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Foliar endophytic microbiome composition and functional capacities vary with soil nutrient inputs.

Linda Kinkel: Department of Plant Pathology/University of Minnesota

<div>Endophytic microbes are of significant interest for their potential to influence plant health and productivity in agricultural and natural habitats. Yet the factors that influence the composition or functional capacities of endophytic microbiomes are not well understood. We studied endophytic microbiomes in the C4 prairie grass <em>Andropogon gerardii </em>within a long-term nutrient amendment experiment. Nitrogen, phosphorous, and potassium (NPK) were applied to plots annually since 2007. In fall 2015, mature, non-senescent leaves were harvested from NPK-amended and non-amended (control) plants. Leaves were surface-disinfested, macerated in sterile water, and dilution-plated onto nutrient media. Bacterial and fungal colonies were randomly selected from plates, and purified and stored at -80C. For every isolate, 16S (bacteria) or ITS2 (fungal) sequence was determined. A random set of 10 isolates from each leaf was further evaluated for nutrient utilization profiles using Biolog plates. We found that NPK dramatically altered fungal, but not bacterial endophytic composition. Fungi, but not bacteria, had significantly smaller niche widths in NPK-treated than control leaves. In the absence of NPK, fungi are significantly better competitors for nutrients than bacteria, but this advantage is lost with NPK. These data suggest that widely-used soil nutrient inputs significantly alter the composition and functional capacities of endophytic microbiomes, with implications for crop productivity.</div>