Fungal endophytes of invasive Phagramites australis populations vary in species composition and fungicide susceptibility

Phragmites australis subsp. australis (Poaceae) is an aggressively invasive reed that threatens both freshwater and saltwater ecosystems in North America. We sampled P. a. australis plants for fungal endophytes at seven sites across a short geographic range near a freshwater lake in Michigan. Compared to previous studies, our data reveal novel variation in the diversity and abundance of fungal endophytes within P. a. australis. Within each sampling site we observed 4-10 morphologically unique, culturable fungi. Since fungal endophytes can confer significant benefits to their plant host, we hypothesized that fungal endophytes are important for mediating plant invasions. To test this hypothesis we first had to establish a protocol to experimentally control fungal endophytes within P. a. australis, which does not easily grow from sterile seed. We therefore investigated the effect of fungicides as a potential method for eliminating fungi from living plant tissue such as rhizomes. We selected the ten most abundant fungi isolated from P. a. australis and tested their susceptibility to three commonly available fungicides. Response to the fungicides varied across fungal isolates, demonstrating physiological variation and fungicide-resistant phenotypes.