Culture-based inventory and functional guild analysis of root-invading fungi associated with grassland plants across multiple regions in China.

Grassland ecosystems harbor diverse plant-associated fungal communities that contribute to ecosystem functioning and plant health. However, large-scale culture-based inventories of root-invading fungi across multiple grassland regions in China remain scarce. In this study, we conducted a multi-region survey of culturable root-invading fungi isolated from surface-sterilized, discolored root and basal stem tissues in contact with the soil. We sampled 33 herbaceous plant species, representing 19 genera and 9 families, across 17 counties in Qinghai, Xinjiang, Inner Mongolia, and Xizang. A total of 273 fungal isolates were preserved and identified using ITS sequence analysis complemented by morphological observations. These isolates were classified into 40 genera and 53 species-level taxa spanning several major fungal lineages. A limited number of genera, including Fusarium, Darksidea, and Preussia, accounted for a substantial proportion of the isolates, whereas numerous low-frequency taxa were also recovered. Fungi were consistently isolated from both root and basal stem tissues, indicating extensive internal colonization of symptomatic tissues across these plant compartments. Significant differences were observed between plant-level and tissue-level isolation rates within both Poaceae and Cyperaceae. Functional guild assignment revealed the presence of endophytic, saprotrophic, and pathogenic taxa, with relative proportions varying among plant groups. Analysis revealed strong fungus-host associations, with Cramer's V of 0.850 indicating a high overall association strength and indicator species analysis identifying eight host-associated taxa. This study provides a culture-based baseline inventory of root-invading fungi associated with natural grassland plants in China and establishes a curated isolate collection for future ecological and functional investigations.