黄瓜抗霜霉性的组织学和超微结构研究

The Histology and Ultrastructure of Cucumber Resistance to Pseudoperonospora cubensis

组织学研究表明，黄瓜霜霉菌在不同抗病类型品种上，其侵入前的过程基本相似，并且都能形成胞间菌丝和吸器。然而，随着品种抗病性的增强，吸器形成速率变慢，数目减少，同时菌丝扩展缓慢；寄主细胞坏死发生时间早，机率高。电镜观察显示，抗病品种中菌丝和吸器的细胞质中液泡数量增加，菌丝和吸器的壁与细胞质膜分离，原生质电子致密度加深，最后菌丝和吸器解体；受侵寄主细胞分泌的胼胝质，可将吸器体完全包围，从而阻止了吸器的进一步发育；在发生坏死的寄主细胞中，吸器也解体坏死。

Histological studies indicated that among cucumber cultivars of variousresistant degrees,the pre-penetration processes of cucumber downy mildew,Pseudoper-onospora cubensis,were similar and that the intercellular hyphae and haustoria wereformebut the formation of haustoria became slower in speed and fewer in number. Themycelial growth slowed down and the host cell necrosis occtired more often and earlierwith resistance increase. TEM observation showed that the vacuoles in cytoplasm of hy-phal cells and the haustoria in resistant cultivars increased in number, and that the wallsof both hyphae and haustoria were seperated from plasmalemma. The cytoplasm of hy-phae andhaustorium became denser and the hyphal cells and haustoria turned otit to bedegenerated. As a result,the collars formed in the infected host cells could thoroughlysurround the haustoria,thus inhibiting further development of the haustoria, resultingin thedegeneration of thehaustoria in the necrosis host cells.