PLoS ONE (2010) 5 (9 - e12567)

Sharon Downes, Tracey Parker and Rod Mahon (2010)
Incipient resistance of Helicoverpa punctigera to the Cry2Ab Bt toxin in Bollgard II® cotton
PLoS ONE 5 (9 - e12567)
Abstract: Combinations of dissimilar insecticidal proteins ("pyramids") within transgenic plants are predicted to delay the evolution of pest resistance for significantly longer than crops expressing a single transgene. Field-evolved resistance to Bacillus thuringiensis (Bt) transgenic crops has been reported for first generation, single-toxin varieties and the Cry1 class of proteins. Our five year data set shows a significant exponential increase in the frequency of alleles conferring Cry2Ab resistance in Australian field populations of Helicoverpa punctigera since the adoption of a second generation, two-toxin Bt cotton expressing this insecticidal protein. Furthermore, the frequency of cry2Ab resistance alleles in populations from cropping areas is 8-fold higher than that found for populations from non-cropping regions. This report of field evolved resistance to a protein in a dual-toxin Bt-crop has precisely fulfilled the intended function of monitoring for resistance; namely, to provide an early warning of increases in frequencies that may lead to potential failures of the transgenic technology. Furthermore, it demonstrates that pyramids are not 'bullet proof' and that rapid evolution to Bt toxins in the Cry2 class is possible.
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Database assignments for author(s): Sharon Downes, Rod J. Mahon

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
resistance/tolerance/defence of host

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Helicoverpa punctigera	Cotton (Gossypium)	Australia (NT+QLD)
Bacillus thuringiensis genes in crops (entomopathogen)	Helicoverpa punctigera	Cotton (Gossypium)	Australia (NT+QLD)
Bacillus thuringiensis Cry2A-toxin (entomopathogen)	Helicoverpa punctigera	Cotton (Gossypium)