Ultrastructural and cytochemical studies on the infection process of Sclerotinia sclerotiorum in oilseed rape
Ultrastructural and cytochemical studies on the infection process of Sclerotinia sclerotiorum in oilseed rape
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DOI：
10.1007/bf03356233
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发表时间：
2008-02-01
影响因子：
2
通讯作者：
Kang, Z.
中科院分区：
文献类型：
--
作者：
Huang, L.;Buchenauer, H.;Kang, Z.
茎腐病是由油菜菌核菌（Sclerotinia sclerotiorum, Lib.） de Bary引起的油菜主要病害之一。利用电镜和细胞化学标记技术研究了菌核病菌侵染寄主叶片和茎的过程以及侵染寄主组织细胞壁成分的变化。用真菌培养的琼脂盘接种叶片和茎后1天，接种组织上通常形成密集的菌丝网。然后，研制不同大小的感染垫。病原体产生的粘液覆盖菌丝和感染垫。菌丝形成的感染垫通常变平，直径增大。除去感染垫后，刺穿钉进入叶和茎角质层的许多孔的直径很小，直径几乎相同。叶片和茎分别发生穿透2和3代。观察到角质层的微小变化。病原菌穿透后，菌丝向角质层和表皮细胞壁之间以及表皮细胞壁内部延伸。光镜和透射电镜观察半薄切片和超薄切片上菌丝在细胞间和细胞内扩散。菌丝也定殖木质部和韧皮部。在定植过程中，检测到宿主组织的显著变化，包括细胞质、细胞器的解体、细胞壁的解体和宿主细胞的崩溃。酶和免疫金标记研究显示，感染组织的宿主细胞壁中纤维素、木聚糖和果胶明显降解。细胞壁成分的降解表明，病原菌在油菜组织感染和传播过程中可能分泌纤维素酶、木聚糖酶和果胶酶等细胞壁降解酶（CWDEs）。
Stem rot, caused by Sclerotinia sclerotiorum (Lib.) de Bary, is one of the major diseases of oilseed rape worldwide. The infection process of S. sclerotiorum in leaves and stems and the alterations of cell wall components in the infected host tissues were examined by electron microscopy and cytochemical labelling techniques. one day after inoculating (dai) leaves and stems with fungal grown agar disks, dense mycelial networks were usually formed on the inoculated tissues. Then, the infection cushions of different size were developed. Mucilage produced by the pathogen covered mycelium and infection cushions. Hyphae forming infection cushions were often flattened and increased in diameter. After removing the infection cushions, the diameters of the numerous pores through which penetration pegs had entered the cuticle of leaves and stems were small and had almost the same diameter. Penetration of leaves and stems occurred 2 and 3 dai, respectively. Small changes in cuticle were observed. After penetration, hyphae of the pathogen extended between the cuticle and epidermal cell walls as well as inside the epidermal cell walls. Then inter- and intra-cellularly spreading hyphae were observed in the hemi- and ultra-thin sections by light- and transmission electron microscopy, 5 dai. Hyphae also colonized xylem and phloem. During colonization marked alterations in the host tissues were detected, including disorganization of cytoplasm, cell organelles, disintegration of cell walls and collapse of host cells. The enzyme- and immunogold-labelling investigations showed obvious degradation of cellulose, xylan and pectin in the host cell walls of infected tissues. The degradation of cell wall components suggests that the pathogen may secrete cell wall degrading enzymes (CWDEs) such as cellulases, xylanases and pectinases during infection and spreading in the oilseed rape tissues.