Canopy tree species and openness affect foliar endophytic fungal communities of understory seedlings

There is growing evidence demonstrating the diversity of foliar endophytic fungi and their ecological roles in the survival of tree seedlings. However, the factors that shape fungal communities in tree seedlings within natural forest ecosystems remain poorly understood. Here, we evaluated the composition of foliar endophytic fungi growing in current-year seedlings of Cornus controversa and Prunus grayana in a cool temperate deciduous forest through a seed-sowing experiment and fungal isolation. The composition of endophytic fungi was affected by canopy tree species, canopy openness, and time after germination. In total, 27 and 22 fungal taxa were isolated from C. controversa and P. grayana seedlings, respectively. The dominant fungal taxa in both seedling species were Colletotorichum spp., and their isolation frequencies were higher under C. controversa canopies than under P. grayana canopies; the frequencies also increased with time after germination. These results suggest that overstory tree species strongly influences the endophytic fungal communities of understory seedlings.