Inheritance of resistance in Indian Helicoverpa armigera (Hübner) to Cry1Ac toxin of Bacillus thuringiensis

The mode of inheritance of resistance to Cry1Ac toxin of Bacillus thuringiensis in the cotton bollworm, Helicoverpa armigera (Hübner), was elucidated through bioassay analysis of the response of resistant, susceptible, F1 hybrid and backcross H. armigera progeny to Cry1Ac using semi-synthetic diet and transgenic Bt cotton plants. The dominance value estimates ranged between 0.42 and 0.57. Resistance was found to be monogenic, autosomal and inherited as a semi-dominant trait. Genetic studies of response of H. armigera to transgenic Bt cotton showed that the effective resistance on transgenic Bt cotton plants was also inherited as a semi-dominant trait.