Genetic Relationships among Japanese Wild Radishes (Raphanus sativus f. raphanistroides Makino), Cultivated Radishes and R. raphanistrum Revealed by RAPD Analysis.

The phylogenetic relationships among Japanese wild radishes, cultivated radishes, and wild R. raphanistrum species were examined using random amplified polymorphic DNA (RAPD) analysis. We compared the PCR products of 61 plants belonging to fourteen strains or varieties within the three categories, by using seven 10 mer random primers. Similarity ratios were calculated for all of the combinations of the individual plants based on 73 polymorphic DNA bands and cluster analysis was performed on these ratios using the average linkage method. Within the strains, the Japanese wild radishes and R. raphanistrum had lower similarity ratios of 51∿73%, those of the cultivated radishes were over 80%. However, these similarity ratios were distinctly higher than those between different strains belonging to the same category. As a consequence, almost all strains and varieties formed unique clusters within themselves. The three strains of the Japanese wild radishes formed a cohesive cluster, showing a genetic resemblance among them, and they clustered with most of the cultivated radishes except for 'Tokinashi' and 'Minowase'. R. raphanistrum stood apart from the large cluster that included the cultivated radishes and Japanese wild radishes. These results indicate that the Japanese wild radishes are a part of a large group of cultivated radishes (R. sativus) which does not include R. raphanistrum.