|YIN, CHUNTAO - Washington State University|
|HULBERT, SCOT - Washington State University|
|BURKE, IAN - Washington State University|
Submitted to: Microbial Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2017
Publication Date: 12/13/2017
Citation: Schlatter, D.C., Yin, C., Hulbert, S., Burke, I., Paulitz, T.C. 2017. Location, root proximity, and glyphosate-use history modulate the effects of glyphosate on fungal community networks of wheat. Microbial Ecology. https://doi.org/10.1007/s00248-017-1113-9.
Interpretive Summary: Glyphosate is the most widely used herbicide for weed control in agriculture, but concerns of non-target impacts on soil and plant-associated microbiomes are persistent. We examined the response of soil and plant-associated fungal communities to repeated glyphosate exposure and the potential for adaptation within microbial communities with a history of glyphosate exposure. We found that the effects of glyphosate on microbiomes were small and inconsistent across soils, plant proximities, and cropping histories. However, a greater number of fungi responded to glyphosate in soils with a history of exposure, indicating that some taxa have adapted to glyphosate use. We also found with network analysis that the relationships between the fungal groups changed with glyphosate application, even if the total numbers did not. We suggest that the small shifts in microbiomes due to glyphosate are primarily a result of nutrients released by dying roots.
Technical Abstract: Glyphosate is the most-used herbicide worldwide and an essential tool for weed control in no-till cropping systems. However, concerns have been raised regarding the long-term effects of glyphosate on soil microbial communities. We examined the impact of repeated glyphosate application on bulk and rhizosphere soil fungal communities of wheat grown in four soils representative of the dryland wheat production region of Eastern Washington, USA. Further, using soils from paired fields, we contrasted the response of fungal communities that had a long history of glyphosate exposure and those that had no known exposure. Soil fungal communities were characterized after 3 cycles of wheat-growth in the greenhouse followed by termination with glyphosate or manual clipping of plants. We found that cropping system, location, year, and root proximity were the primary drivers of fungal community compositions, and that glyphosate had only small impacts on fungal community composition or diversity. However, the taxa that responded to glyphosate applications differed between rhizosphere and bulk soil and between cropping systems. Further, a greater number of fungal OTUs responded to glyphosate in soils with a long history of glyphosate use. Finally, fungal co-occurrence patterns, but not co-occurrence network characteristics, differed substantially between glyphosate-treated and non-treated communities. Results suggest that most fungi influenced by glyphosate are saprophytes that likely feed on dying roots.