Insecticidal Activity Of Bt Proteins And Effect Of Bt Rice On Oviposition Behavior Of Chilo Suppressalis

In China,an amount of loss in both rice productions was caused by rice lepidoptera pests annually.The development of Bt rice added a new solution to pest control toolbox.Due to the high efficiency in pest control and the potential to reduce the use of chemical insecticide,Bt rice was considered having a promising future.However,the evolution of target pest resistance may badly undermine the successful and continual promotion.Currently,“high dose/refuge”strategy is the most widely used method to control the evolution of pest resistance.Thus,to breed the superior Bt rice lines that fulfill the request of"high dose"strategy,this dissertation tried to screen some proper proteins that pose a high toxicity to Chilo suppressalis from widely used Bt protein varieties for Bt rice transformation.Meanwhile,this research also focused on the effect of Bt rice on the oviposition of C.suppressalis,which could provide an valueable scientific basis for C.suppressalis resistance management.And the major results are as following:?1?The susceptibility of C.suppressalis larvae to the five insecticidal proteins in the decreasing order was:Cry1Ca>Cry1Ab>Cry1Ac>Cry2Aa>Cry1Fa.However,the toxicities of the Cry proteins to B.mori were in the order:Cry1Fa>Cry1Ca>Cry2Aa>Cry1Ab>Cry1Ac.The Cry1Ca,Cry1Ab and Cry1Ac proteins exhibited relatively high toxicity to C.suppressalis larvae,with EC₅₀values of 16.4,45.8 and 89.6 ng/g,respectively.The toxicities of the three Cry proteins to B.mori larvae were 8,14,and 22 times lower,with EC₅₀ values of 138.3,628.4 and 1939.2 ng/g,respectively.The Cry1Fa and Cry2Aa proteins showed high toxicity to B.mori larvae,with EC₅₀ values of 135.7 and373.9 ng/g,respectively,and but low toxicity to C.suppressalis larvae,with EC₅₀ values of 6092.1 and1208.5 ng/g,respectively.We thus conclude that Cry1Ab,Cry1Ac and Cry1Ca are appropriate for transforming rice to control lepidopteran rice pests.?2?Both behavioral and oviposition tests showed that Bt rice does not disturb the oviposition behavior of C.suppressalis,and the GC-MS also indicated that compared to non-Bt rice,Bt rice release similar volatiles both in quality and quantity.However,C.suppressalis showed a strong ovipostion preference to healthy plants compared with damaged rice,no matter it was Bt rice or non-Bt rice.In field bioassay,we also found that non-Bt plots suffered a much worse damage from C.suppressalis larvae than Bt plots,and C.suppressalis moths prefer to oviposit in Bt rice plots,not in non-Bt rices.Our results are valueable in the selection of appropriate Bt proteins in Bt rice transformation,and also provide an important scientific basis of the future insect resistance management in Bt rice.