A survey of endophytic fungi of switchgrass (Panicum virgatum) in the Midwest, and their putative roles in plant growth

Endophytic fungi represent a diverse group of Fungi belonging primarily to the Phylum Ascomycota, and exist asymptomatically within tissues of plants. Clavicipitaceous fungal endophytes can promote plant productivity in grasses. Less is known about non-clavicipitaceous endophytes, which are the dominant fungal endophytes in many plants. Panicum virgatum (switchgrass), a prairie grass native to North America, is a potential candidate as a biofuel crop. Our knowledge of the endophytic fungi of switchgrass and their potential effects on biomass production in this species is limited. To characterize and evaluate endophytic fungi in switchgrass, tillers were collected from a range of habitats across Indiana and Illinois in 2008 and 2009. Endophytic fungi were cultured from surface disinfected aboveground tissues. Morphological characters and sequences of the fungal ITS region were used to identify endophytic fungal isolates. In total, 31 operational taxonomic units were identified, representing fungi belonging to over 11 taxonomic orders. All fungi were members of Ascomycota and most belonged to common genera such as Alternaria, Epicoccum, Phoma, Phaeosphaeria and Stagonospora. No members of the Clavicipitaceae were detected. A greenhouse assay was carried out with a subset of endophyte isolates to determine their impacts on switchgrass biomass production. Experimental inoculations demonstrated that fungi had a range of effects on switchgrass biomass, with 12.5% and 62.5% of isolates significantly promoting versus reducing biomass production of test seedlings over controls. Some endophytic fungi of switchgrass may have potential to enhance plant productivity, but net effects of endophyte communities under field conditions need to be explored. ► We isolated and identified endophytic fungi of P. virgatum. ► We found 31 different endophytic fungi of diverse ecology in P virgatum. ► Endophytic fungi had a range of effects on seedling growth. ► Endophytic fungi may impact P. virgatum productivity.