Initial Frequency of Alleles for Resistance to Bacillus thuringiensis Toxins in Field Populations of Heliothis virescens

The risk of rapid pest adaptation to an insecticide is highly dependent on the initial frequency of resistance alleles in field populations. Because we have lacked empirical estimates of these frequencies, population-genetic models of resistance evolution have relied on a wide range of theoretical e...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1997-04, Vol.94 (8), p.3519-3523
Main Authors: Gould, F., Anderson, A., Jones, A., Sumerford, D., Heckel, D. G., Lopez, J., Micinski, S., Leonard, R., Laster, M.
Format: Article
Language:English
Subjects:
Alleles
Animal reproduction
Bacillus thuringiensis
Bacteria
Biological Sciences
Butterflies & moths
Cotton
Heliothis virescens
Immunity (Disease)
Insect larvae
Instars
Larvae
Larval development
Male animals
Mating behavior
Noctuidae
Pests
Proteins
Toxins
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Summary:The risk of rapid pest adaptation to an insecticide is highly dependent on the initial frequency of resistance alleles in field populations. Because we have lacked empirical estimates of these frequencies, population-genetic models of resistance evolution have relied on a wide range of theoretical estimates. The recent commercialization of genetically engineered cotton that constitutively produces an insecticidal protein derived from the biocontrol agent, Bacillus thuringiensis (Bt) has raised concern that we lack data needed to quantify the risk of insect pests such as Heliothis virescens rapidly adapting to this ecologically valuable class of toxins. By individually mating over 2,000 male H. virescens moths collected in four states to females of a Bt toxin-resistant laboratory strain, and screening F1and F2offspring for tolerance of the toxic protein, we were able to directly estimate the field frequency of alleles for resistance as 1.5 × 10-3. This high initial frequency underscores the need for caution in deploying transgenic cotton to control insect pests. Our single-pair mating technique greatly increases the efficiency of detecting recessive resistance alleles. Because alleles that decrease target site sensitivity to Bt toxins and other insecticides are often recessive, this technique could be useful in estimating resistance allele frequencies in other insects exposed to transgenic insecticidal crops or conventional insecticides.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.94.8.3519