An efficient adventitious shoot regeneration system on excised leaves of micropropagated lingonberry (Vaccinium vitis-idaea L.)

An efficient system to regenerate shoots in vitro on excised leaves of lingonberry (Vaccinium vitis-idaea L.) was developed. Leaf explants from shoot-proliferating cultures produced multiple shoots without an intermediary callus phase on zeatin (ZN)-containing shoot induction media within 3-4 weeks of culture initiation. Cultivars Regal and Splendor, and one clone from a natural stand in Estonia (ECL1), were used in the first experiment. Young expanding leaves with the adaxial side touching the culture medium, and maintained for 7 d in darkness, produced the best results. There were significant genotypic differences in adventitious shoot formation. A second experiment studied the effects of ten concentrations of three cytokinins: ZN at 5, 10, 20, 30 and 40 muM; 1-phenyl-3-(1,2,3-thiadiazol-5-yl) urea (thidiazuron, TDZ) at 0.1, 1, 5 and 10 mum; and 6-(gamma-gamma-dimethylallylamino) purine (2ip) at 25 muM were compared with leaf segments of different polarity in 'ECL1'. Zeatin was found to be more effective than TDZ or 2iP as an inductive signal for regenerating many vigorous shoots. Zeatin induced multiple shoot formation at all concentrations tested, but maximum morphogenic response was observed at 20 to 30 muM. The media containing TDZ generally promoted mote callus formation and suppresed shoot elongation. In a third experiment with the lingonberry cultivar Erntedank and the clone 'ECL1', a new medium developed for lingonberry shoot culture proved more effective than the modified Murashige and Skoog medium for regenerating shoots on leaf explants. Elongated shoots Were excised and rooted directly on a 2 peat:1 perlite (v/v) medium after dipping in 0.8% indole-3-butyric acid. Rooted plantlets were acclimatized under greenhouse conditions to evaluate somaclonal variation.