symbiotic germination of seeds of five mycoheterotrophic orchids with and fungi.

We performed germination tests on seeds from five orchids (, var. , var. , , and ) using one and two isolates. sp. 1 promoted germination of all five orchids, with root and/or tuber formation observed in , , and . No additional growth was observed in the other two orchids. sp. 2 induced , var. , and germination, whereas sp. 1 induced and germination. Phylogenetic analyses indicated that the two isolates represent distinct lineages within the . sp. 1 and sp. 1 are closely related to and , respectively. Our results imply that and marasmioid fungi play important roles in early development in species, and that fungi in particular may be common mycobionts of species. Root and/or tuber development was observed with four plant-fungus combinations, implying that these associations persist throughout the life cycle, whereas var. may require different associates over time. Our findings will contribute to elucidating the mycorrhizal associations of mycoheterotrophic orchids throughout their life cycle.