Responses to Host Plant Volatiles and Identification of Odorant Binding Protein and Chemosensory Protein Genes in Bradysia odoriphaga

The chive maggot Bradysia odoriphaga Yang et Zhang (Diptera: Sciaridae) is a devastating agricultural pest that feeds on liliaceous vegetables and edible mushrooms. The shared host plant volatiles and chemosensory genes of B. odoriphaga may together play crucial roles for insects to identify their host. However, the responses of B. odoriphaga to host volatiles remain unclear. Electroantennography (EAG) and behavioral bioassays were performed on 12 volatiles shared in Allium and Pleurotus. Hexanal evoked in both male and female adults extremely significant EAG responses. In behavioral assays, 3rd-instar larvae and female adults can be significantly repelled by methyl propyl disulfide, 1-octen-3-ol, or hexanal at the concentration of 100 mg/mL. Third-instar larvae and female adults were significantly attracted by limonene with a concentration of 10 and 100 mg/mL, respectively. In addition, 57 chemosensory genes, including 51 odorant binding proteins (OBPs) and 6 chemosensory proteins (CSPs), were identified based on transcriptomes of larvae and pupae. Compared with previous adult transcriptomes, 11 BodoOBPs were specifically expressed in adults, and 6 BodoOBPs were specifically expressed in larvae and pupae. BodoCSP2 and BodoCSP3 were exclusively expressed in the adult stage. Our results provided the potential substances in new ecofriendly pest management and the targets for further study of chemosensory gene functions.