Pyrethroid resistance associated with M918 L mutation and detoxifying metabolism in Aphis gossypii from Bt cotton growing regions of China

BACKGROUND The cotton aphid, Aphis gossypii (Glover), is a destructive pest that affects numerous crops throughout the world. Pyrethroid resistance has become endemic in A. gossypii populations in the cotton growing areas of China due to wide- spread application of insecticides. To assess the extent of pyrethroid resistance, bioassays were conducted on field populations collected from several cotton cultivation areas from 2010–2015. The frequency of a known resistance-associated sodium channel mutation (M918L) in A. gossypii was evaluated and the bioassay of bifenthrin with or without the synergist was performed to illuminate the mechanisms underlying resistance to pyrethroids. RESULTS The field populations exhibited very high levels of resistance to both beta-cypermethrin and deltamethrin. Pretreatment with synergists, DEF and PBO, significantly increased the toxicity of bifenthrin to cotton aphid populations collected from Bt cotton fields in China. Further, 96.8%-100% of individuals with the M918L mutation (including both RR and RS individuals) were observed in various populations, and only 2.8%-3.2% of individuals with wild-type homozygotes (SS) were detected. CONCLUSION The mutation M918L in the voltage-gated sodium channel along with detoxifying metabolism was contributed to the pyrethroid resistance in the field populations of Aphis gossypii from cotton growing regions of China. And insecticides with different modes of action should be recommended for the control of A. gossypii in the future.