冠盘二胞Marssonina coronaria侵染不同抗性苹果叶片的组织病理学研究

Histopathology of leaf infection by Marssonina coronaria on resistant and susceptible apple cultivars

利用光学和电子显微镜,从组织细胞学水平系统研究了冠盘二胞Marssonina coronaria在苹果抗、感病品种叶片上的侵染过程及侵染后寄主细胞的超微结构特征。结果表明:冠盘二胞的侵入和定殖过程可以分为6个阶段:孢子萌发与芽管形成、附着胞形成、侵入细胞角质层、在叶肉细胞内产生吸器、菌丝在叶肉细胞间和细胞内扩展、分生孢子盘形成。随着菌丝扩展,受侵寄主细胞出现细胞壁加厚,细胞壁降解,质壁分离,叶绿体内淀粉粒、嗜饿颗粒积累,叶绿体基粒片层瓦解,线粒体空泡化等现象。在不同抗性的苹果品种上,分生孢子萌发率差别不明显,但芽管分枝率、附着胞形成率和侵入后病菌在不同抗性品种叶片组织内的发育进程具有显著差异。在抗病品种上,病菌侵入时间,角质层下菌丝、叶肉细胞内吸器、分生孢子盘的形成时间推迟,芽管分枝少,胞内吸器少,菌丝生长缓慢,菌丝周围沉积有大量电子致密物。苹果不同品种对冠盘二胞的抗病性表现在抗侵入和抗扩展能力两个方面。

The infection process of Marssonina coronaria was investigated on leaves of susceptible and resistant apple cultivars by means of light and electron microscopy. Infection and colonization by the pathogen could be divided into six stages： spore germination and germ tube formation, appressorium formation, penetration, haustorium formation in mesophyll cells, expansion of mycelium between and in mesophyll cells, and acervulus formation. Cell wall swelling and degradation,plasmolysis, accumulation of starch grains and osmiphilic globules, disruption of grana lamellae and vacuolization of mitochondrion were observed during mycelial expansion in host tissues. Branching rate of germ tubes, formation rate of appressoria and expansion of mycelium were significantly different between susceptible and resistant cultivars; however, the conidial germination rate did not show significant differences. For resistant cultivar, the pathogen＇s penetration and formation of subcuticular hyphae, haustoria in mesophyll cells, and acervuli were clearly delayed, and the number of germ tube branches and haustoria in the mesophyll cells were all decreased. Hypha grew more slowly and deposited more electron-dense material in the leaves of resistant cultivars. It is concluded that the resistance of apple cultivars against Marssonina coronaria is related to inhibition of fungal infection, colonization, and mycelial expansion processes in host tissues.