Resistance Risk Assessment And The Exploration Of Metabolic Resistance Mechanism Of Laodelphax Striatellus(fall(?)n)to Triflumezopyrim

The small brown rice planthopper（Laodelphax striatellus,SBPH）is one of the main piercing-sucking mouthparts pests that harm rice,corn and wheat.Triflumezopyrim（TFM）is a new type of dielectric insecticide developed by Du Pont Company,USA,which has good activity against SBPH.However,there are few researches on the risk and mechanism of resistance of SBPH to TFM.In order to evaluate the resistance risk of SBPH to TFM,the resistant strains of SBPH were obtained by continuous resistance selection of relatively susceptible strains with TFM in the laboratory and the resistance heritability,resistance stability,cross resistance and biological fitness were determined.Furthermore,the activities of three detoxification metabolic enzymes and cytochrome P450 genes expression in resistant and relatively susceptible strains were measured and compared,and the metabolic mechanism of resistance of SBPH to TFM was preliminarily discussed.The results showed that after 21 generations of continuous selection of SBPH by TFM,the LC₅₀ values increased from 0.5529 mg·L^-1 to 14.4563 mg·L^-1,and the resistance ratios increased to 26.15,showed the middle resistance level.From F₀ to F₈ generation,the resistance developed slowly,and the resistance ratios only increased to 3.25.From F₈ to F₂₁generation,the development of resistance increased rapidly,and the resistance ratios increaseed from 3.25 to 26.15.The results of resistance risk assessment of SBPH to TFM showed that the heritability of resistance to TFM was 0.0928.The resistance ratios of SBPH to TFM increased to 10 only needed 8 generations when the selected pressure reaches to 90%.The results of resistance stability showed that after 5 generations of continuous feeding without TFM,the LC₅₀ values decreased from 7.1822 mg·L^-1 to 6.0525 mg·L^-1,the resistance ratios decreased by 2.04,and the resistance decline rate was 0.0149.The results of cross-resistance showed that there was no cross-resistance between TFM and imidacloprid,nitenpyram,thiamethoxam,dinotefuran,flonicamid,pymetrozine and cyantraniliprole.The results of biological fitness showed that the cost of fitness of resistant strains was 0.89.Compared with the relatively susceptible strains,the 3^rd and 5^th instar nymph duration,pre-adult stage,APOP,longevity,emergence rate and hatching rate of resistant strains decreased significantly,while the ratio of male to female increased significantly.However,the fertility,life expectancy,inherent growth rate（R）,limited growth rate（λ）,net reproductive rate（R₀）and mean generation time（T）of resistant strains decreased slightly,but there was no significant difference.The results of detoxification metabolic enzyme activity of TFM resistance and susceptible strains showed that the activities of CYP450M and Car E in resistant strains increased significantly compared with susceptible strains,and the activities were 1.71 times and 1.16 times than that of susceptible strains,respectively.However,there were no differences in the activities of GST between the two strains.The results of enzyme inhibitor determination showed that PBO had significant synergistic effect on both resistant and susceptible strains,and the synergistic ratios were 1.88 and 1.52,respectively,the synergistic effect of resistant strains was more obvious.The enzyme inhibitors TPP and DEM have no obvious synergistic effect on two strains.Through the determination of cytochrome P450gene expression level,we found that CYP4CE2 and CYP4C78 genes of resistant strain were significantly over-expressed compared with susceptible strain.And the expression level of CYP4CE2 gene in resistant strain was 8.92 times higher than that in susceptible strains.According to the comprehensive research results,the resistance of SBPH to TFM may be related to the increase of CYP450M activities caused by the overexpression of CYP4CE2gene.