Effects Of The Transgenic Bt Cotton On Phytophagous Pests And Arthropod Natural Enemies And Their Mechanisms

The ecological effects of transgenic Bt cotton was studied in laboratory, cage and field by the view of molecular ecology, autecology and population ecology,Effects of transgenic Bt cotton on the population dynamic of phytophagous pests -and arthropod natural enemies was investigated in field performed in Shandong Province. It's shown that Bt cotton was highly resistant to cotton bollworrn (Helicoverpa armigera), but the degree of its resistance fluctuated during the growth season of cotton. And the expression of Bt toxin in transgenic cotton showed an obvious dynamic of temporal variation. We found the coincidence between resistance degree and Bt concentration fluctuation. There were significant differences between the population number of lacewings and ladybirds in non-sprayed Bt cotton field and sprayed non-Bt cotton field. The former was higher than the latter.Laboratory feeding bioassays using transgenic Cry 1 A(c) Cotton plants were carried out to study the effects of B. thuringiensis-fed herbivorous prey on the predator Chrysopa Formosa Brauer. There was no significant difference in total mean mortality from hatch to pupation between Chrysopa Formosa Brauer larva reared on Bt-fed or Bt-free Tprey(Spodoptera exigua Hiibner). Similarly, no significant differences in total developmental time of O. majusculus was detected when reared on the prey.ELISA (enzyme-linked immunosorbent assay).was used to detect and quantitate the Bt insecticidal protein expressed in transgenic insect-resistant cotton and contained in the body of phytophagous pests and their arthropod natural enemies. The results shown that Bt protein can pass by the food-chain. But once lacewings were stopped eating the Bt-fed prey, the content of Bt protein in the body of lacewings would bedeclined linearly after various starvation duration.Based on these results, it could be summarized that indirect effect was the most possible effect mechanism of transgenic Bt cotton on Chrysopa spp..In addition, the hereditary stability of Bt cotton resistance was also discussed in this thesis.