Microbial Endophytes for Economic and Environmental Sustainability of Biomass Production

Short rotation woody crops such as poplar (Populus sp.) can serve as renewable feedstocks for biochemical and biofuel production. Poplar trees produce a high biomass on a 3-year rotation, are readily amenable to coppicing, and many can be propagated easily through hardwood cuttings. Some strains of the wild poplar microbiome, termed endophytes, enhance growth of cultivated poplar through increased nutrient acquisition and drought tolerance. Nitrogen fixation was quantified in wild poplar and in hybrid poplar inoculated with diazotrophic strains from wild poplar. Phospate solubilization by some endophyte strains increased the bioavailability of this essential micronutrient for plant growth. A large-scale study is now underway to understand the molecular plant-microbe interactions involved in the poplar-endophyte mutualism. While some endophyte strains could enhance the sustainability of poplar biomass production through reductions of required fertilizer inputs, others can improve the success of environmental applications of poplar. Addition of pollutant-degrading endophyte strains to poplar planted on contaminated sites improved the health and performance of poplar trees used in phytoremediation of TCE and PAHs. By combining poplar biomass production with environmental services, the economic viability of bioenergy production and the range of sites on which poplar can be grown are improved.