Phytobiomes: Competition, Coevolution, and Disease Suppression

Microbes and plants exist within complex networks of interacting plant and microbial species, the phytobiome. Our work explores the interacting roles of plant community diversity, plant host, and microbial species interactions in determining the pathogen-suppressive potential and composition of soil microbiomes, and the consequences for plant productivity. Both plant host and plant community diversity play significant roles in mediating microbial competitive interactions in soil, and, consequently, in facilitating specific microbial coevolutionary trajectories. Unraveling the complex coevolutoinary interactions among plants and soil microbiomes can suggest novel insights for active management of soil microbes to support plant productivity. Our results show rhizosphere Streptomyces associated with the same plant host were significantly more pathogen-suppressive when the host grew in monoculture vs. within a high-diversity plant community. In contrast, populations of Streptomyces in the rhizosphere of plant hosts growing in high-diversity communities were more niche-differentiated than populations associated with the same host in monoculture. These data suggest that plant community diversity plays a critical role in determining the likelihood of antagonistic arms race coevolution vs. niche differentiation among sympatric soil populations, with significant implications for plant disease suppression. More broadly, our work illustrates how diffuse networks of species interactions over diverse spatial scales contribute to determining the pathogen-suppressive and plant growth-promoting potential of indigenous soil microbes, and suggests specific crop management approaches targeting species interactions that offer potential for sustainable disease control.