Estimation of genetic parameters for quantitative and qualitative traits in cotton cultivars (Gossypium hirsutum L. & Gossypium barbadense L.) and new scaling test of additive– dominance model

A complete diallel cross of nine cotton genotypes (Gossypium hirsutum L. & Gossypium barbadense L.) viz Delinter, Sindose-80, Omoumi, Bulgare-539, Termez-14, Red leaf (Native species), B-557, Brown fiber and Siokra-324 having diverse genetic origins was conducted over two years to determine the potential for the improvement of yield, its components, oil and fiber quality traits by means of genetic analysis, combining ability, heritability and heterotic effects. The detailed studies were based on F₁ generations where crossed seeds in the first year were used for F₁ generation in the second year. The successful hybrids were recognized and distinguished by morphological markers such as flower color, spot position and their colors in petal, fiber color, seed linter, leaf color and their shapes. Analysis of variance for Simple Square Lattice Design (SSLD) showed highly significant differences (P ≤ 0.01) among various genotypes which allowed genetic analysis by Griffing, Hayman and Hayman-Jinks^, method.  Additive- dominance model and related correlation (Wr, Vr) were adequate for majority of the traits and partially adequate for some traits. Majority of the traits were influenced by non-additive gene action in F₁ generation. These results are encouraging for practical improvement through hybrid breeding programs and the contributions of additive genes through selection method. Significant variation for general combining ability (GCA) effects, specific combining ability (SCA) effects (P ≤ 0.05) and high narrow sense heritability indicates the potential for improvement through selection. On the other hand, over-dominance gene action, low and moderate rate of narrow-sense heritability for some traits suggests that improvements should be made utilizing a combination and hybrid breeding approach.