RNAi targeting Nav and CPR via leaf delivery reduces adult emergence and increases the susceptibility to λ-cyholthin in Tuta absoluta (Meyrick)

The tomato leafminer, Tuta absoluta (Meyrick), one of the most economically destructive pests of tomato, causes severe yields losses of tomato production globally. Rapid evolution of insecticide resistance requires the development of alternative control strategy for this pest. RNA interference (RNAi) represents a promising, innovative control strategy against key agricultural insect pests, which has recently been licensed for Colorado Potato Beetle control. Here two essential genes, voltage-gated sodium channel (Na_v) and NADPH-cytochrome P450 reductase (CPR) were evaluated as targets for RNAi using an ex vivo tomato leaf delivery system. Developmental stage-dependent expression profiles showed TaNa_v was most abundant in adult stages, whereas TaCPR was highly expressed in larval and adult stages. T. absoluta larvae feeding on tomato leaflets treated with dsRNA targeting TaNa_v and TaCPR showed significant knockdown of gene expression, leading to reduction in adult emergence. Additionally, tomato leaves treated with dsRNA targeting these two genes were significantly less damaged by larval feeding and mining. Furthermore, bioassay with LC₃₀ doses of λ-cyholthin showed that silencing TaNa_v and TaCPR increased T. absoluta mortality about 32.2 and 17.4%, respectively, thus indicating that RNAi targeting TaNa_v and TaCPR could increase the susceptibility to λ-cyholthin in T. absoluta. This study demonstrates the potential of using RNAi targeting key genes, like TaNa_v and TaCPR, as an alternative technology for the control of this most destructive tomato pests in the future.