Switchgrass represents a promising feedstock crop for US energy sustainability. However, its broad utilization for bioenergy requires improvement of biomass yields under stress conditions. Our team has been working on harnessing beneficial bacterial endophytes to enhance switchgrass performance under poor growth conditions and to develop a low input feedstock production system for marginal lands that do not compete with the production of food crops. We have demonstrated that one of most promising plant growth-promoting bacterial endophytes, Burkholderia phytofirmans strain PsJN, is able to colonize roots and significantly promote growth of switchgrass cv. Alamo under in vitro, growth chamber, and greenhouse conditions. When grown in field soil with no fertilizer application under sub-optimal environmental conditions, PsJN-inoculated plants produced twice higher biomass than controls, implying the potential benefit of PsJN inoculation for production on marginal lands. Preliminary results also showed that PsJN inoculated Alamo had consistently lower transpiration, lower stomatal conductance, and higher water use efficiency. These physiological changes may significantly contribute to the recorded growth enhancement. In contrast to the growth responses of Alamo, no beneficial effects of PsJN were recorded with the upland cultivar Cave-in-Rock. To identify genetic determinants of these differential growth responses, we have conducted comparative global gene expression profiles for both cultivars following PsJN inoculation using EST microarrays, and have identified over 50 genes for verification by qPCR. So far, five key candidate genes have been chosen for further gene expression studies.
*This research is supported by the Office of Science (BER), U.S. Department of Energy.