Study On The Control Efficiency Of Different Types Of Transgenic Bt Rice Against Target And Nontarget Insect Pests In Paddyfields

In recent years, the development of transgenic rice lines expressing Bacillus thuringiensis (Bt) insecticidal protein provide the new strategy for the control of paddyfield pests and has achieved good control efficacy. However, there is no reliable basis for the control efficiency of Transgenic Bt rice against target pests in long-term planted and the effect on Transgenic Bt rice against nontarget pests is still not sure. In this study, field experiments were carried out to research the occurring characteristics and population dynamics of the main rice pests including the target pests of Chilo suppressalis, Cnaphalocrocis medinalis and Sesamia inferens, the nontarget pests of planthoppers and the natural enemies feeding on transgenic Bt rice with dual CrylAb and CrylAc (cv. HH1), Cry1C with cry1C-gene,Cry2A with Cry2A-gene and the parent line nontransgenic rice (cv. MH63) in a pure or mixed cultivation(Transgenic Bt rice(HH1) mixed with the parent line nontransgenic rice (cv. MH63)).Resistance efficiency of transgenic Bt rice on C. supperssalis, S. inferens and C. medinalis; the effect on the nontarget pests of planthoppers and the natural enemies (Spiders and Cyrtorhinus lividipennis Reuter)were probably conducted. Therefore, the research perhaps provide important scientific basis for the study on the control efficiency of differernt types of transgenic Bt rice on the dominant pest species in the field, important scientific data simulating the sustainable application and healthy development of transgenic Bt rice.The main results were as follows:1. On the one hand, field experiments were conducted to study the population dynamics of two planthoppers, i.e., Nilaparvata lugens Stal and Sogatella furcifera Horvath, feeding on transgenic Bt rice(HH1, Cry1C and Cry2A) and the parent line of nontransgenic rice (cv. MH63). In 2012, there were significant differences in the population abundance of N. lugens and S. furcifera fed on transgenic Bt rice, and the population abundance of N. lugens and S. furcifera fed on transgenic Bt rice(HH1, Cry1C and Cry2A) is more than the population abundance of N. lugens and S. furcifera fed on the parent line of nontransgenic rice (cv. MH63), especially the population abundance fed on transgenic Bt rice HH1 is the most. However, transgenic Bt rice(HH1, Cry1C and Cry2A) showed no significant influence on the population abundance of N. lugens in 2013. But there were significant differences in the population abundance of the Nymphs subpopulation and Total population of S. furcifera fed on transgenic Bt rice in 2013, and the population abundance of the Nymphs subpopulation and Total population of S. furcifera fed on transgenic Bt rice Cry2A is more than the abundance fed on the parent line of nontransgenic rice (cv. MH63). Obviously, it was complicated that the influence of Transgenic Bt rice on the suction pests such as rice planthoppers and still not sure. On the other hand, the field experiments were carried out to study the population dynamics and damage characteristics of two stem borers, i.e., the target pest of C. suppressalis and S. inferens, feeding on transgenic Bt rice. Compared with nontransgenic rice, transgenic Bt rice HH1、Cry1C and Cry2A significantly reduced the population dynamics of C. suppressalis larvae in both 2012 and 2013. In addition, there were more C. suppressalis larvae in the transgenic Bt rice Cry1C and Cry2A than transgenic Bt rice HH1 in 2013. Transgenic Bt rice HH1、Cry1C and Cry2A significantly reduced the population dynamics of S. inferens larvae in 2012 and only transgenic Bt rice HH1 and Cry2A significantly reduced the population dynamics of S. inferens larvae in 2013. Simultaneously, the abundance of S. inferens larvae in transgenic Bt rice was more than the C. suppressalis and there were higher larvae abundances fed on transgenic Bt rice Cry1C and Cry2A than fed on nontransgenic rice sometimes in 2013. So transgenic Bt rice HH1 has higher resistance to the target pest of C. suppressalis and S. inferens while the resistance to the target pest of C. suppressalis and S. inferens of transgenic Bt rice Cry1C and Cry2A was unstable. Thirdly, Consecutive seasons-long field experiments were conducted to study the resistance efficiency of transgenic Bt rice on C. medinalis. The results indicated that transgenic Bt rice showed higher resistance to C. medinalis in a pure cultivation in both 2012 and 2013. Simultaneously, the results indicated no significant differences in the number of eggs between transgenic Bt rice and nontransgenic rice in 2013 while significant differences in 2012. The results may be relevant to the occurrence of C. medinalis and the rice growing situation at that time.In addition, the results indicated no significant differences in the number of eggs in the mixed cultivation. Finally, The field experiments were conducted to study the population dynamics of mainly non-target natural enemies, such as Spiders and Cyrtorhinus lividipennis Reuter. There were no significant differences in the population abundance of Spiders and Cyrtorhinus lividipennis Reuter in 2013. However, There were significant differences in the abundance of Spiders and Cyrtorhinus lividipennis Reuter fed on transgenic Bt rice HH1 and the abundance of Spiders and Cyrtorhinus lividipennis Reuter fed on transgenic Bt rice HH1 was more than fed on nontransgenic rice in2012, while there were no significant differences in the population abundance of Spiders and Cyrtorhinus fed on transgenic Bt rice Cry1C and Cry2A in 2012.2. In the mixed cultivation field experiment, firstly, there were no significant differences in the population abundance of N. lugens fed on transgenic Bt rice(HHl) mixed with the parent line nontransgenic rice (cv. MH63), but there were significant differences in the abundance of Brachypterous females, Brachypterous male, Nymphs subpopulation and Total population of 5. furcifera fed on transgenic Bt rice(HH1) mixed with the parent line nontransgenic rice (cv. MH63), and the abundance of Brachypterous females, Brachypterous male, Nymphs subpopulation and Total population of S. furcifera fed on mixed seeding (5%-20%) and 100% transgenic Bt rice was below fed on the parent line nontransgenic rice. Secondly, there were no significant differences in the population abundance of C. suppressalis larvae and S. infer ens larvae fed on transgenic Bt rice HH1 mixed with the parent line nontransgenic rice (cv. MH63). In addition, significantly lower percentages of dead heart or white head plants and damaged plants were resulted by C. suppressalis and S. inferens fed on mixed cultivation. Obviously, mixed cultivation had higher control efficiency of the damagement of the C. suppressalis and S. inferens. Thirdly, the results indicated that transgenic Bt rice showed higher resistance to C. medinalis in mixed cultivation, and the control efficiency was close to 100%. In addition,compared to the 100% parent line nontransgenic rice, there were no significant differences in the abundance of eggs in the different mixed seeding. Finally, compared to the 100% parent line nontransgenic rice, the results indicated no significant differences in the population abundance of Spiders and Cyrtorhinus lividipennis Reuter in the different mixed cultivations.