Associated fungi, symbiotic germination and in vitro seedling development of the rare Andean terrestrial orchid Chloraea riojana

• Isolation and molecular identification of fungal symbionts from Chloraea riojana.
• Protocol for the symbiotic propagation of the orchid species.
• Compatibility with fungi from sympatric orchid species.
• Mycorrhizal status of the species.
• Distribution of the species.

Chloraea riojana is a rare terrestrial orchid from the Andean region of Northwest Argentina. Here we evaluate the mycorrhizal status, symbiotic germination and protocorm development of the species. Plant material including capsules, roots and whole plant were collected from two natural populations. Symbiotic germination was tested using one fungal endophyte isolated from C. riojana and four fungal endophytes previously isolated from the sympatric orchid species Aa achalensis. Three isolates were able to promote seed germination and further development into plantlets with 1–2 leaves after 16 weeks of in vitro dual culture. Moreover, the strain isolated from C. riojana developed intense melanized coilings and pelotons inside protocorms, a rare feature not observed before. These findings contribute to the general knowledge about the orchid mycorrhiza in the subtribe Chloraeinae, and open an opportunity for the conservation not only of this particular species, but also of other rare and poorly known Andean terrestrial orchids.