Changes of Some Life Parameters in the Resistant BollwormHelicoverpa armigera(Hübner)] Fed on Bt Transgenic Cotton

The responses of two populations of cotton bollworm [Helicoverpa armigera[WT] (Hubner)] with low resistance and susceptibility respectively to Bt (Gene Cry1Ac of with low resistance and susceptibility respectively to Bt (Gene Cry1Ac of Bacillus thuringiensis Berliner) transgenic cotton (Gossypium hirsutum L.) were tested and compared in laboratory. As fed on non transgenic cotton leaves, except the lower fecundity in resistant population, all the larval survival, duration and pupal weight of both populations were similar. While fed on transgenic cotton leaves collected in late June, July and August, the survival of ten days old larvae fed in late July and August and pupation rate of the larvae fed in late August in resistant population were higher than those in susceptible population, but the development of larval survivors was significantly slower and pupal weight was significantly lower than those fed on non transgenic cotton leaves. No pupation of larvae fed in late June was found both in resistant and susceptible population. It was indicated that, the resistant cotton bollworm has increased its adaptation to Bt transgenic cotton, but by such low resistance, it still cannot grow and develop normally like that feeding on non transgenic cotton.