褪黑素对冷藏后芒果果实冷害和后熟的影响及生理机制

Effect of Melatonin on Chilling Injury and Ripening of Postharvest Mango Fruits during Shelf Life after Refrigeration and Underlying Physiological Mechanism

以采后‘贵妃’芒果为试材,在0.5 mmol/L褪黑素(melatonin,MT)溶液中浸泡1 h,晾干后置于4℃贮藏28 d,随后转移至室温(25℃)贮藏4 d,探究MT对冷藏后芒果果实冷害(chilling injury,CI)和成熟的影响及相关机理。结果显示,MT处理有效降低了芒果果实的CI指数,提高了可溶性固形物含量、呼吸速率和乙烯释放量并加速了色相值和硬度下降;MT处理促进了水溶性果胶和螯合性果胶含量升高,提高了多聚半乳糖醛酸酶、β-半乳糖苷酶和纤维素酶活性,加速了果胶甲酯酶活性下降,从而导致细胞壁降解和果实软化。此外,MT处理提高了果实1-氨基环丙烷-1-羧酸合成酶和1-氨基环丙烷-1-羧酸氧化酶活性及其编码基因MiACS和MiACO的表达水平,同时上调了MiETR1、MiERS1、MiERF1、MiEIN2、MiCBF1和MiICE1并下调MiCTR1基因的表达。上述结果表明MT能有效改善冷藏后芒果果实后熟恢复能力并减轻其CI。

We investigated the effect and underlying mechanism of postharvest treatment with 0.5 mmol/L melatonin(MT)treatment 1 h on chilling injury(CI)and ripening of‘Guifei’mango fruits during 4 days of shelf life at 25℃after refrigeration at 4℃for 28 days.The results showed that MT treatment markedly decreased CI and enhanced soluble solids content(SSC),respiration rate and ethylene production,while accelerating the decline in hue value and firmness of chilled mango fruits.Compared with the control group,MT treatment promoted the increase in the contents of water-soluble pectin(WSP)and chelate-soluble pectin(CSP)and the activities of polygalacturonase,β-galactosidase and endo-1,4-β-Dglucanase and accelerated the decrease in pectin methylesterase activity,thereby leading to cell wall degradation and fruit softening.Compared with the control group,higher activities of 1-aminocyclopropane-1-carboxylic acid synthase(ACS)and 1-aminocyclopropane-1-carboxylic acid oxidase(ACO)and the expressions of their encoding genes(MiACS and MiACO)were observed in MT-treated fruits.Moreover,MT up-regulated the expression of MiETR1,MiERS1,MiERF1,MiEIN2,MiCBF1 and MiICE1 while down-regulating the expression of MiCTR1.These results indicated that MT treatment could promote the restoration of ripening and reduce CI in mango fruits during shelf life after storage at low temperature.