title: High Susceptibility to Cry1Ac and Low Resistance Allele Frequency Reduce the Risk of Resistance of Helicoverpa armigers to Bt Soybean in Brazil.
abstract: The Old World bollworm, Helicoverpa armigera (Hübner), was recently introduced into Brazil, where it has caused extensive damage to cotton and soybean crops. MON 87701 × MON 89788 soybean, which expresses the Bt protein Cry1Ac, was recently deployed in Brazil, providing high levels of control against H. armigera. To assess the risk of resistance to the Cry1Ac protein expressed by MON 87701 × MON 89788 soybean in Brazil, we conducted studies to evaluate the baseline susceptibility of H. armigera to Cry1Ac, in planta efficacy including the assessment of the high-dose criterion, and the initial resistance allele frequency based on an F2 screen. The mean Cry1Ac lethal concentration (LC50) ranged from 0.11 to 1.82 μg·mL-1 of diet among all H. armigera field populations collected from crop seasons 2013/14 to 2014/15, which indicated about 16.5-fold variation. MON 87701 × MON 89788 soybean exhibited a high level of efficacy against H. armigera and most likely met the high dose criterion against this target species in leaf tissue dilution bioassays up to 50 times. A total of 212 F2 family lines of H. armigera were established from field collections sampled from seven locations across Brazil and were screened for the presence of MON 87701 × MON 89788 soybean resistance alleles. None of the 212 families survived on MON 87701 × MON 89788 soybean leaf tissue (estimated allele frequency = 0.0011). The responses of H. armigera to Cry1Ac protein, high susceptibility to MON 87701 × MON 89788 soybean, and low frequency of resistance alleles across the main soybean-producing regions support the assumptions of a high-dose/refuge strategy. However, maintenance of reasonable compliance with the refuge recommendation will be essential to delay the evolution of resistance in H. armigera to MON 87701 × MON 89788 soybean in Brazil.
authors.affiliation: Departamento de Entomologia e Acarologia, Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, Piracicaba, São Paulo, Brazil.|Monsanto do Brasil Ltda, São Paulo, São Paulo, Brazil.
authors.forename: Patrick M
authors.identifier: http://orcid.org/0000-0001-8587-3561
authors.initials: PM
authors.lastname: Dourado
authors.affiliation: Monsanto do Brasil Ltda, São Paulo, São Paulo, Brazil.
authors.forename: Fabiana B
authors.initials: FB
authors.lastname: Bacalhau
authors.affiliation: Departamento de Entomologia e Acarologia, Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, Piracicaba, São Paulo, Brazil.
authors.forename: Douglas
authors.initials: D
authors.lastname: Amado
authors.affiliation: Monsanto do Brasil Ltda, São Paulo, São Paulo, Brazil.
authors.forename: Renato A
authors.initials: RA
authors.lastname: Carvalho
authors.affiliation: Monsanto LLC, St Louis, Missouri, United States of America.
authors.forename: Samuel
authors.initials: S
authors.lastname: Martinelli
authors.affiliation: Monsanto LLC, St Louis, Missouri, United States of America.
authors.forename: Graham P
authors.initials: GP
authors.lastname: Head
authors.affiliation: Departamento de Entomologia e Acarologia, Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, Piracicaba, São Paulo, Brazil.
authors.forename: Celso
authors.initials: C
authors.lastname: Omoto
mesh_terms: D000383:Agriculture / Q000379:methods; D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001938:Brazil; D004198:Disease Susceptibility; D004731:Endotoxins / Q000235:genetics* / Q000378:metabolism*; D003368:Gossypium / Q000235:genetics* / Q000469:parasitology; D006460:Hemolysin Proteins / Q000235:genetics* / Q000378:metabolism*; D007305:Insecticide Resistance / Q000502:physiology*; D007306:Insecticides / Q000378:metabolism; D007814:Larva / Q000187:drug effects; D009036:Moths / Q000187:drug effects; D010572:Pest Control, Biological / Q000379:methods*; D018515:Plant Leaves / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism; D013025:Glycine max / Q000235:genetics* / Q000469:parasitology
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; C030956:insecticidal crystal protein, Bacillus Thuringiensis