水杨酸诱导采后龙眼果实对Phomopsis longanae Chi的抗病性生理机制研究

Phomopsis longanae Chi was found to be the main pathogenic fungus inducing fruit decay of harvested longan fruit. Our previous studies suggested that salicylic acid treatment could effectively inhibit the occurrence of longan fruit postharvest decay . However, the mechanism of this inhibition is still unclear. In this research, the effects of salicylic acid at different concentrations on the cell wall and cell membrane compositions, cell constituents and cell membrane permeability of P. longanae in vitro will be determined., and the morphological and cellular ultrastructural changes of P. longanae treated by salicylic acid will be determined by scanning electron microscopy and transmission electron microscopy, respectively. The objective of this study is to clarify the antifungal mechanism of salicylic acid against P. longanae in vitro. At the same time, the mechanism of disease resistance in harvested longan fruit induced by salicylic acid in vivo will also be explained from the aspects of antioxidant reaction, defense response, characteristics of energy formation in tissue, membrane system integrity, membrane lipid compositions and the activities of their degrading enzyme s. The results are expected to put forward a new theoretical basis for elucidating the possible mechanism of SA inhibiting longan fruit decay, and further to provide a scientific basis and practical guidance to control the postharvest disease and prolong the storage period of harvested longan fruit.

龙眼拟茎点霉（Phomopsis longanae Chi）是引起采后龙眼果腐病最主要的病原菌。我们前期的研究发现，水杨酸(SA)处理可有效抑制龙眼果实采后果腐病的发生。但是，有关SA抑制龙眼果实采后果腐病的作用机制尚不明了。本项目拟从离体培养（活体外）条件下研究不同浓度SA对龙眼拟茎点霉细胞壁和细胞膜组成、细胞内含物、细胞膜通透性的影响，以及通过扫描电镜和透射电镜观察SA对龙眼拟茎点霉菌丝形态和细胞超微结构的影响，阐明活体外SA对龙眼拟茎点霉的抑菌机制；同时从龙眼果实（活体内）抗氧化反应、抗病防御反应、组织能量形成特性、膜系统完整性、膜脂组分和膜脂降解相关酶活性变化等方面，阐明活体内SA诱导采后龙眼果实对拟茎点霉的抗病机制。研究成果可望在阐明SA抑制龙眼果实采后果腐病的作用机制方面获得新的理论依据，进而为控制龙眼果实采后病害、延长果实保鲜期提供科学依据和实践指导。

龙眼拟茎点霉（Phomopsis longanae Chi, P. longanae）是引起采后龙眼果腐病最主要的病原菌。水杨酸（Salicylic acid, SA）处理可有效抑制龙眼果实采后果腐病的发生。但有关SA抑制龙眼果实采后果腐病的作用机制尚不明了。本论文以福建省主栽品种‘福眼’龙眼果实为材料，从抗氧化反应、抗病防御反应、组织能量形成特性、膜系统完整性、膜脂组分和膜脂降解相关酶活性变化等方面，研究SA诱导采后龙眼果实对P. longanae的抗病性生理机制。主要研究结果如下：.1. 与P. longanae接种龙眼果实相比，SA能降低P. longanae接种龙眼果实的果皮超氧阴离子自由基（O2-.）产生速率，延缓果皮丙二醛（MDA）含量的上升，保持较高的果皮超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、抗坏血酸过氧化物酶（APX）等活性氧清除酶活性，及较高的果皮还原型抗坏血酸（AsA）、还原型谷胱甘肽（GSH）等内源抗氧化物质含量，延缓果皮DPPH自由基清除能力和还原力的下降。.2. 与P. longanae接种龙眼果实相比，SA能降低P. longanae接种龙眼果实的果皮磷脂酶D（PLD）、脂酶和脂氧合酶（LOX）活性，维持较高的果皮磷酸酰胆碱（PC）和磷脂酰肌醇（PI）含量，延缓果皮油酸（C18:1）、亚油酸（C18:2）、亚麻酸（C18:3）等膜脂不饱和脂肪酸相对含量的下降，抑制果皮棕榈酸（C16:0）、硬脂酸（C18:0）和木蜡酸（C24:0）等膜脂饱和脂肪酸相对含量和磷脂酸（PA）含量的上升；维持较高的果皮膜脂脂肪酸不饱和度（U/S）和不饱和指数（IUFA）。.3. 与P. longanae接种龙眼果实相比，SA能延缓P. longanae接种龙眼果实的果皮三磷酸腺苷（ATP）、二磷酸腺苷（ADP）含量和能荷值的下降，同时降低果皮一磷酸腺苷（AMP）的含量，保持较高的果皮质膜、液泡膜、线粒体膜的Ca2+-ATPase、Mg2+-ATPase和H+-ATPase活性。.4. 与P. longanae接种龙眼果实比较，SA处理促进贮藏中后期龙眼果实的果皮H2O2积累和木质素生成，保持较高的果皮几丁质酶（CHI）、β-1,3-葡聚糖酶（GLU）、过氧化物酶（POD）、多酚氧化酶（PPO）、苯丙氨酸解氨酶（PAL）等抗病物质代谢相关酶活性。