Quercetin inhibits Alternaria alternata in postharvest jujube via disrupting membrane integrity, energy metabolism and stress adaptation

Alternaria alternata is a necrotrophic fungal pathogen that causes postharvest decay in jujube and other fruits. In this study, we investigated the inhibitory effects of quercetin against A. alternata and its impact on the pathogenicity of the fungus by transcriptomic, metabolomic, and molecular docking analyses. In vitro assays demonstrated that quercetin inhibited mycelial growth and sporulation, with a maximum inhibition rate of 46.51% at 200 mg/L. Malondialdehyde content increased by 9.5-fold, indicating lipid peroxidation. Ultrastructural observations revealed pronounced mycelial shrinkage, hyphal breakage, and cytoplasmic vacuolation. In vivo experiments showed that quercetin treatment reduced disease incidence by 48.84% and lesion area by 55.25% in inoculated jujube fruits, while preserving fruit firmness and color. Integrated omics analyses revealed that quercetin downregulated genes involved in trehalose biosynthesis ( Tps1 / Tps2 ), choline/phospholipid metabolism ( CKI1 / PCYT1 ), central carbon metabolism ( HK / AMY ), and the HOG-MAPK signaling pathway ( Ssk2 / 22 / Sko1 / Ctt1 ). Molecular docking further predicted the binding of quercetin to the major allergen Alt a 1. Collectively, these findings suggest that quercetin inhibits A. alternata primarily by disrupting membrane integrity and energy metabolism, providing a basis for its use as a postharvest preservative.