Abstract
Yamato-mana (Brassica rapa L. Oleifera Group), a traditional vegetable of Yamato, has some weak points: its growth is not uniform, and its outer leaves are liable to turn yellow after harvest. To overcome these disadvantages, we bred F1 cultivars by use of the S haplotype, which controls self-incompatibility. By three-way crossing, we succeeded in the breeding of 'Natsunarana', which is suited for cultivation during the high-temperature season, and 'Fuyunarana', which is suited for the cultivation in the low-temperature season. Both cultivars were characterized by their uniform plant shapes; moreover, they were somewhat effective in preventing the yellowing of leaves than conventional cultivars. The period required for breeding of F1 cultivars by three-way crossing was reduced by use of the S haplotype from the beginning of breeding.
