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General Information

Document type
  • Peer-reviewed journal article
GE organism
  • soybean
GE trait
  • herbicide tolerance
Country
  • USA

Results

Equivalence
  • negative effect

Glyphosate affects soybean root exudation and rhizosphere micro-organisms

Kremer, R; Means, N; Kim, S
International Journal of Environmental Analytical Chemistry. 2005 February. 85(15):1165-1174

Link to full text (journal may charge for access)

DOI: 10.1080/03067310500273146

Abstract

Glyphosate is a non-selective, broad-spectrum herbicide that kills plants by inhibiting the enzyme 5-enolpyruvylshikimic acid-3-phosphate synthase (EPSPS), which is necessary for synthesis of aromatic amino acids. A secondary mode of action involves infection of roots of glyphosate-susceptible plants by soil-borne micro-organisms due to decreased production of plant protection compounds known as phytoalexins. Varieties of several crops, including glyphosate-resistant (GR) or Roundup Ready soybean, are genetically modified to resist the herbicidal effects of glyphosate and provide farmers with an effective weed-management tool. After glyphosate is applied to GR soybean, glyphosate that is not bound to glyphosate-resistant EPSPS is translocated throughout the plant and accumulates primarily in meristematic tissues. We previously reported that fungal colonization of GR soybean roots increased significantly after application of glyphosate but not after conventional postemergence herbicides. Because glyphosate may be released into soil from GR roots, we characterized the response of rhizosphere fungi and bacteria to root exudates from GR and non-GR (Williams 82; W82) cultivars treated with and without glyphosate at field application rates. Using an immunoassay technique, glyphosate at concentrations >1000 ng plant-1 were detected in exudates of hydroponically grown GR soybean at 16 days post-glyphosate application. Glyphosate also increased carbohydrate and amino acid contents in root exudates in both soybean cultivars. However, GR soybean released higher carbohydrate and amino acid contents in root exudates than W82 soybean without glyphosate treatment. In vitro bioassays showed that glyphosate in the exudates stimulated growth of selected rhizosphere fungi, possibly by providing a selective C and N source combined with the high levels of soluble carbohydrates and amino acids associated with glyphosate treatment of the soybean plants. Increased fungal populations that develop under glyphosate treatment of GR soybean may adversely affect plant growth and biological processes in the soil and rhizosphere.

Keywords

Glyphosate, Immunosorbent assay, Fusarium, Rhizosphere micro-organisms, Soybean root exudates

Funding

Funding source
  • USDA
  • Ag Spectrum Company
Funding country
  • United States
Funding type
  • government
  • industry: other

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Cite this study

MLA

Kremer, R, N Means, S Kim. "Glyphosate affects soybean root exudation and rhizosphere micro-organisms." International Journal of Environmental Analytical Chemistry 85.15 (2005): 1165-1174. Web. 27 Jul. 2017.

APA

Kremer, R., Means, N., & Kim, S. (2005). Glyphosate affects soybean root exudation and rhizosphere micro-organisms. International Journal of Environmental Analytical Chemistry, 85(15), 1165-1174. doi:10.1080/03067310500273146

Please verify citations before use, citations are automatically generated based on information stored within the GENERA database and therefore may or may not be correct.