Response to Soil Processes to an Above Ground Plant-Fungal Symbiosis from Rhizosphere to Regional Scales

Tall fescue (TF) covers greater than 15 million hectares within the United States and is considered one of the most desirable forage species for grazing livestock. Because of animal toxicity issues associated with common toxic endophyte- TF varieties, novel endophyte infected TF varieties are gaining popularity. Only anecdotal evidence exists which specifically addresses the role of the endophyte in dictating root exudate composition or the role that these exudates may play in altering soil microbial composition or nutrient cycling. The research proposed herein will provide important and novel data on how the soil chemical environment, soil microbial communities, and soil C and N dynamics are altered by shoot-specific common and novel fungal endophyte symbioses with tall fescue. The proposed study will be unique from other studies on this topic in that it will integrate advanced analytical and molecular genetics techniques with classical soil chemical methods to identify root exudates specific to the fungal- TF symbiosis and elucidate their effects on rhizosphere and bulk soil microbial composition, and carbon and nitrogen pools in field soils (specifically addressing #'s 1 and 2 of FY2008 Priorities for Research Projects). These goals will be accomplished by combining methodical pure culture, bioactivity guided assays of root exudates from endophyte infected and endophyte free tall fescue varieties with lab and field-based observations to verify the validity of our results. If funded, our proposal, , will generate basic knowledge on how an agriculturally-important, widely occurring plant-fungal symbiosis impacts soil microbial communities, chemical properties and nutrient cycling.