Antifungal mechanisms and disease control potential of tartaric acid on grape white rot and gray mold

Grape white rot and gray mold are major fungal diseases occurring during harvesting and postharvest storage, which cause severe economic losses to the grape industry. This study explored the differences in organic acid accumulation between susceptible and resistant grape cultivars upon Coniella vitis infection and evaluated the antifungal mechanism of tartaric acid against C. vitis and Botrytis cinerea . The susceptible cultivar ‘Manicure Finger’ presented lower tissue pH and distinct accumulation patterns of organic acid in leaves and berries compared with the resistant ‘Shine Muscat’. In vitro assays showed that tartaric acid significantly inhibited C. vitis conidial germination, and its inhibitory effect was not entirely dependent on ambient pH. Exogenous tartaric acid application effectively reduced disease severity of grape white rot and gray mold in leaves and berries in the field and after storage. Physiological and microscopic detection confirmed tartaric acid damaged fungal cell membrane integrity and increased malondialdehyde (MDA) content of C. vitis and B. cinerea . Tartaric acid reprograms metabolic routes and impairs amino acid and carbohydrate metabolism in C. vitis , as evidenced by transcriptomic and targeted metabolomic analyses, and also downregulates the gene expression and enzymatic activity of plant cell wall-degrading enzymes. This work demonstrates that tartaric acid has antifungal potential against multiple grape pathogens and can serve as a promising natural agent for sustainable control of grape fungal diseases.