Sex Influenced Inheritance of Bacillus thuringiensis Cry1Ac Resistance in the American Bollworm, Helicoverpa armigera (Hiibner)

Inheritance of Bacillus thuringiensis (Bt) Cry1Ac resistance in two naturally occurring strains of Helicoverpa armigera (Hüuber) viz., Sirss aan Coimbatore was stuuied by mating with the suscetible (sus-) Delhi strain. The degree of dominance of Bt Cry1Ac in the F₁ progeny of different crosses showed wide variation; viz., sus-Delhi female x Sirsa male -0.68, sus-Delhi female x Coimbatore male -0.17, Sirsa female x sus-Delhi male 0.93 and Coimbatore female x sus-Delhi male 1.43. The dominance of Bt Cry1Ac inheritance in the progeny of females of the Sirsa and the Coimbatore strains crossed with males of the sus-Delhi strain suggested the influence of female on inheritance of tolerant gene(s). Analysis of F₂ population from F₁ sib-matings, and a backcross of F₁ female (belonging to Coimbatore male and sus-Delhi female) with Coimbatore male parent at a discriminating concentration of 1.0 µg g⁻¹ diet showed that resistance in both Coimbatore and Sirsa strains was a recessive single-gene trait