Exploring the role of cytochrome P450s in insecticide resistance using RNA interference in Bemisia tabaci (Gennadius) populations from Georgia, USA

The sweetpotato whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae), is a major pest of vegetable and agronomic crops in Georgia. Extensive studies of whitefly populations from Georgia have demonstrated the development of resistance to the neonicotinoid active ingredient imidacloprid (IRAC Class 4A), as well as the diamide active ingredient cyantraniliprole (IRAC Class 28). While the underlying mechanisms remain poorly understood for populations from this region, previous studies have revealed that increased cytochrome P450 (CYP450) detoxifying enzyme levels in insect cells are associated with resistance from other locations. Focusing on the MEAM1 B-biotype, an invasive whitefly species in Georgia used in this study to examine potential resistance mechanisms mediated by CYP450 enzymes. Using qPCR analysis, the mRNA expression levels of CYP6CM1 and CYP6DW2 were upregulated after insecticide exposure for both imidacloprid and cyantraniliprole-resistant populations compared to susceptible strains. Interestingly, only the cyantraniliprole-resistant strain exhibits overexpression of CYP6CX2 and CYP6CX3 among the studied CYP450 genes. To study the role of multiple CYP450 genes in both imidacloprid and cyantraniliprole-resistant populations, RNA interference (RNAi) was used to suppress the expression levels of four selected CYP450 genes. Feeding the resistant population with specific dsRNA targeting CYP450 significantly decreased their expression levels, supporting the qPCR results. The effect of these knockdowns on imidacloprid and cyantraniliprole susceptibility is currently under study. Understanding these mechanisms is crucial for developing effective pest control strategies and protecting agricultural interests in the region.