STUDY OF FIBER QUALITY TRAITS IN UPLAND COTTON USING ADDITIVE-DOMINANCE MODEL

Diallel analysis was studied in F1 and F2 hybrids by crossing six upland cotton cultivars (CIM- 109, CIM-240, CIM-1100, FH-682, BH-36 and CRIS-9) following Hayman's diallel approach using Mather's concept of D, H components of variation for additive and dominance genetic variances, respectively. The objectives were to study the additive-dominance model, nature of gene action, heritability and genetic gain in F1 and F2 hybrids and mean performance of the selections (made in F2 population) in advanced segregating generations (F3, F4 and F5) in upland cotton. Genotypes mean values differed significantly for all the fiber quality traits. Additive-dominance model was adequate for fiber length, fiber fineness, and uniformity ratio, while showed partially adequate for fiber strength in F1 generation. In F2s, fiber fineness showed the adequate data, while other three traits manifested partial adequacy. Additive component (D) was found significant for all the traits in F1 and F2 generations. Dominance components (H1, H2) were also significant for all the traits in F1s except the fiber fineness, while were insignificant for all the traits in F2 generation. In F1s the additive gene action was somewhat partial, while in F2s all the traits were controlled by additive gene action as confirmed by average degree of dominance (√H1/DHeritabilities (broad & narrow sense) were moderate to high with appreciable genetic advance. On the basis of transgressive segregation, heritability with appreciable genetic gain, selections made in F2 population of cv. CIM-1100 surpassed the standard cultivar (CIM-446) for fiber quality traits in segregating generations.