Abstract: In this study，culturable fungi were isolated from diseased leaves of 258 individual plants of Oncidium sp.‘Boda 1’in three multi span plastic film greenhouses in Hainan Island in China. Fungal taxa are identified by analyses of the nuclear ribosomal internal transcribed spacer region（ITS）. To test the pathogenicity of the common fungi，the ten most frequently occurring fungal species were inoculated into the aseptic seedlings. One hundred and nineteen strains belonging to 39 OTUs were isolated. The fungal lineage is highly diverse，involving Ascomycota（90%），Mucoromycota（8%），and Basidiomycota（2%）. The isolation was thorough enough to catch 31 common fungal species which contributed 60% seqeuence reads in next generation sequncing. The fungi isolated from the diseased leaves were mainly pathogenic and saprophytic fungi，while the symbiotic fungi were rare. Of the 25 pathogenic fungi，9 species were also reported as symbiotroph，and 6 species as saprotroph-symbiotroph；Nine and one species were reported as saprotroph and saprotroph-symbiotroph，respectively；Trophic mode of the remaining 4 fungal species are unknown. The pathogenicity of top 10 dominant fungi was confirmed by inoculation of aseptic seedling. The most aggressive fungi are Muyocopron alcornii，Colletotrichum gloeosporioides，Diaporthe miriciae that produced distinct symptoms on inoculated seedling one or two days after inoculation.

Key words: Oncidium, fungal disease, phylogeny, trophic mode