Genetic Diversity inBrassica oleraceaL. (Cruciferae) and Wild Relatives (2n=18) using Isozymes

Genetic diversity in 36 populations of wild taxa of the Brassica oleracea L. group (2 n =18) and two cultivated forms was studied using isozyme variation at 11 loci for five enzyme systems (IDH, 6-PGD, PGM, PGI, MDH). Mean values for the percentage of polymorphic loci and expected heterozygosity were 54% and 0.224, respectively. Statistically significant differences among allele frequencies were found with the 6-PGD isozyme system. Intrapopulational genetic diversity was 67% while interpopulational genetic diversity was only 33%. The dendrogram obtained, using genetic distances among taxa, showed three different groups. With the exception of B. incana, they agree to the already accepted relationships among the 14 taxa studied: the West Mediterranean group, with B. oleracea, B. alboglabra, B. bourgeaui and B. incana ; another group of species growing in the central Mediterranean area, which includes B. villosa, B. villosa subsp. drepanensis, B. rupestris, B. macrocarpa (the four taxa together with B. incana are considered the B. rupestris group) and B. montana ; and finally the Aegean group, which includes the three subspecies of B. cretica. Clearly separated were B. insularis and B. hilarionis , showing the maximum genetic distance. Separate dendrograms were also obtained for B. oleracea, B. montana, B. cretica and B. rupestris group, and genetic diversity parameters were estimated. Genetic distances among B. oleracea populations are in the same range as populations of the B. cretica subspecies. Highest genetic distances were found among populations of the B. rupestris group.