Mechanisms of resistance to insecticides targeting RDL GABA receptors in planthoppers

- A2′S/G mutations in RDL GABA receptor confer cyclodiene resistance in various pests.
- A2′S/G mutations confer low level of cross resistance to fipronil.
- A2′N mutation in RDL GABA receptor confers fipronil resistance in planthoppers.
- PCR-RFLP assays were developed for detecting fipronil-resistant planthoppers.
- There is a need to develop novel insecticides effective against A2′ mutations.

Lindane and cyclodienes, such as dieldrin and α-endosulfan, represent the first generation of noncompetitive antagonists (NCAs) against the insect RDL GABA receptor. It has been reported that A2′S and A2′G mutations in the membrane-spanning region M2 of the RDL GABA receptor confer resistance to lindane and cyclodienes. Fipronil is a second-generation NCA, but A2′S and A2′G mutations provide a low level of cross-resistance to fipronil. Moreover, a novel A2′N mutation that confers fipronil resistance was found in M2 of the RDL GABA receptors from fipronil-resistant planthoppers in the heterozygous state. Thus, problems are being caused by a worldwide appearance of cyclodiene-resistant pests. And attention must be paid to development of fipronil-resistant planthoppers, such as Sogatella furcifera and Laodelphax striatellus in Japan.