title: Fitness costs of insect resistance to Bacillus thuringiensis.
abstract: Evolution of resistance by insect pests threatens the continued effectiveness of Bacillus thuringiensis (Bt) toxins in sprays and transgenic crops. Fitness costs of Bt resistance occur when, in the absence of Bt toxins, fitness is lower for resistant insects than for susceptible insects. Modeling results show that fitness costs can delay resistance by selecting against Bt-resistant genotypes in refuges where insects are not exposed to Bt toxins. In 77 studies including 18 species, fitness costs were detected in 62% of experiments testing for declines in resistance and in 34% of fitness component comparisons. Mean fitness costs were 15.5% for survival, 7.4% for development time, and 2.5% for mass. Although most fitness costs were recessive, nonrecessive costs can select more strongly against resistance. Because fitness costs vary with ecological conditions, refuges designed to increase the dominance or magnitude of fitness costs could be especially useful for delaying pest resistance.
authors.affiliation: Department of Entomology, Iowa State University, Ames, Iowa 50011, USA. aaronjg@iastate.edu
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Gassmann
authors.forename: Yves
authors.initials: Y
authors.lastname: Carrière
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Tabashnik
mesh_terms: D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D005075:Biological Evolution; D004731:Endotoxins; D006460:Hemolysin Proteins; D007313:Insecta / Q000502:physiology*; D007305:Insecticide Resistance
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis