PSATHYRELLA CANDOLLEANA (FR.) MARIE, A SAPROPHYTIC FUNGUS FORMING ORCHID MYCORRHIZA IN SATYRIUM NEPALENSE D. DON FROM INDIA

摘要

Psathyrella candolleana (Fr.) Marie is a saprophytic fungus which inhabits litter in the forest ecosystem. Satyrium nepalense var. nepalense, a rare autotrophic terrestrial orchid was found associated with this fungus forming orchid mycorrhiza. Isolation from root and tuber yielded two different fungi on Potato dextrose agar medium. Molecular identification of the fungal cultures was carried out by sequencing ITS region of nuclear rDNA. The isolate from the root was identified as Psathyrella candolleana and the isolate from tuber as Colletotrichum dematium .Light microscopic studies of the roots have shown that 60% of the cortical cells contained both digested and intact pelotons. TEM studies of the root have revealed the fine structure of the pelotons with the hyphae observed in the form of fungal cells with thick chitin wall. Pelotons were surrounded by the host cell membrane as an electron dense interfacial matrix suggesting biotrophic relationship. The cortical cells showed shrinkage of protoplasm indicating digestion of the pelotons. An anatomical study of the tuber has not revealed any pelotons. This is the first report of Psathyrella candolleana as an orchid mycorrhizal fungus colonizing the roots of Satyrium nepalense from the Indian region.