The Influence Of Transgenic Bt Rice On The Health Of Leaf Roller Cnaphalocis Medinalis

In this paper, expression of Bt insecticidal crystal proteins and their resistant effects of transgenic Bt rice on leaf roller Cnaphalocis medinalis were explored by bioassay methods. The insecticidal mechanism of transgenic Bt rice was discussed by determining the influence of transgenic Bt rice on detoxification enzyme and protective enzyme in the midgut of larvae. Main results are listed as following:1,The results from laboratory bioassay showed that there were high resistance of the terminal leave of main stem along the developmental process to the Cnaphalocis medinalis larvae.The corrected mortalities of Cnaphalocis medinalis after feeding on the detached leaves of transgenic Bt rice were up to 90% before filling stage, while decreased nearly down to 70% after filling stage. It was showed that the results of whole plant bioassay were quite coincident with those of the detached leaf bioassay. The tendency of larval mortalities in the detached-leaf bioassay and whole plant bioassay were consistent with that of Bt proteins contents in different growing periods/organs.2,The larvae of Cnaphalocis medinalis were fed with transgenic Bt rice for 4 and 36 hours, the activity of AChE in the midgut of larvae was raised by 52.09%, 128.51% respectively, which had significant differences with CK. The activity of AChE decreased sharply witin 36～48h, which had no difference with CK, it may suggested that Bt insecticidal crystal proteins were piled in the body of Cnaphalocis medinalis larvae , and then destroy the protective enzyme system in the midgut of larvae and kill it.3,The results from the ELISA showed that Bt toxin protein could be detected in all the organs along the developmental process of transgenic Bt rice. The contents of the Bt toxin proteins varied obviously in different tissues at different stages. Generally, the contents of Bt proteins was higher in earlier stage than that in later stage. The highest levels of the Bt proteins in terminal leave of main stem were found at flowering stage, and the lowest level was detected at filling stage. Expression of Bt insecticidal crystal proteins in the terminal leave of main stem was steady along the developmental process of transgenic Bt rice.4,The larvae of Cnaphalocis medinalis were fed with transgenic Bt rice for different hours, Bt insecticidal crystal proteins were detected in both body and dejecta. The larvae were fed with transgenic Bt rice for 6 hours, we found that the Bt toxin in body was higher than that in dejecta; After feding 12 hours with Bt rice, the Bt toxin in dejecta was significantly higher than that in body, and keep a high level all along the experiment.