Flonicamid and knockdown of inward rectifier potassium channel gene CsKir2B adversely affect the feeding and development of Chilo suppressalis.

ABSTRACT

BACKGROUND: The selective insecticide flonicamid shows highly insecticidal activities against piercing-sucking insects and has been widely used for the control of Hemipteran insect pests, whereas its effects on Lepidopteran insect pests remain largely unknown. Recently, inward rectifier potassium (Kir) channel has been verified to be a target of flonicamid, however, functional characterization of Lepidopteran Kir genes is still lacking. RESULTS: Flonicamid shows no insecticidal toxicity against Chilo suppressalis larvae. However, the feeding and growth of larvae were reversibly inhibited by flonicamid (50-1200 mg L-1 ). Flonicamid treatment also remarkably reduced and delayed the pupation and eclosion of Chilo suppressalis. Additionally, five distinct Kir channel genes (CsKir1, CsKir2A, CsKir2B, CsKir3A and CsKir3B) were cloned from Chilo suppressalis. Expression profiles analysis revealed that CsKir2A was predominately expressed in the hindgut of larvae, whereas CsKir2B had high expressions in the Malpighian tubules and hindgut. RNA interference (RNAi)-mediated knockdown of CsKir2B significantly reduced the growth and increased the mortalities of larvae, whereas silencing of CsKir2A had no obvious effects on Chilo suppressalis. CONCLUSION: Flonicamid exhibits adverse effects on the growth and development of Chilo suppressalis. CsKir2B might be involved in the feeding behavior of Chilo suppressalis. These results provide valuable information on the effects of flonicamid on non-target insects as well as the function of insect Kir channels, and are helpful in developing new insecticide targeting insect Kir channels. © 2020 Society of Chemical Industry.