Gene action of seed traits and oil content in upland cotton (Gossypium hirsutum L.)

Gene action was studied for seeds per boll, seed index, and cotton seed oil content in a 6x6 complete diallel cross of Gossypium hirsutum L. in the F-1 and F-2 generations during 2000-2002 at the Agricultural Research Institute, Dera Ismail Khan, Pakistan. An additive-dominance model was found adequate to explain the gene action for seeds per boll and seed index in the F, generation while having partial adequacy in the F-2 generation. For cotton seed oil content, the model was partially adequate on the basis of F-1 data and was adequate in the F-2 generation. According to the mean degree of dominance and components of variance, almost all the traits showed an additive type of gene action in both generations. The exceptions were seeds per boll and cotton seed oil content in the F, generation, which had a dominance type of gene action. Trait-wise narrow-sense heritability was low to moderate for seeds per boll and cotton seed oil content, while high for seed index. Broad-sense heritability was high for all the three traits. An appreciable genetic advance was recorded and, in the presence of additive type of gene action, prompt and effective improvement in cotton seed traits and oil content through selection is possible.