Abstract:

Infection to roots of Astragalus membranaceus var. mongholicus (Bunge) P. K. Hsiao by pathogenic fungi can lead to the occurrence of root rot and subsequently would severely impact its herbal medicinal value and industrial development. In this study, diseased tissue samples from A. membranaceus var. mongholicus were collected by employing the traditional agar plate culture method for the preliminary isolation of pathogenic microorganisms. After multiple rounds of purification, single colony of pathogens were obtained. The pathogenic fungi species were identified through a combination of morphological characteristics and ITS gene sequencing. Antifungal experiments against the isolated strains with thyme essential oil were conducted using the agar diffusion method. The results revealed that the primary pathogenic fungi identified were Fusarium solani, F. oxysporum, and Penicillium chrysogenum. As the concentration of thyme essential oil increased, its antifungal effect was enhanced accordingly. When its concentration reached to 1.5 μL/mL, the highest antifungal rate (88.3%) was observed against P. chrysogenum, which was higher than those against F. solani (85.4%) and F. oxysporum (80.2%). Additionally, the antifungal rate exhibited a positive correlation with time.

Key words: Astragalus membranaceus var. mongholicus, root rot disease, isolation and purification, antifungal activity