The role of B-type esterases in conferring insecticide resistance in the tobacco whitefly, Bemisia tabaci (Genn)

Separation of non-specific esterases on electrophoretic gels has played a key role in distinguishing between races or biotypes of the tobacco whitefly, Bemisia tabaci. One intensively staining esterase in particular (termed E-0.14) has assumed significance as a diagnostic of B-type whiteflies (aka Bemisia argentifolii), despite any knowledge of its biological function. In this study, a whitefly strain (B-Null) homozygous for a null allele at the E-0.14 locus that had been isolated from a B-type population was used to demonstrate a significant role for E-0.14 in resistance of B-type populations to pyrethroids but not to organophosphates (OPs). Bioassays with pyrethroids, following pretreatment with sub-lethal doses of the OP profenofos (to inhibit esterase activity), coupled with metabolism studies with radiolabelled permethrin, supported the conclusion that pyrethroid resistance in a range of B-type strains expressing E-0.14 was primarily due to increased ester hydrolysis. In the same strains, OP resistance appeared to be predominantly conferred by a modification to the target-site enzyme acetylcholinesterase. (C) 2000 Society of Chemical Industry.