Bea-Kei', a new triploid seedless grape cultivar derived from a 'muscat bailey a' × 'kyoho' cross

To breed a seedless grape cultivar that produces large-sized berries with labor saving, 201 triploid hybrid plants were firstly derived from 24 interploid crosses with seven diploid and six tetraploid cultivars. A triploid grape BK9101 derived from a 'Muscat Bailey A' × 'Kyoho' cross was finally selected and given a cultivar name 'Bea-Kei'. 'Bea-Kei' showed high male and female sterility and produced small-sized seedless berries of about 2 g because of its low parthenocarpic ability. One time immersion treatment of the adequately thinned flower clusters with 100 ppm GA₃ at around full bloom, however, resulted in the formation of large-sized black berries of 8-11 g that stuck together. The trees showed high vigor and productivity, and, thus, required summer pruning for vigor control and thinning of flower clusters and flowers for high quality berry production. However, once the flower cluster thinning was carried out so that the each of the clusters had about 70 flowers, fruit thinning was unnecessary because of ideal fruit set and growth rates after the GA₃ treatment of the thinned flower clusters. The berries ripened from late August to early September in field conditions, and the berry quality did not deteriorate on trees by October. The berries were black-purple in rind color and contained high concentration of soluble solid sugars (19-21% in Brix). The rind of 'Bea-Kei' was not so slippery that the seed and pollen parents did. The flesh of 'Bea-Kei' was harder than the parents and showed superior taste than the parents. The estimation of the whole data obtained in this research led to the conclusion that 'Bea-Kei' has high potential as a new leading triploid cultivar that produces very high quality seedless berries with the aid of GA₃ at full bloom.