立枯丝核菌侵染玉米的研究

 用获自水稻及玉米的立枯丝核菌(Rhizoctonia solani Khn) AG-11A接种玉米发生典型纹枯症状,其致病力显著强于AG-4。玉米拔节期,上位叶鞘抗性较强,抽雄及抽丝期抗性减弱,下位叶鞘无论在拔节期或抽雄、抽丝期,均较上位叶鞘感病。接种玉米后8小时,形成侵染垫及附着胞,从这些结构上形成侵入钉侵入,AG-4侵染上位叶鞘时,常以菌丝直接穿透表皮或从气孔侵入。在去掉菌体的叶鞘表面,发现有周边光滑或稍破损的侵入孔。接种后12小时,在叶鞘细胞中发现菌丝,它们在穿过细胞壁进入邻近细胞时,明显变细。接种后16小时,新生出的菌丝从气孔成丛出现。

STUDIES ON THE INFECTION BY RHIZOCTONIA SOLANI ON MAIZE

Corn plants were inoculated in field with Rhizoctomia solani AG-1IA and AG-4. AG-1IA isolated either from maize or from rice caused typical sheath blight symptom, the pathogenicity of it is stronger than that of AG-4. The leaf sheaths with higher position on plants are more resistant than that of the lower position one, but the resistance decreased at the tasseling and silking stage. The infection process of R. solani on maize includes;infection caushion and lobate appressoria are formed at 8 h after inoculation by two of the AGs on the leaf sheath on lower position, and then penetration pegs are formed and penetrate host. Also, the AG-4 can penetrate into plant tissue directly or via stomata without any infection structure when it infects leaf sheath on upper position. After taking away the hypha structure of the pathogen from the surface of leaf sheath,penetratoion pores can be seen, the edges of them are smooth or destroyed slightly. Some hyphae in epidermal cells were found at 12 h after inoculation. The hyphae ramify intracellular and become thinner when it get through the cell wall into adjacent cells. The new mycelia grow out from stomata at 16 h after inoculation.