ENDOPHYTIC FUNGI IN LEAVES OF ERICACEOUS PLANTS

Endophytic fungal assemblages were investigated in different leaf stag es of eight species of Ericaceae (six species of Rhododendron, Enkiant hus perulatus, and Pieris japonica). Guignardia sp. (anamorph: Phyllos ticta sp.), Phomopsis sp., and Colletotrichum gloeosporioides were fou nd in the leaves of all plants. The frequency of Guignardia sp. was hi ghest in senescent leaves, while in young leaves it was lower than tho se 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 lea ves decreased as the leaves became old, while those of Pestalotiopsis, Alternaria, and others increased after the leaves fell. No significan t differences were found among the compositions of endophytic fungal a ssemblages on ericaceous plants at the site investigated. It was consi dered that the endophytic fungi infect young leaves and remain latent in the leaves without producing symptoms while the hosts are physiolog ically active. Discostroma tricellulare was considered to be specific for R. obtusum. The colonization frequencies of the endophytic fungi w ere clearly lower on the leaves of P. japonica than on those of the ot her plants. it is considered that asebotoxin, which is known to be tox ic to animals and insects, and other secondary metabolites retard fung al invasion in P. japonica.