Resistance Monitoring And Sodium Channel Gene Analysing In Adelphocoris Suturalis

The Adelphocoris suturalis (Heteroptera:Miridae), which used to be a minor pest to crops, can damage cotton, cereals, vegetables, fruit crops, etc. Insecticides sprays against cotton bollworm have been reduced in cotton field as a result of the large-scale planting of transgenic Bt cotton, which makes mirids (including A. suturalis) a major problem in the cotton pest control in China.The rise of mirids has driven farmers back to insecticides. Continuous and unreasonable use of insecticides will lead to resistance evolution in A. suturalis. The resistance situation of A. suturalis was revealed in this study by monitoring the resistance to chlorpyrifos, alpha-cypermethrin, emamectin and fipronil in Nanjing, Yancheng, Chuzhou, and Jingzhou populations from2009to2012. Furthermore, an alpha-cypermethrin-resistant strain was selected and the sodium channel gene was cloned and analyzed from A. suturalis. These results will be helpful to further investigate on resistance mechanisms of A. suturalis to pyrethroids.1. The toxicity of insecticides to the susceptible strain of A. suturalisThe toxicities of16insecticides to the susceptible strain of A. suturalis were measured by glass-vial bioassay. The results revealed that fipronil showed the highest toxicity (LC50:0.08mg/L) to A. suturalis while chlorantraniliprole had the lowest toxicity (LC50:549.41mg/L). According to the results, the toxicities of16insectides to A. suturalis were ranked as:fipronil> chlorpyrifos> malathion> fenvalerate> bifenthrin> alpha-cypermethrin> lambda-cyhalothrin> thiamethoxam> imidacloprid> acetamiprid> carbosulfan> indoxacarb> emamectin> chlorfenapyr> diafenthiuron> chlorantraniliprole.2.Resistance monitoring to insecticides and activities determining of detoxification enzyme activities in field populations of A. suturalisResistance to chlorpyrifos, alpha-cypermethrin, emamectin, and fipronil was monitored by glass-vial bioassay in A. suturalis populations collected from Nanjing, Yancheng, Chuzhou and Jingzhou areas from2009to2012. Compared with a susceptible strain, most field populations were still susceptible to chlorpyrifos, alpha-cypermethrin, emamectin and fipronil, but the populations from Jingzhou had developed low levels of resistance to alpha-cypermethrin (9.2-fold in2011, and10.0-fold in2012). The activities of esterase, glutathione S-transferase and monooxygenases in field strains of A. suturalis populations were measured. The results showed that all metabolic enzyme activities in field populations were higher than those in the susceptible strain, but no correlation was observed between activities of detoxification enzymes and resistance levels.3. Selection of alpha-cypermethrin-resistant strain of A. suturalisThe resistant strain of A. suturalis to alpha-cypermethrin (JAR) was selected from a field-derived Jingzhou population. After sevral generations of selection in laboratory, resistance to alpha-cypermethrin in the JAR strain was increased to15.9-fold compared with the susceptible strain.4. Structure and alternative splicing of sodium channel gene of A. suturalisThe full-length cDNA of the sodium channel gene (Aspara) was cloned and characterized from A. suturalis. The cDNA of Aspara encoding2027amino acid residues contains a6,084bp ORF,574bp5’UTR and217bp3’UTR. Aspara shares common structural and sequence features with the sodium channel genes of other insect species. Six different optional exons were detected in Aspara and it may increase functional diversity and complexity of this gene.