title: Fitness costs and stability of Cry1Fa resistance in Brazilian populations of Spodoptera frugiperda.
abstract: BACKGROUND
  The presence of fitness costs of resistance to Bacillus thuringiensis (Bt) insecticidal proteins in insect populations may delay or even reverse the local selection of insect resistance to Bt transgenic crops, and deserves rigorous investigation. Here we assessed the fitness costs associated with Cry1Fa resistance in two strains of fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), derived from field collections in different Brazilian regions and further selected in the laboratory for high levels of resistance to Cry1Fa using leaves of TC1507 corn.
  
  
  RESULTS
  Fitness components were compared using paired resistant and susceptible strains with similar genetic backgrounds and F1generations from reciprocal crosses, all of them reared on non-transgenic corn leaves. No apparent life history costs in the larval stage were observed in the Bt-resistant strains. Moreover, the resistance remained stable for seven generations in the absence of selection, with no decrease in the proportion of resistant individuals. Larval respiration rates were also similar between resistant and susceptible homozygotes, and heterozygotes displayed respiration rates and demographic performance equal or superior to those of susceptible homozygotes.
  
  
  CONCLUSIONS
  In combination, these results indicate the lack of strong fitness costs associated with resistance to Cry1Fa in the fall armyworm strains studied. These findings suggest that Cry1Fa resistance in S. frugiperda populations is unlikely to be counterselected in Cry1Fa-free environments. © 2016 Society of Chemical Industry.
authors.affiliation: Departamento de Entomologia, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
authors.forename: Oscar F
authors.initials: OF
authors.lastname: Santos-Amaya
authors.affiliation: Departamento de Entomologia, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
authors.forename: Clébson S
authors.initials: CS
authors.lastname: Tavares
authors.affiliation: Departamento de Entomologia, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
authors.forename: João Victor C
authors.initials: JV
authors.lastname: Rodrigues
authors.affiliation: Departamento de Entomologia, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
authors.forename: Silverio O
authors.initials: SO
authors.lastname: Campos
authors.affiliation: Departamento de Entomologia, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
authors.forename: Raul Narciso C
authors.initials: RN
authors.lastname: Guedes
authors.affiliation: DuPont Pioneer, Johnston, IA, USA.
authors.forename: Analiza P
authors.initials: AP
authors.lastname: Alves
authors.affiliation: Departamento de Entomologia, Universidade Federal de Viçosa, Viçosa, MG, Brazil.|Instituto Nacional de Ciência e Tecnologia em Interações Planta-Praga, Universidade Federal de Viçosa, Viçosa, MG, Brazil.
authors.forename: Eliseu José G
authors.identifier: http://orcid.org/0000-0002-8957-6465
authors.initials: EJ
authors.lastname: Pereira
mesh_terms: D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D001938:Brazil; D004731:Endotoxins; D006460:Hemolysin Proteins; D007305:Insecticide Resistance / Q000235:genetics*; D012641:Selection, Genetic; D018411:Spodoptera / Q000235:genetics* / Q000502:physiology
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis
keywords: Bt resistance; fall armyworm; intrinsic rate of population increase; isogenic strains; life-history traits; pleiotropic effects; resistance management