Harnessing the Microbiome for Agricultural Sustainability in Bioenergy-based Systems

Declining reserves of mineral phosphorus and growing economic and environmental costs associated with fertilizer use (and misuse) have necessitated efforts to identify cropping systems and strategies that can be sustained under a low-input strategy. One approach to ameliorate such losses is to utilize microbial symbionts that have evolved to promote plant growth through nutrient and water acquisition as well as reduce plant stress when grown on marginal, low-quality soils. Soils such as these are expected to be tapped to grow cellulosic feedstocks for biofuel production. Here, we describe our efforts to maximize the performance and abiotic stress tolerance of switchgrass, a C4 grass native to the prairies of northern OK, through microbial symbiosis. Strain discovery combined with the implementation of high-throughput screens for potentially useful traits, have resulted in a manageable number of bacterial and fungal endophytes that we are testing in greenhouse trials. Results to date suggest that both biomass and drought tolerance can be enhanced by a novel type of mycorrhizae and bacteria have been identified that are being tested for phosphorus solubilization, nitrogen fixation and the alleviation of ethylene-induced plant stress.