Fitness costs of sulfoxaflor resistance in the cotton aphid, Aphis gossypii Glover.

Aphis gossypii Glover is an economically important pest of numerous crops throughout the world. Some field populations of A.gossypii in China have developed moderate level of resistance to sulfoxaflor, a newly released sulfoximine insecticide for management of sap-feeding pests. To evaluate the effect of sulfoxaflor resistance on the fitness cost of A. gossypii, the life history traits of sulfoxaflor-resistant strain (SulR) and an isogenic susceptible strain (SS) were compared using the age-stage, two-sex life table approach. The results showed that the resistant strain had a reduction in fitness (relative fitness = 0.917), along with significantly decreases in longevity, fecundity, net reproductive (R), mean generation time (T) and gross reproductive rate (GRR). Compared to the susceptible strain, SulR strain showing a shorter developmental duration of each nymph instar stage. Moreover, the adult pre-oviposition period (APOP) and total preoviposition period (TPOP) of SulR strain were also significantly shorter than that of the susceptible strain. Investigation of six development and reproduction related genes indicated that EcR, USP and JHBP were overexpressed in the SulR strain, while the mRNA transcript level of Vg was decreased significantly compared to the susceptible strain. These results suggest that there is a fitness cost associated with sulfoxaflor resistance in A. gossypii and the different expression of EcR, USP, JHBP, and Vg may play very important role in this trade-off.