Fungal endophytes associated with Inca nut plants (Plukenetia volubilis L.) in China and Thailand and their plant growth promoting properties

Endophytic fungi have attracted increasing attention because of their roles in plant growth promotion and their potential applications in agriculture. This study aimed to isolate, identify, and evaluate the plant growth-promoting potential of endophytic fungi from healthy leaves of the Inca nut plants (Plukenetia volubilis) collected from three sites located in China (Honghe, Yunnan Province) and Thailand (Fang and Chiang Dao Districts, Chiang Mai Province). A total of 168 fungal strains belonging to 35 previously known genera and one unrecognized genus were obtained, of which Ascomycota were predominant, accounting for 166 strains (98.8%). The results showed that the Honghe site yielded the highest number of fungal strains. For fungal identification, the internal transcribed spacer (ITS) region was used as the molecular marker. Nigrospora and Cercospora predominated in the Honghe and Chiang Dao sites, respectively, whereas Hypoxylon was the dominant genus in the Fang site. Two genera, Colletotrichum and Pseudopithomyces, were found at all three sampling sites. A total of 96 strains tested positive for siderophore production, and 47 strains solubilized insoluble phosphate. Additionally, 13 fungal strains produced indole-3-acetic acid (IAA), among which Colletotrichum strain 1-8-1 yielded the highest concentration at 470.00 μg mL−1. The results showed that 57 strains tested positive for cellulase production and 10 strains for chitinase production. Moreover, fungal culture filtrates containing IAA from Colletotrichum strains 1-1-6, 1-8-1, and 2-1-15 enhanced seed germination in Chinese kale and tomato. Regarding seedling growth, the fungal culture filtrate of strain 1-8-1 also significantly increased root length and shoot height of Chinese kale and tomato seedlings. This is the first comprehensive study documenting endophytic fungi from Inca nut plants in China and Thailand. Furthermore, this study provides valuable insights into beneficial endophytic fungi associated with the Inca nut plant and highlights their potential applications in plant growth promotion.

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This work is licensed under CC-BY 4.0

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DOI:

https://doi.org/10.3389/fmicb.2026.1794613

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