title: Multi-Toxin Resistance Enables Pink Bollworm Survival on Pyramided Bt Cotton.
abstract: Transgenic crops producing Bacillus thuringiensis (Bt) proteins kill key insect pests, providing economic and environmental benefits. However, the evolution of pest resistance threatens the continued success of such Bt crops. To delay or counter resistance, transgenic plant "pyramids" producing two or more Bt proteins that kill the same pest have been adopted extensively. Field populations of the pink bollworm (Pectinophora gossypiella) in the United States have remained susceptible to Bt toxins Cry1Ac and Cry2Ab, but field-evolved practical resistance to Bt cotton producing Cry1Ac has occurred widely in India. Here we used two rounds of laboratory selection to achieve 18,000- to 150,000-fold resistance to Cry2Ab in pink bollworm. Inheritance of resistance to Cry2Ab was recessive, autosomal, conferred primarily by one locus, and independent of Cry1Ac resistance. We created a strain with high resistance to both toxins by crossing the Cry2Ab-resistant strain with a Cry1Ac-resistant strain, followed by one selection with Cry2Ab. This multi-toxin resistant strain survived on field-collected Bt cotton bolls producing both toxins. The results here demonstrate the risk of evolution of resistance to pyramided Bt plants, particularly when toxins are deployed sequentially and refuges are scarce, as seen with Bt cotton and pink bollworm in India.
authors.affiliation: USDA ARS, U.S. Arid Land Agricultural Research Center, Maricopa, AZ 85138 USA.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Fabrick
authors.affiliation: Department of Entomology, University of Arizona, Tucson, AZ 85721 USA.
authors.forename: Gopalan C
authors.initials: GC
authors.lastname: Unnithan
authors.affiliation: Department of Entomology, University of Arizona, Tucson, AZ 85721 USA.
authors.forename: Alex J
authors.initials: AJ
authors.lastname: Yelich
authors.affiliation: Department of Entomology, University of Arizona, Tucson, AZ 85721 USA.
authors.forename: Ben
authors.initials: B
authors.lastname: DeGain
authors.affiliation: Biotechnology Research Institute, National Research Council of Canada, Montreal, QC, Canada H4P 2R2.
authors.forename: Luke
authors.initials: L
authors.lastname: Masson
authors.affiliation: State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, Haidian District, 100193 Peoples Republic of China.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Entomology, University of Arizona, Tucson, AZ 85721 USA.
authors.forename: Yves
authors.initials: Y
authors.lastname: Carrière
authors.affiliation: Department of Entomology, University of Arizona, Tucson, AZ 85721 USA.
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Tabashnik
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000502:physiology; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics; D018556:Crops, Agricultural; D003433:Crosses, Genetic; D004731:Endotoxins / Q000235:genetics; D003368:Gossypium / Q000235:genetics / Q000469:parasitology*; D006460:Hemolysin Proteins / Q000235:genetics; D006790:Host-Parasite Interactions; D007300:Insect Control; D007305:Insecticide Resistance / Q000235:genetics*; D009036:Moths / Q000187:drug effects* / Q000235:genetics*; D030821:Plants, Genetically Modified; D014118:Toxins, Biological / Q000494:pharmacology*
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D014118:Toxins, Biological; C030956:insecticidal crystal protein, Bacillus Thuringiensis