Abstract:

The host plants and symptoms, parasitism and pathogenic mechanism, morphology, life cycle, ultra-structure of the host-pathogen relation-ship, cultural characters, physiological properties, molecular biology of the fungi, and especially with their taxonomy were studied in this paper. The fungi belonging to the genus Exobasidium distribute over Asia, the North America, Europe and Australasia. The fungi are known as the pathogens of cell hyperplastic and hypertrophic disease of several tree plants of five families namedly Theaceae, Ericaceae, Lauraceae, Empetraceae and Symplocaceae. About 50 species of this genus have been known in the world. The symptom type of the disease caused by the fungi is diversiform and is related to phytohormones. The life cycle of the fungi is not clear, although there are a few reports on it. The germtubes of the basidiospores and conidia can enter the leaves of the host through stromata or mechanical injuries, or penetrate the epidermis directly. The mycelia were formed and developed in intercelluar space and the haustorium-like structure with inclusive bodies was observed in infected cell. The standards for classifying this fungi are varied according to researchers. Host, symptom, morphological characteristics, physiological and cultural properties, germination behaviour of basidiospore on PSA have been used as the standards for taxonomy. GC content of DNA and 28SrDNA-PCR-RFLP may be used as taxonomic characters.

Key words: Exobasidium, Fungus