褪黑素处理对采后李果实Priming抗病性的诱导作用

研究了褪黑素（melatonin，MT）处理诱导采后李果实抗病反应的特征和效力。“凤凰”李果实经10 mmol/L褪黑素（melatonin，MT）处理及病原菌匍枝根霉（Rhizopus stolonifer）接种后，于20 ℃下贮藏5 d，期间观察果实病害发展情况，并测定果实H₂O₂、总酚、木质素含量以及抗性相关酶活性。结果显示，10 mmol/L MT处理能有效降低李果实采后R. stolonifer导致的根霉病发病率并延缓增加其病斑直径。单一MT处理能诱导李果实中苯丙烷类代谢酶活性及总酚和木质素含量的上升；但MT处理复合R. stolonifer接种则最显著的诱导果实H₂O₂迸发，同时提升几丁质酶、β-1,3-葡聚糖酶、苯丙氨酸解氨酶、肉桂酸-4-羟基化酶、4-香豆酸辅酶A连接酶、过氧化物酶和多酚氧化酶等抗病相关酶活性以及总酚和木质素含量。通过这些结果可推测，MT处理可诱导李果实priming反应，使果实在遭受病原菌侵染时展现更强烈的抗病反应，从而维持果实贮藏期间的商品性。

Induction of Melatonin Treatment on the Priming Resistance in Postharvest Plum Fruit

This study aimed to research the effectiveness and mode of the disease resistance induced by melatonin (MT) treatment in postharvest plum fruit. Plum fruit Cv ‘Fenghuang’ were treated with 10 mmol/L MT and/or inoculated with R. stolonifer, then stored for 5 days (20 ℃). Disease development, the contents of H₂O₂, total phenol and lignin and the activities of resistance-related enzyme were determined during the storage. The results showed that 10 mmol/L treatment effectively lowered the disease incidence and delayed the increase of lesion diameter of Rhizopus rot caused by R. stolonifer in plums. Single MT treatment could induce the activities of phenylpropanoid metabolic enzymes and the contents of total phenol and lignin in plums. MT treatment combined with R. tolonifer inoculation showed most significantly effects on the induction of H₂O₂ burst, and the activities of disease-resistance related enzymes such as chitinase, β-1,3-glucanase, phenylalanine ammonialyase (PAL), cinnamate-4-hydroxylase (C4H), 4-coumaric acid coenzyme A ligase (4-CL), peroxidase (POD) and polyphenol oxidase (PPO) as well as contents of total phenol and lignin in the samples during the storage. These results suggested that the MT treatment could activate the strong and rapid disease resistance upon the pathogenic infection by an induction of priming defence, by which the treatment resultantly maintained the overall quality in plums during the postharvest storage.