Germination Support and Fungal Community Dynamics in Orchis provincialis Balb.ex Lam. & DC.: Insights from Protocorm and Root Mycorrhizae

Abstract

Research on mycorrhizal fungi is essential for orchid conservation, particularly in key life cycle stages such as seed germination and seedling establishment. This study conducted in situ germination experiments to assess the compatibility of mycorrhizal fungi isolated from protocorms and adult roots in facilitating seed germination and growth in the endangered terrestrial orchid Orchisprovincialis Balb.ex Lam. & DC. The fungal community composition at both developmental stages was also analyzed. Molecular identification analyses identified two fungal strains from protocorms and one from roots as members of the orchid mycorrhizal family Tulasnellaceae. Fungal inoculation significantly influenced protocorm formation, with only one isolate from protocorms (PR4) promoting germination by over 60%. OTU clustering and beta-diversity analysis revealed significant differences in fungal communities between protocorms and roots, with root-associated fungal diversity being considerably lower than that of protocorms. This study demonstrates that fungal identity plays a crucial role in in situ seed germination in terrestrial orchids, with fungi isolated from host protocorms accelerating germination. Additionally, the composition of mycorrhizal fungi associated with O.provincialis shifts throughout ontogeny. These findings highlight the importance of evaluating protocorm-associated fungi in conjunction with adult mycorrhizal fungi to gain a deeper understanding of the conditions required for orchid germination, growth, and reproduction.