Genetic transformation of silver birch (Betula pendula) by particle bombardment

We used in vitro callus and shoot cultures as target material for genetic t ransformation of silver birch (Betula pendula Roth) by particle bombardment . Cultivation of in vitro shoot cultures before particle bombardment and a long selection period, combined with a high concentration of selective agen t after bombardment, led to the production of transformed plantlets that we re stable, and no escapes were found among the tree lines produced. Clonal variation in transformation efficiency was found in transient expression of the beta-glucuronidase gene in callus cultures and in plantlets transforme d by stable integration of the ribulose-1,5-bisphosphate carboxylase/oxygen ase small subunit (RbcS) and neomycin phosphotransferase (npt2) genes.