title: First confirmation and characterization of target and non-target site resistance to glyphosate in Palmer amaranth (Amaranthus palmeri) from Mexico.
abstract: Following the introduction of glyphosate-resistant (GR)-cotton crops in Mexico, farmers have relied upon glyphosate as being the only herbicide for in-season weed control. Continuous use of glyphosate within the same year and over multiple successive years has resulted in the selection of glyphosate resistance in Palmer amaranth (Amarantus palmeri). Dose-response assays confirmed resistance in seven different accessions. The resistance ratio based on GR50values (50% growth reduction) varied between 12 and 83. At 1000 μM glyphosate, shikimic acid accumulation in the S-accession was 30- to 2-fold higher at compared to R-accessions. At 96 h after treatment, 35-44% and 61% of applied14C-glyphosate was taken up by leaves of plants from R- and S-accessions, respectively. At this time, a significantly higher proportion of the glyphosate absorbed remained in the treated leaf of R-plants (55-69%) compared to S-plants (36%). Glyphosate metabolism was low and did not differ between resistant and susceptible plants. Glyphosate was differentially metabolized to AMPA and glyoxylate in plants of R- and S-accessions, although it was low in both accessions (<10%). There were differences in 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) enzyme activity by 50% (I50) between R- and S-accessions. However, no significant differences were found in the basal EPSPS activity (μmol inorganic phosphate μg-1total soluble protein min-1) between R- and S-accessions. A point mutation Pro-106-Ser was evidenced in three accessions. The results confirmed the resistance of Palmer amaranth accessions to glyphosate collected from GR-cotton crops from Mexico. This is the first study demonstrating glyphosate-resistance in Palmer amaranth from Mexico.
authors.affiliation: Department of Agricultural Parasitology, Chapingo Autonomous University, Road México-Texcoco Km. 38.5, 56230 Texcoco, Mexico. Electronic address: jose_dv001@yahoo.com.mx.
authors.forename: Jose Alfredo
authors.initials: JA
authors.lastname: Dominguez-Valenzuela
authors.affiliation: Department of Agronomy, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran. Electronic address: gherekhloo@yahoo.com.
authors.forename: Javid
authors.initials: J
authors.lastname: Gherekhloo
authors.affiliation: Department of Agricultural Chemistry and Edaphology, University of Cordoba, 14071 Cordoba, Spain. Electronic address: pablotomas91@hotmail.es.
authors.forename: Pablo Tomás
authors.initials: PT
authors.lastname: Fernández-Moreno
authors.affiliation: Bayer CropScience, Col. Ampl. Granada, 11520, México D.F, Mexico. Electronic address: hugo.cruzhipolito@bayer.com.
authors.forename: Hugo Enrique
authors.initials: HE
authors.lastname: Cruz-Hipolito
authors.affiliation: Universidade Federal de Viçosa (UFV), Brazil. Electronic address: rychar419@gmail.com.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Alcántara-de la Cruz
authors.affiliation: Department of Agricultural Parasitology, Chapingo Autonomous University, Road México-Texcoco Km. 38.5, 56230 Texcoco, Mexico. Electronic address: eduardosanchezgonzalez@hotmail.es.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Sánchez-González
authors.affiliation: Department of Agricultural Chemistry and Edaphology, University of Cordoba, 14071 Cordoba, Spain. Electronic address: qe1pramr@uco.es.
authors.forename: Rafael
authors.initials: R
authors.lastname: De Prado
mesh_terms: D027721:Amaranthus / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D053209:Herbicide Resistance; D006540:Herbicides / Q000494:pharmacology*; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D057685:Plant Weeds / Q000235:genetics; D012765:Shikimic Acid; D000097797:Glyphosate
chemical_list: D005998:Glycine; D006540:Herbicides; D010940:Plant Proteins; D012765:Shikimic Acid; D000097797:Glyphosate
keywords: Glyphosate; Herbicide resistance; Metabolism; Palmer amaranth; Pro-106; Translocation