Endophytic fungi in leaves of ericaceous plants

Endophytic fungal assemblages were investigated in different leaf stages of eight species of Ericaceae (six species of Rhododendron, Enkianthus perulatus, and Pieris japonica). Guignardia sp. (anamorph: Phyllosticta sp.), Phomopsis sp., and Colletotrichum gloeosporioides were found in the leaves of all plants. The frequency of Guignardia sp. was highest in senescent leaves, while in young leaves it was lower than those of Phomopsis sp., and C. gloeosporioides. Discostroma tricellulare was isolated in high frequency from the leaves of Rhododendron obtusum. The colonization frequencies of these endophytic fungi on fallen leaves decreased as the leaves became old, while those of Pestalotiopsis, Alternaria, and others increased after the leaves fell. No significant differences were found among the compositions of endophytic fungal assemblages on ericaceous plants at the site investigated. It was considered that the endophytic fungi infect young leaves and remain latent in the leaves without producing symptoms while the hosts are physiologically active. Discostroma tricellulare was considered to be specific for R. obtusum. The colonization frequencies of the endophytic fungi were clearly lower on the leaves of P. japonica than on those of the other plants. It is considered that asebotoxin, which is known to be toxic to animals and insects, and other secondary metabolites retard fungal invasion in P. japonica.Key words: endophytic fungi, ericaceous plants, fungal succession.