Abstract
Due to the difficulty in producing cotton F 1 hybrid seed through hand emasculation and pollination, the capture of heterosis in cotton production is limited. The purpose of this study was to evaluate the potential of 6 × 6 F 1 and F 2 intra-hirsutum diallel hybrids relative to heterosis, inbreeding depression, heritability and correlation. Average F 1 hybrids mean values were higher than those of F 2 s, while F 2 s exceeded the parents. However, in F 1 s and F 2 s, the average mean values were 22.30 and 19.48 for seeds boll -1 , 8.87 and 8.56 g for seed index, 112.36 and 87.51 g for seedcotton yield and 30.07 and 28.30% for cottonseed oil. Heterosis over better parents was more pronounced in F 1 s as compared to F 2 s. However, in F 1 s and F 2 s, the average positive heterosis was 11.54 and 4.50%; 3.40 and 2.41%; 46.30 and 28.96% and 6.04 and 1.52%, respectively, for the above traits. Even after segregation and inbreeding depression, the F 2 s expressed about 50% of F 1 s heterosis. The inbreeding depression in F 2 s was -6.51 to -16.92 with low to high heritability, and significant positive correlation of cottonseed oil with other traits. The cultivar CIM-1100 derivatives performed better and exceeded all other hybrids in both generations. Key words: Hybrid vigor, inbreeding depression, cottonseed traits, cottonseed oil, Gossypium hirsutum .
Highlights
Development and utilization of high yielding and stress tolerant cultivars have a fundamental position in crop production technology package, which could be facilitated through introgressive hybridization (Khan, 2003; Khan et al, 2007a)
Hybrid seed produced through hand emasculation and pollination techniques is expanding in China and India because of cheaper labor (Zhang and Pan, 1999), and in China following the commercial exploitation of transgenic Bacillus thuringiensis (BT) cotton (Wang and Li, 2000)
The average F1s seeds per boll, seed index, seed cotton yield and cottonseed oil % were higher than those of F2s, while F2s values for the said traits were higher than parents
Summary
Development and utilization of high yielding and stress tolerant cultivars have a fundamental position in crop production technology package, which could be facilitated through introgressive hybridization (Khan, 2003; Khan et al, 2007a). The success of transgressive segregation depends upon the identification of genotypes with the ability to transmit high production potential into specific genotypic combinations. The potential use of heterosis for increasing cotton yields has been an important objective of breeders in only a few regions of the world. Except in countries where a vast and cheap labor force is available to make emasculations and crosses by hand, essentially, no commercial use of heterosis currently exists in cotton (Chaudhry, 1997; Khan et al, 2007a). Hybrid seed produced through hand emasculation and pollination techniques is expanding in China and India because of cheaper labor (Zhang and Pan, 1999), and in China following the commercial exploitation of transgenic Bacillus thuringiensis (BT) cotton (Wang and Li, 2000).
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