title: Inheritance and Fitness Costs of Resistance to Cry3Bb1 Corn by Western Corn Rootworm (Coleoptera: Chrysomelidae).
abstract: Transgenic crops that produce insecticidal toxins derived from the bacterium Bacillus thuringiensis (Bt) are widely planted to manage pest insects. One of the primary pests targeted by Bt corn in the United States is western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae). Cry3Bb1 corn for management of western corn rootworm was commercialized in 2003, and beginning in 2009, populations of western corn rootworm with field-evolved resistance to Cry3Bb1 corn were found in Iowa. Here we quantify the magnitude, inheritance, and fitness costs of resistance to Cry3Bb1 corn in two strains (Hopkinton and Cresco) derived from field populations that evolved resistance to Cry3Bb1 corn. For Hopkinton, we found evidence for complete resistance to Cry3Bb1 corn and nonrecessive inheritance. Additionally, no fitness costs of Cry3Bb1 resistance were detected for Hopkinton. For Cresco, resistance was incomplete and recessive, and we detected fitness costs affecting developmental rate, survival to adulthood, and fecundity. These results suggest that variation may exist among field populations in both the inheritance and accompanying fitness costs of resistance. To the extent that field populations exhibit nonrecessive inheritance and a lack of fitness cost, this will favor more rapid evolution of resistance than would be expected when resistance is functionally recessive and is accompanied by fitness costs.
authors.affiliation: Department of Entomology, Iowa State University, Ames, IA 50011. Current Address: Department of Entomology and Wildlife Ecology, University of Delaware, Newark, DE 19716. ingber@udel.edu.
authors.forename: David A
authors.initials: DA
authors.lastname: Ingber
authors.affiliation: Department of Entomology, Iowa State University, Ames, IA 50011.
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Gassmann
mesh_terms: D000818:Animals; D000898:Antibiosis; D001413:Bacillus thuringiensis / Q000737:chemistry; D001517:Coleoptera / Q000187:drug effects / Q000235:genetics*; D004731:Endotoxins / Q000494:pharmacology*; D056084:Genetic Fitness; D040941:Heredity; D007305:Insecticide Resistance; D007484:Iowa; D030821:Plants, Genetically Modified / Q000235:genetics / Q000382:microbiology; D003313:Zea mays / Q000235:genetics* / Q000382:microbiology
chemical_list: C507666:Cry3Bbl endotoxin, Bacillus thuringiensis; D004731:Endotoxins
keywords: Bacillus thuringiensis; Bt corn; Diabrotica; resistance management