Communities of fungal endophytes in leaves of Fraxinus ornus are highly diverse

Communities of endophytic fungi in leaves of Manna ash (Fraxinus ornus) were examined to both the north and south of the Alps, i.e. within and beyond the native range of this tree species. Almost all leaves examined had been colonized by endophytic fungi. One hundred and two morphotypes were found, and 62 of them were identified to genus or species level using ITS sequencing and micromorphology. Venturia orni was most frequent and occurred in almost one third (32%) of the 1536 examined leaf segments. It was five times more abundant than Colletotrichum acutatum, the second most frequent endophyte. Other frequently isolated endophytes include Paraconiothyrium sp. 1, Mycosphaerella aurantia, Septoria cretae, Botryosphaeria dothidea and Boeremia exigua. The ash dieback pathogen was not isolated. The endophyte communities differed between the north and south of the Alps and the individual tree types had a distinct influence within sites.