Journal or Publishing Institution: European Journal of Agronomy
Study: https://www.ars.usda.gov/research/publications/publication/?seqNo115=242660
Author(s): Kremer, R.J. and Means, N.E.
Article Type: Journal Publication
Record ID: 1287
Abstract: Current crop production relies heavily on use of transgenic, glyphosate-resistant cultivars (GR). The impacts of widespread cultivation of genetically-modified (GM) crops and the use of one herbicide class on agroecosystems, especially considering potential effects on biological processes, have received considerable attention. This paper reviews impacts of glyphosate on rhizosphere microorganisms and activities and summarizes both previously published and new data from a long-term field project that documents effects of glyphosate applied to GR soybean and maize cultivars on rhizosphere microorganisms including Fusarium spp., pseudomonads, Mn-transforming bacteria, and agrobacteria and soybean root nodulation. We conducted field studies in Missouri, U.S.A. during 1997-2007 to determine effects of glyphosate applied to GR soybean and maize cultivars on root colonization and soil populations of Fusarium spp. and selected rhizosphere bacteria. Fusarium is typically prevalent in the soybean rhizosphere but can become dominant and pathogenic on susceptible plants, often in response to root exudation. We found the frequency of root-colonizing Fusarium increased significantly within one week after glyphosate application throughout the growing season in each year at all sites. Roots of GR soybean and maize cultivars treated with glyphosate were colonized at a considerably higher density by Fusarium spp. than were GR or non-GR cultivars not treated with glyphosate. Several additional microbial groups and functions were affected by glyphosate and GR crops including Mn transformation and plant availability; potential phytopathogen and antagonistic bacterial interactions; and reduction in nodulation. Glyphosate in root exudates may not only serve as a nutrient source for fungi but may also stimulate propagule germination and enhance early growth. The specific microbial indicator groups and processes used in our study demonstrated sensitivity to impacts of GR crops and are considered part of an evolving framework for developing a polyphasic microbial analysis to provide a complete assessment of GR technology that is more reliable than single techniques or general microbial assays.
Keywords: Genetically modified crop Polyphasic microbial analyses Fusarium spp. Glycine max (L.) Merr. Soybean Zea mays L. Maize Microbial ecology Mn transformation Pseudomonad
Citation: Kremer, R.J. and Means, N.E., 2009. Glyphosate and glyphosate-resistant crop interactions with rhizosphere microorganisms. European Journal of Agronomy, 31(3), pp.153-161.
