Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2006
Publication Date: 10/1/2006
Citation: Tabashnik, B.E., Fabrick, J.A., Henderson, S., Biggs, R.W., Yafuso, C.M., Nyboer, M.E., Manhardt, N.M., Coughlin, L.A., Sollome, J., Carriere, Y., Dennehy, T.J., Morin, S. 2006. Dna screening reveals pink bollworm resistance to bt cotton remains rare after a decade of exposure. Journal of Economic Entomology 99(5): 1525-1530.
Interpretive Summary: Protein toxins from the bacterium Bacillus thuringiensis (Bt) have been genetically engineered into crops, such as Bt cotton, to control key agricultural insect pests and reduce reliance on insecticide sprays. The evolution of resistance by pest insects to Bt crops could cut short their usefulness. Monitoring field populations of insect pests for resistance to insecticide is an important component in management strategies that use insecticides. Here we use a molecular technique to detect specific resistance genes in the pink bollworm (Pectinophora gossypiella), a major pest of cotton. We collected and analyzed 5,571 insects from cotton fields in Arizona, California, and Texas from 2001 to 2005. No resistance alleles were detected indicating that resistance genes in field populations of pink bollworm are quite rare. These results confirm bioassay and efficacy data and support the exceptional field performance of Bt cotton against pink bollworm despite a decade of exposure to Bt cotton.
Technical Abstract: Transgenic crops producing toxins from the bacterium Bacillus thuringiensis (Bt) kill insect pests and can reduce reliance on insecticide sprays. Although Bt cotton and Bt corn covered 25 million ha worldwide in 2005, their success could be cut short by evolution of pest resistance. Monitoring the early phases of pest resistance to Bt crops is crucial, but has been extremely difficult because bioassays usually cannot detect heterozygotes harboring one allele for resistance. We report here monitoring of resistance to Bt cotton with DNA-based screening, which detects single resistance alleles in heterozygotes. We used polymerase chain reaction primers that specifically amplify mutant alleles of a cadherin gene linked with resistance to Bt cotton in pink bollworm, Pectinophora gossypiella (Saunders), a major pest. We screened DNA of 5,571 insects derived from 59 cotton fields in Arizona, California, and Texas during 2001 to 2005. No resistance alleles were detected despite a decade of exposure to Bt cotton. In conjunction with data from bioassays and field efficacy tests, the results reported here contradict predictions of rapid pest resistance to Bt crops.