A Novel Delivery System for the Root Symbiotic Fungus, Sebacina vermifera, and Consequent Biomass Enhancement of Low Lignin COMT Switchgrass Lines

Sebacina vermifera (MAFF-305830) is a mycorrhizal fungus originally isolated from the roots of orchids that we have previously shown to be tremendously beneficial in enhancing biomass yield and drought tolerance in switchgrass, an important bioenergy crop for cellulosic ethanol production in the United States. Towards this end, we have developed a bentonite clay particle-based delivery system for mass production and dissemination of S. vermifera for large-scale field trials. A greenhouse-based experiment was conducted to evaluate this novel delivery method for biomass enhancement of wild type and transgenic, low lignin (COMT down-regulated) switchgrass lines compared to an efficient in vitro colonization method. S. vermifera colonization enhanced plant biomass regardless of delivery method, although the percentage of fungal biomass in planta increased with the clay-based delivery system. Further, we found that release of some clay minerals in solution was enhanced in the presence of S. vermifera, while others were seemingly reduced. Intriguingly, the presence of S. vermifera has little or no impact on cell wall composition, including lignification. This research is the first report documenting the development of a bentonite clay particle-based delivery system for mass production of any symbiotic microbe and suggests that S. vermifera can be packaged with a mineral composite and effectively delivered to a target host plant.