Mapping and Characterization of Target-Site Resistance to Cyclic Ketoenol Insecticides in Cabbage Whiteflies, IAleyrodes proletella/I

Cabbage whitefly (Aleyrodes proletella) is a destructive sucking insect pest of brassica crops, particularly white cabbage and kale. Its importance has been increased over the last decade in many geographic regions, particularly in European countries. The control of cabbage whiteflies largely relies on the application of synthetic insecticides to protect yield if populations reach economic damage thresholds. One class of insecticides to control this pest are cyclic ketoenols targeting acetyl-CoA carboxylase (ACC), an enzyme involved in fatty acid biosynthesis. In 2019, reduced efficacy of ketoenol insecticides at recommended label rates were reported. Subsequently, we collected field samples of A. proletella in different European countries and confirmed the presence of ketoenol resistance in laboratory bioassays. The resistance allele was shown to be an autosomal dominant trait in crossing experiments between susceptible and resistant individuals. RNA sequencing and subsequent analysis revealed a mutation, an amino acid substitution, at the ketoenol binding site in ACC. The mutation has been previously functionally validated to confer high levels of ketoenol insecticide resistance in cotton whiteflies, too. A molecular screening of 49 populations revealed the presence of the mutations in several countries. We recommend the implementation of resistance management strategies for sustainable cabbage whitefly control. Cabbage whitefly, Aleyrodes proletella L., is an invasive hemipteran pest of cruciferous plants, particularly field brassica crops. Its importance has been increased over the last decade, particularly in European countries. The control of cabbage whiteflies largely relies on the application of synthetic insecticides, including tetronic and tetramic acid derivatives such as spiromesifen and spirotetramat (cyclic ketoenol insecticides), acting as insect growth regulators targeting acetyl-CoA carboxylase (ACC). In 2019, reduced efficacy against cabbage whiteflies of ketoenol insecticides at recommended label rates has been reported. Subsequently we collected field samples of A. proletella in different European countries and confirmed the presence of ketoenol resistance in laboratory bioassays. Reciprocal crossing experiments revealed an autosomal dominant trait, i.e., heterozygotes express a fully resistant phenotype. Transcriptome sequencing and assembly of ACC variants from resistant strains revealed the presence of an ACC target-site mutation, A2