Finnish Forest Research Institute  Metla

Media release 15.09.2005

Cloning by tissue culture does not affect genome of silver birch

Cryopreservation and micropropagation, i.e. cloning by tissue culture, are useful methods in forest research and regeneration. To enable the use of these methods, it is essential to maintain genomic fidelity during tissue culture or cryostorage that may last for up to several years. The research done by the Finnish Forest Research Institute (Metla) did not show any effects from micropropagation and cryostorage on the growth characteristics of birch plants. In addition, no differences were observed between the genomes of the donor trees and the regenerated plants.

Micropropagation enables the multiplication of tree individuals with valuable genetic characteristics, such as good growth rate, high quality or other special traits. Cryopreservation, i.e. storage of the genetic material in liquid nitrogen at -196 °C can be used for preservation of selected trees. Cryostored tissues are protected from the effects of external conditions.

As tissue culture and cryopreservation periods become longer, the importance of ensuring genetic fidelity of material subjected to these techniques has been emphasized. In the Metla study, it was observed that the length of tissue culture or cryostorage periods (3 months to 5 - 6 yrs) or the use of five different cryopreservation techniques did not affect the growth rate or the branchiness of the produced plants during the first years in nursery.

Furthermore, no differences were found in the cellular and molecular level when the number of chromosomes and DNA-markers were compared between the donor trees and the regenerated birch plants. On the basis of these results, even a long-term tissue culture or cryostorage does not affect the genetic fidelity in silver birch.

Cryopreservation of genetic material is suitable for tree species, such as silver birch, that can be cloned by micropropagation. It can be used as a parallel technique or as an alternative to storage of genetic material using traditional techniques, such as clone collections, when conserving the genomes of selected elite trees as well as trees with rare, valuable or interesting traits. Cryopreservation is used increasingly as a tool in biotechnological research and tree breeding: valuable tissue cultures can be cryostored for future needs.

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