Abstract
The Orchidaceae is by far the world’s largest plant family with more than 27,000 species. Leake (1994) listed 173 species of 43 genera which are non-photosynthetic but associated with fungi to get nutrition, so they are also called “holomycotrophic orchids”. The rarity and full-dependence on fungi characters not only cause fewer complete researches, but also increase difficulty for conservation. At least 305 species in 46 genera of holomycotrophic orchids exist in the world, including 24 mixotrophy. They are grouped into Epodendroideae, Orchidoideae, and Vanilloideae separately, meaning they might evolve independently. These non-photosynthetic orchids distribute in most continents but missing in polar region and most part of South America. There are 61 species grown in China, which is the highest in the world. Taiwan is the second area to grow 51 species. This means Taiwan has rich mycotrophic orchid species. To conserve these orchids, we investigated two endemic species, Gastrodia appendiculata and G. nantoensis, in Taiwan and tried to establish appropriate method for artificial cultivation. Colonization pattern of base region was different to central region of rhizomes, indicating that at least two fungi colonize the rhizome. PCR technique revealed that fungi Mycena spp. colonize mycorrhizae, and fungal colonization patern of base region in rhizome is similar to that of mycorrhizae. Mycena spp. might colonize both base region of rhizomes and mycorrhizae. For seven fungi isolated from the two Gastrodia spp., two belonged to genus Mycena, one in Coprinus, one in genus Pleurotus, and three belonged to Xylaraceae. According to life cycle of G. elata, the isolated Mycena spp. might induce seed germination, whereas Xylaraceae might stimulate further rhizome formation. All of the genera and family are thought to be litter-decomposers, hence G. appendiculata and G. nantoensis might need saprophytic fungi to maintain their growth.