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

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 crop...

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Bibliographic Details
Published in:Journal of economic entomology 2007-06, Vol.100 (3), p.894-902
Main Authors: Mahon, R. J., Olsen, K. M., Garsia, K. A., Young, S. R.
Format: Article
Language:English
Subjects:
Bacillus thuringiensis
Gossypium hirsutum
Helicoverpa armigera
Lepidoptera
Noctuidae
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Summary: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 c ry1Ac 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 (Hü bner) (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 c ry2Ab gene. Although cross-resistant to Cry2Aa toxin, SP15 was susceptible to Cry1Ac and to the Bt product DiPel.
ISSN:0022-0493
0022-0493
DOI:10.1603/0022-0493(2007)100[894:RTBTTC]2.0.CO;2