The beneficial use of essential oils from buds and fruit of Syzygium aromaticum to combat pathogenic fungi of Panax notoginseng

To develop natural fungicides against Panax notoginseng disease, the antifungal effects of Syzygium aromaticum essential oils (EOs) against the pathogenic fungi causing P. notoginseng disease were investigated. The effects of EOs from S. aromaticum buds and fruits on the growth of pathogenic mycelia were determined with in vitro antifungal experiments using the Oxford cup method. The results suggested that S. aromaticum EOs had a strong inhibitory effect on the growth of pathogenic fungi. At a dose of 50 mg/mL, the inhibitory effects of S. aromaticum buds EOs was greater than those of S. aromaticum fruits. Then the chemical constituents of the S. aromaticum EOs were analyzed by GC-MS. The results indicated that the eugenol content was the highest, accounting for 57.95% of the total constituents in the S. aromaticum buds EOs and 39.26% in the S. aromaticum fruits EOs. The minimum inhibitory concentration (MIC) of EOs, the major constituents, and hymexazol were evaluated. In addition, the antifungal effect of their combination was also determined by the fractional inhibitory concentration (FIC). When the buds EOs were combined with hymexazol, they had a synergistic effect in inhibiting Pythium aphanidermatum, Botrytis cinerea, and Colletotrichum gloeosporioides. The combination of S. aromaticum fruit EOs with hymexazol showed an additive effect on Fusarium solani, P. aphanidermatum, and B. cinerea. The preventive effect of S. aromaticum bud EOs combined with hymexazol was up to 60.77% in in vivo experiments. Overall, S. aromaticum EOs had a broad spectrum of antifungal activities against pathogenic fungi influencing the growth of P. notoginseng, which would provide a scientific basis for the ecological control of P. notoginseng disease.