The Impact Of Cry1Ac On Ostrinia Furnacalis (Guenee)and The Metastasis And Accumulation Of Cry1Ac In O.Furnacalis And Chrysoperla Sinica (Tjeder)

Asian corn borer, Ostrinia furnacalis (Guenee) is the most important insect of maize, Zea Mays (L.) and cotton, Gossypium hirsutum (L.), and the transgenic cotton plays a positive role in controlling the O. furnacalis. In order to research the toxic action of Bt toxic protein on the O. furnacalis, accumulation of Bt in insect and the metastasis in food chain and the influence to the environment when Bt protein release to surroundings, we took Cry1Ac, a kind of the Bt toxic protein, as the research object, the impact of Cry1Ac toxic protein on the growth, development and parameters of population growth of O. furnacalis was investigated by life table method. The detoxification enzymes, and the balance of protective enzymes under the effect of Bt in3rd and5th instar larvae of the O.furnacalis feeding on artificial diets with Cry1Ac were evaluated in the laboratory. And the concentrations of Cry1Ac insecticidal protein in different larva instar、insect state、faces of the O.furnacalis after being fed on artificial diets with different content of Cry1Ac were analyzed by using enzyme-linked-immunosorbent-assay(ELISA), the concentrations of CrylAc insecticidal protein in3rd instar of Chrysoperla sinica (Tjeder), which is the nature enemy of lepidoptera insects and fed with the low instar larvae of O. furnacalis larvae raised on various artificial diets contained different content of Bt was also investigated via the same method. The main research results were summarized as follows:1. The results showed that all the larvae were killed in5d at the treatment of2000.0ng/g concentration of toxin Cry1Ac. There were significant differences between200.0ng/g or20.0ng/g toxin Cryl Ac and non-toxin control in the larvae survival rates of10d or15d, pupation, larva to moth emergence, the net reproduction rate (Ro) and the population trend index (I) of O. furnacalis, and these index in the treatments with high concentrations toxin Cry1Ac were reduced significantly than that with low concentrations. Average generation period (T) and doubling population time (DT) at200.0ng/g toxin Cry1Ac were significantly larger than other low toxin concentration treatments, while the finite increase rate (λ) at200.0ng/g toxin Cry1Ac was significantly lower than2.0ng/g and0.2ng/g toxin Cry1Ac. Our study indicated that toxin Cry1Ac at the micro contents could effectively control the growth, development and population dynamics of O. furnacalis, and the control effect was improved along with the increasing of Cry1Ac toxin concentration. 2. The results showed that the activity of acetylcholinesterase in3rd instar larvae with1100ng/g Cry1Ac was significantly higher than those of control and other treatments, which with800ng/g Cry1Ac treatment was significantly higher than that with200ng/g Cry1Ac treatment, and the activity in5th instar larvae fed with1100ng/g Cry1Ac was significantly higher than that with200ng/g Cry1Ac treatment. The activities of a-naphthyl acetate esterase in3rd and5th instar larvae with1100ng/g were significantly lower than those of control and other treatments, the activity of3rd instar larvae with800ng/g was significantly lower than those of control and200ng/g, while that with500ng/g was significantly lower than that with200ng/g. The carboxylesterase activities of3rd instar larvae in treatments of1100、800、500ng/g were significantly lower than control, and in5th instar larvae dealt with1100ng/g was significantly lower than those of control and200ng/g. The activities of glutathione-S-transferase in3rd instar larvae with1100、800、500ng/g were significantly lower than that with200ng/g CrylAc treatment, and which in5th instar larvae with1100ng/g was significantly lower than control The superoxide dismutase activities of3rd instar larvae were significantly higher than control while the CrylAc content were800and500ng/g. The catalase activities in3rd instar larvae were significantly lower than control when the Cry1Ac content were1100、800and500ng/g, while that with1100and800ng/g were significantly lower than that with200ng/g CrylAc treatment, the activity in5th instar larvae with1100ng/g was significantly lower than those of control and200ng/g. Thus it can be seen that the enzyme activities were significantly different among each treatment except superoxide dismutase of5th instar larvae when the Asian corn borer feeding on artificial diets with various content of Cry1Ac. When treated with lower content of CrylAc, parts of the detoxification enzymes and the protective enzymes were activated in defence, but the activities were inhibited along with the increase of Bt content, and significantly lower than control. Whereas the activity of acetylcholinesterase showed a elevatory trend, which may be associated with the resistance of insects. CrylAc interfered the activities of superoxide dismutase and catalase, destroyed the dynamic balance of elimination of free radical, disturbed the normal physiological metabolism, thereby poisoning the insects.3. The results indicated that other than control and3rd instar larvae fed with the diets contained2and0.2ng/g CrylAc, CrylAc could all be detected in O.furnacalis larvae fed on artificial diets with different content of Cry1Ac, and the amount was increased along with the ascending of the content of Cry1Ac toxin. When the Cry1Ac diet was1100ng/g, the Cry1Ac content in the3rd instar larvae and faces were significantly higher than all other treatments, whereas Cry1Ac amount in the5th instar larvae was only significantly higher than2and0.2ng/g. The Cry1Ac amount in pupa was significantly over other treatments other than200ng/g after feeding on artificial diet with1100ng/g Cry1Ac. To the C.sinica fed on O. furnacalis larvae, it showed that there was no Cry1Ac toxin protein detected when the CrylAc content were20、2and0.2ng/g, till the Cry1Ac content was110ng/g, the toxin protein amount in the3rd instar larvae of C.sinica was2.09ng/g. After being ingested, Cry1Ac could accumulate inside the O. furnacalis larvae and pupae to some extent and then caused some effect, what’s more, CrylAc would spread to surrounding environment with the faces of insects according to the study. It also demonstrated that the Cry1Ac can pass to the higher trophic level along the food chain. Contrary to larvae and faces, there was no CrylAc toxin protein detected in eggs laid by the2nd generation of O. furnacalis adults, the comeout may indicated that the Cry1Ac could not pass to the next generation through the fertility of O. furnacalis. The study provided some basis for the risk assessment of Bt transgenic cotton.