Mycobiome of Bioenergy Grasses: Case-study of Dark Septate Endophytes in Giant Miscanthus and Switchgrass

Graduate #64
Discipline: Ecology Environmental and Earth Sciences
Subcategory: Ecology

Ashley Williams - Alcorn State University
Co-Author(s): Margeria Smith, Keerthi Mandyam, Ananda Nanjundaswamy, and Victor Njiti, Alcorn State University, Lorman, MS

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Plants host a collection of microorganisms inside and around their surfaces collectively referred to as the microbiome. Specifically, the fungal communities are referred to as the mycobiome. Plant root microbiomes are thought to impact plant health and productivity just as human gut microbiomes are known to influence human health and well-being. Plant root microbiomes as known to participate in nutrient uptake, modulating host immunity and preventing pathogen colonization. Mycorrhizal fungi are the most important components of root mycobiome as they are mutualistic fungi offering many services to the host plant. Dark septate endophytic (DSE) fungi are also part of the root mycobiome and commonly found in grasslands. Very few DSE fungi have been characterized resulting in poor ecological resolution of DSE. Giant Miscanthus and switchgrass (Panicum virgatum) like other perennial, warm-season grasses have high dependence on arbuscular mycorrhizal fungi. However, their DSE have not been studied. Both grasses are considered as top two bioenergy grasses and their stands last for 15-20 years. Additionally, switchgrass is a native grass used in ecological restoration and soil conservation. In fact, switchgrass has been cultivated in several million hectares for soil conservation in the U.S. as part of Conservation Reserve Program. In the future both switchgrass and Giant Miscanthus are expected to be cultivated to meet the billion ton of biomass requirement by 2030 for fulfilling the U.S. bioenergy vision for energy independence. From an ecological perspective, the long-term and large-scale cultivation of these grasses necessitates the quantitative and qualitative characterization of DSE fungi. Accordingly, we hypothesized that i) both grasses will have an abundance (>90% root length colonized (RLC)) of DSE fungi with seasonal variation, and ii) Periconia macrospinosa will be the most commonly isolated DSE as it is frequently isolated from native grasses in North American and European grasslands. Root samples were collected from Freedom Giant Miscanthus (FGM) and from Kanlow variety of switchgrass cultivated at Alcorn’s Experiment Research Station and Conservation Research respectively in 2015 and 2016. Root samples were stained with sudan IV to visualize DSE, and the percent RLC was recorded according to magnified intersections method. Root colonizing fungi were isolated on four different media and DSE fungi were identified by micromorphology and subsequently testing Koch’s postulates. DSE fungi were found in both grass species and the %RLC was not as high as in native grasses. Several strains of P. macrospinosa were isolated and identified. Our data show that DSE fungi are important components of root mycobiome of two important bioenergygrasses. Accordingly, the data from this study can provide insights not only about DSE fungi, but also contribute to plant mycobiome investigations in general.

Funder Acknowledgement(s): NSF HBCU UP

Faculty Advisor: Keerthi Mandyam, keerthi@alcorn.edu

Role: I collected switchgrass samples, processed the samples, stained the samples for microscopy and evaluated the %RLC of DSE fungi in switchgrass. Further, I isolated root colonizing fungal endophytes by using a variety of media and identified fungi by classical taxonomy. I also participated in processing Giant Miscanthus root samples.