Whiteflies, particularly the greenhouse whitefly (Trialeurodes vaporariorum), are significant pests in vegetable and summer crops, contributing to substantial yield losses worldwide. They cause damage both by feeding on plant sap and by transmitting plant pathogens. Continuous and extensive use of chemical insecticides for whitefly management has led to the development of resistance, especially to ketoenols, a class of insecticides that inhibit acetyl coenzyme A carboxylase (ACC). This study aimed to eva‎luate the resistance of greenhouse whitefly populations from Isfahan province to ketoenols and explore the mechanisms driving this resistance. Bioassays using the leaf dip method on second instar pupae revealed that the Shahrabarishm population exhibited an 8.71-fold resistance to spirotetramat and a 10-fold resistance to spiromesifen compared to the susceptible population (Daneshgah). Synergistic tests showed that pre-treatment with piperonyl butoxide (PBO), a P450 monooxygenase inhibitor, and triphenyl phosphate (TPP), an esterase inhibitor, increased the sensitivity to spirotetramat in the resistant population by 3.07 and 2.79 times, respectively. However, pre-treatment with diethyl maleate (DEM), a glutathione S-transferase inhibitor, did not alter the toxicity of spirotetramat, suggesting glutathione S-transferases play a limited role in resistance development. Further biochemical assays demonstrated significantly higher P450 monooxygenase and esterase activities in the resistant populations, indicating these enzymes are crucial to resistance development. In contrast, glutathione S-transferase activity appeared to have minimal impact, as evidenced by the lack of effect in DEM pre-treatments. Additionally, the study explored cross-resistance, with spirotetramat-resistant populations showing high cross-resistance to spiromesifen but lower cross-resistance to spiropidion. Sequencing of the ACC gene identified an A2083V mutation, where alanine was replaced by valine at position 2083, confirming that this mutation at the target site is likely the primary resistance mechanism. Moreover, symbiotic bacteria have emerged as a significant factor in insecticide resistance. All populations of T. vaporariorum were found to host the obligate symbiont Portiera and the facultative symbiont Arsenophonus. Notably, the resistant population from Shahrabarishm exhibited a significant overexpression of Hamiltonella symbionts, which may play a role in enhancing resistance. Understanding these mechanisms is vital for early detection and mitigation of resistance, thus preventing the escalation of resistance to ketoenol insecticides in greenhouse whitefly populations. Keywords: Bioassay, spirotetramat, spiromesifen, enzyme activity, A2083V mutation, cross-resistance, symbiotic bacteria

جهانگير خواجه علي , نفيسه پورجواد

مرضيه كشكولي , روح الله عباسي

لادن طلايي , مجيد طالبي