Abstract
This study focuses on Eriocaulon nudicuspe , an endangered herbaceous plant endemic to Japan, aiming to analyze the composition of its endophytic fungi and evaluate the antioxidant capacity of fungal isolates. E. nudicuspe samples were collected from three Japanese marshes: Yanami, Kamitaka, and Onshinji. Fungi were isolated using the tissue block method and identified based on morphological and molecular characteristics. The free radical scavenging activity of fungal organic extracts was assessed using the DPPH assay. A total of 69 fungal strains isolated from E. nudicuspe across the three wetlands were identified into 13 genera, among the three marshes, Yanami and Kamitaka Marsh each harbored 9 genera, whereas Onshinji Marsh harbored only 3. The dominant genus was Colletotrichum , which accounted for 39.13% of all isolates from leaves and stems, followed by Stagonospora . Notably, Colletotrichum was significantly more abundant in leaves than in stems, suggesting a strong tissue preference. In contrast, Stagonospora was more prevalent in stems. DPPH radical‐scavenging rates also varied significantly among marshes, with isolates from Yanami Marsh showing higher antioxidant activity, both in average and maximum values. The abundance of Colletotrichum was strongly associated with leaf tissues, while variations in fungal community structure across sample regions suggest that geographical location influences endophytic composition.