褪黑素处理对梨果实采后黑斑病及贮藏品质的影响

[目的]探究褪黑素(Melatonine,MT)处理对梨果实采后黑斑病及贮藏品质的影响,为外源物质调控果实抗采后病害及贮藏品质提供理论依据和参考.[方法]以'翠冠'梨果实为试验材料,喷施0.1 mmol·L-1 MT溶液置室温,48 h后沿梨果实赤道两侧刺直径1 mm、深度3 mm大小两个小孔,待伤口晾干后注入20μL...

Effects of Melatonin Treatment on Resistance to Black Spot and Postharvest Storage Quality of Pear Fruit

【Objective】 The aim of this study was to explore the effects of melatonine (MT) treatment on postharvest black spot disease and storage quality of pear fruit, so as to provide the theoretical basis and reference for exogenous substances regulating postharvest disease and storage quality of pear fruit. 【Method】 ‘Cuiguan’ pears were used as the experimental material, which were sprayed with 0.1 mmol·L^-1 MT solution and then kept at room temperature for 48 h. The treated fruits were inoculated with two 1 mm diameter × 3 mm depth small holes along both sides of the fruit equator. Twenty µL Alternaria alternata spore suspension with 1.0×10⁶ spores/mL were injected into the two holes, and the sterile water treatment was used as control. The fruit was placed at 25℃ after inoculation, and then the lesion diameters and induced effects as well as the genes expression of defense enzymes, such as catalase (PpCAT), peroxidase (PpPOD), polyphenol oxidase (PpPPO), and copper-zinc superoxide dismutase (Cu-ZnSOD), and pathogenesis-related protein including chitinase (PpCHI) and β-1,3 glucanase (PpGLU), were analysed to demonstrate the effect and mechanism of MT-induced pear fruit against black spot disease. In addition, the pear fruits were sprayed with 0.1 mmol·L^-1 MT solution, and then stored at (5±1)℃, 85%-90% relative humidity for 42 d. The sterile water treatment was used as the control. The decay rate, weight loss rate, respiration rate, firmness, total soluble solids, titratable acid, vitamin C, total phenols and malondialdehyde contents were measured at fixed period, and the effect of MT treatment on the storage effect and quality of pear fruit were discussed. 【Result】 The lesion diameters of pear fruits inoculated with A. alternata gradually increased with the time, while the lesion diameters under MT treatment was significantly smaller than those under the control (P<0.05). The MT-induced resistance effects on pear fruits black spot were 29.16%, 45.03% and 23.26% on the 3rd, 5th and 7th day, respectively. The relative expression levels of PpCAT, PpPOD, PpPPO, Cu-ZnSOD, PpCHI and PpGLU in MT-treated group were significantly higher than those of the control group during 4-7 days post inoculation (dpi), and the maximum values of them were 1.35, 2.08, 2.28, 2.02, 2.89 and 3.45 times of control fruits, respectively. The induced expression of PpPOD, PpPPO and PpCHI indicated that MT treatment inducing resistance of pear fruit to black spot disease possible depended on these defense enzyme and pathogenesis-related proteins. For the low temperature storage, the fruit decay rate was not significantly different between MT treatment group and control group, which was probably caused by the inhibition growth of pathogen under low temperature. All of fruit firmness gradually decreased during storage, while the fruit firmness under MT treatment was higher than that under the control with 1.06 times of significant difference at 28 d. Furthermore, the fruit respiration rate increased in the early storage stage (7-14 d) and decreased in the later stage. In comparison with the control group, the effects of MT treatment inhibiting fruit respiration and delaying fruit senescence were more significantly in the early storage stage than in the later stage. In addition, MT treatment also significantly reduced the fruit weight loss rate, maintained the high levels of total soluble solids, and delayed the degradation of titratable acid and vitamin C. Also, it promoted the accumulation of total phenolic content, enhanced the fruit antioxidant capacity, inhibited the accumulation of MDA content, and reduced the damage of cell membrane lipid peroxidation. The above results indicated that MT might enhance fruit quality and storage resistance by regulating fruit sugar, acid, and cell wall metabolism. 【Conclusion】0.1 mmol·L^-1 MT treatment induced the resistance of pear fruit to black spot, stimulated the relative expression of defense enzymes and pathogenesis-related protein coded-genes, and finally improved the storage quality of pear fruit.