Monitofing,Risk Assessment And Mechanisms Of Aphis Gossyppi(Glovet)Resistance To Neonicotinoid Insecticides In Xinjiang

1.The imidacloprid and acetamiprid susceptible strains (LC5o were0.176mg/L and0.180mg/L, respectively) were developed by individual reverse selection. The LC50value of the imidacloprid and acetamiprid susceptible strain had a2and1.73fold decrease compared with the field strain (LC50were0.346mg/L and0.312mg/L, respectively). The resistant strains of A. gossypii were obtained after forty selection with imidacloprid and acetamiprid by group selection. The resistance index of imidacloprid and acetamiprid resistant strain were83.27-fold (LC50was14.657mg/L) and82.33-fold (LC50was14.819mg/L), respectively. The realized heritability (h2) of resistance were0.1478and0.1342by Tabashnik’s methods. In order to estimate the speed of resistance, it would take cotton aphid30.2-38.1and30.3-38.2ages of to obtain100-fold resistance to imidacloprid and acetamiprid, which was under breeding pressure of imidacloprid and acetamiprid. The results showed that A. gossypii had the resistance risk to imidacloprid and acetamiprid.2. The results of cross-resistance to imidacloprid and acetamiprid-resistant strains were analyzed.(1) The results of cross-resistance to imidacloprid-resistant strains showed that the cross-resistaace of imidacloprid less than5folds were pymetrozine and Methyl abamectin, in5-10folds were thiamethoxam, endosulfan, abamectin, bifenthrin, chlorpyrifos, malathion, profenofos and Phoxim, in10-15folds were acetamiprid, beta-cypermethrin and triazophos, more than15folds was Omethoate.(2) The results of cross-resistance to acetamiprid-resistant strains showed that the cross-resistance of acetamiprid-resistant strains less than5folds were pymetrozine and Methyl abamectin, in5-10folds were thiamethoxam, bifenthrin, chlorpyrifos, malathion, profenofos and Phoxim, in10-15folds were endosulfan, abamectin, beta-cypermethrin, triazophos and Omethoate, more than15folds was imidacloprid.3. The survey for susceptible levels of cotton aphid to imidacloprid and acetamiprid of each cotton region in xinjiang showed that the relative resistance multiples to imidacloprid and acetamiprid were3.17-4.87folds and1.7-22.0folds. The resistance development speed to acetamiprid was faster than imidacloprid compared with2011in2012.4. Synergism tests showed that triphenyl phosphate (TPP), piperonyl buoxide (PBO) and diethyl maleate (DEM) resulted in1.12,1.09and0.97-fold synergist ratios, respectively in the imidacloprid-susceptible strain. It was2.02,1.75and1.05-fold SR, respectively in the imidacloprid-resistant strain. It was1.02,1.03and1.02-fold SR, respectively in the acetamiprid-susceptible strain. It was2.02,1.75and1.05-fold SR, respectively in the imidacloprid-resistant strain. TPP and PBO had a good synergistic effect on imidacloprid and acetamiprid.5. The detoxification enzymes tests showed that the activity of CarE, GST and7-ethoxycoumarin O-deethylase (ECOD) in the resisitant strain were higher than in susceptible strain. Among them, the activity difference of the CarE and ECOD reached significant level (P<0.05). The activity of three kinds detoxification enzymes in imidacloprid resisitant strain were3.26-,1.08-and1.60-folds that of the susceptible strain.The activity of three kinds detoxification enzymes in acetamiprid resisitant strain was2.91-,1.04-,1.69-times that of the susceptible strain.6. Determination of individual aphid carboxylesterase (CarE) by microplate assay showed the activity of CarE in imidacloprid, acetamiprid resistant Aphis gossypii strains was higher than in susceptible strains. Determination of individual aphid acetylcholinesterase (AChE) by microplate assay showed the activity of AChE in imidacloprid, acetamiprid resistant Aphis gossypii strains was higher than in susceptible strains.7. The mRNA relative expression level of CarE and P450monooxygenase gene were determined by real-time quantitative PCR. The mRNA relative expression level of CarE gene in imidacloprid resistant strains was1.85-fold of that of the sensitive strain; The mRNA relative expression level of P450CYPCY3-1in imidacloprid resistant strains was1.60-fold of that of the sensitive strain; The mRNA relative expression level of P450CYPCY3-2in imidacloprid resistant strains was2.00-fold of that of the sensitive strain; The mRNA relative expression level of CarE gene in acetamiprid resistant strains was1.91-fold of that of the sensitive strain; The mRNA relative expression level of P450CYPCY3-1in acetamiprid resistant strains was1.44-fold of that of the sensitive strain; The mRNA relative expression level of P450CYPCY3-2in acetamiprid resistant strains was1.30-fold of that of the sensitive strain. Therefore, the overexpression of CarE, P450CYPCY3-1and P450CYPCY3-2in Aphis gossypii were closely related with the resisitance to imidacloprid and acetamiprid.8. The mRNA relative expression level of nAChR beta1subunit were determined by real-time quantitative PCR. The mRNA relative expression level of the imidacloprid resistant strains was0.85-fold of that of the sensitive strain; The mRNA relative expression level of nAChR beta1subunit in acetamiprid resistant strains was0.36-fold of that of the sensitive strain. Therefore, the low level expression of nAChR beta1subunit gene in Aphis gossypii was closely related with the resisitance to imidacloprid and acetamiprid.9. According to the gene sequence logged on NCBI about Aphis gossypii nAChR betal subunit (GenBank:JQ627836.1), the specific primers were designed to detect the susceptible strain R81T position of arginine(codon:AGA) might be replaced by threonine (codon:ACA) in resistant strains. The results showed that the Aphis gossypii population of imidacloprid, acetamiprid-resistant strain, sensitive strain, main cotton region in Xinjiang, Zaoyang city in Hubei, Xihua County in Henan, Xiao County in Anhui, Yuncheng City in Shanxi all were not detected the mutation.