Brassica juncea is an important economic crop of the world; however, the narrow genetic base of this crop has tremendously decreased its crop productivity. As an ancestral species of B. juncea, B. nigra is of great importance in widening the genetic diversity of B. juncea. In the present study, 42 SSR markers were employed to screen the genetic diversity among 83 B. nigra, 16 B. juncea, and other Brassica accessions. The molecular characteristics of 498 virtual B. juncea lines were deduced based on the bands of B. nigra and B. rapa via a virtual allopolyploid strategy, and then compared with natural B. juncea accessions. It was found that B. nigra had rich genetic diversity and could be classified into four subgroups, of which subgroup B-III and subgroup B-IV exhibited the closest and the most distant genetic relationship with B. juncea, respectively. To verify this, a hexaploidy strategy was applied to generated synthetic B. juncea from 20 B. nigra accessions, resulting in 45 new-type B. juncea genotypes. The genetic analyses detected that synthetic B. juncea derived from B. nigra in subgroup B-III was close to natural B. juncea, while B. juncea synthesized with B. nigra from subgroup B-IV exhibited wide genetic diversity and was most distant with current B. juncea. This study revealed a great potential of B. nigra in widening genetic diversity of B. juncea particularly using B. nigra in subgroup B-IV, and is helpful in better understanding of the genetic relationship between B. nigra and B. juncea.

芥菜是世界重要的经济作物；然而，这种作物的遗传基础狭窄，极大地降低了其作物生产力。黑芥作为芥菜的祖先种，对于扩大芥菜遗传多样性具有重要意义。在本研究中，采用42个SSR标记来筛选83份黑芥子、16份芥菜和其他芸苔属品种之间的遗传多样性。基于黑芥子和白菜的条带，通过虚拟异源多倍体策略推导了498个虚拟芥菜品系的分子特征，并与天然芥菜种质进行了比较。结果发现，黑芥子具有丰富的遗传多样性，可分为4个亚类，其中B-III亚类和B-IV亚类分别与芥菜亲缘关系最近和最远。为了验证这一点，应用六倍体策略从 20 个黑芥菜种质中生成合成芥菜，产生 45 个新型芥菜基因型。遗传分析发现，B-III亚群黑芥菜合成的芥菜与天然芥菜接近，而B-IV亚群黑芥菜合成的芥菜表现出广泛的遗传多样性，与天然芥菜的遗传多样性最远。当前芥菜。这项研究揭示了B. nigra在扩大B. juncea遗传多样性方面的巨大潜力，特别是使用B. nigra。 B. nigra属于B-IV亚组，有助于更好地了解B. nigra和B. juncea之间的亲缘关系。