Perennial grasslands are a powerhouse of carbon sequestration. By storing 98% of their carbon underground, in contrast to forest ecosystems, perennial grasslands are able to resist losing stored carbon to common natural disturbances like heat, drought stress, or wildfire. The soil around these grasses’ roots is a complex ecosystem, known as the “rhizosphere,” a nutrient rich environment with a relatively high level of microbial activity. The lives of perennial grasslands also include competition for resources like water and nutrients, and the need to resist plant pathogens such as fungi whose infections result in reduced photosynthesis, reduced nutrient intake, and other disadvantages.
Through a 6-year study in which 16 species of native prairie plants at the UMN Cedar Creek Ecosystem Science Reserve were treated biweekly with foliar fungicide (fungicide applied directly to leaves) or water controls, researchers examined the relationships between foliar fungi, plant health, and the the soil microbial composition around the roots of said plants. Researchers tested aboveground and belowground biomass of the plants, aboveground plant productivity (using foliar reflectance), and rhizosphere microbiome composition. For a full depiction of the methods and findings, please view the paper in full.
While use of foliar fungicide increased the aboveground biomass of the treated plants, this study showed no significant increases in underground biomass, seed count and weight, or seed heads per plot in the foliar fungicide-treated plots. Thus, despite having significantly more photosynthetically-active foliage, there was no evidence that the fungicide-treated plants invested this productivity into roots or seeds. However, increased aboveground productivity was associated with significant shifts in the composition of the rhizosphere microbiome. Intriguingly, changes in aboveground productivity were significantly positively correlated with the differences in the rhizosphere microbiome composition between treated and non-treated plots: greater increases in aboveground productivity resulted in greater shifts in microbiome composition. This suggests that increases in aboveground productivity are translated into (exudate) investments into soil microbiomes, and a mechanism by which plants actively mediate the composition and functional capacities of rhizosphere microbiomes. Further possibilities are explored in the “Discussion” section of the paper.
Importantly, this study suggests a novel connection between above- and belowground microbiomes. With the decreased threat of fungal pathogens, plants are not only able to increase their biomass, but also to have proportional impacts on the rhizosphere microbial community underground. Future work on this topic is exploring the role of plants as engineers of the rhizosphere microbiome, including mediating microbial functions such as nutrient acquisition, soil carbon sequestration, and plant disease suppression to support host plant health.
This research was published by UMN Plant Pathology’s Brett Lane, Zewwei Song, and Linda Kinkel; along with USDA’s Dan Schlatter and UMN Ecology, Evolution, and Behavior’s Molly Kuhs, Max Zaret, Elizabeth Borer, and Eric Seabloom. The full paper can be read in Frontiers in Plant Science Vol. 16 - 2025.
Citation of paper:
Brett R Lane, Kuhs M., Zaret M., Song Z., Borer E., Seabloom E., Schlatter D., Kinkel Linda. “Foliar fungi-imposed costs to plant productivity moderate shifts in composition of the rhizosphere microbiome.” Frontiers in Plant Science Volume 16. 2025. DOI 10.3389/fpls.2025.1558191 https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2025.1558191