Genetic effects on morphological and yield traits in cotton (Gossypium hirsutum L.)

The nature and magnitude of genetic effects on morpho-yield traits were studied in a 6 x 6 F-1 and F-2 diallel cross in upland cotton. An additive-dominance model was adequate for most of the traits except plant height and seed cotton yield, where the model was partially adequate. Genetic parameters were estimated following Hayman's and Mather's model. Additive effects controlled lint percentage and monopodia in both generations, and plant height and sympodia in F-2. Non-additive inheritance with over-dominance controlled yield in both generations, and plant height and sympodia in F-1. Most traits presented an unequal proportion of positive (U) and negative (V) alleles in the loci (H-2 < H-1) and an asymmetrical distribution of genes in the parents (H-2/4H(1) < 0.25 and F different to zero). The value of H-2/4H(1) was lower than maximum value (0.25) for all of traits, which arises when U = V = 0.5 over all loci. The proportion root 4DH1+ F/root 4DH1-F) confirmed by half of the traits that dominant alleles were in excess as compared to recessive alleles. Dominance effects (h(2)) for most of the traits suggested that substantial contribution of dominance was not due to heterogeneity of loci in these parameters. Broad and narrow sense heritabilities were high for most of the traits. Correlation coefficient between the Wr + Vr and mid parental (y) indicated that dominant genes were responsible for increased sympodia, lint % and yield, and recessive genes increased monopodia and plant height. Genetic gain was encouraging for most traits. Cultivar CIM-1100 was identified by genetic advancement as a promising parental cultivar to cross combinations.