Exploring Foliar Fungal Endophyte Communities as a Source of Weed Biological Control Agents

Wavyleaf basketgrass (Oplismenus undulatifolius (Ard.) P. Beauv.) is an invasive perennial grass native to East Asia that is spreading in the Mid Atlantic United States. Basketgrass forms dense mats in forest understories that suppress the growth of desirable, native herbaceous species, homogenize soil microbiomes, and alter insect communities. The relatively recent introduction of this species provides an opportunity to study novel weed microbe associations formed during invasion. The aim of this research was to identify fungi inhabiting healthy basketgrass and assess their potential use as non traditional biological control agents. Previously, 317 foliar endophytic fungi were collected and identified to genus with DNA sequences. Radial growth rates of these fungi were recorded in culture as a measure of saprophytic fitness, and detached leaf assays were conducted to record a preliminary plant fungus interaction phenotype. A subset of phylogenetically dispersed endophytes was evaluated for the presence of phytotoxic secondary metabolites secreted into liquid growth medium. Isolates from Hancock, VA grew significantly faster than those from Edward’s Ferry, MD, and growth rates varied strongly by genus. Less common taxa outperformed “core” isolates in saprophytic fitness, while core isolates elicited the strongest plant interaction responses. Detached leaf assays confirmed significant necrosis and “stay green” effects, though high variability suggests protocol refinement is needed. These findings demonstrate that phylogenetic affiliation reliably predicts key biocontrol traits — saprophytic growth, phytotoxicity, and host interaction phenotypes — and highlight both certain clades and less‐abundant taxa as promising candidates for bioherbicide development.