Clonal propagation of dwarf raspberry (Rubus pubescens Raf.) through in vitro axillary shoot proliferation

A protocol for the micropropagation of dwarf raspberry (Rubus pubescens) was developed by the establishment of axenic shoot cultures from greenhouse-grown plants, induction of shoot proliferation, and rooting in vitro. Cultures were initiated from shoot tip and nodal explants on 1/2 strength MS (Murashige T. and Skoog F. 1962. Physiol. Plant. 15:473) macro-salts and MS micro-salts and vitamins containing 8.9 muM N-6-benzyladenine (BA) and 0.98 muM indole-3-butyric acid (IBA). Zeatin was more effective than BA, and induced proliferation of about 1.5-2 times as many shoots as BA in combination with 0.54-1.1 muM alpha-naphthaleneacetic acid (NAA) or 0.49-0.98 muM IBA. With higher zeatin, shoots did not expand and had a high mortality rate. Shoots growing for more than 10 weeks on medium that contained 9.1 muM zeatin occasionally produced adventitious shoot masses, which appeared to arise from dense calluses growing at the base of the shoots in the medium. Shoots were rooted in vitro in the same medium used for shoot proliferation, but without any growth regulators. Almost all (85-90%) in vitro plantlets survived when transferred to potting medium.