Objective To understand the root endophytic fungal composition and diversity of alpine oaks in the Hengduan Mountains.

MethodsThe root samples of three alpine oak species were collected. The fungal symbiosis within the root system was observed using the root immersion staining method, and the endophytic fungus were isolated and purified. These fungi species were identified by combining morphological and molecular biological methods.

ResultsNumerous DSE fungi and AMF clumped structures were found in these oak roots samples. A total of 27 fungal species in 20 genera of 17 families were identified. one family of ectomycorrhizal fungus uncultured Ceratobasidiaceae (GSL1-7), four species of dark septate endophytes (DSE) Boeremia exigua var.exigua. Phialophora mustea (GSL2-2, GSL2-9), Paraboeremia putaminum (GSL4-F, GSL20-B), and two clearly reported plant growth-promoting fungi Pseudogymnoascus roseus (GSL4-1-A, GSL4-2) and Trichoderma tomentosum (GSL80-D) were also found. The consequence of α-diversity measurement indicated that diversity of culturable fungi in the root systems of three species of alpine oak was rich but not significantly different. Four species of DSE and three species of plant-promoting fungi accounted for 31.3% in the root system.

Conclusion These fungi play an important role in the adaptive growth of alpine oak under the harsh environmental conditions in the Hengduan Mountains. The results of this paper provide a preliminary theoretical basis for elucidating the ecological adaptive mechanism of alpine oak in the Hengduan Mountains region, and provide a living strain resource for developing the use of probiotic fungi in alpine oak seedlings.