To obtain the seedless sudachi of a triploid, 297 flowers were crossed between tetraploid sudachi and diploid sudachi, and 50 triploids were established in 1992. Flowcytometer was used for selection of triploid hybrids. When diploid sudachi were used for seed parents, undeveloped seeds were obtained, and triploids were hardly obtained. When tetraploid sudachi was used for seed parents, developed seeds were formed, and although the rate of establishment was low, a certain number of triploids could be obtained. 'Tokushima 3X No.1' was selected from these and has been submitted for registration under the Law of Seedlings. The flesh color of 'Tokushima 3X No.1' is a pleasant green, and it has no seeds but an abundance of juice. Furthermore, it can be to shipped early after open - field culture of sudachi. It is expected be an early crop cultivar in which quality fruit production is possible. In order to breeding a seedless cultiver, it is thought that production of a triploids is one of the most effective methods not only for sudachi but for other sour citrus plants as well.