Abstract: Endophytic fungi of medicinal plants are important antagonistic microbial resources. However, few studies have focused on the endophytic fungi of Artemisia argyi var. argyi cv. Qiai, which is a national geographical indication product in China and a genuine medicinal material in Hubei Province. In this study, the tissue grinding method was employed to isolate endophytic fungi from the roots, stems, and leaves of Qiai. The antibacterial activity of ethyl acetate extracts from the fermentation broth of these endophytic fungi was screened against five multidrug-resistant bacteria and five common human pathogenic bacteria using the filter paper disk method. Additionally, molecular biological classification and identification of the re-screened strains were conducted by amplifying the ITS sequences. A total of 71 endophytic fungi were isolated from Qiai. Among them, 13 strains exhibited inhibitory effects on two or more indicator bacteria. Notably, 9 out of the 13 effective strains originated from the leaves. Specifically, the strains Aspergillus niger YX-Y-12 and Aspergillus udagawae HQY-Y-15 displayed strong antibacterial activity against carbapenem-resistant Acinetobacter baumannii (CRAB) and methicillin-resistant Staphylococcus aureus (MRSA), respectively. Among them, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the extract of the fermentation broth of strain YX-Y-12 against CRAB-1 were both 0.832 mg·mL^-1, while the MIC and MBC of strain HQY-Y-15 against MRSA were 0.052 and 0.208 mg·mL^-1, respectively. These 13 strains belonged to 1 phylum, 3 classes, 4 orders, 6 families and 6 genera: Aspergillus, Penicillium, Cladosporium, Fusarium, Acremonium, and Cercospora. Five out of the 13 strains belonged to the genus Aspergillus, accounting for 38.5%. Penicillium thomii and Cercospora beticola were isolated from plants for the first time. The ethyl acetate extracts of the fermentation broth of P. thomii, Aspergillus sclerotigenum, and Cladosporium tenuissimum had antibacterial activities against human pathogenic bacteria. Furthermore, A. niger had antibacterial activity against CRAB. Penicillium herquei had antibacterial activity against MRSA and Staphylococcus aureus. A. udagawae had antibacterial activity against Listeria monocytogenes/MRSA/S. aureus. C. beticola had antibacterial activity against Proteus vulgaris and Escherichia coli. Cladosporium cladosporioides had antibacterial activity against P. vulgaris. Moreover, the endophytic fungus A. udagawae HQY-Y-12 of Artemisia argyi var. argyi cv. Qiai may be a new species. Our results laid a foundation for further exploring the action mechanism of the functional endophytic fungi of Artemisia argyi var. argyi cv. Qiai and provided strain resources for the development of new antibacterial substances.

Key words: Artemisia argyi var. argyicv. Qiai, endophytic fungi, isolation and identification, screening, antibacterial activity