1. Frequency of Alleles Conferring Resistance to the Bt Toxins Cry1Ac and Cry2Ab in Australian Populations of Helicoverpa armigera (Lepidoptera: Noctuidae).
- Author
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Mahon, R. J., Olsen, K. M., Downes, S., and Addison, S.
- Subjects
HELICOVERPA armigera ,MALVACEAE ,PLANT fibers ,TOXINS ,BACILLUS thuringiensis ,INSECTICIDES ,PESTICIDES ,PESTICIDES industry - Abstract
Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) is an important lepidopteran pest of cotton (Gossypium spp.) in Australia and the Old World. From 2002, F
2 screens were used to examine the frequency of resistance alleles in Australian populations of H. armigera to Bacillus thuringiensis (Bt) CrylAc and Cry2Ab, the two insecticidal proteins present in the transgenic cotton Bollgard II. At that time, Ingard (expressing CrylAc) cotton had been grown in Australia for seven seasons, and Boilgard H was about to be commercially released. The principal objective of our study was to determine whether sustained exposure caused an elevated frequency of alleles conferring resistance to CrylAc in a species with a track record of evolving resistance to conventional insecticides. No major alleles conferring resistance to CrylAc were found. The frequency of resistance alleles for CrylAc was <0.0003, with a 95% credibility interval between 0 and 0.0009. In contrast, alleles conferring resistance to Cry2Ab were found at a frequency of 0.0033 (0.0017,0.0055). The first isolation of this allele was found before the widespread deployment of Bollgard H. For both toxins the experiment-wise detection probability was 94.4%. Our results suggest that alleles conferring resistance to CrylAc are rare and that a relatively high baseline frequency of alleles conferring resistance to Cry2Ab existed before the introduction of Bt cotton containing this toxin. [ABSTRACT FROM AUTHOR]- Published
- 2007
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