Effects of summer temperature on fungal endophyte assemblages in Japanese beech (Fagus crenata) leaves in pure beech stands

Abstract

Fungal endophyte assemblages in leaves of Japanese beech ( Fagus crenata Blume) trees were investigated in pure beech stands at four localities with different summer temperatures covering the natural distribution range of the species. Ascochyta fagi Woronich was dominant at every site, and the infection density (ID) of this fungus was higher at sites with low maximum air temperatures. The growth rate of A. fagi on potato dextrose agar was inhibited by temperatures above 30 °C. These results suggest that the population density of A. fagi on Japanese beech leaves is influenced by summer temperatures. However, the number of species and Shannon index of diversity (H′) of endophytic fungi increased with increasing air temperature and a negative correlation was observed between the ID of A. fagi and the diversity of other endophytes. The species composition of minor endophytes was site-specific and may reflect geographic and genetic distances between beech stands.