Integration of somatic embryogenesis in a tree breeding programme: a case study with Picea abies

Potential for integration of somatic embryogenesis in a breeding programme of Norway spruce (Picea abies (L.) Karst.), and its limitations, were investigated in a case study with an ordinary breeding population. A standard protocol was used for initiation, proliferation, and cryopreservation of embryogenic cultures; maturation of somatic embryos; and plant regeneration. This is a practical necessity when dealing with a large number of genotypes. Proliferation and maturation were identified as major constraints. Clear differences among families were seen for proliferation and for maturation. For plant regeneration, differences among cell lines within families were considerable while no significant differences were found among families. Significant differences among male parents were obtained for proliferation and maturation. Our calculations show that by using an improved standard protocol, at least one third of the genotypes can be propagated via somatic embryogenesis. No clear relationship was found between embryogenic characters of selected parents based on progenies and corresponding parental breeding values for growth and phenology characters. Three years can be gained by using somatic embryogenesis instead of cuttings in a breeding programme. Maintained propagation ability by including cryopreservation in the breeding programme will provide a very useful link between breeding and mass propagation. The results are encouraging, but further improvement of the standard protocol is necessary.