Diversity and antimicrobial activity of endophytic fungi from the roots of Paeonia lactiflora in different growth years

Objective To study the differences in endophytic fungal composition and antibacterial activity of Paeonia lactiflora (P. lactiflora) roots in different growth years, so as to lay a foundation for the development and utilization of P. lactiflora's fungal resources. Methods Based on a combination of morphological features and molecular evidence, endophytic fungi from the roots of P. lactiflora in different growth years were isolated and identified. Antimicrobial activity was screened using the plate confrontation method and the hyphal growth inhibition rate method. Results A total of 242 endophytic fungal isolates belonging to 35 genera and 51 species were obtained and identified from the roots of P. lactiflora. Among them, Fusarium and Bjerkandera were the dominant bacterial genera, accounting for 25.61% and 10.33% of the total number of isolates, respectively. In plate standoff experiments, Trichoderma harzianum showed significant inhibition of all six plant pathogens, with inhibition rate of Colletotrichum loeosporium, Phytophthora parasitica, Rhizotonia cerealis, Cercospora nicotianae, Sclerotinia sclerotiorum and Fusarium graminearum 77.13%, 70.77%, 75.30%, 78.26%, 81.07% and 86.50%, respectively. Chaetomium globosum inhibited Rhizotonia cerealis by 64.98% in the solid secondary metabolite inhibition assay at the concentration of 100 mg/mL. Alternaria sesame inhibited Fusarium graminearum by 63.29% in the liquid secondary metabolite inhibition assay at the concentration of 100 mg/mL. Conclusion The endophytic fungal community structure of P. lactiflora roots is abundant, and the endophytic fungi of plants in different growth years have certain differences. The antimicrobial activities of endophytic fungi and their secondary metabolites from the roots of P. lactiflora provide a reference for the development of eco-friendly antimicrobial agents.