【作者】 张新春；

【导师】 康振生；

【作者基本信息】 西北农林科技大学 ， 植物病理学， 2003， 硕士

【摘要】 油菜菌核病[(Sclerotinia sclerotiorum) (lib)de bery]是一种世界性病害，在五大州近100多个国家都有发现和流行。我国的长江流域和西南地区危害尤为严重，给油菜产量造成极大损失。为深刻理解油菜菌核病菌侵染过程中与寄主的互作实质，为生产上防治此病提供理论依据，本文采用光镜和电镜技术观察了油菜菌核病菌对油菜叶片和茎秆的侵染过程及侵染后寄主细胞的反应，结果发现，病菌在叶片和茎秆上的侵入方式相似。病菌与寄主接触的初级阶段，病原菌丝先在寄主表面平行扩展分枝，然后集结形成侵染垫，进而产生侵入钉直接侵入。病菌侵入过程中，与病原接触部位的寄主细胞壁颜色变浅，电子致密度明显降低，表明病菌通过机械压力直接侵入的同时，伴有细胞壁降解酶的产生。病菌侵入寄主表皮细胞后可在表皮下平行扩展，也可向内层即叶肉细胞和皮层作纵深扩展，在这些组织内的扩展包括细胞间扩展和细胞内扩展。病菌在茎皮层内扩展时，能迅速到达髓部，引起髓部组织的细胞解体。在病菌侵染的过程中，寄主组织和细胞发生了一系列病理变化，包括细胞变形，细胞壁消解、细胞器及原生质解体坏死，细胞死亡。病菌在茎中的扩展速度很快，与在叶片中到达叶脉时的速度相似。 为深入了解病原与寄主互作过程中的寄主细胞壁成分变化，本文采用细胞化学方法对健康和受油菜菌核病菌侵染的油菜茎表皮组织细胞壁主要成分如纤维素、木聚糖和果胶质等进行了定位分析。电镜观察发现健康茎表皮细胞壁中都含有纤维素、木聚糖和果胶质成分。但受病原菌侵染后的茎表皮组织细胞不仅解体坏死，而且细胞壁的组成成分也发生变化，即受侵组织细胞壁中纤维素、木聚糖、果胶质的标记密度明显下降，并远远低于未接种的健康对照。表明油菜菌核病菌在侵染油菜茎组织的过程中，分泌了细胞壁降解酶如纤维素酶、木聚糖酶、果胶质酶等，这些细胞壁降解酶在受侵组织中的扩散造成了某些寄主细胞壁组成成分的分解，从而有利于病原菌在寄主组织中的侵染和扩展。上述研究结果表明，油菜菌核病菌产生的细胞壁降解酶在侵染茎表皮组织和致病过程中起重要作用。 由于目前国内还没有有效防治油菜菌核病的药剂，而国外利用羟菌唑防治此病较多，故作者利用电子显微镜技术和细胞化学技术，研究了羟菌唑对油菜菌核病菌生长发育的影响。扫描电镜观察发现：药剂处理后病菌菌丝生长明显受到抑制，菌丝粗细不均匀，呈不规则肿大或缢缩，分枝明显增多。超微结构研究表明：菌丝细胞壁不规则加厚，以菌丝顶端细胞壁加厚尤为明显，并有大量电子致密度高的物质存在：与对照菌丝相比，菌丝隔膜肿大、畸形，发育受阻：有的菌丝体内有新菌丝产生，且染色较深。细胞化学标记分析结果表明：药剂处理后，菌丝细胞壁成分的变化表明羟菌唑影响了β-1，3-葡聚糖酶和几丁质酶的标记密度明显高于对照菌丝，说明药剂处理后，这两种成分在细胞壁内显著增加。病菌菌丝细胞壁成分的变化表明羟菌唑影响了病菌细胞结构及其功能。更多还原

【Abstract】 The Sclerotinia sclerotiorum of rapeseed is one of the major disease of canola in the world. It is much severe in our country. Sclerotinia sclerotiorum can infect about 400 kinds of plants.In order to profoundly understand the essence of interactions between host and pathogen during Sclerotinia sclerotiorum infection and provide theory basis for controlling the disease,the infection processes of Sclerotinia sclerotiorum on leaf and stem were observed by light microscopy and election microscopy: At first, the pathogen hyphae grew -. extended on host surface , then produced infected cushions before penetrating .The tip of the rim hyphae on infected cushions were swollen and then directly penetrated host cells. Some infected hyphae extended intercellulary , some broke through cell wall and invaded into inner ,so extended intracellulary. At last the pith including xylem and phloem was infected by hyphae . During the infection of pathogen, a serious of pathological changes occurred in host tissues and cells,such as dissociation of cell wall, decomposed of plasmogen and necrosis of cells.The infection process of Sclerotinia sclerotiorum on leaf was similar to that on stem , but the extending speed on leaf was slower than that on stem. As soon as Sclerotinia sclerotiorum extended into vascular on leaf, the speed was the same to that on stem. When Sclerotinia sclerotiorum penetrated host cells , the colour of host walls around infected hypha usually became shallower, probably pathogen produced cell-wall-degrading enzymes during infection. The cell-wall-degrading enzymes softened , decomposed the cell walls, contributed to the infection of pathogen.In order to further understand the chemical phenomena of interactions between pathogen and host during infection, the cell wall components such as cellulose, xylan and pectin in cell walls of uninoculated healthy and Sclerotinia sclerotiorum-infected rapeseed were detected by means of cytochemical methods. All the cell walls of healthy stem tissues comprised cellulose, xylan and pectin. The components of Sclerotinia sclerotiorum-infected rapeseed stem changed: the labeling densities for cellulose,xylan and pectin were significantly reduced as compared with corresponding cell walls of healthy stem. This phenomenon indicated that Sclerotinia sclerotiorum secreted cell-wall-degrading enzymes, such as cellulase, xylanase and pectinase during the infection of Sclerotinia sclerotiorum on stem tissues, which decomposed and softened the host cell walls, then contributed to the penetration and extension of pathogen.The effects of metconazole , a systemic fungicide from the triazol group were examined on morphology, structure, cell wall components of Sclerotinia sclerotiorum by means of electron microscopy and immunocytochemical labelling techniques. The studies revealed that metconazole not only inhibited the hyphal growth , but also caused a series of markedmorphological and structural alterations of hyphae. These changes included irregular swelling , excessive branching and many tumors on the surface of hyphae, considerable thickening of the hyphal cell walls, particularly at the hyphal tip region. The septum development of the hyphae was inhibited and became malformed . Using cytochemical techniques, the labelling densities of chitin and beta-1,3-glucan in the cell wall of the fungicide-treated hyphae were increased dramatically comparing with those of the untreated control hyphae, indicating that the detrimental effects of the fungicide on structure and function of the hyphal membranes resulted in the changes of the cell walls compositions.更多还原