COS 179-4 - Environmental filtering dominates community assembly processes of arbuscular mycorrhizal fungi in Sorghum bicolor across two ecoregions in the United States

Abstract: Arbuscular mycorrhizal fungi (AMF) contribute to ecosystem services through their role as an interface between plant roots and the surrounding soil environment. They can mediate soil properties and enhance nutrient uptake, drought tolerance and disease resistance in their host plants. Managing agricultural lands to maximize these potential benefits of AMF is a promising approach to sustainable agriculture through reducing the need for high external inputs such as inorganic fertilizers. This is especially relevant to the cultivation of mycorrhizal bioenergy crops such as Sorghum bicolor. To increase its economic feasibility and avoid competition with food crops, sorghum can be grown on marginal land with reduced inputs, presenting a case study that could benefit greatly from the AMF symbiosis. Choosing or breeding sorghum genotypes which can get the most benefit from the AMF symbiosis in a given environment is a pivotal first step in this management strategy. Through a multi-year field trial across sites within contrasting ecoregions, we are working with over 300 accessions from the sorghum Bioenergy Association Panel (BAP) to measure AMF communities as host plant phenotypes. Here, we present a synthesis of results from the pilot study carried out as a time-series analysis featuring a subset of genotypes grown at sites in GA and AZ to determine a baseline of ecological differentiation between sites, and the most appropriate plant age for AMF assessment. We identified a cosmopolitan selection of all major AMF genera across both sites. Environmental filtering was the key factor governing AMF community assembly (PERMANOVA analysis, p < 0.001) in comparison to relative stability across timepoints and the chosen genotypes. Conditions at the AZ site appear to select for a more limited set of AMF that are better adapted to the lower precipitation and nutrient availability. This is supported by a lower species richness of AMF in AZ (ANOVA, p < 0.05). LeFSe analysis also confirms that OTUs belonging to the Diversispora genus are more abundant in AZ. These Diversispora may aid in increased uptake of water and nutrients from the surrounding environment through their preferential biomass allocation to hyphal production. These pilot study results inform our future GWAS investigations by showing that findings at one site may not be generalizable across ecoregions.