Heritability of tolerance to the Cry1Ab toxin of Bacillus thuringiensis inChilo suppressalis (Lepidoptera : Crambidae)

Heritability of Chilo suppressalis (Walker) tolerance to the Cry1Ab toxin o f Bacillus thuringiensis Berliner was estimated using a half-sibling design . Artificial diet with and without Cry1Ab was infested with progenies of 20 males, each mated with 2 females, and mortality was scored 5 d after infes tation. The progeny of each female was reared and scored separately. Mean m ortality of the 20 families on the Cry1Ab diet was 46.5%. The effects of bo th male parent and of female parent within male parent were significant. He ritability was estimated to be 0.52, suggesting that a high proportion of p henotypic variation was because of genetic differences. Mortality on the Cr y1Ab diet was not correlated with mortality on control diet, indicating tha t differences among families in tolerance to Cry1Ab were not attributable t o differences in general fitness. Our results indicate that "high dose" Bt rice plants may be particularly important for Cry1Ab resistance management in C. suppressalis populations.