Resistance Monitoring Of Laodelphax Striatellus,Sogatella Furcifera And Biochemical Resistance Mechanisms Of Buprofezin In Nilaparvata Lugens(St(?)l)

Rice planthoppers are important pests in rice production in Asian countries,there are mainly three kinds of rice planthoppers which damage the rice in China,Laodelphax striatellus(Fallen),Sogatella furcifera(horvath)and Nilaparvata lugens(Stal).Chemical control is still a major measure for controlling rice planthoppers.As a result,it is very significant to know the resistance status of commonly used insecticides and guide the rational use of insecticides in the field.Buprofezin,an important insecticide of IGRs,has been used for control rice planthopper for more than 30 years,N.lugens has been generally reached high level resistance to buprofezin,nevertheless,it is necessary to study the resistance mechanism of the brown planthopper,so that it will play a better role in the control of rice planthoppers.1.Resistance monitoring to insecticides of L.striatellusIn order to know resistance levels of L.striatellus we monitored the resistance of L.striatellus field populations collected from Jiangsu,Anhui and Zhejiang province in 2015 and 2016.The 11 field populations monitored during 2015-2016 were moderate resistance levels to chlorpyrifos(12.4-67 fold),all the monitored populations were susceptible to thiamethoxam(0.7-3.4 fold),nitenpyram(0.5-1.5 fold)and dinotefuran(1.6-4.6 fold),all the monitored populations were susceptible to pymetrozine(2.4-4.4 fold)except GC15 population(6.0-fold),all the tested populations exhibited susceptible to sulfoxaflor(1.5-5.0 fold)except GC16 population(6.0-fold).We suggested to limit applying times of chlorpyrifos.In consideration of L.striatellus was susceptible to nicotine insecticides such as thiamethoxam,nitenpyram,dinotefuran,sulfoxaflor,so nicotine insecticides and pymetrozine can be used in the field to control of L.striatellus,2.Resistance monitoring to insecticides of S.furciferaTo clarify the resistance levels of S.furcifera to 7 insecticides we monitored the resistance of 10 S.furcifera field populations collected from Jiangsu,Anhui,Jiangxi,Zhejiang and Sichuan province in 2015-2016.The 10 field populations monitored during 2015-2016 were moderate resistance levels to chlorpyrifos(18.1-49.6 fold),XY15(191.5-fold),JH15(155.3-fold)and XY16(113.6-fold)populations,which accounted for 30%of the total populations,were high resistance levels to buprofezin,others exhibited moderate resistance levels(33.5-93.6 fold).All the tested populations during 2015-2016 kept susceptible levels to imidacloprid,only the YC2016 population developed low resistance levels to imidacloprid.60%of all the monitored populations showed moderate resistance levels to pymetrozine.The results showed the field populations of S.furcifera were moderate or high resistance levels to chlorpyrifos and buprofezin,so we suggest to reduce using chlorpyrifos and buprofezin in areas with high resistance,S.furcifera was more susceptible to nicotine insecticides such as thiamethoxam,dinotefuran and sulfoxaflor,so nicotine insecticides and pymetrozine can be used in the field of control of S.furcifera.3.Biochemical mechanisms of buprofezin resistance in N.lugensBuprofezin is a selective insecticide which can inhibit the synthesis of chitin and interfere with the normal metabolism of insects,it can kill insects during the molting process,and it has strong insecticidal activity of rice planthopper nymphs.At the end of 1980s buprofezin was introduced into China and applied to control of N.lugens,at present,N.lugens has reached high level of resistance to buprofezin.To identify which metabolic enzymes are involved with buprofezin resistance,the effects of three synergists in the susceptible and buprofezin-resistant N.lugens were compared by synergist experiment,the results showed that the synergistic effect of PBO,a multifunctional oxidase inhibitor,was stronger in the resistant strain than susceptible strain,indicating that buprofezin resistance in N.lugens might be related to the metabolism of P450 enzyme.To make it sure which P450s family genes is related with buprofezin resistance,the mRNA levels of cytochrome P450s family genes in resistant and susceptible strains were detected by qRT-PCR,we found that 7 P450 genes were overexpressed in the BPH resistant strains,and the mRNA level of CYP6ER1 was the most significant difference between the resistant strain and susceptible strain.In order to in vivo evaluate the roles of CYP6ER1 in buprofezin resistance,CYP6ER1 mRNA was decreased by RNA interference,when CYP6ER1 mRNA levels in resistant strain was reduced,buprofezin susceptivity would significantly increase.Use of the GAL4/UAS gene expression system to drive the expression of CYP6ERl would reduce the susceptibility of Drosophila melanogaster to buprofezin.Therefore,we can draw a conclusion:the over-expression of CYP6ER1 is associated with buprofezin resistance in N.lugens.