The Antifungal Activity and Mechanism of Dehydroabietic Acid Against Causing Poplar Leaf Spot.

Dehydroabietic acid (DHA) is a secondary metabolite isolated from rosin, which has certain antifungal activity, but its inhibitory effects against are unclear. In the present study, we found that DHA inhibited the mycelial growth of , , , , and in a concentration-dependent manner, with the best inhibitory effect against . Moreover, DHA can also inhibit the spore germination of . Then, in vivo inoculation experiments showed that the leaf lesions of gradually decreased with the increase in DHA concentration. The disease of leaves inoculated with was not obvious after treatment with 800 mg/L DHA. The scanning electron microscopy showed that the mycelial morphology was abnormal, with crinkles and depressions. Meanwhile, the relative conductivity, soluble protein content, malondialdehyde content and hydrogen peroxide content of were significantly increased after DHA treatment, which affected the integrity of the cell membrane and increased the permeability of , resulting in a large leakage of intracellular substances, exacerbating the degree of lipid peroxidation of the cell membrane of and causing oxidative damage to cells. The enzyme activity assay showed that treatment with 56.015 mg/L (EC) DHA significantly reduced the activities of antioxidant enzymes (superoxide dismutase, catalase, peroxidase) and cell-wall-degrading enzymes (endoglucanase, polygalacturonase, pectin lyase) in ( < 0.05), resulting in a decrease in the activity of pathogenic fungi, as well as a reduction in the ability of the to degrade the cell wall of the host plant, which led to a decrease in the ability of the to infest the host plant. Moreover, the decrease in the relative expression of defense-related enzyme genes () and pathogenicity-related enzyme genes () was consistent with the enzyme activity results. Thus, the present study revealed the fungicidal activity and mechanism of DHA against and the potential of DHA to be developed as a plant-derived antifungal agent was established.