EFFICIENT PLANTLET REGENERATION FROM PROTOPLASTS ISOLATED FROM SUSPENSION-CULTURES OF POPLAR (POPULUS-ALBA L.)

We developed an efficient plant regeneration system from protoplasts f or poplar (Populus alba L.). Protoplasts were isolated from 4-day-old suspension cultures derived from seed-induced calli with a yield of 6. 96x10(6) cells/g fresh weight cells and then cultured at a concentrati on of 2.5x10(5) cells/ml in NH4NO3-free Murashige and Skoog (MS) mediu m supplemented with 5 mu M 2,4-dichlorophenoxyacetic acid (2,4-D), 0.0 5 mu M thidiazuron (TDZ) and 0.5 M glucose as a osmoticum. The plating efficiency of the cultured protoplasts was calculated at 26.5% at day 7 and 31.7% at day 14. Cell colonies were observed after culturing fo r 4 weeks. Regenerated colonies were propagated through subculture in liquid MS medium supplemented with 5 mu M 2,4-D. Buds were induced fro m regenerated calli on MS medium containing 10 mu M kinetin or 1 mu M TDZ. Regenerated shoots were rooted on half-strength MS medium, and th e plantlets were transplanted in soil. Randomly amplified polymorphic DNA analysis did not detect any DNA polymorphism among the regenerated plants.