Enhanced resistance of jujube (Zizyphus jujuba Mill. cv. Dongzao) fruit against postharvest Alternaria rot by β-aminobutyric acid dipping

Considerable losses of jujube (Zizyphus jujuba Mill. cv. Dongzao) fruit caused by Alternaria rot often occurred during storage. In order to evaluate effects of β-aminobutyric acid (BABA) on the infection on jujubes by Alternaria alternata, the fruit were dipped in BABA solutions and then inoculated with the pathogen. Results showed that BABA dipping at concentrations of 0.5, 1.0 and 2.0 g L−1 significantly (P < 0.05) reduced disease incidence and lesion area on the fruit inoculated with A. alternata, whereas BABA did not affect conidial germination and mycelial growth of the pathogen in vitro. In addition, BABA reduced natural infection and postharvest softening of jujubes during the storage at 0 °C and 85–95% relative humidity. Biochemical evaluations revealed that BABA enhanced activities of defence-related enzymes including peroxidase, phenylalanine ammonia-lyase and chitinase of the fruit. BABA altered antioxidant metabolism to trigger disease resistance by significantly (P < 0.05) decreasing catalase activity but increasing superoxide dismutase activity and ascorbic acid content in jujubes. These results suggested that the protective effects of BABA dipping on jujubes might be due to its ability on activating several highly coordinated defence-related responses of the fruit against infection, instead of its direct antifungal activity on the pathogen. These findings suggested that application of BABA would offer a promising approach for controlling postharvest disease and improving storage quality of horticultural products.