title: Frequency of Cry1F resistance alleles in Spodoptera frugiperda (Lepidoptera: Noctuidae) in Brazil.
abstract: BACKGROUND
  The frequency of resistance alleles is a major factor influencing the rate of resistance evolution. Here, we adapted the F2screen procedure for Spodoptera frugiperda (J. E. Smith) with a discriminating concentration assay, and extended associated statistical methods to estimate the frequency of resistance to Cry1F protein in S. frugiperda in Brazil when resistance was not rare.
  
  
  RESULTS
  We show that F2screen is efficient even when the resistance frequency is 0.250. It was possible to screen 517 isoparental lines from 12 populations sampled in five states of Brazil during the first half of 2012. Western Bahia had the highest allele frequency of Cry1F resistance, 0.192, with a 95% confidence interval (CI) between 0.163 and 0.220. All other states had a similar and lower frequency varying from 0.042 in Paraná to 0.080 in Mato Grosso do Sul.
  
  
  CONCLUSIONS
  The high frequency in western Bahia may be related to year-round availability of maize, the high population density of S. frugiperda, the lack of refuges and the high adoption rate of Cry1F maize. Cry1F resistance alleles were not rare and occurred at frequencies that have already compromised the useful life of TC1507 maize in western Bahia. © 2016 Society of Chemical Industry.
authors.affiliation: Department of Entomology and Acarology, University of São Paulo (ESALQ/USP), Piracicaba, São Paulo, Brazil. julianofarias@gmail.com.
authors.forename: Juliano R
authors.initials: JR
authors.lastname: Farias
authors.affiliation: Entomology Departament, University of Minnesota, St Paul, MN, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Andow
authors.affiliation: Department of Entomology and Acarology, University of São Paulo (ESALQ/USP), Piracicaba, São Paulo, Brazil.
authors.forename: Renato J
authors.initials: RJ
authors.lastname: Horikoshi
authors.affiliation: Department of Entomology and Acarology, University of São Paulo (ESALQ/USP), Piracicaba, São Paulo, Brazil.
authors.forename: Daniel
authors.initials: D
authors.lastname: Bernardi
authors.affiliation: Department of Entomology and Acarology, University of São Paulo (ESALQ/USP), Piracicaba, São Paulo, Brazil.
authors.forename: Rebeca da S
authors.initials: RD
authors.lastname: Ribeiro
authors.affiliation: Department of Entomology and Acarology, University of São Paulo (ESALQ/USP), Piracicaba, São Paulo, Brazil.
authors.forename: Antonio Rb do
authors.initials: AR
authors.lastname: Nascimento
authors.affiliation: Dow AgroSciences LLC, Indianapolis, IN, USA.
authors.forename: Antonio C Dos
authors.initials: AC
authors.lastname: Santos
authors.affiliation: Department of Entomology and Acarology, University of São Paulo (ESALQ/USP), Piracicaba, São Paulo, Brazil.
authors.forename: Celso
authors.initials: C
authors.lastname: Omoto
mesh_terms: D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics*; D001938:Brazil; D004731:Endotoxins / Q000235:genetics*; D005787:Gene Frequency; D006460:Hemolysin Proteins / Q000235:genetics*; D007305:Insecticide Resistance / Q000235:genetics*; D030821:Plants, Genetically Modified / Q000235:genetics; D018411:Spodoptera / Q000235:genetics*; 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: Bacillus thuringiensis; Bt maize; TC1507 maize; fall armyworm; resistance management