Date Published: June 14, 2018
Publisher: Public Library of Science
Author(s): Ye Xia, Amna Amna, Stephen Obol Opiyo, Ricardo Aroca.
Plants have a diverse endophytic microbiome that is functionally important for their growth, development, and health. In this study, the diversity and specificity of culturable endophytic fungal communities were explored in one of the most important biofuel crops, switchgrass plants (Panicum virgatum L.), which have been cultivated on a reclaimed coal-mining site for more than 20 years. The endophytic fungi were isolated from the surface-sterilized shoot (leaf and stem), root, and seed tissues of switchgrass plants and then cultured for identification. A total of 1339 fungal isolates were found and 22 operational taxonomic units (OTUs) were sequence identified by internal transcribed spacer (ITS) primers and grouped into 7 orders and 4 classes. Although a diverse range of endophytic fungi associated with switchgrass were documented, the most abundant class, order, and species were Sordariomycetes, Hypocreales, and Fusarium spp. respectively. About 86% of the isolated endophytic fungi were able to enhance the heights of the shoots; 69% could increase the shoot fresh weights; and 62% could improve the shoot dry weights after being reintroduced back into the switchgrass plants, which illustrated their functional importance. Through the Shannon Diversity Index analysis, we observed a gradation of species diversity, with shoots and roots having the similar values and seeds having a lesser value. It was observed that the switchgrass plants showing better growth performance displayed higher endophytic fungal species diversity and abundance. It was also discovered that the rhizosphere soil organic matter content was positively correlated with the fungal species diversity. All these data demonstrate the functional association of these beneficial endophytic fungi with switchgrass and their great potential in improving the switchgrass growth and biomass to benefit the biofuel industry by reducing chemical inputs and burden to the environment.
The global demand for energy is expected to increase by more than 50% by the year 2025 . The increasing problems and concerns regarding greenhouse gas emission due to burning of the fossil fuels and the need for rural economic development are key factors stimulating the development of national and international strategies to increase sustainable biofuel crops production for bioenergy generation.
The cellulosic crop, switchgrass (Panicum virgatum L.) is a large and important component of an economically profitable and environmentally friendly biofuel industry of North America .The identification and application of endophytic fungi possessing growth and biomass promoting activities and imparting resistance to biotic and abiotic stresses could be critical for its sustainable production. Till date, some studies have explored the diversity and function of endophytic fungal communities of the switchgrass   . However, the endophytic fungal community compositions and related functions associated with the switchgrass grown in some special conditions, such as on coal-mining sites, have not been widely studied.
We examined the association between switchgrass plants and their complex endophytic fungal communities grown on a coal-mining site. Our data showed that a majority of the isolated culturable endophytic fungi from the switchgrass were capable of enhancing the switchgrass shoot growth and biomass under greenhouse conditions. Our data also indicated that there might be a high positive correlation of the rhizosphere soil organic matter with the endophytic fungal species diversity and vigorous growth of the switchgrass plants. It was further indicated that there might be functional associations of the endophytic fungi with the switchgrass plants, which may be enhanced by better soil conditions, such as presence of higher organic matter in the rhizosphere soil from part 1 versus part 2. This study highlights the great potential of these fungal endophytes in enhancing agro-ecosystem robustness in this forage and emerging bioenergy crop and possibly many other crops, by way of increased plant growth and yield, and benefit to the environment.