Characterization of endophytic fungi of switchgrass (Panicum virgatum)

Background/Question/Methods

Switchgrass (Panicum virgatum) has great potential as a bioenergy crop in the United States, due in part to its ability to produce abundant biomass in numerous environments, including degraded and marginal soils.  Like many plants, switchgrass hosts fungal endophytes, symbiotic microbes that infect plant tissues and that can have a range of effects on plant health and productivity.  To date, little is known about the fungal endophyte associations of switchgrass.  We characterized fungal endophyte infection of switchgrass collected from12 sites in Indiana and Illinois in 2008. The sites spanned a range of habitats and vegetation histories, including riparian, grassland restored on abandoned mine land, and remnant and restored native tallgrass prairie.  

Results/Conclusions We successfully cultured endophytic fungi from 68 of 70 foliar, stem, and seed samples from these sites, obtaining 39 morphologically distinct fungal groups (morphotypes). Fungal morphotypes were putatively grouped as pathogens (34% of total fungi cultured), saprophytes (27%) and unknown (36%) based on microscopic characteristics.  Pathogenic genera included Cladosporum, Fusarium, and Rhizoctonia, with the greatest proportion of pathogenic fungi similar to Fusarium spp.  Saprophytic fungi included Alternaria and Pithomyces.  Fusarium and Alternaria were the most widely distributed of fungal genera across sites.  Overall, endophyte richness was greatest in samples from restored tallgrass prairie sites and lowest in remnant prairies.  ITS-RFLP is being used to more precisely group morphotypes, and this will be followed by sequencing of the fungal ITS of representatives of each RFLP group.  Lastly, we are inoculating switchgrass seedlings with our cultured endophytes and monitoring growth responses over time to identify fungi with the potential to enhance switchgrass productivity in natural and reclaimed settings.