title: Evidence of Resistance to Cry34/35Ab1 Corn by Western Corn Rootworm (Coleoptera: Chrysomelidae): Root Injury in the Field and Larval Survival in Plant-Based Bioassays.
abstract: Western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is a serious pest of corn in the United States, and recent management of western corn rootworm has included planting of Bt corn. Beginning in 2009, western corn rootworm populations with resistance to Cry3Bb1 corn and mCry3A corn were found in Iowa and elsewhere. To date, western corn rootworm populations have remained susceptible to corn producing Bt toxin Cry34/35Ab1. In this study, we used single-plant bioassays to test field populations of western corn rootworm for resistance to Cry34/35Ab1 corn, Cry3Bb1 corn, and mCry3A corn. Bioassays included nine rootworm populations collected from fields where severe injury to Bt corn had been observed and six control populations that had never been exposed to Bt corn. We found incomplete resistance to Cry34/35Ab1 corn among field populations collected from fields where severe injury to corn producing Cry34/35Ab1, either singly or as a pyramid, had been observed. Additionally, resistance to Cry3Bb1 corn and mCry3A corn was found among the majority of populations tested. These first cases of resistance to Cry34/35Ab1 corn, and the presence of resistance to multiple Bt toxins by western corn rootworm, highlight the potential vulnerability of Bt corn to the evolution of resistance by western corn rootworm. The use of more diversified management practices, in addition to insect resistance management, likely will be essential to sustain the viability of Bt corn for management of western corn rootworm.
authors.affiliation: Department of Entomology, Iowa State University, Ames, IA 50011 (aaronjg@iastate.edu; shrestrb@iastate.edu; dunbar@iastate.edu; eclifton@iastate.edu; apaolino@iastate.edu; masloski@iastate.edu; jdoudna@iastate.edu; cstclair@iastate.edu), Corresponding author, e-mail: aaronjg@iastate.edu.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Gassmann
authors.affiliation: Department of Entomology, Iowa State University, Ames, IA 50011 (aaronjg@iastate.edu; shrestrb@iastate.edu; dunbar@iastate.edu; eclifton@iastate.edu; apaolino@iastate.edu; masloski@iastate.edu; jdoudna@iastate.edu; cstclair@iastate.edu).
authors.forename: Ram B
authors.initials: RB
authors.lastname: Shrestha
authors.affiliation: Department of Entomology, Iowa State University, Ames, IA 50011 (aaronjg@iastate.edu; shrestrb@iastate.edu; dunbar@iastate.edu; eclifton@iastate.edu; apaolino@iastate.edu; masloski@iastate.edu; jdoudna@iastate.edu; cstclair@iastate.edu), Current address: Valent U.S.A. Company, 3800 Old Leland Rd., Leland, MS 38756 (sjakk@valent.com).
authors.forename: Siva R K
authors.initials: SR
authors.lastname: Jakka
authors.affiliation: Department of Entomology, Iowa State University, Ames, IA 50011 (aaronjg@iastate.edu; shrestrb@iastate.edu; dunbar@iastate.edu; eclifton@iastate.edu; apaolino@iastate.edu; masloski@iastate.edu; jdoudna@iastate.edu; cstclair@iastate.edu).
authors.forename: Mike W
authors.initials: MW
authors.lastname: Dunbar
authors.affiliation: Department of Entomology, Iowa State University, Ames, IA 50011 (aaronjg@iastate.edu; shrestrb@iastate.edu; dunbar@iastate.edu; eclifton@iastate.edu; apaolino@iastate.edu; masloski@iastate.edu; jdoudna@iastate.edu; cstclair@iastate.edu).
authors.forename: Eric H
authors.initials: EH
authors.lastname: Clifton
authors.affiliation: Department of Entomology, Iowa State University, Ames, IA 50011 (aaronjg@iastate.edu; shrestrb@iastate.edu; dunbar@iastate.edu; eclifton@iastate.edu; apaolino@iastate.edu; masloski@iastate.edu; jdoudna@iastate.edu; cstclair@iastate.edu).
authors.forename: Aubrey R
authors.initials: AR
authors.lastname: Paolino
authors.affiliation: Department of Entomology, Iowa State University, Ames, IA 50011 (aaronjg@iastate.edu; shrestrb@iastate.edu; dunbar@iastate.edu; eclifton@iastate.edu; apaolino@iastate.edu; masloski@iastate.edu; jdoudna@iastate.edu; cstclair@iastate.edu), Current address: Department of Entomology and Wildlife Ecology, University of Delaware, Newark, DE 19716 (davidngbr@gmail.com), and.
authors.forename: David A
authors.initials: DA
authors.lastname: Ingber
authors.affiliation: USDA ARS North Central Agricultural Research Laboratory, Brookings, SD (wade.french@ars.usda.gov).
authors.forename: B Wade
authors.initials: BW
authors.lastname: French
authors.affiliation: Department of Entomology, Iowa State University, Ames, IA 50011 (aaronjg@iastate.edu; shrestrb@iastate.edu; dunbar@iastate.edu; eclifton@iastate.edu; apaolino@iastate.edu; masloski@iastate.edu; jdoudna@iastate.edu; cstclair@iastate.edu).
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Masloski
authors.affiliation: Department of Entomology, Iowa State University, Ames, IA 50011 (aaronjg@iastate.edu; shrestrb@iastate.edu; dunbar@iastate.edu; eclifton@iastate.edu; apaolino@iastate.edu; masloski@iastate.edu; jdoudna@iastate.edu; cstclair@iastate.edu).
authors.forename: John W
authors.initials: JW
authors.lastname: Dounda
authors.affiliation: Department of Entomology, Iowa State University, Ames, IA 50011 (aaronjg@iastate.edu; shrestrb@iastate.edu; dunbar@iastate.edu; eclifton@iastate.edu; apaolino@iastate.edu; masloski@iastate.edu; jdoudna@iastate.edu; cstclair@iastate.edu).
authors.forename: Coy R
authors.initials: CR
authors.lastname: St Clair
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000494:pharmacology*; D001517:Coleoptera / Q000187:drug effects* / Q000254:growth & development; D004731:Endotoxins / Q000494:pharmacology*; D006460:Hemolysin Proteins / Q000494:pharmacology*; D007305:Insecticide Resistance; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D018517:Plant Roots / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified / Q000235:genetics / Q000502:physiology*; D003313:Zea mays / Q000235:genetics
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis
keywords: Diabrotica virgifera virgifera; bioassay; insect resistance management; integrated pest management; refuge strategy