Submitted to: Society for Invertebrate Pathology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/23/2007
Publication Date: 8/12/2007
Citation: Tabashnik, B.E., Fabrick, J.A., Morin, S., Sisterson, M.S., Carriere, Y., Dennehy, T.J. 2007. Pink Bollworm Resistance to Bt Cotton: Still Rare After All These Years. Society for Invertebrate Pathology Annual Meeting. Available: http://www.sipweb.org/Meeting_Abstracts/2007abstracts.pdf
Technical Abstract: Transgenic crops producing Bacillus thuringiensis (Bt) toxins reduce reliance on insecticides, but evolution of resistance by pests could cut short their usefulness. Pink bollworm is a major pest that has experienced intense selection for resistance to Bt cotton in Arizona since 1997. Unexpectedly, bioassay data show that the frequency of pink bollworm resistance to Cry1Ac, the toxin in Bt cotton, decreased from 1997 to 2006. Field-based estimates also show sustained efficacy during this period. In laboratory-selected strains that survive on Bt cotton and have up to 3,100-fold resistance to Cry1Ac, resistance is linked with three recessive mutations in the gene encoding a cadherin protein that binds Cry1Ac. Each of the three resistant alleles has a deletion upstream of the toxin-binding region of the cadherin protein. We developed a PCR-based method for detecting each of the three alleles to monitor resistance. Screening of DNA from >6,600 insects from 79 cotton fields during 2001 to 2006 detected no resistance alleles. These results show pink bollworm resistance remained rare despite a decade of exposure to Bt cotton, contradicting predictions of rapid pest resistance to Bt crops. These results have important implications for efforts to eradicate pink bollworm from Arizona and neighboring areas.