A two-step procedure for in vitro multiplication of cloudberry (Rubus chamaemorus L.) shoots using bioreactor

Cultures of three cloudberry (Rubus chamaemorus L.) clones collected from natural stands in Newfoundland and Labrador, Canada were established in vitro on a modified cranberry (Vaccinium macrocarpon Ait.) tissue culture medium containing 8.9 mu M 6-benzylaminopurine (BAP). Clones were compared for in vitro shoot proliferation on gelled medium supplemented with varying levels of BAP and thidiazuron (TDZ). Addition of 5.8 mu M gibberellic acid (GA(3)) in 8.9 mu M BAP-contained medium improved shoot proliferation. TDZ supported rapid shoot proliferation at low concentration (1.1 mu M) but induced 20-30% hyperhydricity in a plastic airlift bioreactor system containing liquid medium. Bioreactor-multiplied hyperhydric shoots were transferred to gelled medium containing 8.9 mu M BAP and 5.8 mu M GA(3) and produced normal shoots within 4 weeks of culture. Genotypes differed significantly with respect to multiplication rate with 'C1' producing the most shoots per explant. Proliferated shoots were rooted on a potting medium with 65-75% of survivability of rooted plants. Present results suggested the possibility of large-scale multiplication of cloudberry shoots in bioreactors.