Preliminary Study On Sensitivity Different Of Ostrinia Furnacalis To Chlorantraniliprole And Its Mechanism

Ostrinia furnacalis is one of the most destructive pests of corn.Corn is an important grain and forage crop in China.In recent years,the occurrence of O.furnacalis has intensified.It can cause the lost 9 million tons（more than 30%）of production in an outbreak year,which has seriously threatened the economic benefits of corn.Chlorantraniliprole,a widely used and highly effective insecticide,has unique mechanism of action,non-cross resistance with other pesticides,non-toxic to beneficial insects,such as bees.However,high level of resistance to chlorantraniliprole has been observed with the cycle and frequency of use increasing in a variety of important agricultural pests,such as Plutella xylostella.The resistance of O.furnacalis to chlorantraniliprole has not been reported.In the study,the resistance strains of O.furnacalis to chlorantraniliprole were selected using diet-incorporation and topical application methods,and the resistance level to diamide insecticides of field population of O.furnacalis were assayed.On this basis,the main detoxification enzyme activities and the expression of the ryanodine receptor（RyR）gene in different O.furnacalis strains and population were compared and analyzed,by which the metabolic and target resistance mechanism of the diamide insecticide against O.furnacalis are initially explored.The results can provide basis for scientific,economical and effective control,and lay the foundation for making clear the resistance molecular mechanism of O.furnacalis to diamide insecticides.The major research results are as following:1.Resistance monitoring to diamide insecticides in selection strains and field population of O.furnacalisThe third instar larvae of SLR and SLTR strains were continuously selected by sublethal dose of chlorantraniliprole using diet-incorporation and topical application methods,respectively.And the sensitivities of Changji population（CJ）from Xinjiang to chlorantraniliprole,cyantraniliprole and tetrachlorantraniliprole were assayed by diet-incorporation method.The SLR strain at the 5^thgeneration and the SLR strain F23remained sensitive to chlorantraniliprole with the resistance ratio（RR）of 2.0-and 3.0-fold,respectively.The results of assayed showed that CJ population developed reduced sensitivity to chlorantraniliprole,and remained sensitive to cyantraniliprole and tetrachlorantraniliprole,in which RR was 3.75,1.05 and 1.29-fold,respectively.In summary,there was no significant change in the resistance level to chlorantraniliprole of the selection strains,and the sensitivity to chlorantraniliprole of the field population was decreased,which can be revealed that the resistance in O.furnacalis to chlorantraniliprole developed slowly.2.Activities measure of the detoxifying enzymes in O.furnacalis selection strains and field populationThe activities of cytochrome P450（P450）,esterase（EST）and glutathione S-transferase（GST）of 3^th larvae in SLTR,SLR strains and CJ population were measured by in vitro determination of detoxification enzyme activities.The results showed that the activities of detoxification enzyme in SLR and SLTR strains were significantly different from SS strain.The P450 activity was significantly increased in SLR strain F1,F2,F4,F5,F17 and F18 of SLTR strain compared to susceptible strain with 3.12,3.73,3.32 and 12.3-fold and 5.09,25.94-fold,respectively.The EST activity in SLR strain F1 decreased 45%significantly,whereas activities in F17 and F18 of SLTR strain increased significantly by 3.31-and2.72-fold.The activities of F14,F15,F16,F17 and F18 GST（with CDNB as the substrate）in SLTR showed gradually increased,in which the activity of F16,F17,F18 increased significantly by 1.80,2.48,6.46-fold respectively,and GST（DCNB as substrate）activity in the F1 of SLR strain and F16,F17 and F18 of SLTR strain increased significantly by1.66-fold and 3.01,1.87 and 8.75-fold compared with SS.The results of detoxification enzyme activities in CJ population showed significant increase of P450,EST and GST（CDNB as substrate）activities,which was 5.81,1.79 and 1.35-fold,respectively,while GST（DCNB as substrate）activity decreased significantly by 71%.Based on the above results,it is speculated that P450,EST and GST may have been involved in the resistance production of O.furnacalis to chlorantraniliprole.3.The molecular detection of target resistance of O.furnacalisThe expression of RyR gene in different populations of O.furnacalis were determined by q PCR.The q PCR results show that the relative expression of F15,F17,F19 in SLTR strain and SLR F1,F3,F5 had no significant difference from SS,while the RyR expression in CJ population increased significantly by 1.26-fold.Mutation detection of RyR result by PCR showed that no mutations were detected at E1339,Q4534,I4733 and G4890 positions of RyR in the CJ population.Based on the above results,it is speculated that the reduced sensitivity to chlorantraniliprole in O.furnacalis may be due to increased expression of RyR.