Efficient plantlet regeneration from protoplasts isolated from suspension cultures of poplar (Populus alba L.)

We developed an efficient plant regeneration system from protoplasts for 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 concentration of 2.5x10(5) cells/ml in NH4NO3-free Murashige and Skoog (MS) medium supplemented with 5 mu M 2,4-dichlorophenoxyacetic acid (2,4-D), 0.05 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 for 4 weeks. Regenerated colonies were propagated through subculture in liquid MS medium supplemented with 5 mu M 2,4-D. Buds were induced from 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 the plantlets were transplanted in soil. Randomly amplified polymorphic DNA analysis did not detect any DNA polymorphism among the regenerated plants.