international rice research newsletter vol.15 no.5

IRRN GUIDELINES The International Rice Research Newsletter objective is:

"To expedite communication among scientists concerned with the development of improved technology for rice and for rice- based cropping systems. This publication will report what scientists are doing to increase the production of rice, inasmuch as this crop feeds the most densely populated and land-scarce nations in the worId . . . IRRN is a mechanism to help rice scientists keep each other informed of current research findings." The concise reports contained in

IRRN are meant to encourage rice scientists and workers to con- municate with one another. In this way, readers can obtain more detailed information on the research reported.

guidelines, and research categories that follow.

suggestions. please write the editor. IRRN, IRRI, P.O. Box 933, Manila. Phillppines. We look forward to your continuing interest in IRRN.

Criteria for IRRN research reports • has intertnational, or pan-national,

• has rice environment relevance • advances rice knowledge

Please examine the criteria.

If you have comments or

relevance

uses appropriate research design and data collection methodology

• reports appropriate, adequate data • applies appropriate analysis, using

appropriate statistical techniques • reaches supportable conclusions

Guidelines for contributors (revised)

The International Rice Research Newsletter is a compilation of brief reports of current research on topics of interest to rice scientists all over the world. Contributions should be reports to recent work and work-in- progress that have broad, pan-national interest and application. Only reports of work conducted during the immediate past three years should be submitted.

Research reported in IRRN should be verified. Single season, single trial field experiments are not accepted. All field trials should be repeated across more than one season, in multiple seasons, or in more than one location, as appropriate. All experiments should include replicatlon and a check or control treatment.

All work should have pan-national relevance.

Reports of routine screening trials of varieties, fertilizer, and cropping methods using standard methodolo- gies to establish local recommenda- tions are not accepted.

Normally, no more than one report will be accepted from a single experiment. Two or more items about the same work submitted at the same time will be returned for merging. Submission at different times of multiple reports from the same experiment is highly inappropriate. Detection of such submissions will result in rejection of all.

Please observe the following guidelines in preparing submissions: • Limit each report to two pages of

double-spaced typewritten text and no more than two figures (graphs, tables, or photos).

• Do not cite references or include a bibliography.

• Organize the report into a brief statement of research objectives, a brief description of project design, and a brief discussion of results. Relate results to the objectives.

analysis.

environment (irrigated, rainfed lowland, upland, deepwater, tidal wetlands).

(transplanted, wet seeded, dry seeded).

• Specify seasons by characteristic weather (wet season, dry season, monsoon) and by months. Do not use local terms for seasons or, if used, define them.

• Use standard, internationally recognized terms to describe rice plant parts, growth stages, environments, management practices, etc. Do not use local names.

• Provide genetic background for new varieties or breeding lines.

• For soil nutrient studies, be sure to include a standard soil profile description, classification, and relevant soil properties.

diseases, insects, weeds, and crop plants. Do not use common names or local names alone.

• Report appropriate statistical

• Specify the rice production

• Specify the type of rice culture

• Provide scientific names for

• Quantify survey data (infection percentage, degree of severity, sampling base, etc.).

• When evaluating susceptibility, resistance, tolerance, etc., report the actual quantification of damage due to stress that was used to assess level or incidence. Specify the measurements used.

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

• Use international measurements. Do not use local units of measure. Express yield data in metric tons per hectare (t/ha) for field studies and in grams per pot (g/pot) or per specified length (in meters) row (g/ row) for mall scale studies.

• Express all economic data in terms of the US$. Do not use local monetary units. Economic information should be presented at the exchange rate US$:local currency at the time data were collected.

abbreviations, write the name in full on first mention, followed by the acronym or abbreviation in parentheses. Thereafter, use the abbreviation.

• Define any nonstandard abbreviations or symbols used in a table or graph in a footnote or caption/ legend.

• When using acronyms or

Categories of research published

GERMPLASM IMPROVEMENT genetic resources genetics breeding methods yield potential grain quality pest resistance

diseases insects other pests

stress tolerance drought excess water adverse temperature adverse soils

irrigated rainfed lowland upland deepwater tidal wetlands

seed technology

integrated germplasm improvement

CROP AND RESOURCE MAN-

soils soil microbiology physiology and plant nutrition fertilizer management

inorganic sources organic sources

AGEMENT

crop management integrated pest management

diseases insects weeds other pests

water management farming systems farm machinery postharvest technology economic analysis

ENVIRONMENT

SOCIOECONOMIC IMPACT

EDUCATION AND COM- MUNICATION

RESEARCH METHODOLOGY

CONTENTS GERMPLASM IMPROVEMENT

Genetics 5 Genetic studies of seed dormancy in high grain quality cultivars

Breeding methods 5 A supplementary pollination technique for hybrid rice seed production 6 F 1 fertility in indica/japonica crosses 6 Use of male gametocide to induce complete male sterility in a partially

male sterile rice

Yield potential 7 Genetic nature of high-density rice grain 8 Genotypic differences in rice yield potential and N, P, and K in leaves 9 Developing a functional model of rice panicle growth 9 Herbage potential of rice cultivars

10 Ratooning ability and potential herbage production from ratoon crops of rice cultivars

Pest resistance — diseases 11 Reaction of promising rice cultivars to major diseases in Eastern

11 Evaluation of resistance to blast (Bl) in promising rice cultivars 11 Evaluation of rice germplasm for resistance to grassy stunt virus (GSV)

Vidarbha Zone, India

Pest resistance — insects 12 Development of a brown planthopper (BPH) biotype and change in

varietal resistance in Mekong Delta

Stress tolerance — drought 12 Genetic variability in midday leaf water potential (LWP) of irrigated rice

Stress tolerance — excess water 13 Germination and seedling development of floating rice at different soil

moisture regimes

Stress tolerance — adverse temperature 13 Screening rice cultivars at reproductive stage for low temperature

tolerance in western Nepal

Integrated germplasm improvement — irrigated 14 CICA8 and ITA222, new rice varieties for irrigated areas of Mbo Plain

in West Cameroon

Integrated germplasm improvement — rainfed 15 IET8717, a physiologically efficient rice variety for waterlogged areas of

16 IET10522, a high-yielding medium-duration rice for waterlogged Assam

conditions

CROP AND RESOURCE MANAGEMENT

Soil microbiology 16 Influence of mycorrhizal association and inorganic nutrients on early

growth of rice

Physiology and plant nutrition 17 Effects of paclobutrazol and KH 2 PO 4 on rice seedlings and grain yield

Fertilizer management 17 Effect of straw + (NH 2 ) 2 SO 4 application on rice

Crop management 18 Effect of cultural practice for semideep water rice on yield and net

18 Effect of seedling age on growth and yield of T. aman rice 19 Effect of summer plowing on N volatilization and rice yield in sandy

income

loam soils

IRRN 15:5 (October 1990)

Integrated pest management — diseases 19 Natural infection of rice yellow mottle virus disease (RYMV) on rice in

20 Effect of urea applied with neem cake on disease intensity and insect

20 Efficacy of fungicides against enzyme produced by rice sheath blight

Sierra Leone

population in ricefields

(ShB) pathogen

Integrated pest management — insects 21 Rice grain yield loss due to rice hispa damage 21 Behavior of the wolf spider Lycosa pseudoannulata (Boes. et Str.) 21 Alternate plant hosts of rice leaffolder (LF) 22 Predation of yellow stem borer (YSB) moths by wolf spider 22 Electroantennogram technique for studying olfactory sensitivity of

23 Density-dependent mortality of rice leaffolder (LF) due to larval

24 Attractiveness of light color to selected predators of rice pests 25 Pheromone components of rice leaffolder (LF) Cnaphalocrocis medinalis

insects to volatile compounds

parasitization

and Marasmia patnalis

Integrated pest management — other pests 26 Correlation between Hirschmanniella oryzae population and rice grain

weight

Farm machinery 27 Effect of soil moisture content on tractor wheel slip

ANNOUNCEMENT

27 Modeling in agricultural research 27 New IRRI publications

GERMPLASM IMPROVEMENT Genetics

Genetic studies of seed dormancy in high grain quality cultivars

Bui Chi Buu and Le Thi Hong Loan, Cuu Long Delta Rice Research Institute, Omon, Hau Giang, Vietnam

Rice varieties grown in wet season (He Thu) in the Mekong delta need to possess seed dormancy.

We studied the genetics of seed dormancy in crosses involving three varieties with grain dormancy and five without dormancy but with high grain quality. Two replications of 30 seeds each were grown in the greenhouse. Panicles were tagged as they emerged and harvested 30 d after flowering.

IR24 and OM80 are very susceptible to preharvest sprouting. Seed dormancy in the F 1 was not completely dominant (Table 1). However, KDML/OM80, KDML/IR64, and OM201/IR64 had

Table 1. Germination in the F 1 of rice hybrids and their parents (hull intact treatment) at 10-60 d after harvest.

Germination (%) Designation

10 20 30 40 50 60

MTL 43/1R64 10 27 52 74 91 92 MTL 43/1R24 12 19 20 78 79 80 MTL 43/OM80 41 54 78 99

Cross

MTL 43/OM86-9 16 30 64 78 94 98 MTL 43/OM87-9 22 42 73 81 98 KDML/IR64 6 37 61 84 100 KDML/IR24 40 69 88 93 KDML/OM80 4 39 55 60 85 KDML/OM86-9 25 44 76 88 90 KDML/OM87-9 19 25 54 73 77 85 OM201/IR64 4 21 66 84 93 OM201/IR24 15 36 70 90 OM201/OM80 10 19 49 81 90 OM201/OM86-9 13 31 48 74 93 OM201/OM87-9 18 37 77 78 90

MTL 43 0 2 3 20 41 81 KDML 0 0 0 OM201 0 5 28 49 51 75

Dormant parents

IR64 IR24 78 79 85 92 OM80 60 79 92 100 OM86-9 12 22 55 71 92 OM87-9 40 65 92 96

Nondormant parents 30 48 72 88 99

Table 2. Segregation for seed dormancy in the F 2 10 days after harvest (hull intact treatment), by germination percentage.

F 2 segregants (no.) by germination class Ratio of Cross 0-25:26-100 P

0-25% 26-50% 51-75% 76-100% germination

KDML/OM87-9 21 14 31 58 3:13 0.27 0.75-0.50 KDML/OM80 180 33 24 63 37:27 0.59 0.50-0.25 MTL 43/OM87-9 4 20 44 232 1:63 0.10 0.75-0.50 MTL 43/OM80 58 63 61 118 3:13 0.70 0.90-0.75 OM201/OM87-9 62 55 67 116 3:13 OM20I/OM80 21 29 43 207 1:15 0.29 0.75-0.50

0.72 0.50-0.25

about 75% germination at 40 d after harvest (DAH).

Seed dormancy in the segregating F 2 populations at 10 DAH were tabulated as 0-25%, 26-50%, 51-75%, and 76-100% (Table 2). The F 2 from KDML/OM87-9, MTL 43/OM80, and OM201/OM87-9 segregated in the ratio of 3 dormant: 13 nondormant. This indicates control of dormancy by digenic recessive genes. Two duplicate recessive genes control dormancy in OM201/OM80.

The F 2 populations from KDML/ OM80 and MTL 43/OM87-9 segregated in the ratio of 37:27 and 1:63, respectively, dormant to nondormant. This shows control of dormancy by trigenic gene action.

Breeding methods

A supplementary pollination technique for hybrid rice seed production

Huang Peijin, Lingling District Seed Co., Hunan; and Tang Shande, Hunan Crop Science Institute, China

We monitored the flowering characters of CMS, maintainer, and restorer lines (V20A, V20B, Zhensan 97A, Zhensan 97B, IR26, R314, Zei 64-7, Zei 64-49, and R8312) 1987-89. Three samples of 30 plants each were examined for each line. Maintainer and restorer lines had one or two obvious flowering peaks in a day: 70-90% of the glumes flowered within these peaks (see figure). In lines with two peaks, each peak lasted 30-40 min; in lines with one peak, the peak lasted 40-60 min.

After glume opening, the anther exserted in 2-4 min, anther stalk elon- gated in 4-6 min, and pollen grains appeared in 7-8 min. Pollen grain spread followed the flowering peak, lasting for 10-15 min with two peaks and 20-30 min with one peak. In CMS lines, the flowering peak did not appear before the end of flowering of the male parents.

IRRN 15:5 (October 1990) 5

c 2

These results indicate that supplementary pollination during the pollen grain spreading peak of the male parent had more effect on seed yield than the previous method of pollinating each half hour from maternal flowering to end of flowering of male parent. Seed set increased more than 7.6% and seed yield 8%.

We devised a new technique for supplementary pollination. A nylon rope 0.4 cm in diameter is pulled at 1 m/s along the length of the plots, to scatter pollen grains during the spreading peak. This is carried out two times for each peak, at a 15-min interval, in double peaks; 3-4 times for only one peak.

Time

Flowering curves of CMS, maintainer, and restorer lines. Lingling, Hunan, China, 1987-89.

F 1 fertility in indica/japonica crosses

Zhang Xian-guang, Food Crops Institute, Hubei Academy of Agricultural Sciences, Wuhan 430064, China

Low F 1 fertility in crosses of indica and japonica is still a problem. In 1988, we tested the F 1 fertility of two sets of combinations under irrigated conditions. One set was a direct japonica/indica cross (a native japonica variety was crossed with an exotic indica); the other was a modified japonica/indica cross (an advanced line or native japonica variety de-

Comparison of F 1 fertility in japonica/indica crosses. Wuhan, China, 1988.

Cross Fertility (%)

Direct japonica/indica LK58/IR36 9.75 HLR4/IR36 16.46 Gh 4/IR28 35.35 105/TKM6 19.82 H857/TKM6 24.23

Mean (x 2 ) 21.22 LSD 9.59

Modifed japonica/indica 607 a /Longfu 6 b 86.53 607/Bamboo rice c 90.25 6107 a /VN51 c 77.70 6107/857 b 87.00 HLRS b /GS1 c 86.37 HLR5/I 636 c 74.10

Mean (x 1 ) 83.66 LSD 6.28

t = 13.01 > 1% level

a Advanced line. b Japonica variety derived from an indica/ japonica cross. c Indica variety.

rived from indica/ japonica was crossed with a japonica or an indica parent).

Modified japonicalindica crosses showed significantly higher spikelet fertility (74.1-90.25%) than the typical japonica/indica cross (9.75-35.75%) (see table).

The sterility of F 1 hybrids in direct indica/japonica cross was reportedly the result of genic or cryptic structural hybridity between chromosomes of the

indica and japonica varieties. We infer that the higher fertility in the modified japonicalindica crosses must be the result of the effectiveness of the advanced lines or native japonica varieties used as bridge parents. They presumably carry either dominant genes, to neutralize the effects of recessive complementary lethal genes in the indica and/or japonica variety, or wide compatible genes, to overcome the hybrid sterility barrier.

Use of male gametocide to induce complete male sterility in a partially male sterile rice Huang Qun-ce and Wang Li-zhu, Biological Department, Xiangtan Teacher's College, P.O. Box 411201, Xiangtan, Hunan, China

Photoperiod-sensitive genic male-sterile rice (PGMSR) is also very sensitive to temperature. While photoperiod is relatively even from year to year, temperature is variable. This means a PGMSR grown in the summer can show variation in pollen sterility, making it unsuitable as female parent in hybrid seed production.

We evaluated a new indica PGMSR. CIS28-15, that was isolated from a B 9 F 4 progeny of the cross Caloro/IR28. The critical stage of its sterility-transformation is about 20 Jul, with fertility-transformation 5 Sep under normal conditions in Xiangtan (29° N). But in 1989, male

sterility in the field was not complete between 20 Jul and 15 Aug because the air temperature was unusually low (mean 23 °C) and fluctuated widely.

We sought to induce complete pollen sterility by spraying the male gametocide (CH 3 As O 3 Zn.H 2 O) in 30, 40, 50, and 60 ppm concentrations on the leaves of CIS28-15 at 5 d before heading. Other plants of CIS28-15 were sprayed with plain water. The experiment had four replications, with 20 hills of 1 plant each.

Initiation of panicle primordium starts about 30 d before heading. From 20 Jul to 15 Aug, we recorded the heading date of every panicle, including those of the main shoot and all tillers, to infer the development stage of each panicle when the plant was sprayed with the male gametocide. Observations on pollen and spikelet fertility were made on bagged panicles and open-pollinated panicles.

The results indicated the following (see table):

6 IRRN 15:5 (October 1990)

Effect of male gametocide on pollen and spikelet fertility and outcrossing rate of the PGMSR CIS28-15. Xiangtan, China, 1989.

Panicle develop- Pollen fertility (%) Spikelet fertility (%) on

bagged panicle Seed set on open-pollinated

panicle

tim ment stage at

e of spraying 30 40 50 60 Check 30 40 50 60 Check 30 40 50 60 V20A ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm (check)

1.4

1.1

0

0

Branch 7.5 differentiation Spikelet 3.5 differentiation Reduction 1.1 division of pollen mother cell Pollen wall 0 (exine) formation

7.8

3.1

1.1

0

6.0

3.1

0

0

7.1

3.5

0

0

7.7

7.1

7.4

7.3

1.3

1.1

0.5

0

1.3

1.2

0.5

0

1.4

1.2

0

0

1.39

1.3

1.4

1.4

9.8

10.2

9.8

10.0

11.4

11.0 10.3 10.1

• At the reduction division stage of the pollen mother cell, effectiveness of 30 and 40 ppm spray was best.

• At the pollen exine stage, all spray levels were effective, with no fertile pollen in the anther and no self-fertilization.

We concluded the effect of low temperature can be controlled and complete

• At branch differentiation stage, there was no difference in pollen fertility and self-fertilization between materials sprayed with the male gametocide and check. The male gametocide had no effect on the young panicle.

there was obvious difference, but effectiveness was low.

• At the spikelet differentiation stage,

pollen sterility of CIS28-15 maintained by spraying with the male gametocide 5 d before heading, at the pollen exine stage. A second treatment may be necessary to sterilize all tillers at the appropriate development stage.

crossing rate of CIS28-15. The treatment does not affect the out-

Yield potential for Rewa 353-4/IR28211-43-1-1-2, the HDI of Rewa 353-4/IR28211-43-1-1-2 was very close to that of the higher parent because of the higher number of spikelets. The HDI of Rewa 353-5/IR56 was much lower than the mid-parent value.

In all crosses, mean HD grain was lower in the F 2 than in the F 1 and the better parent. Backcrosses with the better parent produced more HD grains than backcrosses with the lower parent. The F 2 plants produced more than the better parent.

ing of parents and the possibility of get- ting heterotic lines from such crosses.

dicate highly significant additive and

These results indicate scope for select-

Estimates of gene effects (Table 2) in-

sulfate, 2 g single superphosphate, and 2 g muriate of potash. The number of HD grains produced on primary branches (Pb) and secondary branches (Sb) of the panicles was determined by salt solution.

Mean data from 15 plants of parents and F 1 , 50 plants of backcrosses, and 100 plants of F 2 were used for analysis. The HD grain index (HDI) was calculated as the number of HD grains divided by the number of spikelets per plant.

The parents differed significantly in number of HD grains and HDI (Table 1). Rewa 353-5 had the most HD grains (1,088) but IR28211-43-1-1-2 had the highest HDI (53.2%). Although heter- obeltiosis for number of HD grains was 113% for F1 of IRS6/Rewa 353 and 50%

Genetic nature of high- density rice grain

S. Mallik, A. M. Aguilar, and B. S. Vergara, Plant Physiology Department, IRRI

In 1988 dry season, we studied the genetic nature of HD grain production using the parents, F 1 , F 2 , and two backcrosses of Rewa 353-5/IR56, IR56/Rewa 353, and Rewa 353-4/IR28211-43-1-1-2. Single seeds of the six generations were sown separately in 4-liter pots containing 3 kg of Maahas clay soil (Andaqueptic Haplaquolls) mixed with 4 g ammonium

Table 1. Mean HD grains in 6 generations of Rewa 353-5/IR56 (l), IR56/Rewa 353 (2), and Rewa 353-4/IR28211-43-1-1-2 (3). IRRI, 1988.

HD grain/plant (no.) Generation

Primary branch Secondary branch Total HD grain (no.) High density grain index

I 2 3 1 2 3 1 2 3 1 2 3

P 1 P 2

475 p 5.4 253 p 5.3 228 p 4.4 182 p 4.1 274 p 4.5

9 p 0.6

253 p 5.3 273 p 8.2 704 p 5.7 248 p 4.6 203 p 8.8 389 p 5.9

244 p 4.7 530 p 5.3 731 p 5.0 411 p 7.3 173 p 4.6 695 p 9.2

613 p 7.7 317 p 7.1 357 p 6.8 204 p 5.7 376 p 9.7 10 p 0.8

317p 7.1 419p 10.8 771p 8.7 359p 7.2 220p 12.8 595p 8.6

1088 570 585 386 650

19

33.3 25.9 53.6 27.4

41.1 17.5

399 p 9.4 398 p 6.1 719 p 3.8 440 p 7.5 215 p 7.2 561 p 8.9

570 692

1475 607 423 984

643 928

1450 851

1256 388

47.6

23.1 33.3

18.3 27.9

1.0

33.8 53.2 54.7 38.9 18.8 62.7


F 1 F 2 BC 1 BC 2

We studied the yield potential and leaf N, P, and K at peak growth (55 d) in 27 rice genotypes. Soil was alluvial, sandy loam, and alkaline, with pH 7.8, 0.061% N, 0.05% P, 0.45% K, 4.5 ppm available P, and 0.14% total soluble solids. Standard 120 kg N and 60 kg P/ha were broadcast and incorporated before planting. There were 16 hills/m 2 . The plots were laid out in a randomized design with four replications. Normal agronomic practices were followed. The first fully emerged leaf from each genotype was collected at 55 d and its N, P, and K content measured.

Leaves were dried and ground in a wiley mill. A 1-g sample was digested using H 2 SO 4 and H 2 O 2 .P was determined colorimetrically by the vanadomolybdo- yellow color method; N, by micro- kjeldahl method; and K, by flame pho- tometer. Straw and grain yields were measured at harvest (115 d).

Genotypic differences in rice yield potential and N, P, and K in leaves

dominance effects for Rewa 353-S/IR56 and IR56/Rewa 353. In Rewa 353-4/ IR2811-43-1-1-2, only the additive effects were significant for both Pb and Sb. Among the epistatic effects, additive/ dominance was significant for all crosses. In Rewa 353-5/IR56, dominance/dominance was also significant for Pb and Sb. Duplicate epistasis indicated by the negative value of 'h' and positive value of '1' in Rewa 353-5/IR56 may hinder selection.

Heritability estimates for both Pb and Sb were high in Rewa 353-5/IR56 and Rewa 353-4/IR28211-43-1-1-2 and low in IR56/Rewa 353. Estimates of the number of effective factors were very low for Rewa 353-5/IR56, but two and above for IR56/Rewa 353 and Rewa 353-

With the significant additive effects and high heritability in Rewa 353-5/IR56 and Rewa 353-4/IR28211-43-1-1-2, mass

4/IR28211-43-1-1-2.

selection in early generations to improve heterogeneous populations by modifying the frequencies of desirable genes, followed by single plant selection, may be advantageous in increasing the number of HD grains. Because of high variation due to dominance and epistatic effects in IR56/Rewa 353, selection in later generations would be better, to diminish dominance effects.

Table 2. Estimates of gene effects for number of HD grains in Rewa 353-5/IR56 (1), IR56/Rewa 353 (2), and Rewa 353-4/IR28211-43-1-1-2 (3). IRRI, 1989.

Primary branch Parameter

Secondary branch

1 2 3 1 2 3

Mean Additive Dominance Additive/additive Additive/dominance Dominance/dominance Heritability Effective factors

** = significant at the 1% level.

182* 18.7

- 298** 51.3 - 162 85.0

391** 25.5 780** 121.3

70.7 0.5

265** 20.2 248** 20.4 186** 42.4 633** 122.2

- 8 117.8 - 176** 43.0

558** 119.3 15.6 5.5

411** 73.2 - 522** 103.2

436 369.9 92 358.3

- 379** 110.6 408 521.9

85.2 13.6

204** 25.9 366* 43.5

- 152 98.2 - 44 135.4

524** 48.4 916** 215.8

58.8 0.7

359** 32.0 - 375** 61.7

597** 184.0 194 177.9

- 324** 67.2 454 293.6

14.6 1.5

440** 75.1 - 346** 114.6

113 383.4 - 208 377.7 - 346** 126.6

891 563.6 83.5

6.1

Yield potential of rice genotypes and N, P, and K content in plant leaf.

Straw Grain Leaf nutrient content (% dry wt) Rice genotype yield yield

(t/ha) (t/ha) N P K

S. M. Alam and A. R. Azmi, Atomic Energy Agricultural Research Centre, Tandojam, Pakistan

IR6 (control) Mutant IR6-18 Mutant IR6-93 Mutant IR6-104 Mutant IR6-113 IR8 (parent) Mutant IR8-5 Bas 370 (parent) Mutant 370-1 Mutant 370-5 Mutant 370-24 Mutant 370-28 Jajai 77 (parent) Jajai 77-1 Mutant 77-2 Mutant LG-1 Mutant Jajai 30 Sada Gulab (parent) Mutant SG-EF/SD-78 Mutant SG-EF/SD-55 Sonahri SG (parent)

Mutant SS-EF/SD-8 Pokkali (parent) Mutant pokkali Lateefy (Dokri) DR82 (parent)

Mutant SS-EF/SD-6

8.1 6.6 6.7 7.2 7.0 8.2 6.8

12.0 6.7

11.0 7.1 6.7

13.5 12.8

6.5 6.6 8.4

12.8 10.7

9.2 17.9 10.6 10.5 7.0 5.7 5.5 6.7

5.5 5.0 4.7 3.8 4.6 6.1 5.2 3.4 1.9 2.3 2.9 2.8 3.6 2.9 1.7 1.9 2.1 2.7 2.0 2.1 5.2 3.2 2.6 3.8 3.2 3.1 3.7

1.54 1.40 1.35 0.77 0.77 2.10 1.82 1.82 1.60 1.49 1.59 1.69 2.03 1.26 1.61 1.73 1.69 1.82 1.12 1.54 1.68 1.26 1.26 1 .87 1.75 1.68 1.70

0.31 0.33 0.29 0.28 0.30 0.29 0.28 0.30 0.25 0.27 0.28 0.29 0.31 0.24 0.31 0.30 0.28 0.30 0.27 0.24 0.24 0.28 0.23 0.29 0.26 0.27 0.28

1.86 1.96 1.81 1.79 1.69 1.75 1.80 1.89 1.63 1.67 1.48 1.53 1.58 1.73 1.33 1.43 1.53 1.63 1.77 1.61 1.66 1.60 1.53 1.63 1.73 1.68 1.69

LSD (0.05) 4.2 2.0 0.40 ns ns (0.01) 5.5 2.7 0.50 ns ns


ASD16 had a mean relative growth rate (R) of 157 mg/panicle per day, compared with 151 mg in CO 41.

Mean relative growth rate was calculated as

K -

ASD16 W 1 = 295(1+e 1.188-0.242t ) -1.852 ( R 2 = 0.960) CO41 W 1 =1.79(1+e 1.259-0.228t ) -2.0 ( R 2 = 0.945)

Rice mutants and their mother cultivars differed in yield potential (see table). IR6, IR8, Bas 370, Jajai 77, Sada Gulab, Sonahri Sugdasi, Pokkali, Lateefy, and DR82 yielded more straw and grain than their mutants. N and P were higher in the parents than in the mutants; K content was variable.

genotypes contributed to increased yield.

The higher N and P content in parent

Developing a functional model of rice panicle growth

R. Sadasivam, C. Kailasam, R. Chandrababu, A. Arjunan, M. Nagarajan, and S. R. Sree Rangasamy, Crop Physiology Department, Tamil Nadu Agricultural University, Coimba- tore, Tamil Nadu, India

We grew short-duration rice cultivars ASD 16 and CO 41 under field conditions using a randomized complete block design with 12 replications during 1988 wet season. The pattern of panicle growth on 60 panicles/plot that emerged on the same day was studied from emergence to maturity. Five panicles per plot were removed 12 times to 30 d after emergence and dry weight recorded.

Panicle development followed a sigmoidal pattern (see figure). Two distinct lag phases, one at the beginning and one at the end of panicle growth, were evident. These two lag phases were separated by rapid linear growth between 3 and 21 d after emergence. We tried

Herbage potential of rice cultivars

T. Kupkanchanakul, B. S. Vergara, and F. T. Parao, Agronomy, Physiology, and Agroecol- ogy Division, IRRI

Rice herbage can be an important animal feedstuff: it has high nutritive value, it is readily available in most ruminant production areas, and rice grain yield is not sacrificed by herbage removal. We studied the herbage potential of 20 deepwater and 4 lowland rice cultivars under irrigation at IRRI in the 1989 wet season.

Panicle growth in rice cultivars, Coimbatore, India, 1988 wet season.

several growth equations: Richard's rice cultivars. The Richard’s equations of function, logistic function, nonlinear panicle growth follow: function, and negative exponential function.

Type of function Functional form R 2 value

ASD16 CO 41

Richard’s function W 1 = (1+e b-kt ) -1/n 0.960 0.945 Logistic function W 1 = (1+e b-kt ) -1 0.863 0.810 Nonlinear function W 1 = (a+bt) -1 0.780 0.693 Negative

exponential W 1 = ae -b1 0.632 0.542 function

R= (n + 1)

(Suggested by D R Causton and J C Venus [1981])

Richard's function gave the best fit to The biochemistry of plant growth. describe panicle growth in short-duration Edward Arnold, London. p. 92.)

The experimental field was plowed twice. Fertilizer was incorporated basally at 60-40-40 kg NPK/ha 1 d before transplanting. Twenty-day-old seedlings were transplanted at 20- × 20-cm spacing with two seedlings/hill. Herbage was cut at the collar level of the last fully developed leaf 40 d after transplanting (DT) and from different plots at 60 DT. Treatments were repeated three times.

Differences in growth and herbage yield were observed at 40 and 60 DT (Table 1). There was a positive relationship between herbage yield at 40 and 60 DT ( R = 0.595**). Deepwater cultivars Khao Mali, Pan Tawng, Khao Lod

Chong, and Khao Praguad gave high herbage yields, similar to lowland cultivars; Khao Puang Nak, Pin Gaew 56, Ban Daeng, Plai Ngahm, and Sai Bua gave poor herbage yields.

Herbage yields from one cutting were more than 1 t/ha at 40 DT and about 2 t/ ha at 60 DT, suggesting the potential production of rice herbage as animal feed.

Simple linear correlation analysis showed highly significant positive rela- tionships between herbage yield and growth parameters (Table 2). The relationship of herbage yield with sheath and culm weight was high at 40 DT, but


very low at 60 DT. There was no relationship between plant height and herbage yield at 40 DT and a negative association at 60 DT (the sheath and culm became the dominant plant part as rice plants grew taller, especially in tradi- tional tall cultivars).

High herbage yields can be obtained from rice varieties with vigorous growth during vegetative stage. Cultivar differences should be considered in herbage production.

Table 1. Herbage yield at 40 and 60 DT of 24 rice cultivars grown with irrigation. IRRI, 1989 wet season.

Herbage yield (t/ha)

40 DT 60 DT Rice cultivar

Deepwater rice Ban Daeng 0.82 1.39 Huntra 60 0.88 2.00 Khao Hoi 0.74 1.59 Khao Kaset 0.84 1.53 Khao Lod Chong 1.05 1.95 Khao Mali 1.14 2.06 Khao Praguad 1.10 1.89 Khao Puang Nak 0.66 1.38 Khao Rachinee 0.93 1.88 Leb Mue Nahng 111 0.88 1.56 Luang Pratharn 1.11 1.76 Mali Tawng 0.93 1.59 Nahng Khiew 0.93 1.47 Pan Tawng 1.21 1.98 Pin Gaew 56 0.84 1.25 Plai Ngahm 0.83 1.38 RD19 0.91 1.65 Sai Bua 0.93 1.29 Sam Ruang 0.83 1.39 Tapow Gaew 161 0.88 1.83

Lowland rice B4259 1.16 1.98 Binato 1.20 H4 1.32 1.64 IR29723-143-3-2 0.90 1.78

LSD (0.0.5) 0.23 0.44

Table 2. Relationship between herbage yield and growth parameters of 24 rice cultivars at 40 and 60 DT. a IRRI, 1989 wet season.

Parameter 40 DT 60 DT

Active leaves wt

Leaf area index Shoot wt (t/ha) Sheath and culm wt

Dead leaves wt (t/ha) Tillers (no./m 2 ) Tiller wt (g) Root wt (g/m 2 ) Height (cm)

(t/ha)

(t/ha)

+0.948**

+0.714** +0.878** +0.766**

+0.266ns +0.334ns +0.129ns +0.016ns +0.005ns

+0.816**

+0.730** +0.536** +0.137ns

+0.247ns +0.422* -0.283ns

+0.122ns -0.450*

a Significant at the 5% (*) and 1% (**) levels. ns = nonsigni- ficant.


Ratooning ability and potential herbage production from ratoon crops of rice cultivars

T. Kupkanchanakul, B. S. Vergara, and K. Kupkanchanakul, Agronomy, Physiology, and Agroecology Division, IRRI

A rice ratoon crop has high potential for both grain and herbage production. However, most studies on rice ratooning have emphasized grain yield. Using the herbage from a ratoon crop to provide a continuous supply of ruminant feed after harvest of the main rice crop has received little attention.

We evaluated the ratooning ability and potential herbage production from the ratoon crops of 20 deepwater and 4 lowland rices in irrigated fields at IRRI in the 1990 dry season. Cultivars were arranged in a randomized complete block design with three replications.

Main crop straw was cut 15 cm aboveground 7 d after harvest and 60 kg N/ha surface applied. The field was

irrigated to 1-5 cm water depth throughout the ratoon crop.

Of 24 cultivars studied, only 17 produced ratoons (see table). Deepwater cultivars Huntra 60, Khao Rachinee, and Luang Pratharn had very good ratooning ability, similar to that of lowland cultivars.

Plants were sampled 30 and 60 d after ratooning (DAR) and at maturity of the ratoon crop to measure biomass yield (ex- cluding the 15-cm stubble). Deepwater rice cultivars with high ratooning ability showed high biomass yield at 30 and 60 DAR, indicating the potential of a ratoon rice crop as forage during the dry season where natural forage in rice areas is limited.

Cultivars with high ratooning ability also produced higher grain yield, suggesting the potential for grain yield from ratoon crop in areas where water is available.

Herbage and grain production from a ratoon rice crop might be another ap- proach to increasing production, adding crop value, and increasing land use efficiency and farmer income, especially in single-crop deepwater rice areas.

Ratooning ability and production of ratoon crops. IRRI, 1990 dry season.

Ratoon hills Biomass yield a (tha) Grain

30 DAR yield a

60 DAR Maturity (t/ha) Rice cultivar (% of main crop)

Lowland rice B4259 59 1.18 4.89 7.53 2.3 Binato 56 5.44 8.45 2.9 H4

1.41 56 1.29 4.44 9.43

IR29723- 143-3-2 2.3

65 1.48 4.42 8.74 2.6

Deepwater rice Ban Daeng 11 Huntra 60 72 3.30 6.75 10.28 Khao Hoi

2.3 0

Khao Kaset 23 0.80 3.50 6.14 1.6 Khao Lod Chong 20 0.85 3.40 5.35 Khao Mali 10

1.1

Khao Praguad 29 0.65 3.47 9.08 2.0 Khao Puang Nak 9 Khao Rachinee 64 3.30 8.85 9.40 2.7 Leb Mue Nahng III 0 Luang Pratharn 59 1.93 8.80 12.92 2.7 Mali Tawng 0 Nahng Khiew 13 Pan Tawng 43 1.11 4.28 9.25 2.5 Pin Gaew 0 Plai Ngahm 4 RD19 32 0.91 2.43 5.12 1.2 Saibua 0 Sam Ruang 0 Tapow Gaew 161 0

LSD (0.05) 18 1.51 2.70 ns 1.1

a Cultivars with less than 20% ratoons were not sampled.

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- - - -

- - - -

- - - -

- - - -

- - - -

- - - - - - - -

- - - - - - - -

- - - - - - - - - - - -

We screened 20 promising rice cultivars against major diseases prevailing in the Eastern Vidarbha Zone of Maharashtra State for 4 yr (1985-89). Promising high- yielding rices SKL-6, Sye 75, RP4-14, and SKL-6-1-23 were resistant or moderately resistant to blast, bacterial blight, and false smut (see table).

Pest resistance – diseases

Reaction of promising rice cultivars to major diseases in Eastern Vidarbha Zone, India B. G. Patil and P. G. Moghe, Plant Pathol- ogy Department, Punjabrao Krishi Vidyap- eeth, Akola 444104 (MS), India

Resistance c of 4 rice cultures to major diseases in Eastern Vidarbha zone, India, 1985-89.

Reaction Rice culture Duration Yield

Blast a Bacterial blight a False smut (%) (d) (t/ha)

SKL-6 1 1 0.2 115-120 4.0-5.0 Sye 75 2 1 0.4 130-135 4.5-5.5 RP4-14 1 2 0.3 125-130 5.0-5.5 SKL-6-1-23 2 1 0.3 135-140 4.5-5.0

a Scored by the Standard evaluation system for rice.

Evaluation of resistance to blast (BI) in promising rice cultivars B. G. Patil and P. G. Moghe, Plant Pathology Department, Punjabrao Krishi Vidyapeeth, Akola 444104 (MS), India

Screening for Bl caused by Pyricaluria oryzae Cav. in different geographical zones is necessary because of different

physiogenic races and variation in environmental conditions.

vars under field conditions at Sindewahi, Eastern Vidarbha Zone, Maharashtra State.

Resistant cultivars were SKL-6, Pusa 33, and Sye 148-95 in the short-duration group, and RP4-14 and Jaya in the medium-duration group (see table).

We screened 20 promising rice culti-

Reaction of promising rice cultivars to Bl in Eastern Vidarbha, Maharashtra, India.

Score a

Rice cultivar 1985-86 1986-87 1987-88

Mean score 1988-89

Short duration SKL-6 0 0 2 2 1 Nagpur 22 5 4 4 3 4 Tallahmsa 5 5 6 4 5 Ratna 1 3 2 2 2 IR36 2 2 2 1 1.7 Pusa 33 0 1 2 1 1 Sye 148-95 0 2 2 0 1 Tuljapur (check) 7 6 6 5 6

Medium duration Sye 75 2 2 2 2 2 RP4-14 1 1 2 0 1 Jaya 0 2 1 1 1 Sye 14-65-11 5 4 4 3 4 SKL 6-1-23 2 2 2 2 2 Sye 88-13-3-31 2 2 5 4 3.2 CR400-5 (check) 9 7 6 6 7

Long duration Pankaj 3 3 4 2 3 Jagannath 2 2 3 2 2.2 Chinoor 4 3 4 3 RTN68

3.5 3 2 2 2 2.2

Isha (check) 7 5 5 5 5.5

By the Standard evaluation system for rice.

Evaluation of rice germplasm for resistance to grassy stunt virus (GSV) R. Devika, N. R. Bai, A. Regina, and C. A. Joseph, Rice Research Station, Kerala Agri- cultural University, Moncompu, India

GSV is a serious constraint to rice production in the Kuttanad area of Kerala, India. Severe yellowing and stunting were observed in 1988 wet season (kharif) (May-Jun to Aug-Sep). All varieties grown were affected to some degree. Serological tests at Directorate of Rice Research, Hyderabad, confirmed the presence of GSV.

We evaluated 362 rice accessions, including local varieties, under this heavy natural incidence. Each accession was planted in 2-m rows at 20- × 15-cm spacing and disease scored at panicle initiation.

sistant to GSV; 15 were local and the remaining improved cultivars (see table).

Thirty accessions were moderately re-

Rice cultivars with moderate resistance to GSV. Kerala, India, 1988 wet season.

Variety Damage

score a (0-9)

Nampiaparamban 10 Nampiaparamban 133 Navara Thonnooran Pokkali 372 Nanthiyar vattom Vasaramundan Malakkaran Chettiviruppu-Vettackal Anakkodan Ptb 23 (Cheriya Aryan) Athikira mundakan Ponnaryan Mundakan (D) Kuruka ARC6650 ARC 10550 Culture 74 IR42079

K332 IR42076

RP2547-988

RP1579-1367-68 KAU24-79-2 IET6315 IR24

Intan V643 IR42 TN1 susceptible checks IR50

KAU 1533-2

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 3 4 4 3 3 3 4 9 9

a By the Standard evaluation system for rice.


Pest resistance — insects

Development of a brown planthopper (BPH) biotype and change in varietal resistance in Mekong Delta

Luong Minh Chau, Plant Protection Depart- ment, Cuu Long Delta Rice Research lnstitute (CLRRI), Omon, Haugiang, Vietnam

In 1988 wet season, we collected three new BPH Nilaparvata lugens Stal populations developed from BPH biotype 2 on rice variety OM80 at Omon district, northern Haugiang Province, and on IR64 at Chauthanh and Phutan districts, central and northeast Angiang Province, in the Mekong Delta. IR64 (or OM89) was introduced to farmers in 1983 and OM80 in 1984. Their BPH resistance was broken by a new BPH population in 4-5 yr.

We tested for biotype identification and screened varieties by the standard seedbox test. Test lines were sown in 20- cm-long rows at 30 seeds/row in 60- × 40- × 10-cm wood seedboxes filled 5 cm deep with fine soil, in a randomized complete block design with three replications.

ing with second- to third-instar BPH nymphs at 5-8 nymphs/plant. Damage was scored when 95% of susceptible check TN1 had died.

Seedlings were infested 7 d after seed-

Varieties with no resistance gene or with Bph 1 gene were very susceptible or

Table 1. Reaction of differential check varieties to new BPH population. a CLRRI, 1988 wet season.

Variety

TN1 IR8 IR28 IR30 lR36 IR38 Ptb 33

Gene for BPH resistance

None None Bph 1 Bph 1 bph 2 bph 2 digenic

Reaction to BPH populations

Chauthanh Phutan Omon CLRRI (Angiang) (Angiang) (Haugiang) (Biotype 2)

9 9 9 9

9 9 9

7 9

7 7 5

7 7 7

7 7

5 3 1 5 3 1 1 3 1

3 1

a Av of 3 replications, by the Standard evaluation system for rice

Table 2. Comparison of reaction of modern varieties to old and new BPH populations. CLRRI, 1988 wet season.

Variety Year Reaction

introduced Old population New population Omon, 1988 Angiang, 1989

MTL 61 (IR19728-9-3-2) 1986 1 MTL 58 (lR13240-108-2-2-3) 1986 3

5 7

OM87-1 (IR31802-48-2-2-2) 1987 1 5 OM86-9 (IR74) (IR32429-47-3-2-2) OM606-1-1-1-1 (IR42/Tran chau lun) OM87-9 (IR31868-64-2-3-3) OM576-18- 1-1 (Hungary/IR42) OM296 (Than nong do/lR48) OM44-5 (OM90/OM80) NN4B (IR42) IR64 (IR18348-36-3-3) lR66 (1R32307- 107-3-2-2) IR68 (IR28224-3-2-3-2)

CR94-12 (resistant check) IR36 (resistant check) TN1 (susceptible check)

IR70 (IR28228-12-3-1)

1986 1989 1987 1988 1989 1889 1982 1983 1986 1989 1989

3 3

0 3

0 5 1 3 1 1 0 1 9

5 5 5 5 3 3 7 5 5 5 5 5 5 9

susceptible to all new BPH populations; BPH virulence appears to have shifted varieties with bph 2 were attacked by the higher than that of BPH biotype 2 in BPH population in Angiang (damage Angiang. rating 5-7) but were still resistant to the Most varieties resistant to BPH bi- BPH population in Haugiang (Table 1). otype 2 were moderately susceptible to Ptb 33 with digenic resistance genes was the new biotype (Angiang population) resistant to all new BPH populations. (Table 2).

Stress tolerance — drought

Genetic variability in midday leaf water potential (LWP) of irrigated rice

M. K. Bashar, R. K. Das, M. A. Islam, and N. M. Miah, Plant Breedinag Division, Bangla- desh Rice Research Institute; and S. Ahmad, CERDI, Gazpur 1701, Bangladesh

In rice, midday LWP falls, even in irrigated rice, because of a lag between water absorption by roots and transpira-


tion through the leaves. This indicates that midday LWP may be a criterion to use in selecting for drought resistance.

We grew six advanced upland breeding lines and two varieties under irrigated field conditions in 1988 dry season to evaluate genetic variability in midday LWP.

out in a randomized complete block design with three replications. At maximum tillering, the LWP of 10

Experimental 5- × 5-m plots were laid

penultimate, fully expanded leaves of each variety in each replication were measured at 1200- 1 300 h under clear skies, using standard pressure chamber technique.

Differences among varieties were significant (see table). The highest LWP was in BR4290-3-1-10, the lowest in BR4290-3-3-5. The differential LWP observed suggests that LWP may be used as a drought resistance selection criterion.

-

Leaf water potential (LWP) of upland rice breeding lines and varieties in an irrigated field in Gazipur, Bangladesh, 1988.

Variety or line LWP (MPa)

BR4290-3-1-10 - 0.75 BR4290-3-3-5 - 1.24 BR1888-29-2-2-3 - 1.00 BR1888-29-2-3-4 - 1.00 BR1890-12-2-1-1 - 1.11

BR20 - 0.90 BR21 - 0.92

BR1890-1-1-1-2 - 1.14

F-test 184.42** LSD (0.05) 0.04

Stress tolerance — excess water

Germination and seedling development of floating rice at different soil moisture regimes

K. Kupkanchanakul, B. S. Vergara. and T. Kupkanchanakul, IRRI

Farmers usually dry seed floating rices before the onset of monsoon rains. In cer- tain years, when the monsoon is early, dry seeding is not possible. Also, dry seeding is followed by drought, and farmers may have to replant a wet seeded rice.

We studied germination and growth of floating rice under different moisture regimes at crop establishment. Dry seeds and pregerminated seeds of Pin Gaew 56, a Thai floating rice, were planted at 100 seeds/tray in 25- × 33- × 10-cm plastic trays filled with 7 kg Maahas clay soil. Four soil moisture regimes were applied, with three replications (see table).

The pregerminated seeds emerged first. However, differences in percentage

Emergence of Pin Gaew 56 seedlings under different soil moisture regimes. a IRRI greenhouse, 1990.

Emergence (%) at 7 DAS

Dry seed Pregerminated seed Soil moisture

Field capacity 98 a 98 a Saturated 95 ab 95 ab 2 cm clear water 67 c 87 b 2 cm muddy water 71 c 74 c

significantly different at the 5% level by DMRT.

of emergence between dry seeds and The effects were more-pronounced in pregerminated seeds 7 d after sowing seedlings from dry seed than from (DAS) were small. Field capacity and pregerminated seed. Muddy water at saturated soil moisture favored seedling seeding did not have much effect on emergence. As little as 2 cm excess water growth and development at later stages significantly decreased emergence. because the water cleared within 24 h. Pregerminated seeds emerged poorly in The results indicate that field capacity muddy water. or saturated soil moisture regime is favo-

Growth and development were rable for germination, growth, and devel- vigorous at field capacity and at satura- opment of both dry and pregerminated tion (see figure). However, seedlings seeds. Broadcasting dry seeds of floating from pregerminated seeds tended to grow rice is recommended, but pregerminated and develop better in saturated soil than seeds could be an alternative in very wet at field capacity. Standing 2-cm-deep wa- or extremely low areas where rainwater ter significantly retarded seedling growth accumulates during sowing. and development.

Shoot and root dry weight of rice seedlings germinated under different soil moisture regimes. IRRI greenhouse, 1990.

Stress tolerance — adverse temperature

Screening rice cultivars at reproductive stage for low

provement Programme (NRIP), Par- temperature tolerance in wanipur; Department of Agricultural western Nepal Botany (DOAB); and local germplasm

were from IRRI; the National Rice Im-

collected from 1,000-2.300 m altitudes in the western hills.

In 1987, the materials were evaluated at Tapu (1,000 m), Lumle (1,400 m), and

B. R. Sthapit, Crop Science Section, Lumle Agricultural Centre, P.O. Box No. I, Pokhara, Kaski, Nepal

Injury due to low temperature is a major constraint to improvement of rice production in the 1,000-2,000 m high areas of Nepal. No improved variety has yet been developed for elevations above 1,400 m.

In 1987 and 1988, we evaluated rice cultivars at three altitudes. The materials

Chhomro (2,000 m) to identify varietal differences in low temperature tolerance and altitude and the highest limit of varietal adaptation. In 1988, materials identified as promising from the 1987 trials were assessed at Tapu. Sera (1,250 m), and Lumle. Test cultivars were planted in rows in 1.2-m 2 plots, at 20- ×


a In a column, values followed by a common letter are not

20-cm spacing. Low temperature tolerance was measured in terms of spikelet sterility and yield. No serious stress was observed before the preanthe- sis period.

The 1987 yields showed strong varietal differences with altitude. Eleven genotypes produced grain at 2,000 m (Table 1). At 1,400 m, 17 genotypes produced grain. Minimum (night) temperatures ranged from 12.9 to 16.9 °C and maximum (day) temperatures from 23.5 to 23.9 °C. Water temperatures of the higher altitude sites were cooler (18.5- 22.1 °C) than water temperatures at 1,000 m (23.9-25.3 °C) at anthesis. Water tem-

perature at anthesis at the 1,000-m site appears to be warmer than the critical limit for low temperature stress-induced sterility. We believe sterility and poor yield performance were associated with low temperature stress.

Yields in 1988 were higher than in 1987 (Table 2). Fifteen varieties produced some yield at 1,400 m. Spikelet sterility in these cultivars was low. Six exotic lines also showed some low temperature tolerance. But at 1,400 m, more than half the varieties evaluated failed to set grain.

We think the better performance of most of the low temperature-tolerant

Table 1. Performance of low temperature-tolerant rice cultivars at 3 altitudes (1000-2000 m). a Nepal, 1987.

2000 m 1400 m 1000 m

Cultivar Grain Spikelet Grain Spikelet Grain yield

Spikelet sterility yield sterility yield sterility

(t/ha) (%) (t/ha) (%) (t/ha) (%)

Ghandruk local 6.0 Himali Marshi 4.8 Ghara Local 4.0 Chhomro local (check) 3.7 Kalo Dhan 2.7 Banahun local 1.8 Seto Bhakunde 1.6 RP1442-8-2-1-2 1.2 Jumli Marshi 1.2 NR 1066-1 0.8

(NRCTN, 1987 b ) (0-6) (n = 110)

1 1 1 1 5 3 5 7 7 7

( 1-9)

2.4 1 2.5 1 3.7 1 3.2 3

2.4 1 2.3 5

9

(0-3.7) (1-9)

3.2 1.3 2.9 0.5 6.8 3.2 2.9 3.2 0.5 0.5

(0.5-8.3)

1 1 1 1 1 1 1 1 1 1

(1-5)

a Gram yield adjusted to 12% moisture. b Spikelet sterility at growth stage 8-9 rated by this scale: 1 = <1%, 3 = 1-5%, 5 = 5-25%, 7 = 25-50%. 9 = 50-100% spikelet sterility. c National Rice Cold Tolerance Nursery.

Table 2. Performance of low temperature-tolerant rice varieties at 3 altitudes. a Nepal, 1988.

1400 m 1250 m 1000 m

Genotype Grain Spikelet Grain Spikelet Grain Spikelet yield sterility sterility yield (t/ha)

yield (%) (t/ha) (%) (t/ha)

sterility (%)

Chhomro local (check) 7.6 1 3.7 1 2.5 1 Ghara 6.1 3 2.6 1 2.0 1 Himali Marshi 6.0 1 5.0 1 1.7 1 Banahun local 5.4 1 2.5 1 1 .8 1 NR10073-167-3-1 4.7 3 3.6 1 3.1 1 IR8866-393-14-2 4.3 3 5.1 1 4.4 1 IR7167-33-2-3-3 4.0 3 5.1 1 5.5 1

RP1442-8-2-1-2 2.9 3 4.1 1 2.1 1 Raksali (check) 2.9 3 4.6 1 1.7 1 Seto Bhakunde 1.9 7 1.7 1 4.4 1 IR9202-6-1-1 1.9 3 3.5 1 2.0 1 Barkhe-2 1.5 5 1.8 1 3.2 1 Pokhareli Masino 1.4 7 3.4 1 4.2 1 BG400-1 1.0 7 3.1 1 2.5 1

NR15579-24-2 3.3 3 2.2 3 5.2 3

NRCTN, 1988 (0-7.6) (1-9) (1.6-5.5) (1-5) (1.2-5.6) (1-3) (n = 33)

a Grain yield adjusted to 12% moisture. Spikelet sterility (at growth stage 8-9) rated by the scale in Table 1.


varieties at 1,400 m can be associated with the relatively warmer water temperatures at anthesis in 1988 (22.1-2 1.2 °C) than in 1987 (19.0-18.5 °C).

At 1,250 m, 23 genotypes produced some yield. At 1,000 m, almost all varieties showed no symptoms of low temperature stress. Yields of IR7167-33- 2-3-3 and NR15579-24-2 were best at lower altitudes. Varieties that perform better in the high hills (Chhomro, Ghara, Himali, Banahun, Raksali, and Seto Bhakunde) had comparatively poor yields in the lower elevations.

Local varieties Chhomro, Ghandruk, Himali Marshi, Ghara, Banahun, and Seto Bhakunde were identified as having low temperature tolerance. They could be used in breeding programs or extended into areas lacking adapted cultivars.

Integrated germplasm improvement — irrigated

CICA8 and ITA222, new rice varieties for irrigated areas of Mbo Plain in West Cameroon

M. P. Jones and D. Janakiram, National Cereals Research and Extension Project, Dschang; and F. Jeutong and J. A. Ayuk Takem, lnstitut de la Recherche Agronomique (IRA), B.P. 44, Dschang, Cameroon

Mbo Plain, an area of about 30,000 ha, is in the West Province of Cameroon at 700 m altitude. About 10,000 ha are poten- tially suitable for rice cultivation, but only 210 ha are currently under irrigated production.

Major constraints are the disease susceptibility and grain characteristics of the currently grown variety Tainan V.

Although it is susceptible to leaf blast (BI) at early vegetative stages, Tainan V has the ability to recover and yields close to 4 t/ha in farmers’ fields (Table 1). However, its short and bold grain, chalkiness, and cooking quality are not favored by urban consumers, causing difficulty in marketing.

- -

- - - - -

Table 1. Physical and physiological characteristics of IET8717 and Manoharsali. Titabar, Assam, India, 1988.

Character IET8717 Manoharsali

Duration (d) 144 157 Height (cm) 116 Panicles/m 2 271 Grains/panicle 205 1000-grain wt (g) 19.05 Total dry matter at 39.0

maturity (g/hill) Grain yield (t/ha) 5.3 Harvest index 0.55 Postflowering photo- 70.0

synthetic contribu- tion (%)

N content of leaves 1.96 at flowering (%)

Total chlorophyll 4.18 content at flowering (mg/g FW)

Proportion of high- 63.66 50.60 density grain (%)

133 264 132

19.08 45.0

2.7 0.40

48.0

1.72

3.58

K. Chandra, Regional Agricultural Research

initiation. The plants received a basal application of 8.8 kg P as single superphosphate and 16.6 kg K as muriate of potash.

To find varieties with higher yielding ability, B1 resistance, and acceptable grain quality, we have screened more than 6,000 varieties or lines since 1982. Most of the lines rated as resistant or moderately resistant to B1 in other parts of the world were found to be susceptible at Mbo Plain. (Climatic conditions there are highly conducive to Bl.) A few entries, including ITA222 and CICA8, were found to be moderately resistant to both leaf and neck Bl, with consistently higher yields than Tainan V, and superior grain quality (Table 1).

ITA222, a derivative of Mashir/ IET1444 from the International Institute of Tropical Agriculture, has medium duration, medium height, good tillering ability, and an upright flag leaf. Its grains are long, with translucent kernels and flaky cooked texture (Table 2).

CICA8, a derivative of CICA4// IR665/Tetep from Centro Internacional de Agricultura Tropical, is shorter and has a longer growth duration than ITA222 and Tainan V. It has long, slender, translucent grains, which makes it competitive with imported rice in the ur-

Table 1. Yields of ITA222, CICA8, and Tainan V on-station and in farmers’ fields at Mbo Plain, West Cameroon, 1985-88.

Grain yield a (t/ha)

On-station On farm

1985 1986 1987 1988 Mean 1985 1986 1987 1988 Mean

Variety

ITA222 5.8 7.5 5.8 4.8 5.9 5.8 6.1 5.1 4.4 5.4 CICA 8 5.8 5.4 5.8 4.8 5.8 4.8 4.8 4.7 4.4 4.7 Tainan V (check) 8.4 4.1 8.9 4.2 5.6 8.7 8.5 8.8 8.0 8.4 a Mean of 5 on-station and 5 on-farm trials each year.

Table 2. Characteristics of ITA222, CICA8, and Tainan V at Mbo Plain, Cameroon, 1985-88.

Plant Growth Reaction a to

(cm) (d) Leaf blast Neck blast Grain type b Variety height duration

ITA222 95 104 MR MS L/S CICA8 90 111 MR MS L/S Tainan V (check) 108 95 S MR S/B

a By the Standard evaluation system for rice. MR = moderately resistant, MS = moderately susceptible, S = susceptible. b L/S = long and slender, S/B = short and bold.

ban market. CICA8 was released in 1985 rieties, it shows increasing susceptibility to replace Tainan V and is now widely to leaf and neck Bl. Average Bl scores for grown at Mbo Plain. CICA8 and ITA222 were 5.5 and 4.5,

ITA222 is in the pipeline for release, respectively, in 1988 compared with 3.0 but like CICA8 and other promising va- in 1986.

Integrated germplasm improvement – rainfed

IET8717, a physiologically efficient rice variety for waterlogged areas of Assam

Station, Titabar 30; and S. C. Dey and Pradip ch. Dey, Crop Physiology and Agricultural Botany Department, Assam Agricultural University, Jorhat 785013, India

IET8717 is a long-duration, high-yielding rice variety developed from TN1/Lua Ngu by the Directorate of Rice Research, Hyderabad, India. It is suitable for waterlogged conditions.

ing long-duration cultivars, and Manohar- sali as check, under continuous waterlogged conditions (30-50 cm water depth) in the 1988 wet season (Jul-Nov). Entries were transplanted at 20- × 20-cm spacing. Forty kg N as urea was applied in three

We tested IET8717 and other promis-

equal splits: 1 d before transplanting, 20 d after transplanting, and at panicle

Duration of IET8717 was 144 d. It had 271 productive panicles/m 2 , with 6.8% tiller mortality. Its grains were medium slender, with white kernels, and 1,000- grain weight of 19 g. Plant height was 115 cm with leaf area index of 6.6 at flowering, and harvest index of 0.55. High postflowering photosynthetic con- tribution (70%) results in higher panicle and grain numbers/m 2 . Yield was 5.3 t/ha (Table 1).

IET8717 has shown high yielding ability and stability for 3 yr (Table 2).

Table 2. Yield of IET8717 and Manoharsali under continuous waterlogging. Titabar, Assam, India, 1987-89.

IET8717 Manoharsali Year

Yield Duration Yield Duration (t/ha) (d) (t/ha) (d)

1987 5.0 144 2.5 162 1988 4.8 144 2.7 163 1989 5.0 143 3.5 163


IET10522, a high-yielding, medium-duration rice for waterlogged conditions

Performance of waterlogging-tolerant cultures at Agricultural Research Station, Thirupathisaram, Tamil Nadu, India, 1987-88 to 1989-90.

Grain yield (t/ha) Dura- Plant Panicle Straw

1987- 1988- 1989- Mean (d) (cm) (no./hill) (g) (t/ha) tion height Panicles weight yield Variety Parentage

G. Nallathambi, S. Sevugaperumal, J. G. 88 89 90 Robinson, and A. S. Mathar, Agricultural Research Station, Thirupathisaram 629901,

IET10522 RP31-49-2/LMN 4.9 4.1 4.2 4.4 140 102 8 IET10205 Manasarovar/CO 14 2.9 3.2 2.4 2.8 130 132

2.19 12.2 7

Tamil Nadu, India IET10207 Manasarovar/CO 14 2.2 2.4 1.8 2.1 138 90 1.08 12.3

7 IET10208 RP31-49-2/LMN 2.9 2.6 2.0 2.5 138 94

0.99 10.0 7 1.20 10.5

In Kalkulam and Vilavancode taluks of H4 3.4 2.2 2.3 2.7 137 92 7 ADT40 Sona/RP6/1 3

1.10 8.4 3.6 3.4 3.1 3.4 138 97 8

Kanyakumari district, nearly 10,000 ha of CO 42 RP31-49-2/LMN 3.5 3.5 2.9 3.3 139 119 1.38 10.0

8 1.17 9.3 ricefields are waterlogged in both the wet LSD (0.05) 0.6 0.5 0.4 0.5 1.1 and dry seasons. Standing water depth ranges from 15 to 30 cm throughout the 3-m plots, with 20- × 10-cm spacing, in a Mean grain yield was 4.4 t/ha. Yields cropping period. randomized block design with three were 29.5 and 33.8% higher than yields

We evaluated four deepwater rice replications. The nursery was raised in of ADT40 and CO 42, respectively. cultures and medium-deep varieties Sep and transplanting was in Oct. IET10522 is medium tall, nonlodging,

to 1989-90. The trial was laid out in 4- × found promising in all 3 yr (see table). ADT40, CO 42, and H4 for 3 yr, 1987-88 IET10522 (RP31-49-2/LMN) was with long slender white grains.

CROP AND RESOURCE MANAGEMENT Soil microbiology

Table 1. Root and shoot dry weight of rice grown in sterilized soil with inorganic nutrients and VAM fungi. a

Influence of mycorrhizal association and inorganic nutrients on early growth of rice

S. S. Dhillion, Biological Sciences Depart- ment, Illinois State University, Normal, Illinois 61761, USA; and L. Ampornpan, Biological Sciences Department, Srinakhar- inwirot University, Bangkok, Thailand

We examined the vesicular-arbuscular mycorrhizae (VAM) fungal association of young rice plants and its response to

Root dry weight (g) Shoot dry weight (g)

Without VAM With VAM Without VAM With VAM Nutrient treatment

Phosphorus 1.21 ± 0.31 b 0.44 ± 0.10 a 1.48 ± 0.44 b 0.53 ± 0.12 a Nitrogen 0.74 ± 0.12 a 0.59 ± 0.09 a 0.80 ± 0.15 a 0.58 ± 0.13 a Phosphorus + nitrogen 1.25 ± 0.27 b 0.29 ± 0.15 a 1.28 ± 0.25 b 0.37 ± 0.26 a Deionized water 1.44 ± 0.37 b 0.39 ± 0.23 a 1.42 ± 0.27 b 0.59 ± 0.23 a

a Mean (X ± SD). In a column, means with the same letter are not significantly different by Duncan's mean separation test (p < 0.05).

Plants were watered daily for moisture Table 2. VAM colonization of rice roots grown in conditions similar to those of rice seedlings growing in nonflooded fields.

sterilized soil with inorganic nutrients and VAM fungi inoculum. a

Plants grown in NON-VAM sterilized Nutrient treatment VAM colonization (%)

inorganic nutrients. soil and supplied with P, P + N, and

obtained from the Louisiana State root and shoot dry weights than plants University Rice Research Station grown in soil with VAM fungi and the Deionized water 43.65 ± 11.33

Seeds of rice variety Lebonnet were deionized water had significantly higher Nitrogen Phosphorus 29.76 ± 9.87 a

32.00 ± 6.53 a Phosphorus + nitrogen 27.83 ± 7.10 a

(LSURRS). VAM fungal inoculum (rice roots and rhizosphere soil) was obtained by growing rice plants in soil from LSURRS.

Plants were grown to the early growth stage (50 d) in sterilized soil with mycorrhizal (VAM) and without mycorrhizal (NON-VAM) propagules and supplied with 2.5 ml of nutrient solution at 160 µg/g (nutrient availability after application = 11.2 µg/g) applied every 7 d. Nutrient treatments were P, N, P + N, and deionized water (control).

same nutrients (Table 1). There were no differences between the plants supplied with N alone, with or without VAM.

water had significantly higher fungi colonization than all other treatments (Table 2).

supplied with P, P + N, and deionized water had significantly lower root and shoot biomass than plants grown in soil without VAM but with the same nutrients. In the NON-VAM treatments, plants

Control plants supplied with deionized

Plants inoculated with VAM fungi and

a Mean (X± SD). Means followed by the same letter are not

0.05). significantly different by Duncan's mean separation test (p <

supplied with P and P + N did not differ in biomass from those grown with only deionized water. This may be due to the availability of nutrients upon soil sterilization.

The results of the VAM treatments suggest that colonization by VAM fungi may be a carbon drain on the plant. However, this may be true only during


–

early growth of rice (land not flooded), when VAM fungi are colonizing young plants not yet fully established. It is possible that older, established rice plants in flooded fields may show a different response to VAM fungal colonization.

In all cases where nutrients were supplied, colonization of rice roots was significantly lower than that in roots of plants supplied with deionized water. It is

possible that higher availability of nutrients to plant roots depressed VAM fungal colonization. Other studies have suggested this depression in colonization may be due to the reduction of exudate leakage and/or the greater availability of inorganic nutrients in the rhizosphere.

The high biomass of plants in the deionized water treatment may be due to

Physiology and plant nutrition

Effects of paclobutrazol and KH 2 PO 4 on rice seedlings and grain yield

We evaluated the effect on yield of applying Pac alone and in a mixture with KH 2 PO 4 to rice seedlings. All treated

Guang Jian Liang, Biology Department, Xijiang University, Zhaoqing, P.O. Box 526061, China

plants were shorter, had wider seedling base, and more tillers than untreated controls.

Pac alone did not increase the height Paclobutrazol (Pac) treatment reduces of the first tiller, production of new roots rice seedling height in summer and after transplanting, yield components, or lodging in autumn, but does not signifi- yield. Pac plus KH 2 PO 4 , however, cantly increase yields. increased first tiller height and new root

Table 1. Effect of paclobutrazol and KH 2 PO 4 application on rice seedlings. Zhaoqing, China, 1988-89 early season.

Seedlings Treatment 1st tiller New

Height Base Tillers length roots a

(cm) width (no./seedling) (cm) (no./plant) (mm)

Control 270 ppm Pac 270 ppm Pac + 30 ppm KH 2 PO 4

LSD (P = 0.05)

Control 270 ppm Pac 270 ppm Pac + 30 ppm KH 2 PO 4

LSD (P = 0.05)

32 27 29

2

28

25 24

2

Shan You 2 4.0 4.5 5.8 0.6

Shan You 63 3.6 4.5 5.4 0.6

0.6 2.0 2.5 1.1

2.3 3.0 3.8 1 .0

15.0 17.5 22.0

3.0

11.5 12.5 19.2 3.0

3 4 5 2

4 5 7 2

a Measured 5 d after transplanting.

Table 2. Effect of paclobutrazol and KH 2 PO 4 application on grain yield and yield components. a Zhaoqing, China, 1988-89 late season. a

Panicles Filled grains 1000-grain Yield Treatment (no./m 2 ) (no./panicle) wt (g) (t/ha)

Shan You 2 Control 297 106 27.0 270 ppm Pac

8.5 296 105 27.6 8.6

270 ppm Pac + 30 ppm KH 2 PO 4 306 108 28.0 9.2 7.5 4.0 0.9 0.4 LSD (P = 0.05)

Control 292 116 270 ppm Pac 295 114

28.1 9.5

270 ppm Pac + 30 ppm KH 2 PO 4 300 29.0 10.6 28.2

122 9.2

7.8 4.2 0.8 0.4

Shan You 63

LSD (P = 0.05)

Fertilized with 225 kg N, 66 kg P, 149 kg K/ha.

higher VAM fungal colonization in this treatment.

This study suggests that VAM fungi may have a detrimental effect on early growth of rice, reducing establishment. This relationship may change as rice plants grow and become better established. The significance of the roles of VAM fungi and inorganic fertilizer needs further investigation.

number (Table 1), thereby increasing the capacity for absorption of mineral nutrients.

As a result, panicle number, filled grain number, and 1,000-grain weight increased.

Shan You 63 yielded 10.6 t/ha in the late season (Table 2), a new record in a 200,000-ha area of Zhaoqing.

Fertilizer management

Effect of straw + (NH 4 ) 2 SO 4 application on rice

Jian Luo and Zhi-wu Huang, South China Agricultural University, Guangzhou 510642, China

We studied the influence of C:N ratio and preflooding on rice growth and production when rice straw was applied with (NH 4 ) 2 SO 4 in a greenhouse pot experiment, 1988 late season.

Pearl River alluvial soil (medium loam, pH 6.5, 0.15% total N, 2.5% organic C, CEC 14 meq/100 g soil) was air dried and screened, and placed in pottery pots at 5 kg/pot. Superphosphate (5.0 g/pot) and KCl (2.0 g/pot) were basally applied. Rice straw (0.72% total N, C:N ratio 53) of 0, 9.8, 37.3, and 127.1 g, respectively, needed to establish 0, 10, 25, or 40 C:N ratio was thoroughly mixed with the soil. N (300 mg) as (NH 4 ) 2 SO 4 solution was banded 5 cm deep into each pot in an 8-cm-diameter circle. The pots were preflooded at 2, 4, or 6 wk, and 9 seedlings/pot transplanted. The experiment was laid out in a completely randomized block design.

on tiller number, panicle dry weight, or Preflooding had no significant effects


Table 1. Effect of C:N ratio and preflooding on panicle number and rice yield. a Guangzhou, China, 1988.

Panicle Dry matter (g/pot)

Straw Panicle C:N ratio no.

Preflooded 2 wk 0 31 a 63 b 33

10 28 b 65 ab 29 25 23 c 45 c 29 40 9 d 16 d 3

Preflooded 4 wk 0 29 ab 72 a 21

10 25 c 63 b 22 25 24 c 51 c 21 40 10 d 16 d 6

Preflooded 6 wk 0 31 a 67 ab 23

10 27 bc 61 b 23 25 23 c 45 c 28 40 10 d 15 d 10

a In a column, means followed by the same letter are not significantly different by DMRT, P = 0.05.

straw yield (Table 1). Significant differences in tiller number and straw yield occurred with C:N ratio treatments (Table 1, 2).

With a C:N ratio of 25, tillers were fewer than those with no added rice straw and with a C:N ratio of 10, but more than those with a C:N ratio of 40.

The panicle number at harvest and straw dry weight were significantly lower with increased C:N ratios (Table 1).

Panicle dry weight did not differ significantly among C:N 0, 10, and 25 treatments, but was much lower with C:N 40.

Adding large quantities of rice straw appeared to reduce the efficiency of applied N. Preflooding did not change this effect. At C:N ratios above 10, mi- croorganisms and rice plants may compete for available N as organic materials decompose.

Table 2. Effect of C:N ratio on rice tiller number at 2-15 wk after transplanting. a Guangzhou, China, 1988.

Tillers b (no.) C:N ratio

3 4 5 6 7 9 11 13 15

0 6.0 a 24.8 a 27.9 a 32.4 a 33.4 a 31.6 a 24.6 a 22.6 a 22.1 a 10 5.7 a 24.3 a 28.8 a 31.4 a 31.4 a 29.8 a 20.8 b 18.7 b 17.2 b 25 4.0 b 19.7 b 22.6 b 25.7 b 25.9 b 24.3 b 17.7 c 15.0 c 14.7 c 40 0.3 c 2.2 c 1.8 c 2.9 c 2.9 c 2.8 c 1.7 d 1.8 d 1.9 d

a In a column, means followed by the same letter are not significantly different by DMRT, P = 0.05. b No tillers appeared at 2 wk after transplanting.

Crop management Effect of seedling age on growth and yield of T. aman

Effect of cultural practice for We compared five cultural practices rice semideep water rice on yield and net income

C. Singh, O. P. Singh, R. A. Yadav, and R. S. Singh, N.D. University of Agriculture and Technology, Crop Research Station, Chugharaghat, Bahraich 271901, UP, India

Poor crop stands due to low seeding rates, poor germination under premature flooding, high seedling mortality, and inadequate and untimely fertilizer application result in low productivity of direct seeded rice grown in semideep water.

during the 1988 and 1989 wet seasons (see table). The trial was laid out in random block design with four replications. Soil was clay loam with pH 8.2, 0.53% organic C, 10 kg P, and 234 kg K/ ha. Rice cultivar Madhukar was seeded at 100 kg/ha. Maximum water level was 65 cm in Sep 1988 and 59 cm in Oct 1989.

Crops direct seeded at 100 and 150 kg/ha with recommended fertilizer (40 kg N + 8.8 kg P/ha) before the onset of monsoon had the highest yields. Their gross income, net return, and benefit:cost ratio were also the highest.


M. A. Mannan and S. B. Siddique, Bangladesh Rice Research Institute (BRRI), Gazipur, Bangladesh

We evaluated growth and yield of 30-, 40-, and 60-d-old seedlings of rice varieties BR11, BR22, BR23, and Nizersail during 1988 T. aman season at BRRI, Joydebpur. Test plots were transplanted 15 Sep.

Tiller and panicle numbers did not differ significantly with seedling age in BR11 and Nizersail (see table). In BR22, seedling age was inversely related to tiller and panicle numbers. With 60-d-old seedlings, BR23 had the lowest tiller

Effect of cultural practices on yield and net income at Ghagharaghat, U.P., India, 1988 and 1989 wet number but the most panicles. Grain seasons. yield, however, was no higher than at

Grain yield Gross income Total Net income Net income/ other seedling ages, probably, because (t/ha) ($/ha) cost ($/ha) $ invested late tillers increased competition for

All the varieties are photoperiod

Treatment a (US$/ha) 1988 1989 1988 1989 1988 1989 1988 1989 nutrients.

FPOF 1.2 1.4 154 178 134 20 44 0.15 0.32 FPWF 1.5 2.0 193 257 162 31 95 0.19 0.58 sensitive so days to flowering and DSNS 2.4 2.9 309 377 168 141 209 0.84 1.24 maturity of the different seedlings were DSES 2.8 3.4 360 436 181 179 255 0.99 1.40 DSPI 2.1 2.3 263 292 193 70 99 0.36 0.51 similar.

a FPOF = farmer’s practices without fertilizer (direct sown with onset of monsoon) - check. FPWF = farmer’s practices with fertilize r seedlings of BR23. (40 kg N + 8.8 kg P/ha) - direct sown at onset of monsoon. DSNS = direct sown with normal seeding rate (100 kg/ha) and 40 kg N + 8.8 kg P/ha in well-prepared field before onset of monsoon. DSES =direct sown with 150 kg seed/ha + 40 kg N + 8.8 kg P/ ha in well-prepared field before onset of monsoon. DSPI = dry sowing with 40 kg N + 8.8 kg P/ha and presowing irrigation o n

lings had no significant effect on grain 15 May; crop was grown with supplementary irrigation till onset of monsoon. yield of BRl1, BR22, or Nizersail. These

LSD (0.05) 0.5 0.1 Grain yield was highest with 45-d-old

Transplanting 30- to 60-d-old seed-

- - - - - - -

Effect of seedling age on yield components of T. aman rice varieties. a BRRI, Joydebpur, Bangla- desh, 1988.

Seedling age (d) BR11 BR22 BR23 Nizersail

Tillers (no./m 2 ) or 25 DT 30 205 a 221 a 194 a 259 a 45 207 a 150 b 180 a 279 a 60 187 a 135 b 99 b 255 a

Panicles (no./m 2 ) at harvest 30 216 a 246 a 191 b 308 a 45 238 a 230 ab 205 b 308 a 60 219 a 206 b 236 b 310 a

30 Flowering (DT)

65 56 60 55 45 67 55 58 55 60 67 53 57 53

Duration (DT) 30 94 87 89 84 45 93 85 88 82 60 93 83 86 81

Grain yield (t/ha) 30 3.1 a 3.0 a 3.8 a 2.9 a 45 2.5 a 3.1 a 4.1 a 3.2 a 60 2.6 a 3.4 a 2.3 b 2.8 a

a In a column, means followed by the same letters are not significantly different at the 1% level. DT = days after transplanting.

varieties are recommended for areas where planting 45 d after sowing cannot be guaranteed.

Effect of summer plowing on N volatilization and rice yield in sandy loam soils T. Lakshminarayanan, T. Ramalingam, S. P. Mustafa, P. Singaravelu, M. SheikDawood, and V. S. Shanmugasunduram, Soil and Water Management Research Institute, Thanjavur, India

Farmers in Thanjavur district think summer plowing results in poor establishment of rice seedlings, loss of soil N (by volatilization), and loss of yield.

plowing on yield in a split-plot design on sandy loam "New Delta" soil of Cauvery Delta. Treatments were four tillage methods and three levels of N (see table).

N volatilization in all plots was monitored for 24 d. Volatilization from summer-plowed plots (141 g/ha per d) was 4 times higher than from conventionally plowed plots (32 g/ha per d).

Seedling establishment and water requirement did not vary appreciably among tillage treatments (see table).

We studied the effect of summer

Grain yield averaged over all N treatments was not significantly affected by tillage, but increased as N increased from 100 to 150 kg N/ha. This response was greatest (about 2 t/ha) with summer plowing and no puddling. All treatments

that involved puddling gave similar yields and similar responses to N.

We conclude that when at least 150 kg N/ha is applied, summer plowing (with or without puddling) can be recommended for the sandy loam soils of Cauvery Delta.

Effect of tillage on seedling establishment, water requirement, and grain yield of rice. Thanjavur, India.

Grain yield (t/ha) Seedlings Water at N level of Mean

Tillage method established requirement yield (no./m2) (mm) 100 125 150 (t/ha)

kg/ha kg/ha kg/ha

Conventional puddling 62 648 5.5 5.8 6.4 5.9 (without summer plowing)

Summer plowing without 58 634 4.7 5.8 6.7 5.7 puddling

Summer plowing with one 64 602 5.2 5.7 6.4 5.8 puddling at planting

Summer plowing with two 60 584 5.5 6.3 6.5 6.1 puddlings at planting

Mean 5.2 5.9 6.5 5.9

LSD N level Between 2 tillage practices

at any one level of N Between 2 levels of N at

0.2 0.5

0.5 any one tillage practice

Integrated pest management – diseases

Natural infection of rice yellow mottle virus disease (RYMV) on rice in Sierra Leone

D. R. Taylor, A. S. Fofie, and M. Suma, Rice Research Station, PMB 736, Freetown, Sierra Leone

Occurrences of RYMV in Sierra Leone have increased, particularly in the low- lands. We studied the effect of natural infection on rice variety IR65 in our associated mangrove swamp at Rokupr in the northwest.

Pregerminated seeds were sown in 5- m 2 plots with 20 cm between rows and 10 cm between hills, with three replications.

Fertilizer was applied at 80-40-40 kg NPK/ha, using urea, single superphosphate, and muriate of potash. P was applied basally; N and K were applied in three equal splits at early tillering, maximum tillering, and panicle initiation.

Severe mottling and stunting occurred in two plots; the third plot had healthy plants with no apparent symptoms.

We examined 25 hills randomly selected from each plot.

Natural infection by RYMV disease resulted in 17% stunting, 72% increase in spikelet sterility, 66% increase in grain discoloration, and 82% reduction in yield (see table). Viral infection increased tiller production but did not significantly affect number of panicles/hill.

Effect of RYMV on IR65. Rokupr, Sierra Leone, 1989 wet season.

Plant Tillers Panicles Empty Discolored Yield Yield Hill height (no./hill) (no.hill) spikelets grains (g/hill) reduction

(cm) (%) (%) (%)

Healthy 83.0 9 7 11 17 9.4 Infected 69.3 13 9 83 87 1.6 82

LSD (0.05) 8.3 3.6 ns 12 8.3 2.7


- - -

Effect of urea with neem cake on disease intensity and insect population of rice. a Tamil Nadu, India, 1989- 90.

Disease intensity Insect population Additional Additional Treatment (%) (no./hill) Yield cost b benefit b Benefit:

(t/ha) ($) (%) cost B1 BLS GLH BPH

Urea + neem cake + 8.2 a 13.1 a 6.2 a 16.3 a 5.8 a 12.9 84.0 6.51 pesticides

Urea + pesticides 8.3 a 14.6 a 7.4 a 18.2 a 5.7 a 8.2 51.6 6.29 Urea + neem cake 18.7 b 23.8 b 23.8 b 24.8 b 5.6 ab 4.8 29.9 6.23 Urea alone (control) 20.1 b 34.2 c 34.2 c 42.5 c 5.4 b

a In a column, means followed by the same letter are not significantly different at 5% level. b Cost and benefit were covnvered to US dollars from Indian rupees.

Effect of urea applied with neem cake on disease intensity and insect population in ricefields

R. Viswanathan and K. Kandiannan, Sagayathottam Institute of Agriculture and Rural Development, Takkolam 631151, Tamil Nadu, India

We compared blast (B1) and brown leaf spot (BLS) incidence and green leafhop- per (GLH) and brown planthopper (BPH) populations in farmers' fields where urea with and without neem cake was applied with and without insecticides in two seasons, Sep 1989-Mar 1990.

Rice variety ADT39 was fertilized with 100-50-50 kg NPK/ha. Half the N and all the PK were applied as basal; the remaining N was split-applied during tillering and panicle initiation. Neem cake (20%) was mixed with urea at a 1.5 ratio for all N applications. Monocroto-

phos and edifenphos were sprayed at panicle initiation.

B1, BLS, GLH, and BPH incidence was measured 15 d after panicle initiation (10 sited/0.40 ha). Data from both seasons (Sep-Dec and Dec-Mar) were pooled.

Applying neem cake with urea was no more effective against diseases and insects than pesticide application (see table). But it significantly reduced BLS

intensity and GLH and BPH populations compared with control. Neem cake + pesticide gave higher yields than the other treatments.

The benefit:cost ratio of all treatments was about 6.0. Neem cake can be recommended to minimize disease and insect problems and reduce N loss in rice. In epidemic areas, pesticides can be used to check pests rapidly.

Efficacy of fungicides against enzyme produced by rice sheath blight (ShB) pathogen

R. P. Shukla, R. K. Singh, and R. S. Dwivedi, Laboratory of Plant Pathology, Botany Department, Banaras Hindu University, Vanarasi 221005, India

The pathogenic mechanism of Rhizoctonia solani Kuhn, which incites rice ShB disease, is complex, varied, and inadequately explored. The activity of enzyme tools of the pathogens for causing diseases, however, is known to be affected by different chemicals, including fungicides.

Of the fungicides that have been tested, carbendazim (systemic) was most effective in reducing mycelial growth, production and germination of sclerotia, and lesion length. We studied the effect of this fungicide on the activity of enzymes of R. solani.

Three enzymes—cellulase (Cx), polygalacturonase (endo PG), and protease—were produced in Richard's solution containing 0.5% carboxyl methyl cellulase (CMC) or 0.05% sodium


polypectate as a C source, or 1% casein as a N source. A stock solution of carbendazim (100% active ingredient basis) was prepared in buffer solution at experimental pH levels.

Efficacy was determined by visco- simetric method (Fenske-Ostwald's Viscometer, size-300). Components of the reaction mixture were poured into the large arm of the viscometer at appropriate rates: 1.2% CMC for cellulase, or 1.2% sodium polypectate for PG, or 1% casein for protease; buffer (acetate at pH 5.2 for cellulase and endo PG, or acetate at pH 7.0 for protease); carbendazim. distilled water, and the enzyme source prepared from 8-d-old cultures. Carbendazim from stock solution was added to the viscometer placed vertically in a water bath at 30 °C to give concentrations of 25, 50, and 100 µg/ml. The quantity of the remaining chemicals was substrate 5 ml, buffer 2 ml, and enzyme source 1 ml. Final volume was adjusted to 10 ml by adding distilled water. The efflux time of the reaction mixture for 0, 20, 40, 60, and 80 min was recorded. Autoclaved enzyme was used as control.

Carbendazim significantly reduced the activity of endo PG. Loss in viscosity of

sodium polypectate for 20, 40, 60, and 80 min was 18.5, 24.8, 25.9, and 26.1%, respectively, at 100 µg carbendazim/ml. Maximum inhibition in Cx activity was 16.6, 39.1, and 49.5% at 25, 50, and 100 µg carbendazim/ml, respectively. At all concentrations, carbendazim was effective in inhibiting loss in viscosity of casein. The inhibition of the pectic enzyme (PG) might be due to pectate binding properties; protease activity might be disturbed because the conforma- tion in amino acid sequences might be affected.

The fungicides that affect disease development might be doing so by hindering the activity of the enzymes essential in pathological manifestations induced by biotic agents.

Surveys of disease or insect incidence/ severity in one environment are useful only if the information is related to other variables (e.g., climatic factors, crop intensification, cultivars, management practices, etc.). By itself, information on incidence in one environment does not increase scientific knowledge.

Integrated pest management – insects

Rice grain yield loss due to rice hispa damage P. B. Chatterjee and P. K. Bera, Rice Research Station, P.O. Chinsurah R.S. 712102, West Bengal, India

Rice hispa Dicladispa armigera Olivier appears sporadically in West Bengal ricefields. In favorable years, infestation starts on summer or boro rice and spreads to wetland (aman) rice. In most cases, population buildup and dispersal are aggregated.

We studied yield loss caused by rice

attack, beginning with transplanting in mid-Jan to harvest in Apr. Highly irregu- lar patterns of damage were visible as white lesions in leaves. We marked 10 samples of 1 m 2 each that exhibited 5- 80% leaf area damage. Undamaged samples were also marked. Each sample contained 35 hills.

Individual samples were separately harvested, threshed, and weighed. Yield loss caused by rice hispa in a short- duration variety like IR36 was negatively correlated ( r = 0.9927387**) with increase in leaf area damaged, and correspond-

hispa in an IR36 crop in boro. The crop ingly less grain yield was recorded (see suffered repeated waves of rice hispa figure). grain yield.

Effect of different degrees of rice hispa attack on

Behavior of the wolf spider Lycosa pseudoannulata (Boes. et Str.) W. L. Morrill, Entomology Research Labora- tory, Montana State University, Bozeman, Montana 59717, USA; and E. G. Rubia, Entomology Department, IRRI

L. pseudoannulata is a common spider in wetland ricefields. Unlike other species, the wolf spider can hide under water. We have observed silver bubbles covering the body of a wolf spider under water. Perhaps hairs present all over the body of the spider trap air films for a period of time, allowing the spider to breathe.

We studied the factors that enable L. pseudoannulata to hide under water. A 35-d-old TN1 potted rice plant was placed in a 35- × 25- × 30-cm aquarium half-filled with water and covered with nylon mesh. Spiders at different stages were released one at a time and subjected to the following conditions: light change, splashing water, plant movement. and physical injury.

For light change, the aquarium was covered with black muslin for 5 min, then the cloth was slowly removed. The change from darkness to light did not affect the spiders, except for a female carrying an egg sac and a spiderling (see table). These moved up near the junction of the leaves and stems.

Time spent under water by Lycosa pseudoannulata. a

Time range (min)

Adult Condition

Spiderling Male Female

Light change 0 0 0 Splashing water 0 0 0 Tapping rice plant 0 0 2.35-13.09 Physical injury 1.33-10.15 - 3.25- 8.59

a n=12.

Splashing water on the rice plant caused all spiders to move up and down the rice plant or away from the rice plant, if they were hit by water. This has also been observed in ricefields during spider collection.

Tapping the rice plant caused early- instar spiderlings and newly molted male spiders to move up and down the rice plant or to hide at the base in between tillers. A female spider carrying an egg sac went under water 4 out of 11 times the plant was tapped. Duration of her stay under water ranged from 3 to 13 min.

Pinching a leg using forceps caused a newly molted male and a female with egg sac to go under water for 1-10 min.

The underwater hiding behavior explains why some sampling methods, such as D-vac, are not efficient in collecting the wolf spider in ricefields. Air coming from a D-vac machine

disturbs the canopy and the spiders dive. The FARMCOP sampling device does not disturb the spiders so much, although sometimes we had to wait for spiders to emerge.

Alternate plant hosts of rice leaffolder (LF) L. R. Bharati, Hari Om, and K. S. Kushwaha, Haryana Agricultural University (HAU), Rice Research Station (RRS), Kaul 132021 Haryna, India

LF Cnaphalocrocis medinalis (Guenée) was a minor and sporadic pest in Haryana until 1986. Epidemics occurred in 1987 and 1989 wet seasons.

influence LF number are important in understanding epidemic patterns. It is also essential to establish the relative suitability of wild or cultivated hosts that contribute to LF carryover from Nov to May, when rice is not grown, as a basis for a sound integrated pest management strategy.

The normal cropping pattern in the region is rice - wheat. We found that rice LF could survive winter on wheat. Under fluctuating temperatures in the screen- house (max 23.5 °C and min 8.7 °C with 4-30 °C range) from Nov to the first week of Mar, rice LF completed one generation

Annual or perennial plant habitats that


on wheat. Incubation, larval, and pupal periods lasted 5, 94-96, and 33-35 d, respectively. Total development period from egg to adult emergence was 132- 136 d. Pupation was 30%.

We surveyed rice-growing areas in Sep 1989 to locate other alternate hosts. LF was found on nine host plants of Gramineae family and the order Graminales: Agropyron repens (L.)

Predation of yellow stem borer (YSB) moths by wolf spider E. G. Rubia, L. P. Almazan, and K. L. Heong, IRRI

The wolf spider Lycosa pseudoannuluta Boes. et Strand common in ricefields feeds on a variety of prey, including hoppers, collembolans, flies, and the mirid predator Cyrtorhinus lividipennis. Studies have shown that the spider exhibits a functional response: consump-

Functional response of the wolf spider to yellow stem borer moths. a'= attack rate, Th = handling time.


Beauv., Brachiaria mutica (Forsk.) Stapf., Dactyloctenium aegyptium (L.) Beauv., Digitaria sanguinalis (L.) Scop., D. setigera Roth ex R&S, Echinochloa colona (L.) Link., E. crus- galli L., Saccharum munjo L., and Sorghum halepense (L.) Pers.

All hosts except B. mutica, E. colona, and E. crus-galli were not known before. Larvae were found

tion of prey by individual spiders increases with prey density.

the wolf spider to 1-d-old female YSB moths. Spiders were reared in the laboratory and starved for 3 d prior to the experiment. A spider was released in 19- cm-diam mylar cages containing 1, 2, 3, 5, or 10 moths, with five replications. Three stages of rice TN1 were used as substrates: 13- and 35-d-old plants and rice stubble.

We studied the functional responses of

L. pseudoannulata searched for YSB moths most efficiently on 13-d-old rice plants (see figure). At this stage, there was less foliage and the search area was smaller than on 35-d-old rice plants with more than 10 tillers and denser leaves. It is also possible that moths hide better in 35-d-old plants.

stubble, perhaps because the color of moths and stubble looked similar to the spider.

Moth consumption was lowest on rice

Electroantennogram technique for studying olfactory sensitivity of insects to volatile compounds

R. Ramachandran and Z. R. Khan, ICIPE- IRRI Project, IRRI

Volatile compounds produced by plants or conspecific species may have complex effects on an insect's fitness in a given environment. Host plant-derived volatile compounds may be used by insects to colonize the plant. Compounds produced by conspecifics may be used to locate mates.

Identifying the volatile compounds mediating the interaction between an

feeding on these hosts in and alongside the ricefields. The perennial weed A. repens was most preferred (85% damaged leaves), followed by E. crus-galli, S. halepense, and E. colona. Least preferred hosts were D. setigera, Dactyloctenium aegyptium, B. mutica, Digitaria sanguinalis, and Saccharum munjo (3.7-20.3%).

insect and its environment may have potential in insect management strategies. However, volatile compounds produced by a plant or an insect are numerous (a rice plant may produce as many as 30 to 40 volatile compounds) and often chemically very closely related.

Identifying compounds that are biologically active requires screening a large number of compounds rapidly. Electroantennogram suits this purpose. The technique is based on the principle that biologically active volatile chemicals pass through microtubules on the antenna of the insect and bind with receptor proteins, initiating electrical reactions in the dendrites of the olfactory cells as receptor membrane depolarization.

sum of many olfactory receptor potentials, recorded more or less simultane- ously by an electrode connected to the sensory epithelium of an insect.

The procedure involves connecting the tip and the base of an insect's antenna to a recording and a reference electrode, respectively. The electrodes are connected to an amplifier and an oscilloscope (Fig. 1). The electrodes are silver nitrate-coated silver wires placed inside glass capillaries containing a saline solution (0.1% KCl). Charcoal-filtered air generated by a pump is blown continu- ously over the antenna through a delivery tube.

The olfactory stimulus (pure chemicals applied on filter paper or leaves) placed in a disposable pasteur pipette is inserted into the side of the delivery tube. A calibrated amount of air is passed through the pasteur pipette for a specific period of time (usually 1 s). The air carries the odorant chemicals over the antenna. The electrical signals generated

The electroantennogram measures the

1. Line diagram of a setup for measuring electroantennogram response of insects to volatile compounds.

in the antenna are amplified and dis- concentration of the chemical stimulus played on the oscilloscope. until a saturation level is reached.

The response is usually a negative Although it was thought that the potential. Positive potentials may also be electroantennogram technique did not obtained, however, depending on the permit conclusions about the behavioral chemistry and biological activity of the significance of a compound (i.e., attrac- compound involved (Fig. 2). tant or repellent), results from our

The amplitude of the response, which laboratory and elsewhere suggest that correlates with the frequency of gener- compounds eliciting very high negative ated nerve impulses, increases with potential may be attractant at low con-

2. (a) A typical negative potential elicited in response to stimulation with 1-hexanol. (b) A positive potential elicited in response to thymol.

centrations while compounds eliciting positive potential may be repellents.

We have successfully used electroantennogram technique to study the role of volatiles in the resistance of rice plants to insects, identify rice plant volatiles that are biologically active, and identify pheromones of leaffolders and stem borers.

Density-dependent mortality of rice leaffolder (LF) due to larval parasitization

Guo Yujie and K. L. Heong, Entomology Division, IRRI

LF, a pyralid that feeds on rice leaves, is often attacked by parasitoids. More than 100 species from various regions have been recorded.

We studied the relationship between LF and its larval parasitoids in Victoria, Laguna, and Zaragosa, Nueva Ecija, Philippines, during 1989 wet season. Samples were taken at weekly (in Victoria) and biweekly (in Zaragosa) intervals from 2 wk after transplanting. A sample consisted of 20 hills from 1 m 2 .

All LF larvae collected were placed individually in test tubes and brought to the laboratory for parasitoid emergence.

Mortality due to parasitization was expressed as k-value (a measure of killing power) by function, k = log ( N/S ), where N is total larvae collected and S the unparasitized larvae. Four density dependence models were fitted to the data using PROC NLIN available in SAS.

The models satisfactorily described the data, but the model according to Bellows (1981) provided the best fit. It has the basic form

k = aN b

where a and b are constants. The parameter b determines density dependence.

Results showed that parasitization is directly density dependent. The mortality rate k changes in a negative acceleration as host density increases (Fig. 1).

We further plotted the k values against log host density in a time sequence (Fig. 2). It showed that density dependence was undercompen- sated because slope was 0<b<1. Time lag was important and an anticlockwise spiral was apparent, indicating delayed density dependence.

Stability analysis showed that this relationship will inevitably result in dampening exponential growth of the LF population. Thus larval parasitoids play an extremely important role in checking LF abundance.


1. Plots of k -value against log density of LF larva in Victoria and Zaragosa, Philippines. The solid line is the best fit curve of Bellows’ model: k = aN b .

2. Density-dependent mortality (expressed as k -value) of LF due to larval parasitoids in relation to LF larva density. Data are serially linked to show the delayed density dependence.

Attractiveness of light color to selected predators of rice pests M. L. P. Abenes and Z. R. Khan, ICIPE-IRRI Project, IRRI

Light traps are commonly used to monitor insect pest populations in ricefields. We used different colors of light as attractants to rice insect pests in 1988 wet season in Calauan, Laguna, Philippines.

attracted to white and yellow lights. And light had the same attraction to various beneficial insects.

Four important predators of rice pests— Microvelia sp., Cyrtorhinus sp., Opius sp., and members of Formicidae family—were collected in significantly higher numbers from the white light trap compared to other light colors tested (see figure). Numbers from yellow, ultraviolet, and green light traps were moderate (see table). Even in traps with the least attractive colors of light (violet, blue, red, and orange), the four predator species were collected.

Spectrometric analysis of the light produced by the eight bulbs tested revealed that not one emitted the pure colors visible to the human eye (see table). Different color combinations, from violet to red, ranging from 4,000 to 7,300 Å, produce the eight colors distinct to human vision.

the light emitted by the white bulb contained the most distinct color bands. These bands were contained in a range from 4,100 to 6,300 Å, which could be the most attractive color combination for the predator species observed in the light traps.

The attraction of the four predator species to white light, coupled with studies on actual predator population, natural mortality, and migratory habits could be used in a rice-pest predator monitoring system.

Several insect pests were most

Among the eight colors of light tested

Space limitations prevent IRRN from publishing solely yield and yield component data from fertilizer field trials that are not conducted for at least two cropping seasons or at two differing sites. Publication of work in a single season or at one site is limited to manuscripts that provide either a) data and analysis beyond yield and yield components (e.g., floodwater parameters, microbial populations, soil mineral N dynamics, organic acid concentrations, or mineralization rates for organic N sources), or b) novel ways of interpreting yield and yield component data across seasons and sites.


We measured electroantennogram responses of C. medinalis and M. patnalis to 20 pheromone standards. Ten µl of 5

mg/ml solutions of each pheromone standard were applied on filter paper and allowed to evaporate for 1 min to remove the solvent.

Responses of males of both species to these stimuli were higher for Z11-16:Ac and Z13-18:Ac (Fig. 1). Female moths did not respond.

Dose-response curves indicate that M. patnalis is more sensitive to Z13-18:Ac; C. medinalis is more sensitive to Z11-

16:Ac (Fig. 2). Z13-18:Ac was positively identified in the pheromone gland extracts of M. patnalis.

It appears that both species use both compounds in their pheromone blends. Species isolation is maintained because of different ratios of the compounds in the pheromone blends.

Based on the EAG responses and the GC-MS analysis of crude extracts of M. patnalis pheromone glands, the ratio of Z13-18:Ac and Z11-16:Ac was tenta-

Average weekly catches of predators of rice pests in light traps of different colors. IRRI, 1988.

Selected predators caught in different color light traps. IRRI, 1988.

Visible light Color wavelength

range (A) a Microvelia sp. Opius sp. Cyrtorhinus sp. Formicidae

Insects (no.)/trap per night b

Ultraviolet Violet Blue Green Yellow Orange Red White

4400-7300 4000-5700

4700-6500 5200-6900

4300-7300 4100-6300

4400-5500

5600-6700

10.31 bc 5.12 cd 6.71 cd 9.00 c

14.86 b 4.94 d 3.91 d

30.64 a

7.07 b 4.81 bc 4.46 c 8.30 bc 9.52 bc 1.54 d 1.15 d

13.04 a

3.75 c 3.40 d 1.71 de 4.21 c 7.18 b 1.04 de 1.01 e

26.66 a

39.39 b 24.59 cd 21.99 c 57.34 b 78.72 b 25.58 d 21.05 cd

109.81 a

a Measurements done using a Welch Spectroscope. b Av of catches over a 10-wk period. In a column, means followed by a common letter are not significantly different at the 5% level by DMRT.

Pheromone components of rice leaffolders (LF) Cnaphalocrocis medinalis and Marasmia patnalis

R. Ramachandran, P. Caballero, and Z. R. Khan, IRRI

Space limitations prevent IRRN from publishing solely yield data and yield component data from routine germplasm screening trials. Publica- tion is limited to manuscripts that provide either a) data and analysis beyond yield and yield components (e.g., multiple or unique resistances and tolerances, broad adaptability), or b) novel ways of interpreting yield and yield component data across seasons and sites.


1. Electroantennogram responses of C. medinalis and M. patnalis to pheromone standards. * Indicates a significant higher response.

Integrated pest management – other pests

Correlation between Hirschmanniella oryzae population and rice grain weight

L. Arayarungsarit and S. Junbuathong, Pathumthani Rice Research Center, Thanyahuri Pathumthani 12110, Thailand

We collected 20 plant samples of rice variety RD10 at ripening randomly from the experimental field in 1989 wet season. The number of rice root nematodes Hirschmanniella oryzae extracted from roots was compared with grain weight of each sample.

The correlation coefficient between number of nematodes in 1 g root with 100-grain weight was -0.677. The regression analysis of a linear model for the number of nematodes in roots ( X ) and 100-grain weight ( Y ) was Y = 2.942 - 0.002X (see figure).

We also compared the nematode population in 1 g root with plant height. The correlation coefficient was not significant.

2. Dose response curves of C. medinalis and M. patnalis for Z13-18:Ac and Z11-16:Ac.

tively fixed at 96:4 for M. patnalis and studies with different ratios of the two 2:98 for C. medinalis. compounds are needed to determine the

Further analysis of a larger number of blend that is most effective for monitor- pheromone gland extracts and behavioral ing the two LF species.


Estimated regression of grain weight of RD10 because of Hirschmanniella oryzae population under field conditions at Pathumthani Rice Research Center, 1989.** = significant at the 1% level.

Farm machinery

Effect of soil moisture content on tractor wheel slip T. M. Lando, Agricultural Engineering Department, Marcos Research Institute for Food Crops, P.O. Box 173, Ujung Pandang, South Sulawesi, Indonesia

At Pulung Kencana Village, North Lam- pung, the soil is clayey, red yellow Pod- zolic. It is very hard when dry but very sticky when wet. The area is flat and covered by cogon grass Imperata cylin- drica. The cogon grass was cut and burned before the experiment started.

We studied the interaction of soil moisture and plowing depth in a split-plot design with four replications. Treatments were 10, 15, 20, 25, and 30% soil moisture and 10-, 15-, and 20-cm plowing depth. Plowing width was 20 cm and tractor speed during plowing was 5.4 km/ h (1.5 m/s).

tractor IH354, a stopwatch, a soil moisture meter, and a measuring tape. Tractor wheel slip was calculated as

D 1 - D 2 D 1

Equipment used was a 4-wheel 45 hp

S = × 100

Relationship between soil moisture and wheel slip of tractor at 3 plowing depths, South Sulawesi, Indonesia.

where S = wheel slip

tions of tractor wheel (measured on hard soil without plow attached)

tions of tractor wheel in experimental condition

D 1 = distance covered by 10 revolu-

D 2 = distance covered by 10 revolu-

Wheel slip varied significantly with soil moisture and plowing depth (see figure). Wheel slip was lowest with 15% soil moisture and highest with 25 and 30% soil moisture. At 20-cm plow depth,

wheel slip did not significantly differ at 10, 15, and 20% moisture level.

Wheel slip at plowing depths 10 and 15 cm is less at 15% soil moisture than at 10% because of lower draft resistance. (At 10% moisture, soil was harder than at 15%.)

slip tends to increase because of soil resistance as well as the semimuddy condition of the soil.

At 25 and 30% soil moisture, wheel

ANNOUNCEMENT Modeling in agricultural research

An international symposium on Systems approached for agricultural development will be held in November 1991 in Bangkok. The 5-d symposium will focus on food crops, particularly in rice-based cropping systems.

agricultural scientists from developing countries, North America, Australia, and

About 150 senior research leaders and

Europe with interest in systems research, simulation, and modeling are expected to participate.

Papers, posters, and demonstrations will cover genotypic, weather-related, soil, and biological constraints to crop production; farming systems; and training in systems research. For further information, contact Drs. F.W.T. Penning de Vries or P.S. Teng, IRRI, P.O. Box 933, 1099 Manila, Philippines.

New IRRI publications

Review of advances in plant biotechnol- ogy, 1985-88, ed. by A. Mujeeb-Kazi and L.A. Sitch

Annual report for 1988 Research highlights 1989 Climate and food security Dibble sticks, donkeys, and diesels: ma-

chines in crop production, by J.K. Campbell

Publications of the international agricultural research and development centers, 1989

IRRN subject index for 1989 IRRN index of varieties, cultivars and

lines, 1989


international rice research newsletter vol.15 no.5

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