The Resistance Research Of Different Types Of Insecticides Against On Field Laodelphax Striatellus

Laodelphax striatellus is a notorious pests of rice,so far,chemical control is an effective way to control their population outbreak.Understanding the field resistance levels and resistance mechanism of L.Striatellus is an important measure for effective controlling in this pest.In this paper,the resistance levels and potential resistance mechanisms as well as the target sequence variations were investigated,the results will provide the new perspective for pest management.1.The degree of resistance of the JH,NJ,JY,LY of jiangsu province,songjiang of shanghai province and DB of jilin province strains of L.striatellus against chlorpyrifos,buprofezin,thiamethoxam and pymetrozine were assayed by the rice seedling dip bioassay method using the susceptible strain of yunnan as a control.The result showed different field strains of L.strziatellus had produced higher resistance levels against pymetrozine and buprofezin than the yunnan strain:the average resistant levels of huadong region was more than 100 fold,of which liyang strain reach as to 156 fold,and relative lower resistance strain of changchun also showed as much as 26 fold;the resistance degree of different strain against pymetrozine was between 18-34 fold,and had no significant difference among changchun strain and huadong strains,but the chlorpyrifos and thiamethoxam all showed lower resistance levels than other two insecticides(below 10 fold);moreover,changchun strain had lower resistance levels in comparison with all huadong strains of china,and this was accord with the characteristics of the preliminary resistance development steps.The results of synergistic effects of PBO,TPP and DEM on different resistance strains indicated that esterase inhibitor TPP synergized buprofezin 4.8 fold in the lijiang strain but not in strain YN strain.The glutathione depleter DEM showed 2.0 fold and 2.1 fold synergism with thiamethoxam and pymetrozine in liyang strain,respectively.In addition,most results had little synergistic effects apart from the situation discussed above,which indicated the complex resistance mechanism might exist in the different insecticide application backgrounds.Above all,the resistance mechanism of different geographical population remained to be further elucidated in future.2.We designed the JY,LY,NJ as resistance strains,jilin(DB)and yunnan(YN)as susceptible contrast strains.The detoxification gene quantitative analysis found that Ls.CarEl,Ls.CarE14,Ls.CarE15 of carboxylesterase gene and CYP305 and CYP6CW1 of cytochrome P450s showed synchronous overexpression in different resistance strains compared to the susceptible strains.The specific results as follows,Ls.CYP6CWl spectively showed 8.87-22.24 fold overexpression in jiangsu strains,CYP305 and CYP6CW1 spectively showed fold overexpression.Moreover,Ls.GSH7 overexpressed(14.98 fold and 7.13 fold)in the resistance strains of LY and DB strains.Ls.CYP6CWl and LS.CYP18A1 overexpressed(22.24 fold and 9.73 fold)in the resistance strains of JY strains;Ls Car E1,Ls.CarE14,Ls.CYP6CW1 and Ls.CYP4G76 overexpressed(11.67 hold,14.98 fold,14.96 fold and 14.27 fold)in the resistance strains of LY strains;Ls.CarEl,Ls.CarE14,LS.CYP6CW1 and Ls.CYP4G76 overexpressed(6.56 fold,4.99 fold,8.87 fold and 4.42 fold)in the resistance strains of NJ strains.In DB resistance strains,the inconspicuous overexpression of Ls.CarE11,Ls.GSH7 and Ls.CYP4G7 separately showed 4.82 fold,7.13 fold and 6.13 fold.These results externalized each corresponding enzyme gene overexpression may be associated with resistance to insecticides related,it needs further study.3.In this section,we found and sequence verified 18 acetylcholine receptor genes based on the transcriptome data,among of 8 sequences had the complete coding frame.Phylogenetic analysis showed that its spectively belong to alpha 1,alpha 2,alpha 3,alpha 4,alpha 5,alpha 6,alpha 8 and beta 1 subunits,and amino acid sequence alignment revealed that they had high amino acid identities compared with other insect species.Further sequence analysis of alpha 2 found it only existed the nucleotide polymorphisms but not the mutation of amino acids.In summary,different levels resistance were engender to L.Striatellus strains for several pesticide.The overexpression of Ls.CarEl,Ls.CarE14,Ls.CarE15,CYP305 and CYP6CW1 was the importantc reason for the produce metabolism resistant.We sequence verified 18 acetylcholine receptor genes based on the transcriptome data,among of 8 sequences had the complete coding frame.L.Striatellus resistant and susceptible strains to imidacloprid have some nucleotide polymorphisms,but amino acids comparison did not have divergence.These results will provide material insecticide resistance research and field resistance monitoring and early warning.