All orchids have an obligate relationship with mycorrhizal symbionts during seed germination, with most of the symbionts being Rhizoctonia-like fungi (Arditti, 1992⇓). Understanding the mycorrhizal symbiosis is of great importance, as availability of the fungal symbionts may play a key role in determining orchid distribution and diversity. Furthermore, most studies of orchid mycorrhizal interactions have concentrated on terrestrial orchids from temperate regions, whereas the majority of orchid species are epiphytes in tropical regions.