Possibilities and limitations of vegetative propagation in breeding and mass propagation of Norway spruce

The use of vegetative mass propagation in practical forestry with Norway spruce (Picea abies (L.) Karst.) is limited at present, although its potential to deliver high genetic gains is obvious. The objective of this thesis was to study possibilities and limitations of vegetative propagation when applied in different parts of a breeding/mass propagation system for Norway spruce. Two vegetative propagation methods were studied: somatic embryogenesis and cutting propagation. Somatic embryogenesis was accompanied by losses of genotypes during the propagation process. The embryogenic response at proliferation and maturation was under family control, while germination was obtained for all families. Parental effects on proliferation and maturation were found for male parents but not for female. However, no correlations between embryogenic characters and breeding goal traits could be detected on parental level. Shortening of treatment with abscisic acid (ABA) during somatic embryo development gave pronounced positive effects on height growth of regenerated plants. An improved protocol, including five weeks ABA treatment and root development in liquid medium significantly improved performance of the resulting plants. The number of plants with lateral roots at the time of ex vitro transfer increased substantially with this protocol. Lateral roots at ex vitro transfer were shown to be a marker for good height growth and clonal uniformity during the next two years. Selection for height of cutting propagated clones in the nursery resulted in low responses in height after six years in field. The likely reason for this was low correlations between nursery traits and field traits. Genotype x environment interactions in the studied clonal test series varied from close to zero to more than 50% of the clone component. A tendency towards increased interaction components with age was obtained in one of the series. In situations with large genotype x environment interactions, clonal stability over sites should be included in the selection criteria