Abstract

                                A diallel set of 10 parents of upland cotton was evaluated under artificial American bollworm infestation for seed cotton yield per plant, boll number and bollworm damage. A significant role of both additive and dominance components of gene action was observed for all the characters studied. Epistasis influenced the performance of seed cotton yield per plant, number of bolls and eggs of H. armigera. The net directional dominance was operative towards high mean performance for egg and larval count, green boll damage. open boll damage open locule damage and seed cotton yield per plant. A greater frequency of dominant alleles for all the traits studied except seed cotton yield per plant where equal proportion of dominance and recessive alleles were observed. In general the parents AET 5. Okra and JK 276-4 were the best parents and in particular the pigmented line 9-1487 for bollworm damage in desired direction. Okra x 9-1487 and Frego x 9-1487 were good sources of desirable selections in further generations. In view of the selections for favourable recessive alleles any form of recurrent selection which allow intermating among selects may be more effective as the potentiality of recessive alleles remains hidden in the heterozygous condition.

Key words : Upland cotton,tolerant donor, American bollworm