Journal
PEST MANAGEMENT SCIENCE
Volume 69, Issue 4, Pages 457-461Publisher
WILEY
DOI: 10.1002/ps.3460
Keywords
insecticide resistance; whitefly; pymetrozine; cytochrome P450; neonicotinoids
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BACKGROUND Resistance to neonicotinoid insecticides such as imidacloprid in the cotton whitefly, Bemisia tabaci, is linked to its hydroxylation by constitutively overexpressed CYP6CM1, a cytochrome P450 enzyme. Here, an investigation was conducted to establish whether CYP6CM1 functionally expressed in Sf9 cells also detoxifies pymetrozine, a selective homopteran feeding blocker known to be cross-resistant to neonicotinoids in whiteflies. RESULTS Incubation of pymetrozine with functionally expressed Bemisia CYP6CM1 and subsequent LC-MS/MS analysis revealed a rapid formation of two pymetrozine metabolites by hydroxylation of its heterocyclic 1,2,4-triazine ring system. Enzyme kinetics revealed a Km value of 5.9 +/- 0.3 mu M and a time-dependent depletion of pymetrozine. CONCLUSION The known cross-resistance between imidacloprid, other neonicotinoid insecticides and pymetrozine in B. tabaci is most likely conferred by the very same detoxification mechanism, i.e. a monooxygenase-based hydroxylation mechanism linked to the overexpression of CYP6CM1. These insecticide chemistries should not be alternated in whitefly resistance management strategies. (c) 2012 Society of Chemical Industry
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