First report of the kdr pyrethroid resistance mutation in a French population of the English grain aphid, Sitobion avenae

The lack of recent insecticide innovations and the withdrawal of efficient, but ecotoxic molecules (e.g. neon-icotinoids) may lead to a shift to older insecticidal active substances, particularly pyrethroids. The evolution of resistance to this family of insecticides has long been recognized, including in many aphid species such as the grain aphid Sitobion avenae. The target-site resistance mechanism involved, named kdr (knock-down resistance), was first identified in the United Kingdom in 2014. In this study, we screened for the presence of this mutation in 25 French populations of S. avenae sampled between 2017 and 2021 on various cultivated cereals. Aphids were genotyped individually for the kdr mutation using PCR-RFLP or partial sequencing of the voltage-gated sodium channel gene. Of the 400 S. avenae individuals tested, one carried a heterozygous kdr mutation. This S. avenae kdr mutant was sampled in Northern France, the French region closest to the United Kingdom. The low frequency of the detected mutation and the geographical proximity to the UK suggest that it arose from a migration event and not an independent convergent mutation event, although this hypothesis remains to be confirmed. Our study also reveals that partial sequencing of the voltage-gated sodium-channel gene can be used for another cereal aphid species, Rhopalosiphum padi.