How does the fungal endophyte Neotyphodium coenophialum affect tall fescue (Festuca arundinacea) rhizodeposition and soil microorganisms?

The goal of our study was to investigate the impact of fungal endophytes in tall fescue (Festuca arundinacea) on rhizodeposition and in turn, the soil microbial community. Sand-based, aseptic microlysimeter units were constructed for the collection of rhizodeposit solutions for chemical analyses from the roots of endophyte-free (E-) and endophyte-infected (E+) tall fescue plants. E+ plants were infected with Neotyphodium coenophialum, the most common endophyte found in tall fescue. Rhizodeposit solutions collected over nine weeks from E+ grass contained more organic carbon and carbohydrates than E-. These solutions were allowed to percolate through columns of plant-free soils to assess the response of the soil microbial communities. Soils to which solutions from E+ grass were applied had significantly higher respiration rates than those receiving solutions from E- grass, suggesting that microbial activity was stimulated by changes in the rhizodeposits. Culture-based assays of the soil microbial community (plate counts and community-level physiological profiling) suggest that the basic structure of the microbial community was not affected by application of rhizodeposit solutions from E+ plants as compared to E-. Our results indicate that the presence of a fungal endophyte may enhance rhizodeposition by tall fescue and could consequently influence microbial mineralization processes in the soil. In grasslands where nutrients may be limiting, hosting a fungal endophyte has the potential to enhance plant nutrient supply indirectly via a stimulatory effect on the soil microbial biomass.