Propagation of Ornamental Plants
7(1): 23-28, 2007
PHENOTYPIC EXPRESSION OF LEAF VARIEGATION IN TWO BETULA PENDULA ROTH GENOTYPES FOLLOWING MICROPROPAGATION, CRYOPRESERVATION AND GRAFTING
Leena Ryynanen1* and Tuija Aronen1
1Finnish Forest Research Institute, Punkaharju Research Unit, Finlandiantie 18, FI-58450 Punkaharju, Finland, *Fax: +358 10 211 4201, *E-mail: firstname.lastname@example.org
There are few native deciduous tree species with colourful summer foliage among the trees adapted to the harsh conditions in northern latitudes. The woody plants of more southern origin imported for landscaping need a more temperate climate than that prevailing e.g. in Finland, and they often die during the deep midwinter temperatures that can fall to -40°C, or suffer from spring frosts. Nowadays it is possible to micropropagate almost all the Nordic deciduous tree species, and several ornamental forms of native, well-adapted species, mostly with dark red foliage, have become commercially available. The aim of this study was to clone two new decorative forms of native birch (Betula pendula Roth) having specific leaf colouration. The “golden-veined” (GV) and “white-flecked” (WF) forms of birch were cloned by grafting and micropropagation, and cryopreservability of the in vivo buds of the birches was also tested. All the methods were applicable for both forms, but the WF birch was easier to propagate than GV birch. Grafting of WF birch was more successful, and its regrowth percentages following micropropagation and cryostorage were many times higher than those of GW birch, which were only 6.3% and 6.9%, respectively. In the greenhouse and nursery, the 1- and 2-year-old micropropagated progenies of both leaf colour forms, with or without cryopreservation, failed to express leaf colouration. The typical leaf colouration was, however, observed in the leaves growing on the 2-year-old stems and branches of WF birch grafts. The WF donor tree showed this same phenomenon where more pronounced leaf colouration was found on leaves growing in the more mature parts of the tree.
Key words: Betula pendula Roth, cryopreservation, epigenetic regulation, grafting, micropropagation, leaf colouration