Study on mycorrhizal symbioses in Orchidaceae

Abstract

Mycorrhizal fungi of a myco-heterotrophic orchid, Epipogium roseum, were isolated, and one of them was identified as Coprinellus disseminatus based on the morphological characteristics of basidiomata induced under an artificial condition. This fungus was used for symbiotic cultivation, in which seed germination, stolon elongation, rhizome development, shoot growth and flowering were successively observed. To study on a myco-heterotrophic orchid, Chamaegastrodia sikokiana, the mycorrhizal fungi were identified as a member of Ceratobasidiaceae, and one of the isolate formed ectomycorrhiza on seedlings of Abies firma, suggesting tripartite symbiosis between C. sikokiana, mycorrhizal fungi and ectomycorrhizal tree. The mycorrhizal fungi of Stigmatodactylus sikokianus were isolated and identified to be Sebacina spp. in Sebacinaceae. The fungal sequences obtained from several habitats were quite similar one another, which suggested the high specificity of this fungi group. The distribution of S. sikokianus is restricted in a narrow area, where the high specificity of mycorrhizal fungi may have some effects. On the other hand, a myco-heterotrophic orchid Epipogium aphyllum is distributed to a wide area of northern part of the Eurasian continent to Japan. This orchid has a symbiotic relationship with many species of Inocybe in Cortinariaceae, which may correspond to the wide distribution of this orchid