Soil properties and environmental factors across different altitudes influence biodiversity of root endophytic fungi in the orchid Bletilla sinensis

Context Bletilla sinensis is a perennial orchid herb widely used in Chinese herbal medicine. The endophytic fungi associated with its roots significantly affect plant growth and secondary metabolite accumulation, whereas environmental factors crucially determine the community and diversity of these fungi. Aims This study investigated the impact of habitat environment on the symbiotic relationship between B. sinensis and its endophytic fungi by analysing the community composition and diversity of endophytic fungi in B. sinensis roots at various altitudes. Methods B. sinensis roots were sampled from three altitudes (HXJ1, HXJ2, HXJ3) in Jinjiang Town, Shangri-La County, Yunnan Province, China. Endophytic fungi were isolated and analysed using high-throughput sequencing technology. Key results The endophytic fungi were dominated by Ascomycota (85.4%) and Basidiomycota (14.6%). α-Diversity analysis showed that HXJ2 had the highest species richness (Chao1 = 34), while HXJ1 exhibited the highest diversity (Shannon = 2.25, Simpson = 0.84). β-Diversity analysis revealed moderate community similarities between sampling sites (Bray–Curtis indices: 0.433–0.597). Notably, fungal abundance showed strong positive correlations with soil total phosphorus (r = 1.000, P < 0.01) and total carbon (r = 0.998, P < 0.05) in HXJ1. Conclusions The study revealed a clear altitudinal pattern, where higher altitudes exhibited lower fungal diversity. However, the mid-altitude site (HXJ2) showed higher fungal diversity compared with both higher (HXJ3) and lower altitudes (HXJ1), suggesting that local environmental factors, such as soil nutrients and surrounding vegetation, may interact with temperature to influence fungal diversity. Implications This study sheds light on the symbiotic relationship between B. sinensis and its endophytic fungi, with implications for the cultivation and medicinal properties of this herb.