Nathan Lee's Graduate Exit Seminar

Nathan Lee will present Long-Term Glyphosate Effects on Roundup Ready Soybean Rhizosphere Microorganisms Friday, May 4th at 9am in 333C Kottman Hall.

Glyphosate's widespread usage in partnership with Roundup ready crops has increased concern of unknown long-term effects on rhizosphere microorganisms. Previous research has demonstrated that glyphosate can stimulate fungal and gram-negative microorganisms in the rhizosphere, and anecdotal evidence has shown increased occurrence of soybean root rot and sudden death syndrome in long-term glyphosate tolerant cropping systems. There is also concern regarding glyphosate’s environmental accumulation and the accumulation of its metabolite aminomethylphosphonicacid (AMPA), which has been shown to have a half-life more than twice as long as glyphosate in agricultural soils. To address these concerns a simulated long-term glyphosate tolerant cropping greenhouse experiment was conducted using two soil managements, one with and one without a history of glyphosate application. The objectives were to study glyphosate's effects on soybean rhizosphere microbial communities in these soil managements, use stable isotope probing to identify glyphosate incorporating microbial functional groups, and to investigate the accumulation of glyphosate and AMPA in the rhizosphere and bulk soil. Results from this study indicate that glyphosate induces changes in the rhizosphere microbial communities of a soil management that has never been exposed to glyphosate and likely adapts to use glyphosate as a substrate, most notably by fungus. Additionally, glyphosate and AMPA accumulate heavily in the bulk soil. This study adds to the current knowledge base of glyphosate and AMPA accumulation, and rhizosphere microbial responses to glyphosate. This study provides a starting point for future in situ field investigations.