Studies on improvement of wild Rubus species native to Japan and it's application to horticulture

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In order to establish some bramble cultivars adaptable to Japan, we collected 52 wild species native to Japan (28) or foreign countries (24), 12 Raspberry and 6 Blackberry cultivars and 18 unknown species of Rubus. The ecological and physiological studies on flower bud differentiation, characteristics of blooming and hruit ripening and hruit growth of some Rubus species were investigated. And we also tried to obtain some interspecific hybrids among wild species and between Blackberry or Raspberry cultivars and some wild species of Rubus. The results are as follows.Flower bud initiation of Rubus crategifolius started at August and the stamen primordia in the terminal flower were differentiated within the year. Flowering and yielding periods on the bearing shoots came out from upper part of the main floricane were earlier than those of lower part in Blackberry "Merton"The size and fresh weight of seven wild Rubus species at maturity were smaller than those of three Blackberry cultivars. Compared with Blackberry and Raspberry cultivars, however, the total sugar contents in berries of some wild Rubus species were higher and the total organic acid contents were lower at maturity stage.The aggregate fruits of some wild Rubus species and Blackberry cultivars showed double sigmoid growth curve. Total cytokinin-like activity, IAA content and total gibberellin-like activity in fruit increased at the first phase, the second phase and the third phase of fruit development respectively. ABA content in hruit was high at bloom, decreasing gradually to a low level at the second phase, thereafter increase slightly during fruit maturation again. Both ethylene and CO_2 exhaustion from fruit increased dramatically during ripening.Further we obtained many interspecific hybrids among wild species and between Blackberry or Raspberry cultivars and some wild species of Rubus native to Japan. These hybrids will be evaluate in breeding program in the near future.