Symbiotic mycorrhizal fungi for inducing seed germination of Cephalanthera longifolia (L.) Fritsch colonized in landfill site

An endangered orchid, Cephalanthera longifolia, recently expands their habitat to developed lands, such as parks and landfills. This shows that developed lands can be available for the habitat of the endangered orchids, that is an interesting model for considering the ecosystem in urban area. However, the factors that allow this orchid to colonize in developed lands still remain unclear. This orchid, which is so-called “partially mycoheterotrophic plants”, depends on the symbiotic mycorrhizal fungi for their nutrient supply, especially in germination stage. To clarify which fungal groups induce its seed germination and are involved in its colonization in developed lands, we conducted in situ seed germination method in the landfill site and identified the symbiotic fungi of the seedlings. Three Thelephoraceae fungi were mainly involved in the seed germination of C. longifolia. These fungi were found from various growth stages of the seedlings and distributed across the study site regardless the soil depth and the inoculation point, suggesting that they play a key role in the seed germination and development of the seedlings. Thelephoraceae fungi have ectomycorrhizal association with the Pinaceae and Fagaceae trees. Stable symbiotic relationships were developed between these planted trees and Thelephoraceae fungi, and these relationships allowed this orchid to colonize in the developed land.