Study of seedless cultivation in short pruning grapevine 'Kyoho', 2

A dense fruit cluster with large seedless berries is recently required in the tetraploid grapevine 'Kyoho' from the market and consumers. In grapevine, twice gibberellic acid (GA) treatment is very effective for inducing seedless berries and addition of forchorfenuron (Fulmet, a commercial synthetic cytokinin) (CPPU) to the first or the second GA treatment induces enlargement of the berries and increases the berry density because of reducing shattering. Furthermore, a streptomycin (SM) treatment combined with the GA+CPPU treatment is also effective for inducing seedless berries in 'Kyoho' (Suzuki and Suganuma, 2002). In previous study, we investigated various treatments about GA, CPPU and SM but no treatment implemented all of the complete seedlessness, the dense fruit cluster and the large berries (Kishida et al., 2006). In this study, we investigated the effect of the addition of SM to GA+CPPU treatment and the triple treatment, the SM treatment combined with the twice GA treatment, for the dense fruit cluster with large seedless berries in short pruning 'Kyoho'. All of three GA+CPPU+SM treatments at full bloom suppressed the seed formation completely. The berry density was high in the GA+CPPU (+SM) treatments at full bloom or seven days before full bloom. Moreover, these treatment were also effective the enlargement of berries. Taken together, GA+CPPU+SM treatment at full bloom would be most useful for the dense fruit cluster with large seedless berries because the fruit quality in this treatment was almost same as those in other treatments in spite of less labor of the treatment.