Are Fungal Endophytes of Fire Adapted Plants also Fire Adapted?

Dowd, Alex

ABSTRACT: Fungal endophytes are fungi that asymptomatically inhabit living plant tissue. This study examines heat tolerance as a mechanism of endophytic succession at burn sites of the 2016 Chimney Tops 2 Fire in the Great Smoky Mountains National Park. We hypothesized that the majority of endophytes found at these burn sites would be heat tolerant and that a greater number of heat tolerant endophytes would be found in pine seedlings (fire-adapted, found in severe burn areas) than in Rhododendron shrubs (not fire-adapted, found in moderate burn areas). We cultured endophytes isolated from seedling needles and regenerating rhododendron leaves on malt extract agar plates. These isolates were heated at 65°C for treatments of 0, 10, 20, and 30 minutes. Their growth was monitored for two weeks, after which heat resistance was determined based on presence or absence of growth after 30 minutes of heating. Less than half of the endophytes we tested were heat resistant. Heat resistant endophytes were not significantly associated with fire adapted host plants. Intraspecific variation of heat resistance was found in many taxa, suggesting that endophytic heat resistance varies at the level of genotype rather than species. Possible mechanisms of genotype-level heat resistance include epigenetic effects, heat shock proteins, or thermostable cellulases. In the face of climate change, further research on fungal heat resistance could contribute to novel issues within the fields of fungal epidemiology and fire ecology.