Comparison and structure of fungal diversity in roots and rhizosphere soils of wild and reintroduced populations of three Paphiopedilum species

Mycorrhizal fungi play critical roles in the seed germination and the growth of orchid plants. The investigation of fungi, especially mycorrhizal fungi, associated with orchid roots is important for both the protection and sustainable utilization of the plants. The Paphiopedilum orchid genus is severely endangered, and thus analysis of the composition and diversity of rhizosphere mycorrhizal fungi in wild and reintroduced Paphiopedilum species is beneficial for protecting wild Paphiopedilum resources and significant for the large-scale reintroduction and cultivation of Paphiopedilum. Here, high-throughput sequencing (HTS) was used to analyze the species and composition of mycorrhizal fungi in the roots and rhizosphere soils of wild and reintroduced populations of Paphiopedilum dianthum, Paphiopedilum hirsutissimum, and Paphiopedilum micranthum. The clustering of operational taxonomic units (OTUs) and determination of diversity indices showed significant differences between the fungal communities associated with the roots and rhizosphere soils of these three species of Paphiopedilum, with markedly fewer OTUs associated with the roots (3465) than the rhizosphere (5221). The numbers of mycorrhizal fungi in the roots (226) of these three species of Paphiopedilum were also less than in the rhizosphere (259). P. micranthum showed the greatest diversity of associated fungi compared to the two other species. The dominant fungal taxa associated with these orchids included Sebacina (Basidiomycota) and Tulasnella (Basidiomycota). Among these, Tulasnella and Sebacina are well-known orchid mycorrhizal fungi (OMF) that form essential symbiotic structures. These findings provide a reference for the reintroduction, protection, and resource development of the Paphiopedilum species.