Resistance Risk Assessment And Preliminary Study On Metabolic Mechanism Of Nilaparvata Lugens To Yizuochongmiding

Brown planthopper is an important migratory pest in rice growing areas of China,which has seriously affected the yield and quality of rice.At present,the control of brown planthopper mainly relies on chemical insecticides.However,long-term inappropriate use of insecticides has resulted in increasingly severe resistance to brown planthopper.Yizuochongmiding is a kind of novel meionic insecticide developed by Guizhou University,which is expected to play an important role in the effective control and resistance management of brown planthopper.In this study,the sublethal effect of Yizuochongmiding on brown planthopper was studied in order to register and rationally use it in the field and prolong the future application periods in the field.A resistance strain of brown planthopper to Yizuochongmiding（ZMR）was obtained by indoor resistant strain screening,and the resistance risk of brown planthopper to ZMR was evaluated.The detoxification mechanism of brown planthopper against Yizuochongmiding was studied preliminarily.The main research results are as follows:1.Sublethal effect of Yizuochongmiding on brown planthopperThe effects of Yizuochongmiding on the growth,development and reproduction of the present and next generation of brown planthopper were investigated by the construction of a two-sex life table.The results showed that the treatment of Yizuochongmiding with LC₃₀had no significant effect on the adult longevity and fecundity of the F₀generation brown planthopper.However,the hatchability rate of F₁generation brown planthopper eggs decreased significantly under the treatment of Yizuochongmiding with LC₃₀,and the developmental duration of eggs and first-instar nymphs,the preadult stage,the longevity of female adults,APOP and TPOP of F₁generation brown planthopper were significantly shortened,which was mainly manifested in the significantly shortened mean generation duration T of F₁generation brown planthopper.The results showed that the sublethal concentration of Yizuochongmiding shortened the developmental duration of brown planthopper offspring.2.Risk assessment of resistance of brown planthopper to YizuochongmidingThe resistant strain（ZMR）with resistance ratio of 10.28-fold was obtained after 10successive generations screening by rice seedling dipping method.The resistant reality heritability h²of the resistant strain（ZMR）was estimated to be 0.25,indicating that Yizuochongmiding is a medium risk insecticide.The results of the cross resistance spectrum showed that Yizuochongmiding had no obvious cross resistance to triflumezopyrim,buprofezin and imidacloprid,but showed negative cross resistance to isoprocarb,ethofenprox,nitenpyram,cycloxaprid,chlorpyrifos,clothianidin,thiamethoxam,dinotefura and sulfoxaflor respectively.3.Biochemical mechanism of resistance of brown planthopper to YizuochongmidingDetoxification enzyme inhibitors and detoxification enzyme activities of brown planthopper（ZMR）and（ZMS）were tested.The results of detoxification enzyme inhibitor assay showed that the susceptibility of ZMR could be restored by enzyme inhibitor PBO treatment,and the relative synergism ratio was 1.76-fold.The results of detoxification enzyme activity assay showed that the activity of P450 increased significantly in the resistant strain（ZMR）,which was 2.31-fold than that of the susceptible strain（ZMS）.Further,the differential expression of P450 genes between the resistant strain（ZMR）and the susceptible strain（ZMS）was investigated by q RT-PCR.The results showed that among the 54 P450 detoxification enzyme genes,the expression of 3 genes was significantly down-regulated,and that of 12 genes was significantly up-regulated,among which CYP6CW1 was significantly up-regulated by 3.40-fold.Preliminary studies have shown that CYP6CW1 is related to the resistance of brown planthopper to Yizuochongmiding.