Growth promotion and colonization of switchgrass (Panicum virgatum) cv. alamo by bacterial endophyte burkholderia phytofirmans strain PsJN

Abstract

Background: Switchgrass is one of the most promising bioenergy crop candidates for the US. It gives relativelyhigh biomass yield and can grow on marginal lands. However, its yields vary from year to year and from location tolocation. Thus it is imperative to develop a low input and sustainable switchgrass feedstock production system. Oneof the most feasible ways to increase biomass yields is to harness benefits of microbial endophytes.Results: We demonstrate that one of the most studied plant growth promoting bacterial endophytes, Burkholderiaphytofirmans strain PsJN, is able to colonize and significantly promote growth of switchgrass cv. Alamo underin vitro, growth chamber, and greenhouse conditions. In several in vitro experiments, the average fresh weight ofPsJN-inoculated plants was approximately 50% higher than non-inoculated plants. When one-month-old seedlingswere grown in a growth chamber for 30 days, the PsJN-inoculated Alamo plants had significantly higher shoot androot biomass compared to controls. Biomass yield (dry weight) averaged from five experiments was 54.1% higher inthe inoculated treatment compared to non-inoculated control. Similar results were obtained in greenhouseexperiments with transplants grown in 4-gallon pots for two months. The inoculated plants exhibited more earlytillers and persistent growth vigor with 48.6% higher biomass than controls. We also found that PsJN couldsignificantly promote growth of switchgrass cv. Alamo under sub-optimal conditions. However, PsJN-mediatedgrowth promotion in switchgrass is genotype specific.Conclusions: Our results show B. phytofirmans strain PsJN significantly promotes growth of switchgrass cv. Alamounder different conditions, especially in the early growth stages leading to enhanced production of tillers. Thisphenomenon may benefit switchgrass establishment in the first year. Moreover, PsJN significantly stimulatedgrowth of switchgrass cv. Alamo under sub-optimal conditions, indicating that the use of the beneficial bacterialendophytes may boost switchgrass growth on marginal lands and significantly contribute to the development of alow input and sustainable feedstock production system. © 2012 Kim et al.; licensee BioMed Central Ltd.