Resistance Monitoring In Field Populations Of Bemisia Tabaci And Genomic Structure Analysis Of Btgluclαl

The whitefly (Bemisia tabaci) has become a serious pest of global importance. It has caused huge losses on cotton and vegetable production. Due to resistance to insecticides, the whitefly is hard to control by insecticides in the field. In order to determine resistance status and screen for effective insecticides, resistance levels of insecticides in field populations of Bemisia tabaci collected from Jiangsu, Fujian, and Guangdong Provinces of China were monitored. Abamectin is one of the most effective insecticides for the whitefly control, and insect glutamate-gated chloride channel receptor is the major target site of abamectin. Full length cDNA and genomic DNA of an alpha subunit of glutamate receptors from B. tabaci (BtGluClal) were sequenced and cloned. Genomic structure and alternative splicing of this receptor gene were analysed.Insecticide resistance levels were determined in ten field populations of B. tabaci collected in 2008 from Jangsu, Fujian, and Guangdong Provinces of China. Seven insecticides (abamectin, fipronil, spinosad, imidacloprid, thiamethoxam, chlorpyrifos, and a-cypermethrin) were included in this monitoring program. When a laboratory strain of B-type B. tabaci (NJ-S) was used as a reference, moderate to high levels of resistance to neonicotinoids were observed in all populations from three provinces, and a field population (JS-YC) from Yancheng of Jangsu province exhibited more than 1,000-fold resistance to both imidacloprid and thiamethoxam. All populations showed either decreased susceptibility or low levels (less than 10-fold) of resistance to abamectin, spinosad, fipronil, chlorpyrifos, and a-cypermethrin, except that the JS-YC population had a middle level of resistance to fipronil (25-fold). When compared with the susceptible SUD-S strain, all populations tested had middle to high levels of resistance to both chlorpyrifos and a-cypermethrin. The glutamate-gated chloride channel (GluC1) receptor is the major target site of abamectin in insects. The full-length cDNA and genomic DNA (about 30kb) of a glutamate receptor gene (BtGluClal) in B. tabcai were cloned and sequenced based on previous work. The coding sequence of BtGluClal is splited by 10 introns, of which the intron-4 is the shortest (475 bp) and the intron-3 is the longest (5.8 kb). Five different transcripts were obtained after sequencing 10 full-length cDNAs of BtGluClal. By alignment of cDNA and gDNA sequences of BtGluClal, three alternative splicing sites in the exon2, exon9, and exonlO were detected. Multiple transcripts of BtGluClal may increase functional diversity and complexicity of this gene, and this work provided useful information for study on target site resistance to abamectin in B. tabaci.