Botanical Extracts and Metabolomic Profiling of <i>Zingiber officinale</i> for Ecofriendly Management of Cucumber Powdery Mildew Caused by <i>Podosphaera xanthii</i>

ABSTRACT Powdery mildew, caused by Podosphaera xanthii , represents a significant constraint on cucumber production, highlighting the need for sustainable alternatives to synthetic fungicides. This study assessed the antifungal potential of botanical extracts from Citrus maxima , Allium sativum , Zingiber officinale and Syzygium aromaticum under in vitro and greenhouse conditions. The identity of P. xanthii was confirmed via morphological examination and sequencing of the rDNA internal transcribed spacer (ITS) 5.8S and 28S regions. Extracts at concentrations of 25–75 g/mL were evaluated for their effects on conidial germination, disease incidence and severity, plant growth, chlorophyll content and activities of defence‐related enzymes (peroxidase, catalase, polyphenol oxidase and superoxide dismutase). Microscopic analyses were conducted to examine structural changes in fungal hyphae and conidia. Bioactive constituents in Z. officinale were characterised using ultrahigh‐performance liquid chromatography coupled with tandem mass spectrometry (UHPLC–MS/MS) and compounds were annotated using HMDB and KEGG databases. The Z. officinale extract showed the greatest antifungal effect, significantly reducing conidial germination, disease incidence (0.46) and severity (0.8) ( p ≤ 0.05). Treated plants exhibited enhanced growth, with increased leaf length (13.55 cm), stem girth (5.89 cm) and chlorophyll content (1.54 mg/g FW in acetone and 5.20 mg/g FW in dimethylformamide). Microscopy revealed marked structural abnormalities in P. xanthii . Metabolite profiling identified 6‐gingerol, oxysophocarpine, tetrahydrocurcumin, N ‐feruloylserotonin and 423 additional metabolites associated with key metabolic pathways. These findings suggest that Z. officinale extract may serve as an effective biocontrol agent against P. xanthii , offering a potential component for integration into sustainable disease management strategies.