The Effects of Plant Root Phenotypic Traits on Root-Associated Soil Microbial Communities and Their Combined Effects on Seedling Performance in the Poaceae

Soil microbes play a crucial role in plant communities, but the influence of plant traits on root-associated microbial communities and their impact on plant performance remains poorly understood in the Poaceae. To address this, we conducted greenhouse experiments controlling for environmental variations and integrated microbial community data along with measurements of plant physiological traits including root exudation and plant growth rates. Our first study focused on maize seedlings and examined the role of root hairs and other phenotypic traits on soil microbial communities and plant performance. We found that root hairs have a small yet significant effect on microbial community structure, likely mediated by variations in root which ultimately impacted maize growth. This highlights the multifaceted role of root hairs in promoting plant growth by reducing root system investment and interacting with soil microorganisms. In our second study, we explored the effects of soil legacy from prairie grasses and maize on root-associated soil microorganisms and subsequent plant performance of maize and wild relatives using a plant-soil feedback approach. Five maize genotypes and two prairie grass species were used to condition the soil. Our results showed that maize genotypes often had negative feedback effects, while wild grasses had positive feedback effects on maize and teosinte seedlings. These findings indicate that wild relatives of maize can counteract the domestication effects on soil microbial communities. The third study employed a comparative phylogenetic approach, focusing on 18 prairie grass species, to investigate whether rhizosphere microbial communities could be considered a plant trait. Although there was no phylogenetic signal across species, we observed significant effects of plant roots on rhizosphere microbial communities, suggesting a co-evolutionary pattern related to phylogenetically conserved root trait variations. Understanding the interactions between soil microbes and plants is crucial for supporting the agricultural productivity of Poaceae, which includes important cereal crops and rangeland species. This research contributes to our comprehension of the mechanisms underlying plant-microbe interactions and their implications for plant community functions