Clubroot is one of the most serious diseases in Cruciferous crops, caused by Plasmodiophora brassicae, a soil-born, obligate parasite with quick variation. In this study, the pathotype of 32 P. brassicae were classified by using Williams' system. The distribution of simple sequence repeats (SSRs) was analyzed in P. brassicae genome, and new SSR markers were developed for genetic diversity. According to Williams' system, pathotype 2, 4, 7 and 11 were identified among 32 P. brassicae collections from 31 regions in 8 provinces. A total of 3 164 SSR were detected in P. brassicae genome, and the average distance of SSR was 7.6 kb. Moreover, 2 and 3 nucleotides repeat were predominant SSR type, and their distribution frequencies were 45.92％ and 53.04％, respectively. Among 62 developed SSR markers, 31 showed polymorphism in 32 P. brassicae collections, with an average PIC value of 0.407. Phylogenic relationship analysis revealed that most P. brassicae from the same region clustered together, even if with some extented variation.%芸薹根肿菌(Plasmodiophora brassicae)专性寄生于十字花科作物根部引起根肿病,且变异迅速.本研究利用Williams鉴别寄主系统鉴定了32株根肿菌,根据根肿菌基因组序列分析了根肿菌基因组中简单重复序列(simple sequence repeats,SSR)的分布特性,并结合SSR标记开发研究了根肿菌遗传多样性.主要结果:从收集自8个省市31个地区的32株根肿菌中,鉴定出2、4、7和11号生理小种;根肿菌基因组存在3 164个SSR,即每7.6 kb存在1个SSR.核苷酸重复类型以2和3为主,分布频率分别为45.92％和53.04％.从62对SSR引物中,筛选出31个多态性标记,多态率50％,平均PIC值为0.407;聚类分析表明,同一地区的根肿菌大多聚类到一起,但同时存在变异.
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