Inheritance and cross-resistance of Bacillus thuringiensis insecticidal crystal protein CrylAc resistance in cotton bollworm Helicoverpa armigera Hubner population from Tamil Nadu, India

摘要

Cotton bollworm, Helicoverpa armigera Hubner selected for five generations with Bacillus thuringiensis insecticidal crystal protein CrylAc in the laboratory developed 12.98-fold resistance. Resistance and susceptible populations were mass crossed to study the dominance of resistance. The Cry 1 Ac--selected (BCR) population showed 5.8-fold resistance to Cry 1 Aa and 5.04-fold resistance to Cry 1 Ab. The degree of dominance (D) was 0.34 and 0.40 for the R X S and S X R hybrids, respectively, which indicates incomplete recessive character of CrylAc resistance in the population. The estimated realized herita-bility (h~2) and response quotient (Q) of resistance for CrylAc were 0.52 and 0.15, respectively. This indicated the lower phenotypic variation inthe selected population. The resistance risk assessment based on h2 indicated that the resistance would increased tenfold after <9 generations for Cry 1 Ac in the resistant population. The results show the ability of H. armigera to develop resistance against Cr 1 Ac and cross-resistance to CrylAa and Cry 1 Ab.