1559 Genetic Resource Enhancement for Fibre traits in Cotton ( Gossypium spp) Through Inter-specific

Hybridization

Dr. Ishwarappa S. Katageri , University of Agricultural Sciences, Dharwad 580 007, India Dr. Basavaraj Khadi , Cental Institute for Cotton Research, Nagpur, India

Mr. Chandrakant Soregaon , Cental Institute for Cotton Research, Nagpur, India Mr. Veeresh Gowda R.P. , Cental Institute for Cotton Research, Nagpur, India

Mr. Shivaprasd U , Cental Institute for Cotton Research, Nagpur, India Mr. Vikrant Deuigi , Cental Institute for Cotton Research, Nagpur, India Ms. Savita Mantri , Cental Institute for Cotton Research, Nagpur, India

Mr. Narayan K , Cental Institute for Cotton Research, Nagpur, India Dr. Patil Shreekant , Cental Institute for Cotton Research, Nagpur, India

Summary

Cotton is an important agricultural commodity, providing income to millions of farmers in industrial and developing countries. Technological changes in the textile industry mean that priorities concerning fibre properties have also changed and cotton breeders have concentrated on improvement in fibre traits to meet the demands of industry. Because of adoption of rotor spinning that converts raw fibre into yarns at a speed of 150 mmin-1 as compared to 20m min-1 of ring spinning, the requirements of textile industries of raw cotton have changed. According to these new norms, fibre strength is a greater determinant of yarn quality. India is the only country where all four of the cultivated species of cotton are grown for commerce. Gossypium hirsutum cultivars and hybrids have been grown to meet the demands of medium to superior medium staple cotton requirement followed by diploid desi cottons, G.arboreum and G.herbaceum, for medium to short staple cotton, while the demand for long and extra-long staple cottons have been met by growing interspecific hybrids (G. hirsutum x G. barbadense: DCH32, Varalaxmi, etc) and G. barbadense cultivars (e.g., Suvin,Sujata). Most of the genotypes popularly under cultivation in all staples of cotton are not meeting the requirement of fibre strength of new industrial norms. We attempted to improve fibre strength of G. hirstum and G. herbaceum through intespecific hybridization and we discuss the results of selections of early and late generations. G. barbadense , G. tomentosum, and G. hirsutum were used as donors in improvement of fibre strength of G. hirsutum where as in herbaceum improvement G. barbadense and G. anomalum were used. Desirable G. hirsutum plants with more than 23 g tex-1 and G. herbaceum with more than 21 g tex-1 fibre strength were developed.

Abstract

We started genetic introgression studies through interspecific crosses viz., G hirsutum x G barbadense, G hirsutum x (Gcot.11 x G tomentosum), G hirsutum x G. hirsutum, G herbaceum x G barbadense, G herbaceum x G anomalum, to improve fibre strength of G. hirsutum and G. herbaceum cottons. Pedigree method of selection from F2 through F8 or limited back cross followed by selection was followed. Observations on fibre traits and seedcotton yield, gin turnout were recorded. The fibre strength varied from 17.6 to 29.9 g tex-1in F8 generation plants of G. hirsutum x G. barbadense cross. The plants with fibre strength more than 23 g tex-1 also recorded 20-75% more seedcotton yield than female parent plants having 18-20 g tex-1 fibre strength. Fibre strength of the male parent was 26-27 g tex-1. All selected plants resembled G. hirsutum. From G. hirsutum x (Gcot.11 x G. tomentosum) crosses, seven F4 plants with more than 23 g tex- 1 fibre strength compared

with 20 g tex-1 of the female parent were observed. All of these produced 44-50 g plant-1 seedcotton, the same as the female parent. Jayadhar, an herbaceum cotton, recorded 22 mm fibre length with 17 g tex-1 fibre strength, 5.0 micronaire and 32 g plant-1 seedcotton. When G. barbadense was used as donar parent, selected plants in BC1F2 , BC2 and F3 recorded 24-32 mm fibre length, 20-27 g tex-1 fibre strength, 2.9-4.5 micronaire and 3-123 g plant-1 seedcotton yield. Observations of F4, BC1F3, BC2 F2, and BC3 of crosses between G.herbaceum x G anomalum indicated that more plants with high fibre strength (> 21 g tex-

1) were found in F4 and BC1F3 generations than in BC3F1 or BC2F2.

INTRODUCTION

Cotton is an important agricultural commodity, providing income to millions of farmers in industrial and developing countries. Technological changes in the textile industry mean that priorities concerning fibre properties have also changed (May and Lege, 1999) and cotton breeders have concentrated recently on improvements in fibre traits to meet the demands of industry (May, 2002). India has a major role in the global cotton with 22.0 % of the world’s production area and 18.3 % of world production at 9.1 million ha and 24.5 million bales, respectively, and an average productivity of 502 kg ha-1 (Anon., 2007). Because of adoption of rotor spinning, which converts raw fibre into yarns at a speed of 150 mmin-1 as compared to 20 mmin-1 of ring spinning, the norms of requirement of textile industries of raw cotton have changed. According to the new norms, fibre strength is a more important fibre attribute. The inherent breaking strength of individual cotton fibres is considered to be the most important factor in determining the strength of the yarn spun from the cotton fibres (Moore, 1996). The fibre properties of the present day cultivars and hybrids of our country are not meeting the requirements of the textile industry. The fibre properties of some of the leading Indian cultivars and hybrids are presented in Table 1 and the new norms of fibre properties are presented in Table 2. The occurrence of this mismatch between required fibre qualities and available fibre properties in the commercial cultivars and hybrids produced in India requires research on elevation of fibre properties to the point that the Government of India launched its Technology Mission on Cotton to improve and enhance cotton trade with particular attention to improving fibre traits of Indian cottons.

Classical breeding studies have shown that fibre properties tend to be moderately to highly heritable (Meredith and Bridge, 1972). Upland cotton, G. hirsutum, dominates the world’s cotton production with 90% share because of their early maturing and high yielding attributes. The second most cultivated species, G. barbadense, has superior fibre length, strength, and fineness, giving higher spinning and manufacturing performance. Both G. barbadense and G. hirsutum arose as interspecific disomic (2n = 52) tetraploids, perhaps monophyletically, along with three other extant species with 52 chromosomes (Cronn and Wendel, 2004). Although the AD genomes of G. barbadense (AD2) and G. hirsutum (AD1) are now extensively diploidized and their plant morphologies quite distinct, the genomes exhibit high meiotic affinity in hybrids and undergo high rates of recombination (Reinisch et al., 1994). Scientists have attempted hybridization between these species to exploit the advantages of both the species at F1 level or deriving lines from selection (Katarki, 1971 and 1981; Katageri and Kadapa, 1989 Khadi, 1996; and Katageri et al., 2003, El-Hattab et al. 1974, Culp and Harrell, 1980, Soregaon,2004, Knight, 1956, Kadapa and Gangaprasad 1965, Arutyunova 1970, Sagidulina 1978, Omel-chenko et al. 1979, Akhmedov et al. 1990). The bidirectional genome exchange between these two species is well documented in these studies. The level of genetic diversity is low in G. hirsutum, especially among agriculturally elite types (Gutie´rrez et al. 2002; Ulloa and Meredith 2000; Wendel et al. 1989). It is true with respect to India also as yield levels are stagnant. Increasing diversity is therefore another essential advantage from such interspecific crosses.

Although introgression of genes across species boundaries is difficult, it is quite desirable because the gene pools of cultivated species do not contain all of the desired alleles. Tanksley and McCouch (1997) have documented that beneficial alleles exist cryptically in wild germplasm. Such studies increase the awareness of the benefits from interspecific introgression projects that target essentially any multigenic trait, irrespective of the performance of the donor species. A good account of distant hybridization in cotton was reported earlier by Richmond (1951) and he indicated that recovery of high fibre strength segregated from a small backcross population during introgression of fibre strength from the triple hybrid Gossypium thurberi x Gossypium arboreum x Gossypium hirsutum as evidence for only a few major genes controlling strength. MD51ne obtained from a cross between G. hirsutum and a wild Hawaiian species (G. tomentosum) has an HVI fibre strength of averaged 30.9 mNtex_1 (Meredith, 1993). Omel-chenko et al. (1979) derived high yielding plants with strong fibre and resistance to sucking pests from interspecific hybridization of cultivars of G. hirsutum (AD1) and G. barbadense (AD2) with G. tomentosum (AD3). Investigations with G. hirsutum x G. tomentosum crosses reported by Dark (1960) with intensive selection over a considerable period by five back crosses produced a genotype with long lint.

Diploid cultivated cotton species G. herbaceum and G. arboreum suitable for 6-22 count yarns have been under cultivation since time immortal in India. However, production of tetraploid cotton has been intensified since 1790 due the superiority of tetraploids over diploids in terms of both seedcotton yield and fibre traits Tetraploids now occupy 70 % of the cotton growing area in India. The remaining 30 % of India’s cotton growing area is suitable for only diploids and the harsh situations. G. herbaceum is suitable for 20s count yarns with ring spinning but they cultivars with low fiber strength will not produce even 20 count. So, improvement of fibre strength and reducing micronaire to 4.0 – 4.5 from above 5.0 is most important and urgent need of breeding program.

G. anomalum, a wild species belonging to the B genome which is nearest to G. herbaceum (Hutchinson and Stephen, 1947 and Gerstel, 1953) and known to be a donor for fiber strength (Saunders, 1961) has been utilized in the present study. Advanced backcross and straight cross derivatives of G. arboreum with G. anomalum showed improvement in fibre weight and strength (Ramachandran et al., 1964). Qian et al. (1992) selected G. hirsutum cv. 86-1 and G. anomalum as the parents in their breeding programme. In over 10 years of breeding and selection, they were able to derive 31 lines with high fibre quality. These included five lines with longer fibre, higher fibre strength, and low gin turnout, and 15 lines with moderately improved fibre length and strength, but with high gin turnout. The lines obtained involved recombination of genes in genomes A2, B1, D1, AD and AD2.. ‘Arogya’ is the recently released G. hirsutum cotton cultivar from CICR, Nagpur for its resistance to bacterial blight and high fibre strength. These two desirable characters were incorporated into upland cotton from G. anomalum (Santhanam, 1997). To transfer fibre fineness characteristic from G. anomalum, Apparthurai et al. (1964) crossed cultivated coarse G. arboreum with G. anomalum. They obtained partially fertile F1 plants which were backcrossed with G. arboreum to produce a fine quality cotton strain in this species. Niu et al. (1998) used two cultivated species (G. hirsutum and G. arboreum), four wild species (G. thurberi, G. anomalum, G. sturtianum and G. bickii) and one semi-wild species (G. mexicanum) to create 76 new germplasm lines of nine types through various methods of hybridization, in vitro culture, selection, identification, and multiplication. These lines have various desirable characteristics including high fibre quality (specifically strength and fineness). They reported that some lines (BZ701 - BZ712) had a span length of 33.4-37.7 mm and some lines (BZ901- BZ903) were very early having a growth period of 100-115 days. The first attempt at the deliberate utilization of G. anomalum to improve the fineness of G. arboreum was that of Afzal et al., (1945). Among the diploid wild species, G.

anomalum (2n=26) possesses extreme fineness and good strength of fibre along with other useful attributes. Iyengar et al. (1958) transferred lint fineness from G. anomalum to Karunganni cotton (G, arboreum). Fully fertile and fine linted plants with a good fiber length were obtained in both the F2 and F3 generations. In selecting the progeny, an optimum standard for fineness was fixed at a mature fiber weight of about 1.50 x 106 gcm-1 and a swollen hair diameter of 20.0 microns. Patel and Desai (1963), with the objective of improving local G. herbaceum types for quality characters, used the Persian-211(G. barbadense) for crossing with improved G. herbaceum strains at Surat and synthetic cultures viz., 1802, 1773, 1777, 1789 and 1799 were derived from the cross (1027 ALF x Per-211) FI x 1627 A.L.F. They possessed gin turnout from 26.1 to 40.1 %, fibre length ranging from 25 to 29 mm but were low in yield in comparison with the local improved strain. They were therefore further crossed with the promising Surat and Buroach types to improve their yield and as a result some of the promising cultures possessing good combination of yield, gin turnout and fibre qualities were obtained. Rajashekar et al., 2003 and 2005 successfully obtained cross between G. herbaceum and G. barbadense. F1 male fertility further helped to derive F2 and back cross progenies.

Handling of interspecific hybrids is a difficult task due to the occurrence of sterility and haploids. Several studies indicated occurrence of haploids in different interspecific crosses (Skovsted, 1935; Kimber and Riley, 1963; Lee, 1970; Thombre and Mehetre, 1979). The degree of interspecific introgression in certain Gossypium hybrid populations is often restricted by genetic breakdown in the F2 and subsequent generations (Stephens, 1949). Interspecific F1 hybrids between G. barbadense and G. hirsutum are often vigorous and fertile, while selective elimination of certain genotypes and aberrant segregation occurs in later generations of selfing or backcrossing. Interspecific derived progeny frequently revert to phenotypes approaching those of the parents. According to Richmond (1951), even though large spectrum of variability can be released in progenies of interspecific cotton hybrids, the majority of the recombinants are ill balanced; genetic differentiation of two genomes and small scale structural differences are considered to be limiting factors in isolating balanced recombinants. Sterility of F2 plants from hybrids obtained by crossing G. hirsutum and G. barbadense may be due to homozygosity of the asynaptic recessive as1 and as2 alleles commonly found in G. hirsutum and G. barbadense (Endrizzi et al., 1984). However with all these problems associated with interspecific hybridization, noticeable success has been achieved by some workers. Harland (1936) indicated the possibility of developing interspecific types with desired features of G. barbadense and G. hirsutum species. Mention may be made of successful development of cultivars, MCU-2 and MCU-3 of interspecific origin in Madras. The former involving hirsutum x barbadense, is the ruling commercial cultivar grown in summer Cambodia tract in Tamil Nadu, while the latter derived from the combination of upland sea island Moco crosses, has shown its adaptability to winter Cambodia tract by virtue of its vigour and tolerance to stem weevil and jassids (Santhanam and Krishnamurthy, 1961). Direct introgression of fibre quality into adapted G. hirsutum from G. barbadense was described by Davis (1978) as a component of parent breeding for hybrid cotton. Stable, near homozygous, progenies were derived from interspecific hybrids of G. hirsutum and other Gossypium spp. that exhibit a wide range of combinations of parental morphological characteristics and fibre quality (Cantrell and Davis, 1993).

G. anomalum belongs to the B genome and is a lintless wild diploid. However, it is known for contributing to superior fibre qualities. Several germplasm lines with improved fibre properties have been derived. Deodikar (1949) carried out cross between G. hirsutum and G. anomalum, and derived hirsutum type plants with superior fibre properties. Pandya and Patel (1956) obtained jassid resistant G. hirsutum cultures known as co-ano from cross between G. hirsutum (co-types) and G. anomalum. Gill and Bajaj (1984) reported that

hybrids from cross between asiatic diploids and G. anomalum were intermediate in morphology. Based on genetic and cytogenetic studies between G. anomalum and Asiatic cotton like G. herbaceum and G. arboreum by Gerstel (1953), he indicated clearly that G. herbaceum is more closely related to G. anomalum than G. arboreum.

MATERIALS AND METHODS

The field experiments were conducted at the University of Agricultural Sciences, Agricultural Research Station, Dharwad, which is situated in the northern transitional zone of Karnataka state ( INDIA ) with a latitude 15°17' N, longitude of 76°46' E and at an altitude of 678 m above mean sea level. Development of genetic material and its evaluation was carried out under isolation. Normal production practices were followed. Specific crosses and their generational data are given below.

G. hirsutum x G. barbadense: DS 28 X SBYF 425

As the aim of this research was to improve fibre traits, thus the first level of selection in the field was made through measuring fibre length through a halo disc. Detailed fibre investigation under HVI in ICC mode was made for selected plants which produced sufficient lint. Records on seedcotton , gin turnout and lint yield for selected plants was also made. T tests were used to compare the means of selected plants from segregating populations with the mean of 50 plants of a control genotype/cultivar. Analysis of variance F tests were used to compare means of selected progenies tested under replicated trial in comparison with suitable cultivars as checks.

RESULTS AND DISCUSSION

G. hirsutum x G. barbadense : DS 28 X SBYF 425

The male parent [SB (YF)-425] has superior fibre properties, but it is more susceptible to biotic and abiotic stresses than female parent (DS-28). Of the 283 F2 plants that produced lint, sufficient lint was available for only 80 plants. Of these 80 F2 plants halo length varied widely, from 18.00 to 35.33 mm (Table 3; Figure 1). Fibre strength varied from 18.1 to 29.1 gtex-1 (Table 3). Such variation was also observed by Kohel et al. (2001), Paterson et al., 2003 and Lazo et al. (1994) in F2 population of crosses between hirsutum and barbadense. We already reported the status of the F3 and F4 segregating populations of this cross (Katageri et al., 2003), thus we present selected data for the F5 to F8 generations below.

Evaluation of fibre properties in F5

The enormous variation (14.3 mm to 38.72 mm) was seen for halo length among 5214 plants across 184 families in the F5 generation (Figure 2). As many as 324 plants were placed in the range of 32 mm and above, with 46 plants having 34-35 mm length and 3 plants above 38 mm. Recombinant plants with superior in fibre length (>34 mm) relative to the superior parent, i.e. the female parent at 30 mm, have been isolated. The female parent of this cross, DS 28, averages 29.59 mm fibre length (2.5% SL), 20 gtex-1 fibre strength, 3.78 micronaire, and 43.4 % uniformity (Nijagun and Khadi, 2001). Plants with very long fibre length (>32 mm) and high fibre strength (>24 gtex-1) and hirsutum looking (based on observations on morphological characters, not included in this paper) have been isolated (Table 4). In the studies of Kadapa and Gangaprasad (1965), similar fibre length improvement (25 to 30 mm) over the female parent, Laxmi (24 mm), from a cross between G. hirsutum var. Laxmi and G. barbadense var. Raichur and Lingasugur has been observed. Mention may be made of the evolution of the long staple cultivars like Sea Island Andrew in North Carolina (Thomas, 1952), BP-52 in East Africa (Hutchinson, 1951), HA-2 in Mysore (Dorasami and Srinivas Iyengar, 1948) and MCU-2 and 0892-B in Madras, as instances where interspecific hybridization involving hirsutum and barbadense resulted in transferring extra long staple and fineness from the latter species to former. Ratio of fibre strength to length is more than 0.80 in 13 plants compared with a ratio of only 0.67 in the hirsutum, DS-28, parent. Plants 42-18 and 78-22 possessed all required superior fibre qualities.

Evaluation of fibre properties in F6 generation

Halo length of all 1,848 plants belonging to 23 progenies of the F6 generation were evaluated for fibre properties. The enormous variation (16.0 mm to 40.6 mm) was seen for halo length among recombinants and as many as 52 plants were placed in the range of 33.0 mm and above. Frequency distribution of plants for fibre length indicates the presence of a

higher number of plants, 787, in the range of 27.0-30.0 mm and only 28 in the above 34.0 mm category (Figure 4).

Out of 13 selected recombinant plants, four plants (7-2, 16-4, 48-10 and 64-19b) had fibre length of more than 30.0 mm and fibre strength of more than 23.0 gtex-1. Three other plants (9-16, 21-2 and 32-22) recorded fibre strength of more than 24.0 gtex-1 with fibre length of more than 29.0 mm. Plant number 16-4 and 64-19b exhibited greater than 32.0 mm fibre length (2.5% SL), compared with 29.5 mm fibre length (2.5% SL.) of DS-28. These plants also possessed fibre strength of more than 24.0 gtex-1 (Table 5).

Evaluation of Seedcotton Yield (SCY) and Yield contributing characters of F6 generation

The plants with high fibre length (halo length) were observed for various yield contributing characters, including seedcotton yield per plant (Table 5). These data indicated the possibility of enhancing not only fibre properties but also yield and yield contributing characters from such interspecific crosses. Seedcotton yield per plant ranged between 44.0 g to 65.0g compared with 38.0 g for DS-28. It also indicated the possibility of fixing the interspecific heterosis for seedcotton yield. Per cent increase over DS-28 was observed for SCY in all the selected recombinant plants that exhibited elevated fibre properties. Plant number 2-18 had the highest per cent increase (105.26) over DS-28 for SCY, whereas plant no. 7-2, which was superior in fibre length (30.8 mm) and fibre strength (27.0 gtex-) exhibited a 60.5 % increase over DS-28 for SCY. All of the recombinant plants had increased lint weight over DS-28. There were three plants (2-18,7-2, and 9-16) which showed an increase of 60% or greater over DS-28. Among these, one plant (7-2) was also superior in fibre length (30.8 mm) and fibre strength (27.0 gtex-1).

Evaluation of F7 and F8 generations

Thirteen progenies were evaluated in the F7 generation, with halo length ranging from 18.00 to 37.33 mm. Twenty F7 progeny (18.00 – 37.33 mm halo length) were advanced to the F8 generation. On an average, 54 to 68 plants were maintained per progeny. Variability within each progeny for halo length existed with the difference in range within the progeny varing from 2.22 to 11.67 mm (Table 6). Progenies in the range of SB (YF)-425, the barbadense parent, halo length had relatively higher CVs than those of other categories. Although fibre length is said to be controlled by polygenes, recent studies (Reinisch et al., 1994; Shappley et al., 1996, 1998; Ulloa and Meredith Jr., 2000; Kohel et al., 2001; Ulloa et al., 2002; Lacape et al., 2003; Paterson et al., 2003; Zhang et al., 2003; Mei et al., 2004; Lacape et al., 2004; He et al., 2005; Lacape et al., 2005; Lin et al., 2005; Zhang et al., 2005) based on QTL analysis have brought the possibility of presence of major QTLs. Our present study also revealed similar indications as it is possible to classify these plants into distinct groups of fibre length. Twenty F8 plants were selected based on halo length, covering all ranges of halo lengths and which had produced sufficient quantity of lint for fibre testing, were subjected to detailed fibre property analysis. The fibre traits of F8 plants having all 12 morphological characters of hirsutum, are superior to the G. hirsutum, DS-28, female parent of these progenies (Table 7). The fibre strength varied from 17.6 to 29.9 gtex-1. Plant number 01-11 exhibited the highest fibre strength (29.9 gtex-1) followed by plant number 03-37 (27.6 gtex-1). Whereas the lowest fibre strength (17.6 gtex-1) was recorded by plant number 18-12. The mean fibre strength of selected plants in F8 generation was 22.6 gtex-1. The range of variation for fibre length was from 21.0 to 34.1 mm. The shortest fibre length was recorded by plant number 18-12 (21.0 mm) while plant number 01-11 possessed longest fibre length (34.1 mm). The mean fibre length of selected plants was 27.4 mm. The variation observed for this character was from 0.76 to 0.93 mm. The highest

strength to length ratio (0.93) was recorded by plant number 10-03 whereas lowest strength to length ratio (0.76) was recorded by plant number 14-15. The mean strength to length ratio was found to be 0.83. The range for micronaire varied from 2.1 (plant number 10-03) to 5.5 mginch-1 (plant number 17-05) with an average of 3.3 mginch-1. The selected plants are capable of meeting the new CIRCOT norms. Out of ten classes of cottons based on these norms, plants derived from this study are fulfilling the needs of five classes. We have at least isolated one to two plants in each class. It also indicates that superior fibre quality from G. barbadense can be integrated in G. hirsutum. There are few reports (Harland, 1936; Stephens, 1950; Richmond, 1951) a possibility of reversing back to hirsutum type from crosses between hirsutum and barbadense and in their opinion introgression of fibre traits from barbadense is a difficult task. However, several other studies (Knight, 1956; Kadapa and Ganga prasad, 1965; Hyer, 1973; El-Hattab et al., 1974; Culp and Harrell, 1980; McCarty et al., 1995; Galanopoulu-Senduca and Roupakias, 1999; Saha et al., 2004), including our present study, indicates that the possibility of introgression between hirsutum and barbadense. So it is essential to pursue these kinds of studies to promote fibre traits of high yielding, abiotic and biotic stress tolerant hirsutum cottons.

Seedcotton yield and yield component characters of F8 generation

The range of variation in seedcotton yield was from 52 to 84 g (Table 7). The highest seedcotton yield was recorded by plant number 10-03 (84 g), followed by plant number 09-03 (78 g). The lowest seedcotton yield was recorded by plant number 17-05 (52 g). The mean seedcotton yield was 67.45 g. Lint weight ranged from 20.0 (plant number 16-33 and 17-05) to 30.0 g (plant number 10-03) with a mean of 23.75 g. The range of gin turnout was from 32.00 to 38.46. The highest gin turnout was recorded by plant number 17-05 (38.46) followed by plant number 09-03 (37.18). Whereas, lowest gin turnout (32.00) was recorded by plant number 18-12. The mean gin turnout of selected plants was 35.24. The range of variation in seed index was from 8.9 (plant number 11-50 and 14-15) to 10.9 g (plant number 12-37) with a mean of 9.76 g. The range of lint index varied from 4.66 to 6.38 g. The highest lint index was recorded by plant number 17-05 (6.38) followed by plant number 12-37 (6.23) whereas, the lowest lint index (4.66) was recorded by plant number 18-12. The mean lint index of selected plants was 5.31 g. Improving fibre traits and seedcotton yield at a time is said to be difficult task (Hyer, 1973; McCarty et al., 1995). The present study demonstrated the possibility of fixing positive heterosis for seedcotton yield, yield components and fibre traits. El-Hattab et al. (1974), Munshi Singh et al. (1985), Galanopoulou-Senduca and Roupakias (1999) had also observed this possibility in their studies.

G. hirsutum, var.Abhadita x (G.cot11 x G.tomentosum): F3 and F4 generations

We evaluated the F3 population of this interspecific cross that consisted of 171 plants obtained from 171 F2 plants. They were grouped under 12 different frequency classes based on fibre strength. The highest fibre strength (26 to 27 gtex-1) was recorded in seven plants, with 12 plants having between 25 to 26 gtex-1 (Table 8) Highest number of plants (30) exhibited 21 to 22 gtex-1 and another 30 plants had 22 to 23 gtex-1 fibre strength . Twenty-five plants exhibited 24 to 25 gtex-1 fibre strength. As many as 24 plants were observed in the low fibre strength category (24 gtex-1 fibre strength distributed in different fibre length groups (medium to long staple) is depicted in Fig. 5, with the greatest number recovered in long stable range. The progenies of these 44 plants, 25 plants F4 plants each, were evaluated along with Abhadita , the female parent (hirsutum) of this cross. The data of only selected plants are presented here in table 9). Though we carried forwarded plants with

more than 24gt-1 fibre strength, we noticed here plants with lower than that limit of fibre strength could be accountable to environment variance or the presence of many genes for fibre strength which are difficult to fix in the homozygous state during early generations. These high fibre strength plants recorded higher seedcotton and lint yield than Abhadita. Simultaneous improvement for both fibre and lint yielding ability indicates the accumulation of desirable alleles from this diverse cross. Decrease in micronaire value was evident, but it remained within the limits of spinning.

G herbaceum, var. Jayadhar x G. barbadense, var. BCS 23-18-7

Jayadhar belongs to the G. herbaceum species and was released during the 1950s. It has been under commercial cultivation in India until today. The data of yield trials along with fibre properties for the last 10 years (AICCIP reports 1995-96 to 2004-05) indicates that Jayadhar is a stable genotype, producing high yields but poor fibre strength. An attempt was made to enhance the fibre strength of this genotype through an interspecific cross between G. herbaceum var. Jayadhar and the allotetraploid, G. barbadense var. BCS23. The F1 was not completely sterile because of presence of two copies of the A genome and one copy of D genome. Fertile pollen was used to cross with Jayadhar to generate the BC1 genseration and the F1 was also selfed to generate the F2. During, 2002-03 we evaluated these F2 and BC1 generations. Halo length was measured for 154 and 134 plants of BC1 and F2 populations, respectively. The plants were classified under 3 groups based on halo length viz., 1 and F2) showed high variation for halo length, from 19.11 mm to 28.11 mm and 19.22 mm to 27.30 mm, respectively. As sufficient quantity of lint for HVI testing was available for 11 plants, the detailed fibre investigation was made for 3 BC1 and 8 F2 plants (Table 10). Not only significant but large increases in fibre length (24-26 mm) and fibre strength (20-23 gtex-1) were observed in 3F2 and 1 BC1 plants. The ratio between fibre strength and length of the selected plants is around 0.80, which is most desirable. The micronaire value of Jayadhar is more than 5.0 which is most undesirable for textile industry. One selected BC1 plant was selfed and backcrossed to Jayadhar and selfed seeds of 3 F2 plants were used to develop the BC1F2, BC2 and F3 generations, respectively, during 2003-04. Halo length of 646 plants across all generations was measured using the halo disc. The halo length ranged between 17.0 mm and 29.0 mm with a mean value of 22.3 mm. Finally, fifty plants were selected which exhibited halo lengths of more than 25.0 mm. The maximum number of plants (304) was observed in the 20 to 22.0 mm category and the minimum number of plants (one) categorized as 16.0-18.0 mm halo length. Other categories of 18.0 to 20.0 mm, 22.0 to 24.5, 24.5 to 27.0mm and 27.0 to 29.0 mm contained 83, 172, 64 and 4 plants, respectively (Figure 7). Sufficient lint was available for 29 plants across the different populations for HVI test. Among the selected recombinant 29 plants, four plants (1-1 of BC2, 31-4 of F3, 23-5 of F3 and 29-4 of F3) had fibre length of more than 26.0 mm and fibre strength of more than 25.0gtex-1, and another three plants (18-2 of F3, 27-6 of F3 and 27-25 of F3 ) exhibitd fibre strength of 23.0 gtex-1 with more than 28.0 mm fibre length.

We scored nine morphological characters which distinguish G. herbaceum and G. barbadense (data not shown). All of the plants with more than 23gt-1 fibre strength had all seven morphological characters of herbaceum. Because of their high seedcotton yielding ability and gin turnout, they also exhibited high lint yield (Table 11). Progenies of selected plants were carried forward and finally plants selected during F5 and BC2F3 were tested under replicated trial during 2005-06 (data not shown).

G. herbaceum var. DDhc-11 x G. anomalum

The high yielding G. herbaceum cultivar, DDhc-11, was crossed with G. anomalum. Hybrids with several intermediate characters were successfully developed in the present study and these F1s were partially pollen fertile and linted. Although the fibre length of the F1 was smaller than the DDhC11, it is possible to improve fibre length and strength of recurrent parent by repeated backcrossing. Here 147, 281, 85, and 49 plants, respectively, of the BC1F3, BC2F2, BC3F1, and F4, populations have been studied, with results reported herein.

The mean halo lengths of BC1F3 (22.70 mm), BC2F2 (21.96 mm) and BC3F1 (21.61 mm) were significantly less than DDhc-11 (23.48 mm), while selected F4 plants were significantly superior (28.97 mm). However, in all four populations, plants showing 10-15 % more halo length than DDhC-11 were isolated. Eighteen F4 plants were isolated which possessed greater halo lengths than the DDhC-11 (data not shown). Increases in mean halo length was reported in backcross progenies of G. hirsutum and G. raimondii synthetic hexaploids using G. anomalum by Santhanam (1958) and Ramachandran et al. (1964). The plants which produced sufficient yield to obtain lint for detailed fiber trait analysis have been tested for fibre analysis at The Gadag, Cooperative Textile Mill Ltd., Hulkoti. The results are presented in table 12-15.

Significant improvement in mean fibre length of selected plants over DDhC-11 (23.11 mm) was observed in the BC1F3 (24.61 mm) and F4 (25.91 mm) generations while the BC2F2 (24.04 mm) and BC3F1 (23.02 mm) populations did not differ. However, 11 of 14 BC1F3 plants, 7 of 16 BC2F2 plants, 5 of 10 BC3F , and eight F4 plants had higher fibre length than DDhC-11. This result shows that either one or no backcrosses provided more opportunity for introgression of fibre traits compared to BC2F2 and BC3F1. At Indore, F6 progeny from crosses of G. thurberii with G. arboreum and cultivated American species showed a length of 27 mm (Anonumoys, 1950b). The mean of selected plants was significantly more in in the F4 (19.58 gtex-1) and BC1F3 (18.61 gtex-1) than the DDhC-11 parent (17.6 g tex-1), whereas the BC2F2 (17.62 gtex-1) was equal to the DDhc-11 recurrent parent and the BC3F1 (16.22 gtex-1) was inferior in fibre strength. However, eight plants in BC1F3, five plants in BC2F2, and five plants in the F4 population showed fibre strength higher than the DDhC-11 (17.6 gtex-1). In texas, Beasley’s complex polyploid arboreum x thurberi has been backcrossed to upland cottons and a good number of high lint strength segregants have been obtained (Cuany, 1952). Micronaire values of all the four populations, i.e., BC1F3 (4.37), BC2F2 (4.53?), BC3F1 (4.99) and F4 (3.99) were significantly lower than DDhC-11 (5.09). Uniformity ratios of all four populations, i.e., BC1F3 (50.92%), BC2F2 (51.51), BC3F1 (52.19%) were significantly higher than DDhC-11 (50.50) except the F4 (50.23) which showed lower uniformity than DDhC-11. Maturity ratio of all the four population i.e., BC1F3 (0.83), BC2F2 (0.86), BC3F1 (0.88) and F4 (0.76) were significantly higher than DDhc-11 (0.72). Elongation percentage of all four populations i.e., BC1F3 (5.32), BC2F2 (5.31), BC3F1 (5.34) and F4 (5.48) were significantly inferior than DDhc-11 (7.31). All Recombinant plants obtained in limited backcross (one) followed by pedigree method of selection and pedigree method of selection without backcrossing have yielded plants suitable for spinning 20s, 30s and 40s count yarn. Some of these plants have also recorded higher seedcotton yield than DDhc-11 (Table 16)

Acknowledgments We thank ICAR , New Delhi for providing grants to carry out these studies under Technology Mission On Cotton , MM1.

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