Insights into the Mycosphere Fungal Community and Its Association with Nucleoside Accumulation in Ophiocordyceps sinensis

Soil microbiomes are critical environmental factors influencing the occurrence and quality formation of <i>Ophiocordyceps sinensis</i>, a valuable medicinal fungus endemic to the Qinghai-Tibet Plateau. However, few studies have explored the relationship between mycosphere soil fungal communities and the quality characteristics of <i>O. sinensis.</i> This research aimed to systematically analyze the structural characteristics and diversity of fungal communities in mycosphere soils of <i>O. sinensis</i> from eight geographical regions using Illumina high-throughput sequencing, and compare the nucleoside contents in <i>O. sinensis</i> from the corresponding sites. Alpha diversity indices showed that soil samples from Yushu and Guoluo in Qinghai Province exhibited higher fungal richness and diversity compared to other regions, whereas samples from Qamdo in Tibet showed the lowest diversity. Beta diversity analysis indicated significant differences in fungal community structure across various regions (<i>R</i> = 0.861, <i>p</i> = 0.001). At the phylum level, Ascomycota overwhelmingly dominated throughout all mycosphere soils of <i>O. sinensis</i> (96.30-99.88%), followed by Mortierellomycetes (0.25-2.25%). Network analysis revealed that <i>Ophiocordyceps</i> emerged as the core taxon in the mycosphere fungal communities, suggesting its central role in shaping the structure of the fungal networks. Additionally, <i>O. sinensis</i> from Yushu contained the highest total nucleoside content, indicating that the accumulation of nucleosides in <i>O. sinensis</i> may be affected by the composition of mycosphere soil fungi. Furthermore, correlation analysis indicated a significant positive relationship between several mycosphere fungal abundances and nucleoside accumulation in <i>O. sinensis</i>, such as <i>Naganishia</i>, <i>Acicuseptoria</i>, <i>Nectria</i>, <i>Serendipita</i>, and <i>Humicola</i>. These findings would provide a theoretical foundation for improving artificial cultivation strategies of <i>O. sinensis</i>.