Preventing Extinction of the Critically Endangered Dactylorhiza incarnata subsp. ochroleuca in Britain Using Symbiotic Seedlings for Reintroduction

The yellow early marsh-orchid (Dactylorhiza incarnata subsp. ochroleuca) is critically endangered in the UK. Reintroduction of this threatened orchid to former haunts that have been restored is a long-term objective of this study. Identifying germination-specific mycorrhizal fungus lineages from closely related species is used as a method due to the extremely small number of plants left in the wild. A putative orchid mycorrhizal fungus of the family Tulasnellaceae, isolated from Dactylorhiza praetermissa, supported in vitro seed germination to produce reintroduction-ready seedlings. Reintroduced symbiotic seedlings survived over the winter months in the flooded reintroduction site (RS). The comparative soil analysis for key nutrients before reintroduction showed that phosphorus content in the RS is very low compared to the soil collected from the wild site (WS) where the last viable population exists. On the other hand, C:N ratio in the soil at the WS and RS were not significantly different. To our knowledge, this is the first-ever report on the reintroduction of symbiotic seedlings of a threatened orchid back to the wild in the UK.