Intraspecific Genetic Variability of Brassica cretica Lam. (Brassicaceae) Using SSR Markers

Unraveling the evolutionary history of Brassica L. crops and their wild relatives remains a key challenge in plant evolutionary biology. Brassica cretica is considered the closest living relative of the cultivated B. oleracea. It is mainly distributed in the Aegean Islands and the neighboring mainland regions of Greece and Anatolia, and exhibits extensive phenotypic variability, obscuring its infraspecific classification. In this study, we analyzed five Greek populations of B. cretica and one B. oleracea botanical variety using SSR markers to assess genetic diversity and differentiation. High genetic diversity was detected within natural populations, with a mean of 21.9 alleles per locus and an expected heterozygosity of 0.647. Significant genetic differentiation (Fst = 0.812) revealed the presence of four distinct gene pools, partly supporting the current infraspecific classification of B. cretica. The cultivated plants cluster closely with B. cretica subsp. cretica, supporting the hypothesis of an Eastern Mediterranean origin. Our findings suggest that B. cretica subsp. cretica may have been introduced to suitable habitats or that cultivated plants may have reverted to a feral state in the Peloponnese, given the genetic similarity between populations from Crete and northern Peloponnese. The identified genetic diversity underscores the importance of B. cretica as a genetic resource for breeding programs and highlights the need for conservation, particularly for populations exhibited unique genetic traits.