Optimization of in vitro micro propagation and regeneration for Populus x interamericana and Populus x euramericana hybrids (P-deltoides, P-trichocarpa, and P-nigra)

A rapid and efficient micropropagation method has been established for six European poplar cultivars of economic interest - four Populus x interamericana and two Populus x euramericana. Using a three-step procedure, we were able to regenerate plantlets from callus and acclimate them within 4 months. In the first step. callogenesis was induced when explants were cultured for 25 days on culture medium supplemented with 10 muM alpha-naphthaleneacetic acid and 5 muM N-6(2-isopentenyl) adenine. Bud regeneration followed by shoot elongation was then obtained from callus tissue by combining the cytokinin-like compound thidiazuron with the surfactant Pluronic F-68 at concentrations adjusted for each cultivar. The usefulness of this procedure in the area of genetic engineering is discussed.