| Laboratory food-chain feeding experiments were conducted to evaluate effects of transgenic Bt cotton cultivars on non-target pest insects and predators. Host plants were three transgenic Bt cotton cultivars GK-12, 99B and 33B and a non-transgenic cotton Simian-3 (the GK-12 corresponding untransformed parental line). The aims were to quantify the effects of Bt-fed prey on the predator development and fecundity and to determine whether observed effects were caused by Bt toxin. The main results are as follows.Compared with non-transgenic cotton, evolving leaves in the middle part (6th leaves from the top) and old leaves in the lower part (14th leaves from the top) of GK-12 had significant toxicity to common cutworm Spodoptera litura larvae. Newly stretched leaves in the upper part (1st and 3rd leaves from the top) and old leaves in the lower part of 33B had significant toxicity to S. litura larvae. Other cotton organs, such as buds, flowers and bolls had no effects on S. litura larval mortality. Pupation, emerging and development period was not significantly affected if the larvae were transferred to artificial diet 10 days after they fed on relative part of cotton plants.Compared to those fed on tobacco whitefly Bemisia tabaci developed on non-transgenic cotton, larval mortality of Chinese green lacewing Chrysopa sinica (F1) fed on B. tabaci on 33B was 33.7% lower. Laval development and cocoon duration were significantly prolonged by 1.1d and 2.3d respectively. There was no significant influence on C. sinica (F1) larvae fed on B. tabaci on GK-12. No negative effects on F2 and F3 C. sinica larvae fed on B. tabaci on transgenic Bt cotton 33B or GK-12 were observed.Compared to those fed on cotton aphid Aphis gossypii on non-transgenic cotton, mortality and development of C. sinica larvae (F1) fed on aphids on transgenic Bt cotton 99B or GK-12 were not significantly affected. Cocoonduration of C. sinica larvae (F2) fed on aphids on 99B and GK-12 were 1.0d and 1.2d shorter respectively. Adult oviposition period of C. sinica (F2) fed on aphids on GK-12 were 4.3d longer. Cocoon duration of C. sinica (F3) fed on aphids on 99B or GK-12 was 0.5d shorter. Oviposition period of C. sinica (F3) prolonged 4.9d when fed on aphids on 99B.Compared to those fed on cotton aphid A. gossypii on non-transgenic cotton, larval development time and coccon duration of beautiful lacewing Chrysopa formosa (F1) were 0.7d and 0.8d shorter respectively when fed on aphids on 99B and the hatching rate lowered 11.1%. Coccon weight was 0.5mg and 1.7mg lighter respectively when C. formasa larva (F1) fed on A. gossypii on GK-12 and 99B. And number of eggs laid per female adult was 288.0 and 344.7 lesser respectively. Cocoon duration of C. formasa (F2) fed on aphids on 99B was 0.6d shorter. Hatching rates of F2 C. formosa eggs were 13.7% and 12.7% lower when C. formasa (F2) fed on aphids on GK-12 and 99B respectively.Compared to those fed on cotton aphid A. gossypii on non-transgenic cotton, mortality, development, fecundity and egg hatching of large green lacewing Chrysopa septempuctata (F1 and F2) fed on aphids on transgenic cotton GK-12 and 99B were not negatively affected.Compared to those fed on tobacco whitefly B. tabaci on non-transgenic cotton, larval and pupal mortality of ladybird Propylaea japonica were 56.0% and 44.4% lower respectively when fed on whiteflies on 33B. Pupal mortality was reduced by 40.0% and development time of the 4th instar larvae prolonged 1.4d when P. japonica fed on B. tabaci on GK-12.Compared to those fed on cotton aphid A. gossypii on non-transgenic cotton, larval development time of multicolored Asian ladybird Harmonia axyridis was 0.33d and 0.35d shorter respectively, when fed on aphids on GK-12 and 99B. And the adult weight lessened by 5.1mg and 3.4mg respectively. Fed on aphids on GK-12, egg hatching rate H. axyridis increased by 14.0%. When H. axyridis larva fed on A. gossypii on non-transgenic Simian-3,while its adult on aphids on 99B, its oviposition period was 3.4d l... |
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