苜蓿假盘菌侵染苜蓿叶片的细胞学研究

Cytological observations of infection on Alfalfa leaves of Pseudopeziza medicaginis

采用微分干涉相差显微镜、扫描和透射电镜技术系统研究了苜蓿假盘菌Pseudopeziza medicaginis在苜蓿叶片的侵染过程及超微结构特征。结果表明,接种4h后,子囊孢子萌发产生芽管;12h后,芽管以直接侵入的方式进入表皮细胞形成侵染菌丝;24h后,表皮细胞中侵染菌丝向相邻表皮细胞扩展,同时侵入到叶肉细胞以胞内生长方式扩展;接种72h后,侵染菌丝在表皮细胞下的叶肉组织中形成初始菌落;第5d后,菌丝扩展至整个叶片组织,大量菌丝聚集形成子座组织,并进一步形成子囊盘与子囊。病菌菌丝在侵入寄主细胞初期,并不穿透寄主质膜与原生质,而是被其所包围。但随着菌丝进一步扩展,叶片组织发生了一系列的病理变化,其中包括叶肉细胞肿胀、细胞质消解、叶绿体等细胞器解体以及寄主细胞坏死塌陷,并最终在叶表面产生典型的褐斑病症状。

The infection process of Pseudopeziza medicaginis on leaves of Medicago sativa was observed by using of differential interference phase contrast microscope, and scanning and transmission electron microscope. The results showed that ascospores began to germinate and form germ tube four hours after inoculation. The germ tubes penetrated the host epidermal cells directly and formed infection mycelium in 12h. The infection mycelium reached to nearby epidermal cells, penetrated into mesophyll cells and showed intracellular growth in 24h. The infection mycelium formed initial colony in mesophyll tissue under the epidermal cell in 72h. The mycelium extended within the host tissues in 5 days and gathered to form stroma tissue, from which apothecium and asci were then developed. At earlier stage of infection, the mycelium did not penetrate the host protoplast membranes and cytoplasm. With mycelial extension in host tissues, a series of alterations occurred in host tissues, including swelling of mesophyll cells, degeneration of cytoplasm, disintegration of organelles such as chloroplasts and collapse of host cells, resulting in appearance of brown necrotic spots on the infected host leaves.