STUDIES ON RUBUS LACINiATUS CULTURE IN VITRO——Ⅰ. The effect of various growth regulators on adventitious bud formation from leaf explants

Leaf explants of Rubus laciniatus Wild cv. 'Thornless Evergreen' blackberry were cultured in vitro on modified Nitsch and Nitsch (1969) medium containing either 2 to 4 mg/l 6-benzylaminopurine (6 -BAP) and 0.1 to 0.2 mg/13-naphthaleneacetie acid (NAA) or 1 to 3 mg/1 2, 4dichlorophenoxyacetic acid(2, 4-D)and 0.1 mg/l NAA. Adventitious buds formed directly from complete leaf blades as well as the lower leaf and petiole segments. About 20 to 48% of the explants formed buds, but most complete plants developed from leaf rachises or at the base of the petioles. Whole leaves and leaf segments formed buds at about the same rate. However, the highest number of shoots formed on petiole segments near the base of the petiole. 6-BAP more strongly affected shoot formation than 2, 4-D. without subculture a single leaf blade could produced 10 to 20 shoots in about 40 days. With subculture onto identical medium, a leaf blade can produce 40 to 60 shoots after only 30 days. The relationship of adventitious shoot formation to polarity is discussed.