title: Confirmation and mechanism of glyphosate resistance in tall windmill grass (Chloris elata) from Brazil.
abstract: BACKGROUND
  Overreliance on glyphosate as a single tool for weed management in agricultural systems in Brazil has selected glyphosate-resistant populations of tall windmill grass (Chloris elata Desv.).
  
  
  RESULTS
  Two C. elata populations, one glyphosate resistant (GR) and one glyphosate susceptible (GS), were studied in detail for a dose-response experiment and for resistance mechanism. The dose causing 50% reduction in dry weight was 620 g a.e. ha(-1) for GR and 114 g ha(-1) for GS, resulting in an R/S ratio of 5.4. GS had significantly higher maximum (14) C-glyphosate absorption into the treated leaf (51.3%) than GR (39.5%), a difference of 11.8% in maximum absorption. GR also retained more (14) C-glyphosate in the treated leaf (74%) than GS (51%), and GR translocated less glyphosate (27%) to other plant parts (stems, roots and root exudation) than GS (36%). There were no mutations at the Pro106 codon in the gene encoding 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). There was no difference in EPSPS genomic copy number or EPSPS transcription between GS and GR populations.
  
  
  CONCLUSIONS
  Based on these data, reduced glyphosate absorption and increased glyphosate retention in the treated leaf contribute to glyphosate resistance in this C. elata population from Brazil. © 2015 Society of Chemical Industry.
authors.affiliation: Department of Horticulture, University of São Paulo, Piracicaba, SP, Brazil.
authors.forename: Caio Acg
authors.initials: CA
authors.lastname: Brunharo
authors.affiliation: Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO, USA.
authors.forename: Eric L
authors.initials: EL
authors.lastname: Patterson
authors.affiliation: Department of Horticulture, University of São Paulo, Piracicaba, SP, Brazil.
authors.forename: Daniela R
authors.initials: DR
authors.lastname: Carrijo
authors.affiliation: Department of Horticulture, University of São Paulo, Piracicaba, SP, Brazil.
authors.forename: Marcel Sc
authors.initials: MS
authors.lastname: de Melo
authors.affiliation: Agrocon Assessoria Agronômica LTDA, Santa Bárbara d'Oeste, São Paulo, Brazil.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Nicolai
authors.affiliation: Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO, USA.
authors.forename: Todd A
authors.identifier: http://orcid.org/0000-0003-1485-7665
authors.initials: TA
authors.lastname: Gaines
authors.affiliation: Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO, USA.
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Nissen
authors.affiliation: Department of Horticulture, University of São Paulo, Piracicaba, SP, Brazil.
authors.forename: Pedro J
authors.initials: PJ
authors.lastname: Christoffoleti
mesh_terms: D051229:3-Phosphoshikimate 1-Carboxyvinyltransferase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D001938:Brazil; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D053209:Herbicide Resistance / Q000235:genetics*; D006540:Herbicides / Q000494:pharmacology*; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006109:Poaceae / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D000097797:Glyphosate
chemical_list: D051229:3-Phosphoshikimate 1-Carboxyvinyltransferase; D005998:Glycine; D006540:Herbicides; D010940:Plant Proteins; D000097797:Glyphosate
keywords: copy number; gene amplification; gene mutation; herbicide absorption; herbicide resistance; herbicide translocation