title: Field-evolved resistance to Cry1Ab maize by Spodoptera frugiperda in Brazil.
abstract: BACKGROUND
  The first Bt maize in Brazil was launched in 2008 and contained the MON 810 event, which expresses Cry1Ab protein. Although the Cry1Ab dose in MON 810 is not high against fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), MON 810 provided commercial levels of control. To support insect resistance management in Brazil, the baseline and ongoing susceptibility of FAW was examined using protein bioassays, and the level of control and life history parameters of FAW were evaluated on MON 810 maize.
  
  
  RESULTS
  Baseline diet overlay assays with Cry1Ab (16 µg cm(-2) ) caused 76.3% mortality to field FAW populations sampled in 2009. Moderate mortality (48.8%) and significant growth inhibition (88.4%) were verified in leaf-disc bioassays. In greenhouse trials, MON 810 had significantly less damage than non-Bt maize. The surviving FAW larvae on MON 810 (22.4%) had a 5.5 day increase in life cycle time and a 24% reduction in population growth rate. Resistance monitoring (2010-2015) showed a significant reduction in Cry1Ab susceptibility of FAW over time. Additionally, a significant reduction in the field efficacy of MON 810 maize against FAW was observed in different regions from crop season 2009 to 2013.
  
  
  CONCLUSIONS
  The decrease in susceptibility to Cry1Ab was expected, but the specific contributions to this resistance by MON 810 maize cannot be distinguished from cross-resistance to Cry1Ab caused by exposure to Cry1F maize. Technologies combining multiple novel insecticidal traits with no cross-resistance to the current Cry1 proteins and high activity against the same target pests should be pursued in Brazil and similar environments. © 2015 Society of Chemical Industry.
authors.affiliation: Department of Entomology and Acarology, Escola Superior de Agricultura 'Luiz de Queiroz', University of São Paulo, Piracicaba, São Paulo, Brazil.
authors.forename: Celso
authors.initials: C
authors.lastname: Omoto
authors.affiliation: Department of Entomology and Acarology, Escola Superior de Agricultura 'Luiz de Queiroz', University of São Paulo, Piracicaba, São Paulo, Brazil.
authors.forename: Oderlei
authors.initials: O
authors.lastname: Bernardi
authors.affiliation: Department of Entomology and Acarology, Escola Superior de Agricultura 'Luiz de Queiroz', University of São Paulo, Piracicaba, São Paulo, Brazil.
authors.forename: Eloisa
authors.initials: E
authors.lastname: Salmeron
authors.affiliation: Department of Entomology and Acarology, Escola Superior de Agricultura 'Luiz de Queiroz', University of São Paulo, Piracicaba, São Paulo, Brazil.
authors.forename: Rodrigo J
authors.initials: RJ
authors.lastname: Sorgatto
authors.affiliation: Monsanto of Brazil Ltda, São Paulo, Brazil.
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Dourado
authors.affiliation: Monsanto of Brazil Ltda, São Paulo, Brazil.
authors.forename: Augusto
authors.initials: A
authors.lastname: Crivellari
authors.affiliation: Monsanto of Brazil Ltda, São Paulo, Brazil.
authors.forename: Renato A
authors.initials: RA
authors.lastname: Carvalho
authors.affiliation: Monsanto Company, St Louis, Missouri, USA.
authors.forename: Alan
authors.initials: A
authors.lastname: Willse
authors.affiliation: Monsanto Company, St Louis, Missouri, USA.
authors.forename: Samuel
authors.initials: S
authors.lastname: Martinelli
authors.affiliation: Monsanto Company, St Louis, Missouri, USA.
authors.forename: Graham P
authors.initials: GP
authors.lastname: Head
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000494:pharmacology*; D005075:Biological Evolution; D001938:Brazil; D004731:Endotoxins / Q000494:pharmacology*; D006460:Hemolysin Proteins / Q000494:pharmacology*; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D030821:Plants, Genetically Modified / Q000235:genetics; D018411:Spodoptera / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D003313:Zea mays / Q000235:genetics*
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; C030956:insecticidal crystal protein, Bacillus Thuringiensis
keywords: Bt maize; Cry1Ab protein; fall armyworm; insect resistance management