Sustainable Biomass Production Using Plant Growth Promoting Microbial Endophytes

Symbiotic microorganisms can have profound impacts on plant growth and resilience.  Poplar and willow are early-successional pioneer plant species that thrive in N-limited environments across the Northern hemisphere.  We have quantified N-fixation in wild poplar plants at a natural, cobble-dominated riparian area.  A variety of diazotrophic (N₂ fixing) endophytes (microbes within plants) were isolated from within the wild poplar.  These endophytes not only fix N2, they also produce plant hormones, solubilize phosphate, and produce siderophores and antifungal compounds.  They were shown to be mutualistic symbionts by adding them to other plant species, including turfgrasses, Douglas-fir, corn, rice, and a variety of other agronomically-important plants for improved growth and health in nutrient-limited conditions.  When the endophytes from wild poplar were added to hybrid poplars under greenhouse conditions, there was a significant increase in nitrogen fixation.  The endophytes also conferred drought tolerance, reduced ROS, increased plant growth and improved photosynthetic parameters during drought stress.  Genomic analysis of the strains provided information on multiple potential mechanisms by which the endophytes could promote plant growth and resilience.  By using symbiosis with microbial endophytes, substantial increases in plant biomass and yields could be attained with reduced inputs, improving the economic and environmental sustainability of bioenergy production.