Linkage analysis of insecticide-resistant acetylcholinesterase in Heliothis virescens

The noctuid moth Heliothis virescens is a significant pest of several crops including cotton, where the predominant control method relies on chemical insecticides. In the 1970s H. virescens became highly resistant to the organophosphorus insecticide methyl parathion. Organophosphorus and carbamate insecticides inhibit the enzyme acetylcholinesterase (AChE) by binding to the active site, and one mechanism of resistance is an altered AChE insensitive to this inhibition. We characterized Aceln, an autosomal locus controlling AChE insensitivity in H. virescens, and mapped it to linkage group 2. This is the first linkage assignment for a gene conferring insecticide resistance in a lepidopteran. The apparent translocation of this autosome to the sex chromosome in many species of the family Tortricidae leads to the prediction that if organophosphorus resistance due to target-site insensitivity occurs in these tortricids, it should be sex linked. This prediction is novel because sex-linked insecticide resistance genes are rare among insects.