Population genetics structure of glyphosate-resistant Johnsongrass (Sorghum halepense L. Pers) does not support a single origin of the resistance

Authors

  • Luis Fernández,

    1. Instituto de Biotecnología, Instituto Nacional de Tecnología Agropecuaria (INTA Castelar), Hurlingham, Argentina
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  • Luis Alejandro de Haro,

    1. Instituto de Biotecnología, Instituto Nacional de Tecnología Agropecuaria (INTA Castelar), Hurlingham, Argentina
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  • Ana J. Distefano,

    1. Instituto de Biotecnología, Instituto Nacional de Tecnología Agropecuaria (INTA Castelar), Hurlingham, Argentina
    2. Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (UBA), Ciudad Universitaria, Argentina
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  • Maria Carolina Martínez,

    1. Instituto de Biotecnología, Instituto Nacional de Tecnología Agropecuaria (INTA Castelar), Hurlingham, Argentina
    2. Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (UBA), Ciudad Universitaria, Argentina
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  • Verónica Lía,

    1. Instituto de Biotecnología, Instituto Nacional de Tecnología Agropecuaria (INTA Castelar), Hurlingham, Argentina
    2. Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (UBA), Ciudad Universitaria, Argentina
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  • Juan C. Papa,

    1. Estación Experimental Agropecuaria Oliveros, Instituto Nacional de Tecnología Agropecuaria, Oliveros, Santa Fe, Argentina
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  • Ignacio Olea,

    1. Sección Malezas, Estación Experimental Agroindustrial Obispo Colombres, Las Talitas, Tucumán, Argentina
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  • Daniela Tosto,

    Corresponding author
    1. Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (UBA), Ciudad Universitaria, Argentina
    • Instituto de Biotecnología, Instituto Nacional de Tecnología Agropecuaria (INTA Castelar), Hurlingham, Argentina
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  • Horacio Esteban Hopp

    1. Instituto de Biotecnología, Instituto Nacional de Tecnología Agropecuaria (INTA Castelar), Hurlingham, Argentina
    2. Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (UBA), Ciudad Universitaria, Argentina
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  • LF and LAH contributed equally to this study.

    DT and HEH contributed equally to this study.

Correspondence

Daniela Tosto, Instituto de Biotecnología, INTA Castelar, N. Repetto y Los Reseros, 1686 Hurlingham, Argentina. Tel: 54 11 4621 1447; Fax: 54 11 4621 0199; E-mail: dtosto@cnia.inta.gov.ar

Abstract

Single sequence repeats (SSR) developed for Sorghum bicolor were used to characterize the genetic distance of 46 different Sorghum halepense (Johnsongrass) accessions from Argentina some of which have evolved toward glyphosate resistance. Since Johnsongrass is an allotetraploid and only one subgenome is homologous to cultivated sorghum, some SSR loci amplified up to two alleles while others (presumably more conserved loci) amplified up to four alleles. Twelve SSR providing information of 24 loci representative of Johnsongrass genome were selected for genetic distance characterization. All of them were highly polymorphic, which was evidenced by the number of different alleles found in the samples studied, in some of them up to 20. UPGMA and Mantel analysis showed that Johnsongrass glyphosate-resistant accessions that belong to different geographic regions do not share similar genetic backgrounds. In contrast, they show closer similarity to their neighboring susceptible counterparts. Discriminant Analysis of Principal Components using the clusters identified by K-means support the lack of a clear pattern of association among samples and resistance status or province of origin. Consequently, these results do not support a single genetic origin of glyphosate resistance. Nucleotide sequencing of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) encoding gene from glyphosate-resistant and susceptible accessions collected from different geographic origins showed that none presented expected mutations in aminoacid positions 101 and 106 which are diagnostic of target-site resistance mechanism.

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