Over-expression of CYP6A2 is associated with spirotetramat resistance and cross-resistance in the resistant strain of Aphis gossypii Glover

•PBO significantly increased the toxicity of spirotetramat in resistant strain of A. gossypii.•The transcriptional level of CYP6A2 increased significantly in the resistant strain than that in susceptible.•Knockdown of CYP6A2 transcripts by RNAi dramatically increases the toxicity of spirotetramat to resistant aphids.•High level cross resistance to alpha-cypermethrin and bifenthrin was developed in resistant strain.

A laboratory-selected spirotetramat-resistant strain (SR) of cotton aphid developed 579-fold and 15-fold resistance to spirotetramat in adult aphids and 3rd instar nymphs, respectively, compared with a susceptible strain (SS) [26]. The SR strain developed high-level cross-resistance to alpha-cypermethrin and bifenthrin and very low or no cross-resistance to the other tested insecticides. Synergist piperonyl butoxide (PBO) dramatically increased the toxicity of spirotetramat and alpha-cypermethrin in the resistant strain. RT-qPCR results demonstrated that the transcriptional levels of CYP6A2 increased significantly in the SR strain compared with the SS strain, which was consistent with the transcriptome results [30]. The depletion of CYP6A2 transcripts by RNAi also significantly increased the sensitivity of the resistant aphid to spirotetramat and alpha-cypermethrin. These results indicate the possible involvement of CYP6A2 in spirotetramat resistance and alpha-cypermethrin cross-resistance in the cotton aphid. These together with other cross-resistance results have implications for the successful implementation of resistance management strategies for Aphis gossypii.

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