Genetics of pink bollworm Resistance to Bacillus thuringiensis toxin CrylAc

Laboratory selection increased resistance of pink bollworm (Pectinophora gossypiella) to the Bacillus thuringiensis toxin CrylAc. Three selections with CrylAc in artificial diet increased resistance from a low level to >100-fold relative to a susceptible strain. We used artificial diet bioassays to test F₁ hybrid progeny from reciprocal crosses between resistant and susceptible strains. The similarity between F₁ progeny from the two reciprocal crosses indicates autosomal inheritance of resistance. The dominance of resistance to CrylAc depended on the concentration. Resistance was codominant at a low concentration of CrylAc, partially recessive at an intermediate concentration, and completely recessive at a high concentration. Comparison of the artificial diet results with previously reported results from greenhouse bioassays shows that the high concentration of CrylAc in bolls of transgenic cotton is essential for achieving functionally recessive inheritance of resistance.