In this work, tissue culture techniques were developed for two purposes: the production of Norway spruce (Picea abies [L.] Karst.) forest regeneration material with somatic embryogenesis (I–III) and the conservation of genetic resources of European white elm (Ulmus laevis Pall.) and wych elm (Ulmus glabra Huds.) with cryopreservation and organogenesis (IV, V).
In P. abies somatic embryogenesis, zygotic embryos are used as explants to produce embryogenic tissue, which can be matured into copies of the initial embryo for clonal propagation. In Paper I Plantform temporary immersion system bioreactors were tested for P. abies somatic embryogenesis. The production of cotyledonary embryos in bioreactors required adding steps to the protocol and the bioreactors were laborious to use. In Paper II growing embryogenic tissue in suspension culture was evaluated. Suspension culture is more scalable than propagation on a semi-solid media. However, it required rinsing the tissue before maturation and it could benefit from optimizing the media composition. Higher hydrogen peroxide content was observed in embryogenic tissue grown in suspension than on semi-solid media, but no conclusive evidence of higher oxidative stress in suspension culture was found. In Paper III, filter disc cultures grew faster than clumps on semi-solid media and produced slightly more embryos. The storage compound profile of somatic embryos was most similar to the zygotic embryos at 4–8 weeks of cold storage.
In organogenesis, plant organs and new plants are clonally propagated from meristematic tissues or through a callus phase. In Paper IV, a micropropagation protocol was developed to regenerate U. laevis and U. glabra dormant buds from cryostorage. Both elm species are endangered in Finland and globally threatened by Dutch elm disease. The main challenges were surface sterilization and poor regeneration of U. glabra from cryostorage. In Paper V, dehydration was successfully implemented to improve the regeneration rate.