CRISPR/Cas9-mediated mutation of nicotinic acetylcholine receptor (nAChR) α subunit confers moderate levels of resistance to spinosad and imidacloprid in the natural predator Coccinella septempunctata without fitness cost

Abstract

Chemical insecticides and natural enemies are important components of integrated pest management (IPM) and are usually incompatible in the field environment. The ladybird beetle Coccinella septempunctata is a generalist predator of aphids worldwide. However, its field application is seriously restricted because it is highly susceptible to insecticides. Here, we constructed CRISPR/Cas9-edited C. septempunctata harboring mutations in the nicotinic acetylcholine receptor α subunit (nAChRα). The C. septempunctata nAChRα (Csnα) knockout strain (Csnα-D7) showed moderate resistance to spinosad (28.56-fold) and imidacloprid (17.28-fold), but no resistance to abamectin. The survival rates of the caged Csnα-D7 C. septempunctata treated with spinosad and imidacloprid at field concentrations were significantly higher than the survival rates of the caged wild-type ladybird beetles treated with field label doses of the same insecticides. The Csnα-D7 strain exhibited normal growth, development, reproduction, and predation performance compared to wild-type ladybird beetles, suggesting a low fitness cost caused by the Csnα mutation. Heritance analysis demonstrated that the resistance to spinosyns in Csnα-D7 was autosomal, incompletely recessive, and closely related to the Csnα mutation. This study significantly enhanced the compatibility of insecticides with natural enemies using CRISPR/Cas9 technology, contributing to the reduction in insecticide usage and improvement of the ecological environment.