Skip to main content
ARS Home » Midwest Area » Columbia, Missouri » Cropping Systems and Water Quality Research » Research » Publications at this Location » Publication #189068
Title: RHIZOSPHERE ECOLOGY IS ALTERED IN GLYPHOSATE RESISTANT SOYBEAN

Author
item Kremer, Robert
item MEANS, NATHAN - UNIVERSITY OF MISSOURI

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 1/6/2006
Publication Date: 2/3/2006
Citation: Kremer, R.J., Means, N.E. 2006. Rhizosphere ecology is altered in glyphosate resistant soybean [abstract]. Weed Science Society of America Meeting. CD-ROM.

Interpretive Summary:

Technical Abstract: The environmental assessment of glyphosate-resistant (GR) soybean on soil- and root-associated microbial communities is not well understood. Changes in the dynamics of soil and rhizosphere microbial community structure may lead to functional consequences with either positive or negative effects on plant growth and long-term effects on the soil ecosystem. Objectives of this review are to illustrate the relationship of GR soybean to changes in root- and soil-associated microorganisms based on research conducted during 1997-2005. Glyphosate applied to GR soybean consistently affected root-associated Fusarium. Populations often increased 2-5 times within five days after glyphosate application and continued to increase during the growing season. Fusarium and total fungal populations on roots and in rhizosphere soil did not increase in soybean receiving no herbicide or "conventional" tank-mix herbicides. Fusarium colonization of the soybean root surface was directly correlated with Fusarium populations in the rhizosphere soil. Soybean cyst nematode populations and reproduction on soybean roots were not affected consistently by glyphosate. Substrate-induced respiration and selected enzyme activities in rhizosphere soils were only slightly affected by glyphosate treatment. Consequences of increased Fusarium may include alteration in soil microbially-mediated processes such as decomposition and increases in potential pathogenic effects of certain Fusarium spp. on soybean and other rotation crops. We subsequently found that glyphosate released in root exudates of glyphosate-treated GR soybean coupled with increased exudation of carbohydrates and amino acids from GR roots stimulated growth and colonization of Fusarium spp. in the GR soybean rhizosphere. Results suggest that analyses of selected indicator groups of microorganisms (i.e., Fusarium spp.) provide the most reliable and relevant information on GR soybean effects on the soil ecosystem. Effects of GR soybean on other components of the soil and rhizosphere microbial communities and the linkage to microbial functions are other areas that need to be investigated.