N epeta meyeri essential oil ameliorates fungal infection and the antioxidant response in grapevines (Vitis vinifera) infections by gray mold (Botrytis cinerea)

The essential oil (EO) obtained from Nepeta meyeri Benth. used to struggle allelopathically with gray mold (Botrytis cinerea Pers.), which causes significant damage to vineyards (Vitis vinifera L. cv. Karaerik). The EO from N. meyeri was determined to contain 4aα, 7α, 7aα-nepetalactone (71.68%) at the highest rate when analyzed with GC/MS. Then, the doses (0.6, 0.8, and 1.0 µL/leaf) of 1 ppm EO solution were applied to the leaves together with the fungus inoculation (EO + F), as well as 1 day (EO + F1D) and 2 days (EO + F2D) before inoculation. The fungus application alone was evaluated as a control. Seven days after the inoculations, fungus development, lipid peroxidation level (as malondialdehyde), the contents of reactive oxygen species (ROS), photosynthetic pigments and soluble proteins, and the activities of antioxidant enzymes (superoxide dismutase, catalase, peroxidase, and glutathione reductase) were determined in the leaves. Findings revealed that EO + F1D among the applications and 1.0 µL/leaf among the EO doses significantly prevented fungus development on the leaf, compared to the control. Moreover, the same applications decreased ROS levels, such as H2O2 and O2·− and lipid peroxidation, while they increased antioxidant enzyme activities, as well as chlorophyll and soluble protein contents. Therefore, it can be suggested that the EO from N. meyeri has a potentially powerful usage as biofungicide in the allelopathic struggle against the infection of B. cinerea in vineyards.