Original Article

Planta

, Volume 226, Issue 2, pp 395-404

First online:

Investigating the mechanisms of glyphosate resistance in Lolium multiflorum

  • Alejandro Perez-JonesAffiliated withDepartment of Crop and Soil Science, Oregon State University Email author 
  • , Kee-Woong ParkAffiliated withDepartment of Crop and Soil Science, Oregon State University
  • , Nick PolgeAffiliated withSyngenta Crop Protection, Inc., Vero Beach Research Center
  • , Jed ColquhounAffiliated withDepartment of Horticulture, University of Wisconsin
  • , Carol A. Mallory-SmithAffiliated withDepartment of Crop and Soil Science, Oregon State University

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Abstract

Evolved resistance to the herbicide glyphosate has been reported in eleven weed species, including Lolium multiflorum. Two glyphosate-resistant L. multiflorum populations were collected, one from Chile (SF) and one from Oregon, USA (OR), and the mechanisms conferring glyphosate resistance were studied. Based on a Petri dish dose–response bioassay, the OR and the SF populations were two and fivefold more resistant to glyphosate when compared to the susceptible (S) population, respectively; however, based on a whole-plant dose–response bioassay, both OR and SF populations were fivefold more resistant to glyphosate than the S population, implying that different resistance mechanisms might be involved. The S population accumulated two and three times more shikimic acid in leaf tissue 96 h after glyphosate application than the resistant OR and SF populations, respectively. There were no differences between the S and the glyphosate-resistant OR and SF populations in 14C-glyphosate leaf uptake; however, the patterns of 14C-glyphosate translocation were significantly different. In the OR population, a greater percentage of 14C-glyphosate absorbed by the plant moved distal to the treated section and accumulated in the tip of the treated leaf. In contrast, in the S and in the SF populations, a greater percentage of 14C-glyphosate moved to non-treated leaves and the stem. cDNA sequence analysis of the EPSP synthase gene indicated that the glyphosate-resistant SF population has a proline 106 to serine amino acid substitution. Here, we report that glyphosate resistance in L. multiflorum is conferred by two different mechanisms, limited translocation (nontarget site-based) and mutation of the EPSP synthase gene (target site-based).

Keywords

Glyphosate resistance Lolium multiflorum Translocation EPSP synthase Shikimic acid