Legumes are an ecologically and agriculturally important plant group

The Department of Agriculture National Institute of Food and Agriculture awarded $224,204 to the Regents of the University of Michigan on January 1, 2026, under the Agriculture and Food Research Initiative (AFRI), CFDA 10.310, to characterize the rhizosphere microbiome of legumes and determine how microbiome composition and function influence legume productivity and nitrogen fixation following auxinic herbicide drift exposure. The research uses genomics techniques to examine the rhizosphere microbiome—the community of root-associated microbes—across legume agroecosystems in the United States, with the goal of identifying how microbiome variation defends against auxinic herbicide-mediated damage and maintains ecosystem services under modern agricultural practices. The project also supports the principal investigator's professional development toward a future research professor career. Performance takes place in Ann Arbor, Michigan, with a period of performance from January 1, 2026, through December 31, 2027. This is a Project Grant, a form of assistance funding that supports research in one of AFRI's six farm bill priority areas, including Bioenergy, Natural Resources, and Environment.

The root symbiosis between legumes and nitrogen(n)-fixing rhizobia bacteria contributes to ecosystem nutrient cycling, and sustainable agriculture aims to utilize this service to improve crop yields. However, human-mediated stressors such as herbicides which harm plants by mimicking the plant hormone auxin can degrade legume productivity and symbiotic n fixation. Moreover, incidents of auxinic herbicide 'drift', or off-target herbicide movement by wind, are rising. A promising force which could mitigate the consequences of auxinic herbicide drift is the rhizosphere microbiome – the community of root-associated microbes which can promote plant growth and stress tolerance. Yet, the role of the rhizosphere microbiome in defending legumes against auxinic herbicide-mediated damage is unknown. In this project, PD iriart will use genomics techniques to characterize the composition, function, and diversity of the rhizosphere microbiome of legumes across agroecosystems in the USA, and determine how microbiome variation influences legume productivity and symbiotic n fixation following auxinic herbicide drift exposure. This work will provide novel insights into the function of the rhizosphere microbiome for maintaining essential ecosystem services and how IT is impacted by modern agricultural practices. Furthermore, the proposed research and professional development plans will help iriart achieve her career goal to become a future research professor.