Genetic diversity and relationships among loose-curd cauliflower and related varieties as revealed by microsatellite markers

• Cauliflower cultivars/lines tested in our study were divided into three relatively independent types.
• The loose-curd cauliflower might evolve separately subsequent to and outside the origin center of cauliflower.
• Accessions with early maturity showed closely related.
• It is possible to improve the genetic diversity through enhancing the gene introgression between different cultivar types.

Loose-curd cauliflower is widely cultivated in China for its excellent quality, but most of the genetic studies have used the compact-curd variety that is more popular in Europe and America. In the present study, we analyzed the genetic diversity of 57 Brassica oleracea genotypes worldwide, including 33 loose-curd cauliflower accessions, by using 14 simple sequence repeat primer pairs. The overall genetic similarity for all the cauliflower genotypes was 0.74 but that of the loose-curd cauliflower accessions was 0.83. The genetic similarity values were used to conduct a two-dimensional principal coordinate analysis and a cluster analysis that generally classified loose-curd cauliflower and compact-curd cauliflower into separate groups. Cauliflower accessions that displayed early maturity or had close geographic origins tended to be clustered together. On the basis of these results, 49 cauliflower genotypes were classified into three relatively independent types (loose-curd cauliflower from China, compact-curd cauliflower from China, and compact-curd cauliflower from Europe and America). This study suggested that commercial cauliflower cultivars have a very narrow genetic diversity, and that it is important to enhance gene introgression among different types to improve their genetic diversity.