Over-expression of P450 CYP6CM1 associated with resistance to imidacloprid in Australian Bemisia tabaci MEAM1

Abstract

The cotton industry is one of Australia’s most significant contributors to the agricultural sector with exports worth around $2 billion per year. Cotton crops are regularly impacted by insect pests like Bemisia tabaci, commonly called the silverleaf whitefly. B. tabaci consists of a complex of phloemfeeding morphologically indistinguishable cryp c species. The invasive B. tabaci MEAM1 cryp c species was detected in Australia in 1994 and is now widely distributed. Neonico noids including imidacloprid have been successfully used to control whitefly in Australia, but cases of resistance in co on have been documented. Using bioassay and molecular techniques, we inves gated crossresistance and resistance mechanisms in a known resistant MEAM1 strain. Bioassays were conducted using a field-isolated MEAM1 resistant strain and the results showed that cross-resistance was not equivalent with high resistance to imidacloprid and clothianidin, while resistance to acetamiprid was low, and the strain demonstrated no resistance to dinotefuran. We also used transcriptional analysis to investigate resistance mechanisms. The analysis showed up-regulation of the cytochrome P450 CYP6CM1 gene in the resistant strain compared with susceptible insects. The over-expression of P450 CYP6CM1 and its associa on with neonico noid resistance has been reported in overseas B. tabaci MED populations, however, it is the first time that such resistance mechanism is reported in Australia.