黄瓜不同抗病品种与疫霉菌相互作用的超微结构研究

ULTRASTRUCTURAL STUDY ON THE INTERACTIONS BETWEEN THREE RESPECTIVELY DIFFERENT DISEASE RESISTANT CUCUMBER CULTIVARS AND PHYTOPHTHORA MELONIS 

电镜观察发现，黄瓜（ＣｕｃｕｍｉｓｓａｔｉｖｕｓＬ．）的不同抗病品种在与疫霉菌（ＰｈｙｔｏｐｈｔｈｏｒａｍｅｌｏｎｉｓＫａｔｓｕｒａ）的相互作用过程中有不同的表现。感病性品种易被疫霉菌侵染，被侵染的叶肉组织及周围细胞中胶层解离、胞质凝聚、细胞器解体，叶片组织内有大量胞间及胞内生长菌丝。中抗病性品种也被疫霉菌侵染，但表现出胞间连丝断裂、内质网和高尔基体增多等抗病性反应，与菌丝相接触的细胞出现质膜内陷。抗病性品种出现过敏性坏死反应，叶肉细胞与入侵菌丝一同解体死亡，胞间菌丝向细胞内穿透处形成壁附加物。中抗病性品种和抗病性品种在与疫霉菌的相互作用过程中表现出不同的抗性机制。

Ultrastructural changes during the process of interactions between three different disease resistant, susceptible, moderately resistant and resistant cucumber ( Cucumis sativus L.) cultivars and Phytophthora melonis Katsura were respectively compared and the associated factors in the observed differences in colonization were determined. During the process of interaction in the susceptible cultivar, both inter and intracellular growth of hyphae associated with extensive colonization of healthy hyphae and marked alteration of mesophyll cells, such as aggregation of cytoplasm and disintegration of cellular organelle were demonstrated. The general disorganization of host cell was observed in areas directly adjacent to the fungal hyphae and in cells several layers from the nearest visible hyphae. In the moderately resistant cultivar during interaction the host showed limited hypha growth with responses of resistance including 1) breakage of plasmodesmata to prevent the host cells to contact the hyphae, 2) increasing the quantity of endoplasmic reticulum and Golgi apparatus so as to increase the quantity of secretory protein, 3) a plasmalemma invagination containing granular material at the site in contact with the intercellular hyphae. The interaction in the resistant cultivar was characterized as a hypersensitive reaction (HR) which means a rapid necrosis of the infected cells and the cells surrounding the invaded hyphae, resulting in death of the invaded hyphae. Formation of cell wall appositions right at the penetration sites of hyphae and haustorium like structure was observed. The results indicate that the mechanism of host response to P. melonis invasion was different between the moderately resistant and the resistant cucumber cultivars.