مقاومت به آبامکتین در جمعیت‌های ایرانی عسلک‌‌پنبه (Bemisia tabaci) و سفیدبالک گلخانه (Trialeurodes vaporariorum)

The sweet potato whitefly (Bemisia tabaci) and greenhouse whitefly (Trialeurodes vaporariorum) are among the most damaging species among whiteflies. Abamectin is a broad spectrum insecticide/acaricide belongs to the group of avermectins, which mainly act on the GABA-gated and glutamate-gated chloride channels. The mechanisms of resistance in different arthropod species have been linked to the mutations in the target sites and enhanced detoxification by overexpression of cytochrome P450 monooxygenases, glutathione S-transferases, esterases and uridine diphosphate glycosyltransferases. The aim of this study was to evaluate the resistance in several B. tabaci and T. vaporariorum populations to abamectin. For this purpose, six B. tabaci populations and six T. vaporariorum populations were collected from different regions of Isfahan province, and the sensitivity of the populations to abamectin was determined by the toxicity bioassays using a leaf dip method. Based on the LC50 values, a 14-fold resistance ratio was determined in Sin population (B. tabaci) and a 19-fold resistance ratio in Tiran population (T. vaporariorum). To elucidate the resistance mechanisms, the effects of pretreatment with three synergists, pipronil butoxide (PBO), triphenilphosphat (TPP) and di ethyl maleat (DEM), were investigated. In the resistant populations, the synergistic ratios of PBO, DEM and TPP on abamectin were 5.06, 3.87 and 2.08 in Sin, 6.46, 4.03 and 2.5 in Tiran, respectively. Also, the activity of cytochrome P450 monooxygenases, esterases and glutathione S-transferases (GST) were determined. The results showed that the activity of cytochrome P450 monoxygenase enzymes, glutathione S-transferases and finally carboxylesterase activity was higher in resistant populations. The cross-resistance levels in these populations were also assessed against emamectin benzoate, chlorpyrifos, deltamethrin, fipronil and spinosad. Abamectin resistant populations of Sin and Tiran exhibited a high cross resistance to emamectin benzoate, 9.09-fold and 13.23-fold, respectively. In conclusion, in both B. tabaci and T. vaporariorum populations, enhanced metabolism, especially P450s, seems to have a major role in abamectin resistance. The results might have implications in the early detection of abamectin resistance in whitefly populations and are potentially valuable in reducing insecticide use.