Abstract: Fiftyfive Rhizoctonia solani samples were collected in rice from five distinctive ecological regions of Sichuan Province, China. The 55 representative samples were isolated and purified, and the pathogenicity and molecular genetic variation were analyzed. Hyphal fusion identification results revealed that all the 55 strains belonged to AG1IA group except strain D42. In addition, some of the bacteria were identified to be fused with several groups simultaneously, acting as bridge flora. Pathogenicity identification analysis from leaves in vitro indicated that the pathogenicity among the strains was significantly different. The 55 strains could be classified into 8 groups by further RAPD cluster analysis when the similarity coefficient was 0941. The results suggested that in the certain ecological conditions in Sichuan Province, most of the Rhizoctonia solani were genetically stable, but quite a few changed drastically.

Key words: Rhizoctonia solani, anastomosis group, randomly amplified polymorphic DNA, cluster analysis, pathogenicity

摘要： 通过对四川省东、南、西、北、中5个区域、55个县（市）水稻立枯丝核菌（Rhizoctonia solani）样本进行分离、纯化和菌丝融合鉴定，发现分离得到的55株立枯丝核菌菌株除了D42菌株外，其余均属于AG1IA群。还发现其中一些菌株同时能与多个群发生融合，具有桥梁菌群属性。通过离体叶片致病力鉴定发现，各菌株间致病力差异显著。进一步的RAPD聚类分析显示，在相似系数为0.941处，该55株菌株可聚为8类。这一结果表明，在四川特殊的生态区条件下，四川省水稻立枯丝核菌大多数菌株保持了良好的遗传一致性，但少数菌株发生了较大程度的变异。

关键词: 立枯丝核菌, 菌丝融合群, 随机扩增多态性DNA, 聚类分析