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Abstract. Endophytic fungi were isolated from four healthy tissues (new leaf, old leaf, bark, and xylem) of three Japanese tea cultivars (Hokumei, Sayamakaori, and Yabukita) at the Saitama Tea Research Institute, Japan in July 2015. A total of 520 isolates was obtained from 600 segments and were classified into 44 fungal taxa; the majority (93.2%) belonged to the phylum Ascomycota. The lowest infection rate was found in the xylem tissue of all cultivars. The total infection rate did not differ significantly among the cultivars. Colletotrichum gloeosporioides f. sp. camelliae and Pleosporales sp. were the predominant endophytes in all tissue types and cultivars. Most of the dominant endophytes showed obvious cultivar and tissue preferences. Tissue type played a more important role in shaping community structure than did cultivar. Colletotrichum gloeosporioides f. sp. camelliae preferred bark and old leaf tissue while Pleosporales sp. preferred new leaf tissue. The colonization frequency of C. gloeosporioides f. sp. camelliae was significantly lower in the Yabukita cultivar. Stem tissues harbored more diverse endophytes than did leaf tissues.

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Summary To examine the effects of salicylic acid (SA), the ethylene precursor 1‐aminocyclopropan‐1‐carboxylic acid (ACC) and methyl jasmonate (MJ), which induce defence responses against pathogen in plants, on foliar endophytic fungi, we performed exogenous treatments of Quercus serrata leaves with these chemicals and subsequently isolated endophytic fungi. SA and ACC significantly reduced the isolation frequency of the most dominant fungus, a Xylaria species as identified by sequence analysis of the internal transcribed spacer (ITS) region of the ribosomal DNA. In contrast, the frequency of the second most frequent fungus increased by SA and ACC. A few other fungi were also affected positively or negatively. Shannon diversity indices decreased by all treatments because of the uneven isolation frequencies of the endophytes. Our results imply that host defence responses induced by the chemical treatments reduced the number of infections of some endophytes while the frequency of some other endophytes increased benefiting from the reduction of competitors.

Foliar fungal endophytes are ubiquitous and hyperdiverse, and tend to be host-specific among dominant forest tree species. The genus Tubakia s.l. comprises foliar pathogens and endophytes that exhibit host preference for Quercus and other Fagaceae species. To clarify interspecific differences in ecological characteristics among Tubakia species, we examined the endophyte communities of seven evergreen Quercus spp. at three sites in eastern Japan during summer and winter. We also compared their spore germination rates at different temperatures. Host tree species was the most significant factor affecting endophyte community composition. The Tubakia species found at the study sites were divided into five specialists and three generalists according to their host ranges. Specialists were dominant on their own host in summer, and their dominance declined in winter. In contrast, generalist Tubakia species 3 became dominant in some tree species in winter. This seasonal variation in Tubakia species dominance was consistent with their cold tolerance, which was evaluated in spore germination tests. This is the first study to report ecological differentiation among endophytic fungal species within a genus.