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.Résumé : Le potentiel et les limites de l'intégration de l'embryogenèse somatique dans un programme d'amélioration génétique de l'épinette de Norvège (Picea abies (L.) Karst.) sont évalués dans une étude de cas d'une population normale de croisements. D'un point de vue pratique, lorsqu'un nombre important de génotypes est considéré, un protocole standard a été utilisé pour l'induction, la maintenance et la cryoconservation des cultures embryogènes, la maturation des embryons somatiques et la régénération en plants. La maintenance et la maturation ont été identifiées comme des contraintes majeures. Des différences claires entre les familles ont été observées pour ces étapes. Pour la régénération en plants, les différences entre lignées cellulaires d'une même famille étaient considérables alors qu'il n'y avait pas de différence significative entre les familles. Des différences significatives entre les parents mâles ont été observées pour la maintenance et la maturation. Nos calculs montrent qu'avec l'utilisation d'un protocole standard amélioré, au moins le tiers des génotypes peut être multiplié par embryogenèse somatique. Aucune relation claire n'a été trouvée entre les caractères embryogènes des parents sélectionnés, basé sur leurs descendances, et les valeurs reproductives correspondantes des parents pour la croissance et les caractères phénologiques. On peut gagner trois ans dans un programme d'amélioration génétique par l'utilisation de l'embryogenèse somatique au lieu du bouturage. Le maintien de la capacité multiplicati...

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Height growth during the first and second growth periods (i.e., the June-September period in consecutive years) and intraclonal variation were assessed in 13 Norway spruce (Picea abies (L.) Karst.) clones propagated by somatic embryogenesis. The plants were acclimatized and grown in a greenhouse until mid-July and then transferred outdoors. The clonal mean heights after the first and second growth periods were lower for somatic embryo plants than for seedlings from corresponding families sown at the time of somatic embryo plant ex vitro transfer, because a large proportion of somatic embryo plants were small. We determined whether certain selection criteria at ex vitro transfer can be used to identify somatic embryo plants with height growth characteristics comparable with those of seedlings. Epicotyl length and presence of lateral roots proved to be important parameters for selection, whereas main root length was less useful. A combined selection for somatic embryo plants with lateral roots and with an epicotyl length exceeding 8 mm resulted in taller plants and reduced intraclonal variation after the first and second growth periods. The growth of somatic embryo plants selected in this way was similar to that of seedlings from the corresponding families. We conclude that selection according to these criteria at ex vitro transfer can result in improved performance of clonal stock propagated by somatic embryogenesis.

The potential to use somatic embryos for large-scale propagation of elite genotypes, for integration into breeding programmes and for connecting breeding and mass propagation, is receiving much attention. However, before the methods are applied it is important that the plants regenerated via somatic embryogenesis grow as expected, i.e. as seedlings or cuttings. Growth of somatic embryo plants is under a cumulative in uence of a number of treatments given during the in ×itro phase and during the ex ×itro establishment phase. The aim of this study was to identify treatments with a negative in uence on the subsequent growth of somatic embryo plants of Norway spruce (Picea abies L. Karst.). Based on the results, the time of contact with abscisic acid during somatic embryo maturation and the length of continuous light treatment (CLT) during the rst growth period strongly affect the height growth during two successive growth periods. In both cases longer treatments exerted negative effects. Based on these results a new method was set up, which includes: (1) prematuration treatment of the suspension culture in a growth regulator-free medium, by which the maturation step is synchronized and contracted; and (2) a two-phase germination treatment, rst on a solidi ed medium and then in a liquid medium. This treatment avoids extended CLT during the rst growth period. Another advantage of the two-phase germination treatment is a better root-system development. Somatic embryo plants produced according to this method can be transferred directly from in ×itro conditions to the greenhouse.

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