Functional Divergence and Stage-Specific Symbiosis of Endophytic Tulasnella Fungi in the Endangered Orchid Paphiopedilum Malipoense

Paphiopedilum malipoense, a critically endangered orchid, depends entirely on mycorrhizal fungi for germination, complicating its conservation. This study isolated 12 fungal strains from wild roots, all identified as Tulasnella, confirming strict host specificity. Cross-species germination assays revealed functional divergence: strains MLP116, MLP027, and MLP232 supported full protocorm-to-seedling development with germination rates of 54.27%, 54.88%, and 62.01%, respectively, while others induced developmental arrest. Seedling symbiosis showed stage-specific effects: MLP217, ineffective during germination, increased seedling biomass by 131%. MLP232 performed excellently in both stages, achieving the highest germination rate and 98% biomass increase, with elevated IAA and soluble protein. Physiological profiling demonstrated functional complementarity: MLP161 enhanced nutrient acquisition; MLP246 boosted chlorophyll and antioxidants; and MLP281 increased antioxidant activity but suppressed growth. These results indicate that part Tulasnella strains exhibit stage-specific efficiency and functional complementarity. We recommend using tailored fungal consortia in orchid conservation to synergistically support complete life cycle development, providing a practical framework for safeguarding endangered species like P. malipoense.