西瓜幼苗枯萎病侵染的解剖学研究

Anatomic Studies on the Infection of Watermelon Seedlings by Fusarium Oxysporum f. sp. Niveum

本试验对西瓜抗、感枯萎病品种幼苗侵染的解剖学进行了研究。结果表明，西瓜幼苗根毛区是枯萎病菌最易侵染的部位。病菌由根表皮入侵后，菌丝向皮层、维管束横向扩展的同时，也沿着根的纵轴方向在各种组织中扩展，且纵向扩展比横向扩展更快。下胚轴菌丝侵染的途经是根的纵向传导和表皮入侵。下胚轴表面的凹陷较根、茎部多，内部结构也不相同。凹陷处表皮细胞体积大，排列疏松，细胞间有空隙，菌丝在此常大量聚积并入侵。西瓜抗、感病品种接种后，根表菌量和病菌侵染速度存在明显差异。抗病品种根表菌量少，病菌侵入慢。感病品种则相反。

Anatomic studies on the infection of watermelon seedlings by Fusarium Oxyzporum f. sp.niveum were made in the wilt-resistant and--susceptible cultivars. The results showed that the root hair zone was the most susceptible region. After infection through the epidermis of the root,the hyphae spread transversely along the cortex andvascular stele, and spread faster into all the tissues at the direction of longitudinal axis of the root.Infection of the hypocotyl was through the longitudinal spreading of the hyphae along the root and through the infection of epidermis. There were more sunken areas at the surface of the hypocotyl than those at the root and the stem. and the internal structure were also different.The epidermal cells at the sunken areas were larger and sparsely arranged,and there were gaps between the cells at which the hyphae aggregated and infected. After inoculation, there appeared marked differences in the amount of F. oxysporum f. sp. niveum at the root surface as well as the speed of infection between the -resistant and -susceptible cultivars. The amount was less and infection speed was slower in the former than in the latter.