A scaled-up system for in vitro multiplication of thidiazuron-induced red raspberry shoots using a bioreactor

A procedure for the mass propagation of adventitious shoots regenerated from leaf explants of red raspberry (Rubus idaeus L.) using a liquid medium-containing bioreactor system combined with gelled medium has been described. Leaf segments of the raspberry cultivars 'Festival', 'Heritage', and 'Latham' produced multiple buds and shoots in 4.5 mu M thidiazuron (TDZ)-containing shoot induction medium within 6 8 weeks of culture initiation:The raspberry cultivars differed significantly with respect to their shoot regeneration and multiplication rate, with 'Heritage' producing the highest number of adventitious shoots per explant. TDZ supported rapid shoot proliferation at low concentrations (1.2 2.3 mu M) in the bioreactor system, but shoot elongation was improved in medium containing 4.4 mu M 6-benzyladenine (BA). BA-induced, elongated shoots rooted in the bioreactor vessel containing the same medium, but without any plant growth regulators. In vitro-derived plantlets were acclimatised and eventually established in a greenhouse and in the field. These results suggest the possibility of large-scale multiplication of raspberry shoots using a bioreactor-based system.