Genetic Diversity in broccoli rabe (Brassica rapa L. subsp. sylvestris (L.) Janch.) from Southern Italy

Broccoli rabe (Brassica rapa L. subsp. sylvestris (L.) Janch.) is a vegetable crop cultivated in southern Italy where it is part of local traditional recipes and heritage. Despite its economic importance, there are no cultivars patented, giving rise to many cultivated landraces that are characterized by wide phenotypic variability and named according to their harvesting time or the size and shape of their primary inflorescence. We report the first study of genetic diversity of 67 landraces of broccoli rabe collected in Apulia region and genotyped by means of 18 very informative SSR markers. A total of 243 alleles were detected in 552 genotypes, with a mean of 13.5 alleles per locus. The molecular variance was partitioned for 64% within accessions and for 36% among accessions, revealing a high level of genetic variation within landraces and a significant genetic differentiation across themselves. Remarkably, the results of genetic structure inference, as well as principal coordinates analysis and hierarchical clustering indicated as the clustering was largely in accordance to the germplasm origin, highlighting the presence of geographic stratification. We established a comprehensive germplasm collection of Apulian broccoli rabe landraces, currently stored at the Genebanks of IBBR-CNR and University of Bari. Finally, our study lays a foundation for future bio-agronomic characterizations addressing the identification of superior accessions for breeding purposes and solving cases of homonymy and synonymy.