2008 Volume 58 Issue 1 Pages 15-22
Nucleotide sequence variations of the trnK/matK region were investigated in cultivated and wild radish species and related Brassica species. Two insertions/deletions and 9 substitutions were detected among the Raphanus accessions. The value of the nucleotide diversity (π) was found to be higher in cultivated radish (0.00184) than in the wild species (0.00134). Based on the nucleotide diversity, the phylogenetic relationships of Raphanus and its related species were inferred by constructing a Neighbor-Joining tree. Raphanus species and Brassica barrelieri formed a sister clade located between the Rapa/Oleracea group and the Nigra group of Brassica. These results were in complete agreement with those obtained by Warwick and Black. The placement of Raphanus species at this position showed the existence of a paraphyletic relationship among the Brassica species. Each of the three varieties of cultivated radish, R. sativus var. sativus (European small radish), var. hortensis (East Asian big radish) and var. niger (black radish), belonged to a different cluster of the phylogenetic tree, suggesting the existence of independent multiple origins of these varieties. Based on the phylogenetic tree, problems related to the identification of the wild ancestral species of cultivated radish and original birthplaces of cultivated radish varieties were discussed.
