白粉病菌侵染南瓜苗期叶片过程的细胞超微结构观察

Observation on cell ultrastructure of pumpkin seedling leaves infected by powdery mildew fungus

为了揭示南瓜(Cucurbita moschata)与白粉病菌(Podosphaera xanthii)互作的结构响应机制,对高抗白粉病南瓜自交系03112-2幼苗期叶片接种白粉病菌,观察南瓜叶片与白粉菌互作引起的超微结构变化。结果发现:白粉病菌孢子出芽形成菌丝时,胞质外流,在寄主细胞中形成吸器,获取寄主的营养物质。吸器存在于寄主细胞的细胞壁与细胞膜之间,由白粉病菌附着胞产生的侵入钉穿透细胞壁形成。寄主通过细胞壁加厚、T型与半球型乳突形成、内含物与液泡增加等结构反应抵御病原菌入侵。白粉病菌侵染造成栅栏组织叶肉细胞中叶绿体肿胀变形,淀粉粒积累严重,基本结构遭受破坏,部分表皮细胞出现质壁分离现象。综上所述,在接种白粉病菌后,病菌通过吸器获取营养物质,寄主通过形成乳突、加厚细胞壁等反应抵御病原菌入侵,叶肉细胞出现叶绿体肿胀,质壁分离等变化。

In order to reveal the structural response mechanism of the interaction between pumpkin(Cucur-bita moschata)and powdery mildew fungus(Podosphaera xanthii),the ultrastructural changes of the high-resistant pumpkin inbred line 03112-2 leaves inoculated with P.xanthi at seedling stage were ob-served.The results show that when the spores of powdery mildew pathogens buded and formed hyphae,the cytoplasm effluxed,and haustoria were formed in the host cells to obtain nutrients from the host.Haustoria existed between cell walls and cell membranes of host cells,and were formed by the invading spikes produced by powdery mildew pathogens appressoria penetrating cell walls.The host resisted the invasion of pathogens through structural reactions such as thickening of cell walls,formation of T-shaped and hemispherical papillae,and increasement of contents and vacuoles.Powdery mildew pathogens caused swelling and deformation of chloroplasts in mesophyll cells of palisade tissue,serious accumulation of starch grains,destruction of basic structure,and separation of cytoplasmic walls in some epidermal cells.Therefore,after inoculation with powdery mildew pathogens,pathogens obtain nutrients through haustoria,and the host resists the invasion of the pathogens by forming papillae and thickening cell walls,as well as the mesophyll cells with the changes of chloroplast swelling and plasmolysis.