Abstract: A better understanding of genetic diversity and its distribution are essential for its conservation and use. The research of it will help us to determin what and where to be conserved, and improve our understanding of the taxonomy, origin and evolution of plant species. The genetic diversities of 108 accessions including 101 entries of Brassica juncea from western China, 2 from Australia, 4 entries of B. rapa, and 1 entiry of Eruca sativa Mill.were analysed by SRAP with 23 pairs of primer combinations, AFLP with 11 primer combinations, and SSR with 10 pairs of primer combinations. The results showed that totally 313 loci were detected in these materials. The genetic similarity coefficients of 108 accessions varied from 0.378–0.936, while 103 accessions of B. juncea from 0.545–0.936. The clustering analysis indicated that the genetic similarity coefficients of 5 checks including B. rapa, Eruca sativa Mill., were less than 0.558. At the point of genetic similarity coefficient, 0.700, the 103 accessions of B. juncea were divided into 5 groups, those were group A from Yunnan-Guizhou and Southern Shaanxi, group B from Guanzhong of Shaanxi, group C and group D from Xinjiang, and group E from western China. Groups A and B were winter type, groups C, D, and E were spring type. The genetic difference among the accessions in group A was the largest, and higher than that in group B. The accessions from Shaanxi and Xinjiang were distributed into 3 groups respectively, and showed abundant genetic diversity. Group E including the most spring accessions, was divided into 3 sub-groups. The accessions in the sub-group I were from Tibet, with the genetic similarity coefficient higher than 0.83, belonging to an independent genetic system with narrow genetic background. The accessions of yellow mustard in the sub-group II were from Northern Shaanxi, showed higher genetic diversity and belonged to another independent genetic system. In the sub-group III, two accessions from Australia were similar to the spring type in China. Therefore the genetic differences in B. juncea were mainly related to geological and biological conditions. The genetic diversities in winter type of B. juncea were higher than those in spring type in China. The genetic background of B. juncea in Shaanxi and Xinjiang was wide.

Key words: Brassica juncea, Genetic diversity, SRAP markers, AFLP markes, SSR markers