Sublethal Dose of β-Cypermethrin Impairs the Olfaction of Bactrocera dorsalis by Suppressing the Expression of Chemosensory Genes

SIMPLE SUMMARY: The oriental fruit fly, Bactrocera dorsalis, is a pest that causes huge economic losses in the fruit and vegetable industry. β-cypermethrin has been widely used in the orchard to control this major pest. According to a previous study, the oriental fruit fly developed significant resistance against β-cypermethrin in fields, which indicated that the oriental fruit fly has been exposed to sublethal concentrations of β-cypermethrin in the field for a long time. However, the sublethal effect and its mechanism are still unclear. In our present study, after treatment with sublethal concentrations of β-cypermethrin, the olfaction was disrupted significantly and the chemosensory genes were suppressed obviously. Our data demonstrated that the sublethal dose of β-cypermethrin impairs the olfaction of the pest insects by suppressing the expression of chemosensory genes, which provided theoretical guidance for the rational use of pesticides in fields. ABSTRACT: The oriental fruit fly, Bactrocera dorsalis, is one of the most destructive fruit insect pests. β-cypermethrin has been widely used in the orchard to control this major insect. Based on the resistance monitoring in 2011, B. dorsalis developed significant resistance against β-cypermethrin in fields. This indicated that the B. dorsalis has been exposed to sublethal concentrations of β-cypermethrin in the field for a long time. Thus, it is urgent to understand the sublethal effects of β-cypermethrin on this fly to guide the rational use of an insecticide. According to the olfactory preference assays and electroantennogram (EAG) recording, the B. dorsalis after β-cypermethrin exposure (LD(30) = 10 ng/fly) severely decreased the ability to perceive the tested odorants. Moreover, we then performed quantitative real-time PCR and found the chemosensory genes including odorant receptor co-receptor (BdorORco) and ionotropic receptor co-receptors (BdorIRcos) were obviously suppressed. Our results demonstrated that the sublethal dose of β-cypermethrin impairs the olfaction of the pest insects by suppressing the expression of chemosensory genes (BdorORco and BdorIRcos), which expanded our knowledge of the sublethal effects of the pesticide on insects.