Heterosis and Combining Ability for Yield and Fiber Qualities of Upland Cotton Under High Density Planting Conditions for India
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India is the leading producer of cotton in the world producing 33.8 million bales (170 kg each) from 11.5 million ha. However, the lower yields per unit area stimulated the concept of high density planting system in India. India grows Gossypium hirsutum (upland cotton) hybrids with Bt transgenic technology over 90% of the total hectareage. Current genotypes require a long growing season and the non-synchronous maturity demands multiple cycles of hand harvest. Breeding programs are working aggressively on product development suitable for high density planting. Identification of phenotypes that can be planted at higher densities, compact phenology, and improved agronomics will help India achieve an average yield of 766 kg ha^-1, which is the global average for upland cotton. This study was conducted to compare level of heterosis and combining ability of compact and synchronous maturity US upland cotton cultivars when grown in US and India. Findings from this study should help Indian breeders to identify promising US cultivars for use in their breeding programs to transform the current robust, long duration genotypes to compact and synchronous maturity suitable for high density planting. Of the thirty three diverse upland cotton cultivars from US used for line x tester study, significantly high best parent heterosis was observed in F1 hybrids for yield (72.1% in US and 136.7% at India) and yield contributing traits. For fiber qualities medium to high heterosis was observed. Select US upland cotton cultivars were observed to be good general combiners for yield and quality traits. Tamcot 73 had good GCA for seed cotton yield both at US (805 kg ha-^1) and India (259 kg ha^-1). For fiber length UA48 and TAM 94L-25 combined well at US and India while UA48 and Acala 1717-99 had significant GCA for fiber strength. To reduce the plant height TAM 73840 and TAM 0155 can be used since they had negative GCA both at India and US locations. The line x tester results indicated preponderance of additive gene action over non additive for all the traits since variance due to line x tester interaction was less than variance to lines or testers. The results suggest that careful selection of US cultivars and utilizing them to transform current Indian upland cotton genotypes suitable for high density planting is possible. Secondly, reasonably high heterosis observed for yield and other agronomic traits indicates that compact x compact F1 hybrids can be bred without losing yield. Lastly pure line breeding scheme is recommended for improving fiber quality traits considering preponderance of additive gene action observed in this study.
Saitwal, Vishal Madhukar (2017). Heterosis and Combining Ability for Yield and Fiber Qualities of Upland Cotton Under High Density Planting Conditions for India. Doctoral dissertation, Texas A & M University. Available electronically from