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Resistance to Bacillus thuringiensis Toxin Cry2Ab in a Strain of Helicoverpa armigera (Lepidoptera: Noctuidae) in Australia

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Transgenic cotton, Gossypium hirsutum L., expressing the cry1Ac and cry2Ab genes from Bacillus thuringiensis (Bt) Berliner variety kurstaki in a pyramid (Bollgard II) was widely planted for the first time in Australia during the 2004–2005 growing season. Before the first commercial Bollgard II crops, limited amounts of cotton expressing only the cry1Ac gene (Ingard) was grown for seven seasons. No field failures due to resistance to Cry1Ac toxin were observed during that period and a monitoring program indicated that the frequency of genes conferring high level resistance to the Cry1Ac toxin were rare in the major pest of cotton, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae). Before the deployment of Bollgard II, an allele conferring resistance to Cry2Ab toxin was detected in field-collected H. armigera. We established a colony (designated SP15) consisting of homozygous resistant individuals and examined their characteristics through comparison with individuals from a Bt-susceptible laboratory colony (GR). Through specific crosses and bioassays, we established that the resistance present in SP15 was due to a single autosomal gene. The resistance was recessive. Homozygotes were highly resistant to Cry2Ab toxin, so much so, that we were unable to induce significant mortality at the maximum concentration of toxin available. Homozygotes also were unaffected when fed leaves of a cotton variety expressing the cry2Ab gene. Although cross-resistant to Cry2Aa toxin, SP15 was susceptible to Cry1Ac and to the Bt product DiPel.

Keywords: Bacillus thuringiensis; Bt resistance; Cry1Ac; Cry2Ab; Helicoverpa armigera

Document Type: Research Article

DOI: http://dx.doi.org/10.1603/0022-0493(2007)100[894:RTBTTC]2.0.CO;2

Publication date: June 1, 2007

More about this publication?
  • Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.
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