Insecticide Resistance Monitoring And The Detoxification Enzyme Activity Analyses Of Lithocolletis Ringoniella In Shaanxi Province

The apple leaf miner,Lithocolletis ringoniella Mats is an important pest which causes serious damage to apple trees and distributes widely in China.Larvae of the pest feed on mesophyll under leaf epidermis and seriously affect apple yields each year.Since its outbreak in China in the 1990s,this moth has gradually become an important pest in apple orchards.Irrational use of insecticides has led insect field populations to develop resistance.Monitoring the insecticide resistance level,investigating the population dynamics,identifying the detoxification enzyme genes and analyzing the enzyme activity of L.ringoniella is of great significance for controling this moth.In this study we monitored the insecticide resistance of L.ringoniella in Shaanxi Province,analyzed the detoxification enzyme activity associated with resistance in field populations,identified detoxification enzyme gene sequences by transcriptome data,and studied the changes of P450 genes expression level under pesticide induced conditions.The main results as follow:1.Population dynamics of L.ringoniellaBy investigating population dynamics of L.ringoniella in different fruit orchards of Yangling area in Shaanxi Province for two consecutive years,we found that L.ringoniella had five generations a year in this area.The overwintering generation of adults occurred in early May,the first generation of the adults occurred in late May,the second generation occurred in late June to early July,the third generation occurred in early August,and the fourth generation occurred in mid-September.2.Insecticide resistance monitoring of L.ringoniella in Shaanxi ProvinceThe leaf dipping method was used to determine the insecticide resistance level of L.ringoniella field populations from apple orchard in Baishui,Liquan,Fufeng and Xunyi areas.The results showed that different populations of the moth had different susceptibility to abamectin,lambda-cyhalothrin,diflubenzuron,and chlorantraniliprole.The highest sensitivity to abamectin,diflubenzuron and chlorantraniliprole was found in the field population from Fufeng area.The relative resistance ratio to diflubenzuron of Xunyi population was 7.26 in comparison with the Fufeng population.The correlation analysis showed that there was a significant positive correlation between the relative resistance of the L.ringoniella to lambda-cyhalothrin and diflubenzuron.3.Detoxification enzyme activity and effect of insecticide induction on the detoxification enzyme activity of different L.ringoniella populationsThe detoxification enzyme activity varied among different L.ringoniella populations.The P450 activity of the population from Xunyi was significantly higher than that the population from Baishui.After induction of LC₅₀ concentrations of abamectin,lambda-cyhalothrin,diflubenzuron and chlorantraniliprole,the activities detoxification enzyme of L.ringoniella larvae changed with different patterns.The P450 enzyme activity of L.ringoniella from Fufeng was significantly increased after the induction with abamectin,diflubenzuron and chlorantraniliprole,respectively.4.Identification of detoxification enzyme genes and the effect of insecticide induction on P450 gene expression of L.ringoniella field populationsWe identified the gene sequences of detoxification enzyme of L.ringoniella using the transcriptome data obtained.The P450,GST and Car E gene sequences identified were used for phylogenetic analyses,respectively.The P450 expression level of L.ringoniella under LC₅₀ concetration of abamectin,diflubenzuron and chlorantraniliprole concentrations induction was analyzed,respectively.The expression level of three P450 genes（Lri53793,Lri49134 and Lri51659）genes was increased after abamectin and chlorantraniliprole induction.The expression of Lri53793 gene was increase 1.72,6.53 and 7.41 fold after abamectin,diflubenzuron and chlorantraniliprole induction,respectively.This study shows that L.ringoniella had five generations a year in Yangling area.According to the results of bioassay,there is a risk of resistance to lambda-cyhalothrin and diflubenzuron in Shaanxi.It is recommended to rotate with other insecticides.We preliminarily explored the expression pattern of P450 genes induced by pesticides.This study provide knowledge for the the rational use of pesticides and integrated control of L.ringoniella.