cryopreservation method maintaining the genetic fidelity of a model forest tree, Populus tremula L. X Populus tremuloides Michx

The aim of the present study was to develop an effective cryopreservation method for hybrid aspen (Populus tremula L.xPopulus tremuloides Michx.), an economically important woody plant and widely used model system of forest scientists. Specific attention was paid to genetic fidelity of cryopreserved materials and transgene stability after retrieval. Three different kinds of cryopreservation protocols were applied, i.e. the slow cooling of PGD- treated in vitro apical segments, the vitrification of PVS2-treated in vitro buds and the slow cooling of dormant in vivo buds. The slow cooling of in vivo buds proved to be the most appropriate way to cryopreserve the samples, resulting in a generally excellent regrowth rate of 72-96%. According to random amplified polymorphic DNA (RAPD) assays the genetic fidelity of the cryostored materials was maintained during both slow cooling and vitrification. In addition, neomycinphosphotransferase II (nptII) gene was found to be stable in transgenic lines after cryopreservation. The results clearly indicate that it is possible to apply cryopreservation techniques to preservation of valuable clones and transgenic lines of hybrid aspen.