and is alsohome to numerous wild species of Oryza.Two wild species, O. rufipogon and O.nivara, are abundant in many parts of Asiaand are known to hybridize with O. sativa

under natural conditions. Several types ofweedy rice also occur in Asia, derived fromO. sativa, wild species, and hybrids be-tween wild rices and O. sativa. Geneticengineering of rice for resistance to insects,diseases, and abiotic stresses has been rap-idly advancing, although no transgenic va-rieties have as yet been widely field-tested.This paper provides an introduction to the“outcrossing issue” for transgenic rice inAsia and outlines an interdisciplinary setof research activities to help predict theconsequences of transgene outcrossing towild and weedy rices. The proposed re-search includes (1) an updated survey ofthe ecogeographical distribution and diver-sity of O. rufipogon, O. nivara, and weedyrices (hereafter referred to as the “targetspecies”); (2) identification of key factorsthat determine the distribution and abun-dance of the target species; (3) analysis ofgene flow among the target species; (4)determination of fitness of hybrids be-tween improved varieties and the targetspecies; and (5) quantification of the tol-erance of the target species for selectedabiotic stresses, particularly drought andsubmergence. The authors propose thatthis research should be conducted beforetransgenic varieties with enhanced stressresistance are extensively released into theenvironment, so that the findings can as-sist scientists and policymakers in decid-ing whether and how particular transgenicrice should be released.

Go BreAk into The Code

IRRI has produced a video on how Institutescientists are redesigning the rice plant, thatmost important food staple, using biotechno-logical tools. This visually entertaining andfast-paced 13-minute film, in NTSC systemand in VHS format, is now available at IRRI.For more information on the video and otherfilms, contact:

Marketing and DistributionCommunication and Publications ServicesIRRI, MCPO Box 3127, Makati City 1271PhilippinesE-mail: e.ramin@cgiar.org orj.nepomuceno@cgiar.org

45IRRN 24.2

NEWS

IRRI scientist winsIRRI scientist winsIRRI scientist winsIRRI scientist winsIRRI scientist winsinternational awardinternational awardinternational awardinternational awardinternational award

Dr. Achim Dobermann, a soil nutrient spe-cialist of the Soil and Water Sciences Divi-sion at IRRI, will receive the prestigiousRobert E. Wagner Award from the UnitedStates-based Potash and Phosphate Insti-tute (PPI) later this year.

Dr. Dobermann will receive theaward in the young scientist division. Prof.Zhu Zhonglin, the president of the SichuanAcademy of Agricultural Sciences inChengdu, China, won the award in the se-nior scientist category.

The award recognizes the contribu-tions made by young and senior scientiststo improve crop yields through maximumyield research and maximum economicyield (MEY) management. It honors Rob-ert E. Wagner, a retired president of PPI,whose achievements and development ofthe MEY concept led to more profitableand efficient agriculture worldwide.

The award cites Dr. Dobermann’s“widely recognized scientific accomplish-ments in soil fertility and integrated nutri-ent management. His outstanding publi-cation record in major international jour-nals documents important contributionsto the basic understanding of soil nutrientdynamics in relation to plant availabilityand uptake, and the use of geospatial sta-tistical approaches to improve predictionsof crop nutrient requirements.”

Dr. Dobermann has served as IRRI’ssoil nutrient specialist since 1996 and is theproject leader of the mega project “Revers-ing Trends of Declining Productivity in In-tensive Irrigated Systems” funded by theSwiss Agency for Development and Coop-eration (SDC), International Fertilizer In-dustry Association (IFIA), PPI, and Inter-national Potash Institute (IPI).

The project employs a site-specificintegrated nutrient management or SSNMapproach to overcome low productivityand low nutrient efficiency in intensive ir-rigated systems in Asia. About 40 scientistsand 200 rice farmers from China, India,Indonesia, the Philippines, Thailand, and

Vietnam are actively collaborating in theproject.

Dr. Dobermann has also began amajor course for “training trainers,” whichhas provided rice researchers and exten-sion workers in the developing countriesof Asia with current information.

In welcoming the announcement ofthe 1999 Robert E. Wagner Award, Dr.Dobermann said: “I interpret this as anaward given to all the people who haveparticipated in this research (nutrient man-agement in intensive rice systems) in Asia.IRRI has provided a perfect environmentfor this work and we have enjoyed substan-tial and stable financial support for ourresearch, with the SDC, PPI, IFIA, and IPIas donors.

“I see this as a model for collabora-tion between a strategically oriented re-search institution, locally oriented nationalresearch institutions, the public sector, andthe private sector. I think our research willsoon move into a phase where it will havea real impact at the farm level, which isperhaps the greatest reward one can getas a scientist.”

Source: IRRI Hotline

IRRI establishes SenadhiraIRRI establishes SenadhiraIRRI establishes SenadhiraIRRI establishes SenadhiraIRRI establishes SenadhiraAward for Asian rice scientistsAward for Asian rice scientistsAward for Asian rice scientistsAward for Asian rice scientistsAward for Asian rice scientists

IRRI has launched an important awardcalled the “Senadhira Rice ResearchAward.” The award honors Dr.Dharmawansa Senadhira, a rice breeder

from Sri Lanka, who led IRRI’s researchprogram on flood-prone rice and did im-portant work in several key areas includ-ing soil-related stresses, low temperatures,and submergence in rice. He died tragi-cally in an accident in Bangladesh in July1998. The award will be given to Asian sci-entists working in rice research.

An endowment of US$65,000 hasbeen established by the Senadhira familyand from personal contributions of friendsand colleagues of Dr. Senadhira. Fundswere also obtained from the prize moneyfor an award from Japan given to Dr.Senadhira just before he died as well asfrom the late scientist’s retirement ben-efits.

Part of the endowment will be givenas a cash award for the chosen rice scien-tist, who will also be presented with aplaque at the International Rice ResearchConference to be held at IRRI in 2000. TheSenadhira Rice Research Award (a certifi-cate or plaque together with a cash award)will be given every 2 years.

Any rice research scientist employedby a national agricultural research system(NARS) linked to IRRI or a citizen of a rice-growing/consuming country in Asia is eli-gible for nomination.

Nominees will be evaluated basedon their contributions to rice research—such as successful varieties developed, sci-entific papers published, and any othertangible contributions to rice develop-ment.

IRRI will administer the endow-ment. IRRI has established a committeethat will oversee the selection of awardees

46 August 1999

Former IRRI scientist shares1999 Tyler World Prize forEnvironmental Achievement

Te-Tzu (T.T.) Chang of Taiwan, an IRRIscientific staff member for 30 years (1961-91) and Joel E. Cohen of the United Stateshave been awarded the 1999 Tyler WorldPrize for Environmental Achievement. Thetwo scientists “have made monumentalcontributions to solving the related prob-lems of food production and distribution,and understanding the dynamics of popu-

Rice rats:Rice rats:Rice rats:Rice rats:Rice rats:a taste treat?a taste treat?a taste treat?a taste treat?a taste treat?

Rats eat huge amounts of rice, butfarmers in Battambang and otherprovinces in Cambodia are fightingback. As the rats are caught in traps,they are killed, skinned, gutted,roasted, and eaten. The Cambodia-IRRI-Australia Project (CIAP) Inte-grated Pest Management (IPM) Teamhas tasted this culinary delight and canattest to the delicious flavor of thelean smoky meat. Villagers spice themeat with a variety of herbs. Chilies,garlic, and salt are the most commonseasonings.

Because of the possibility ofcontracting diseases or parasites,people eating rice rats should followthese guidelines:

sources conservation and is credited withstarting the assemblage of a large and richrice germplasm collection. Under Dr.Chang’s leadership, IRRI’s genetic re-sources program has stimulated interna-tional activities on conservation, evalua-tion, and use of the rich and diverse ricegermplasm worldwide. The InternationalRice Genebank now holds the world’smost comprehensive collection of rice ge-netic resources.

Dr. Cohen, the corecipient fromRockefeller University, USA, was recog-nized for his contributions to demography,epidemiology, ecology, and populationgenetics. Dr. Cohen also has a connectionto IRRI: he spent 3 months at the Institutein 1989, and applied a food web approachto analyze IRRI’s extensive database on ricefield arthropods. This work led to severalpublications with members of IRRI’s En-tomology and Plant Pathology Division andthe Crop Protection Division of the Philip-pine Rice Research Institute.

The Tyler World Prize for Environ-mental Achievement is an internationalaward established in 1973 to honor signifi-cant achievements in all disciplines of en-vironmental study and environmental pro-tection.

1. Do not eat dead rats.2. Gut the rats properly. Remove all

organs intact. If the contents ofthe bladder, intestines, orstomach accidentally spill into themeat, discard the entire rat.Spilling organ contents onto themeat could result in transmissionof bacterial diseases, parasites, ortoxins.

3. Cook the rats thoroughly.Overcooked meat is safer thanundercooked meat. The farmersin Battambang appear to befollowing all these precautionsalready.

Eating rice field rats is really notstrange when one considers that, inBattambang, wild animals such as deerand wild boar are part of the tradi-tional diet.

Source: CIAP Bulletin 4(7) July 1999

lation growth.” They shared a cash prizeof $200,000 and received gold Tyler Prizemedallions at a black-tie awards ceremonyon 16 April in Los Angeles.

“Their work in agriculture and con-servation, and the demands that growingpopulations bring to bear on them, spansbasic scientific and practical applicationswith a lasting impact on both,” said Dr.Robert P. Sullivan, chair of the 11-memberTyler Prize Executive Committee, whichannually selects the Tyler Prize recipients.

Dr. Chang, 71, introduced Dee-geo-woo-gen, a semidwarf rice variety from Tai-wan, into IRRI’s infant breeding programin 1962, which led directly to the first high-yielding, semidwarf rice varieties. He isconsidered the “father” of rice genetic re-

and administration of the award. The com-mittee is composed of Dr. Gurdev S. Khush(chair), Dr. Sant Virmani, Ms. Eliza Panes,Dr. Robert Raab, and Dr. NeemalRanaweera (designated by the Senadhirafamily).

Done in close collaboration with theNARS, Dr. Senadhira’s most recent re-search had focused on developing im-proved germplasm with higher concentra-tions of micronutrients, such as iron andzinc in rice grains. He was selected to re-ceive the prestigious Fukui InternationalKoshihikari Rice Prize in 1998 in recogni-tion of his outstanding achievements in de-veloping rice varieties.

The varieties developed under hisleadership are planted in most of the ricelands in Sri Lanka and in several countriesin Asia and Africa. His contributions to riceimprovement were recognized by the SriLanka President’s Award for ScientificAchievement (1981) and the Ceres Medalfrom FAO (1982).

Dr. Senadhira was born in Sri Lankaon 18 January 1944. He completed his BS(agriculture) in 1967 at the University ofCeylon, Sri Lanka, and his MS (genetics)in 1974 and PhD (genetics) in 1976 at theUniversity of California, Davis, USA. He wasa rice breeder, senior rice breeder, andcoordinator of the rice improvement pro-gram, and senior breeder and deputy di-rector for research for the Department ofAgriculture, Sri Lanka, before he joinedIRRI in 1985.

Source: IRRI Hotline

T.T. Chang

47IRRN 24.2

IRRN welcomes three types of submittedmanuscripts: research notes, mini reviews, and“notes from the field.” All manuscripts musthave international or pan-national relevance torice science or production, be written in En-glish, and be an original work of the author(s),and must not have been previously publishedelsewhere.

Research notesResearch notes submitted to IRRN should

• report on work conducted during theimmediate past 3 yr or work in progress

• advance rice knowledge• use appropriate research design and

data collection methodology• report pertinent, adequate data• apply appropriate statistical analysis,

and• reach supportable conclusions.

Routine research. Reports of screen-ing trials of varieties, fertilizer, cropping meth-ods, and other routine observations using stan-dard methodologies to establish local recom-mendations are not ordinarily accepted.

Preliminary research findings. Toreach well-supported conclusions, field trialsshould be repeated across more than one sea-son, in multiple seasons, or in more than onelocation as appropriate. Preliminary researchfindings from a single season or location maybe accepted for publication in IRRN if the find-ings are of exceptional interest.

Preliminary data published in IRRN maylater be published as part of a more extensivestudy in another peer-reviewed publication, ifthe original IRRN article is cited. However, anote submitted to IRRN should not consistsolely of data that have been extracted from alarger publication that has already been or willsoon be published elsewhere.

Multiple submissions. Normally,only one report for a single experiment will beaccepted. Two or more items about the samework submitted at the same time will be re-turned for merging. Submitting at differenttimes multiple notes from the same experi-ment is highly inappropriate. Detection willresult in the rejection of all submissions on thatresearch.

Manuscript preparation. Arrangethe note as a brief statement of research ob-jectives, a short description of project design,and a succinct discussion of results. Relate re-sults to the objectives. Do not include abstracts.Up to five references may be cited. Restrain ac-knowledgments. Limit each note to no morethan two pages of double-spaced typewrittentext (approximately 500 words).

Each note may include up to two tablesand/or figures (graphs, illustrations, or pho-tos). Refer to all tables and figures in the text.Group tables and figures at the end of the note,each on a separate page. Tables and figuresmust have clear titles that adequately explaincontents.

Apply these rules, as appropriate, to allresearch notes:

Methodology• Include an internationally known check

or control treatment in all experiments.• Report grain yield at 14% moisture con-

tent.• Quantify survey data, such as infection

percentage, degree of severity, and sam-pling base.

• When evaluating susceptibility, resis-tance, and tolerance, report the actualquantification of damage due to stress,which was used to assess level or inci-dence. Specify the measurements used.

• Provide the genetic background for newvarieties or breeding lines.

• Specify the rice production systems asirrigated, rainfed lowland, upland, andflood-prone (deepwater and tidal wet-lands).

• Indicate the type of rice culture (trans-planted, wet seeded, dry seeded).

Terminology• If local terms for seasons are used, de-

fine them by characteristic weather (dryseason, wet season, monsoon) and bymonths.

• Use standard, internationally recog-nized terms to describe rice plant parts,growth stages, and management prac-tices. Do not use local names.

• Provide scientific names for diseases, in-sects, weeds, and crop plants. Do notuse local names alone.

• Do not use local monetary units. Ex-press all economic data in terms of theUS$, and include the exchange rateused.

• Use generic names, not trade names,for all chemicals.

• Use the International System of Unitsfor all measurements. For example, ex-press yield data in metric tons per hect-are (t ha-1) for field studies. Do not uselocal units of measure.

• When using acronyms or abbreviations,write the name in full on first mention,followed by the acronym or abbrevia-tion in parentheses. Use the abbrevia-tion thereafter.

• Define any nonstandard abbreviation orsymbol used in tables or figures in afootnote, caption, or legend.

Mini reviewsMini reviews should address topics of currentinterest to a broad selection of rice research-ers, and highlight new developments that areshaping current work in the field. Authorsshould contact the appropriate editorial boardmember before submitting a mini review toverify that the subject is appropriate and thatno similar reviews are already in preparation.(A list of the editors and their areas of respon-sibility appears on the inside front cover of eachIRRN issue.) Because only 1-2 mini reviews canbe published per issue, IRRN will require highquality standards for manuscripts accepted forpublication. The reviews should be 2000-3000words long, including references. Refer to theguidelines for research notes for other aspectsof writing and content.

Notes from the fieldNotes from the field should address importantnew observations or trends in rice-growing ar-eas, such as pest outbreaks or new pest intro-ductions, or the adoption or spread of newcrop management practices. These observa-tions, while not the result of experiments, mustbe carefully described and documented. Notesshould be approximately 250 words in length.Refer to the guidelines for research notes forother aspects of writing and content.

Review of manuscriptsThe IRRN managing editor will send an ac-knowledgment card or an email message whena note is received. An IRRI scientist, selectedby the editorial board, reviews each note. De-pending on the reviewer’s report, a note willbe accepted for publication, rejected, or re-turned to the author(s) for revision.

Submission of manuscriptsSubmit the original manuscript and a duplicate,each with a clear copy of all tables and figures,to IRRN. Retain a copy of the note and of alltables and figures.

Send manuscripts, correspondence,and comments or suggestions about IRRN bymail or email to:

The IRRN Managing EditorIRRI, MCPO Box 3127Makati City 1271PhilippinesFax: (63-2) 845-0606E-mail: k.s.lopez@cgiar.org

INSTRUCTIONS TO CONTRIBUTORS

ISSN 0115-0944

INTERNATIONAL RICE RESEARCH INSTITUTEMCPO Box 3127, Makati City 1271, Philippines

Printed Matter

New IRRI Publications

Advances in Hybrid Rice TechnologyS.S. Virmani, E.A. Siddiq, and K. Muralidharan

Impact of Rice ResearchP.L. Pingali and M. Hossain

Sustainability of Rice inthe Global Food System

N.G. Dowling, S.M. Greenfield, K.S. Fischer

Rainfed Lowland Rice: Advances inNutrient Management Research

J.K. Ladha, L. Wade, A. Dobermann, W. Reichardt,G.J.D. Kirk, and C. M. Piggin

Resource Managementin Rice Systems: Nutrients

V. Balasubramanian, J.K. Ladha, G.L. Denning,

Upland Rice Weeds of South andSoutheast Asia

M.I. Galinato, K. Moody, and C.M. Piggin