Salvia japonica essential oil as biocontrol agent: suppressing Fusarium oxysporum in Pinus sylversteis Var. Mongolica seedling blight

Salvia japonica essential oil (SJEO) is a natural active substance that has been widely used in medicine and food preservation. However, the antifungal mechanism of SJEO against plant pathogens is not well understood. This study examined the antifungal activity of SJEO against Fusarium oxysporum (F. oxysporum). The results demonstrated that SJEO significantly inhibits the mycelial growth and conidial germination of F. oxysporum in a dose-dependent manner. Scanning electron microscopy (SEM) confirmed that SJEO induces mycelial shrinkage, deformation, and rupture. Moreover, SJEO treatment substantially reduced the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), with decreases of 82.49%, 82.82%, and 58.38%, respectively, in the EC₅₀-treated group compared to the control group at 60 h. In contrast, the levels of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) were significantly elevated. SJEO also increased the permeability of the cell membranes of F. oxysporum, which led to the reduction of the cell contents. Additionally, SJEO at the EC₅₀ concentration significantly decreased the activities of endo-1,4-β-glucanase (EG), polygalacturonase (PG), and pectin lyase (PL) by 18.66%, 40.62%, and 80.19%, respectively, compared to the control group at 60 h. Blight in Pinus sylvestris var. mongolica was significantly reduced following SJEO treatment (p < 0.05). In summary, SJEO disrupts cellular redox balance and intensifies lipid peroxidation in cell membranes, leading to increased membrane permeability and ultimately cell death, and reduces the pathogenicity of F. oxysporum. These findings indicate that SJEO holds promise as a novel fungicide for controlling blight in Pinus sylvestris var. mongolica.