台灣地區外擔子菌科之研究

Abstract

外擔子菌科(Exobasidiaceae)為植物寄生菌，會產生裸露的子實層，屬於Ustilaginomycetes, 外擔子菌目(Exobasidiales)，其中包含Exobasidium和Muribasidiospora兩屬真菌，以Exobasidium最常見。本研究欲調查台灣地區Exobasidiaceae之菌類分布及種類。調查結果顯示，共發現十一種Exobasidium和一種Muribasidiospora，其寄主涵蓋杜鵑花科和茶科植物。其中新紀錄種為E. cylindrosporum、E. pieridis和E. yoshinagai；而造成毛蕊木 (Vaccinium japonicum var. lasiostemon) 黃斑型的Exobasidium及大頭茶 (Gordonia axillaries)葉斑病的Muribasidiospora可能為新種。此外，感染栽培種杜鵑 (Rhododendron sp.)和紅毛杜鵑(R. rubropilosum var. rubropilosum)及玉山杜鵑(R. pseudochrysanthum)的Exobasidium目前尚未確定。此外，除了形態鑑定分類外，亦利用ITS (Internal Transcribed Spacer)分析Exobasidium間的親緣關係。結果顯示，依據寄主的不同，可將Exobasidium分成三大類群，分別為: 杜鵑花屬(Rhododendron)、越橘亞科(Vaccinioideae)和茶科(Theaceae)，顯示寄主親緣關係較近者，其上所分離的Exobasidium關係也較近。

Exobasidiaceae is a phytoparasitic family that belongs to Ustilaginomycetes and consists of two genera, Exobasidium and Muribasidiospora. About 50 Exobasidium species and 3 Muribasidiospora species have been recorded in the world. Twelve Exobasidium species, including 9 new species, have previously been recorded in Taiwan. In the present study, 11 Exobasidium species and one Muribasidiospora are included. Among them, E. cylindrosporum, E. pieridis and E. yoshinagai are newly recorded in Taiwan. The Exobasidium species occurring on Vaccinium japonicum var. lasiostemon and Muribasidiospora on Gordonia axillaries are likely new species. The Exobasidium species infecting horticultural rhododendrons, R. rubropilosum var. rubropilosum and R. pseudochrysanthum, remains to be further identified. Exobasidium japonicum from different hosts displays slight morphological variations. Analysis of ITS sequences indicates that Exobasidium species are correlated to their respective hosts and can be grouped into three clades corresponded with host taxonomic groups, Rhododendron, Vaccinioideae and Theaceae.