Developing a scale-up system for the in vitro multiplication of thidiazuron-induced strawberry shoots using a bioreactor

The use of large-scale liquid cultures in a bioreactor system has the potential to resolve the manual handling of the various stages of micropropagation and increases shoot multiplication in vitro significantly compared with those cultured on semi-solid gelled medium. In an attempt to improve the micropropagation protocol for strawberry (Fragaria x ananassa Duch.), a procedure for the mass propagation of adventitious shoots regenerated from leaf, sepal and petiole explants of cultivar Bounty using a liquid medium-containing bioreactor system combined with gelled medium is described. Leaf disks, sepals and petiole halves produced multiple buds and shoots without an intermediary callus phase on 2-4 mu M thidiazuron (TDZ)-containing shoot induction medium within 5-6 wk of culture initiation. TDZ supported rapid shoot proliferation at low concentrations (0.1 mu M), but induced hyperhydricity in a bioreactor system. Bioreactor-multiplied hyperhydric shoots were transferred to gelled medium containing 2-4 mu M zeatin, and produced normal shoots and root within 4 wk of culture. In vitro-derived plantlets were acclimatized and eventually established in the greenhouse and in the field. Present results suggested the possibility of large-scale multiplication of strawberry shoots in bioreactors.