اثر نانوامولسیون اسانس‌ تعدادی گیاه دارویی در پیشگیری از بیماری سفیدک پودری خیار در گلخانه و تغییر در ترکیبات فنولی گیاه

Cucumber (Cucumis sativus) is an annual plant belonging to the Cucurbitaceae family. Among the various diseases affecting this crop, powdery mildew caused by the fungus Podosphaera fusca is one of the most important limiting diseases in greenhouse cucumber production. The daily harvest of cucumbers and their consumption as fresh food highlights the risk of residual chemical toxins in this crop. Therefore, it is necessary to find effective natural alternative compounds with low risk, such as plant essential oils. Considering that essential oils are volatile and unstable, their formulation in the form of nanoemulsions can increase their stability, protect them against environmental conditions, and increase their antimicrobial properties through cellular absorption. In this research, stable nanoemulsions of essential oils of Satureja khuzistanica (Khuzestani savory), Syzygium aromaticum (clove) and Cymbopogon citratus (lemon grass) after optimizing the type and concentration of surfactants, were prepared using a homogenizer. Their efficiency in inhibiting cucumber powdery mildew disease and changes in plant phenolic compounds were studied. Nanoemulsions were sprayed in three concentrations of 1, 2 and 3 per 1000, on Nagin cucumber variety in the greenhouse, 48 hours before inoculation with Podosphaera fusca as well as fungicides Topas and Kresoxim methyl with the recommended dose of 0.5 and 0.4 per 1000, respectively. The results showed that the nanoemulsions of Khuzestani savory, lemon grass, and cloves are effective in disease prevention by 59.5, 45.33, and 34%, respectively, whereas Topas and Kroxexim methyl showed 34%, and 25.5% efficiency. The results of total phenol and flavonoid content assay showed that there is a significant difference between the treatments. Also, the investigation of phenolic compounds by HPLC-DAD method showed that there is a significant difference after 24 and 48 hours spraying with nanoemulsions and fungicides in cucumber leaf metabolites in terms of the content of 3 and 4-dihydroxybenzoic compounds. acid, caffeic acid, ferulic acid, gallic acid, rutin and rosmarinic acid contents in comparison to the control. Encapsulating essential oil particles in the nano scale, may improve physical stability, and reduces the limitations related to the mass transfer of active essential oil molecules to the treated areas, while protecting them from adverse environment conditions and reducing the required effective dose. In the end, it seems that the nanoemulsions of essential oils and especially the essential oil of Khuzestani savory have a high potential in inhibiting the powdery mildew of cucumber and inducing phenolic compounds in the plant.