Cross-resistance among common insecticides and its possible mechanism in Laodelphax striatellus Fallén (Hemiptera: Delphacidae)
Laodelphax striatellus Fallén, is a serious pest of rice, has developed resistance to various chemical insecticides. Thus, clear documentation of resistance and cross-resistance is required for good resistance management. This study examined cross-resistance among common insecticides acting on different targets and its mechanism. First, the L. striatellus strains selected with chlorpyrifos, deltamethrin and imidacloprid were tested for cross-resistance to common insecticides. Then, these three resistant strains underwent mixed breeding for two generations, as an original population and reselected for seven generations by corresponding insecticides, resulting in three new resistant strains. These strains were tested for confirmation of the cross-resistance and the mechanism was analysed by comparing the expression levels of related detoxification enzyme genes. The results demonstrated that cross-resistance existed among chlorpyrifos, deltamethrin and imidacloprid. The detoxification enzyme gene CYP6AY3v2, CYP306A2v2 and CYP353D1v2 were found to be up-regulated in the chlorpyrifos-selected strain; CYP6AY3v2, CYP6FU1, CYP353D1v2, and CYP439A1v3 in the Deltamethrin-selected strain; and CYP4C72, CYP6AY3v2 and CYP353D1v2 in the Imidacloprid-selected strain. Furthermore, overexpression of CYP6AY3v2 and CYP353D1v2 was in concert with cross-resistance in selected strains. These results suggest that CYP6AY3v2 and CYP353D1v2 might be associated with the cross-resistance among chlorpyrifos, deltamethrin and imidacloprid in L. striatellus.