Critical factors affecting ex vitro performance of somatic embryo plants of Picea abies

The potential to use somatic embryos for large-scale propagation of elite g enotypes, for integration into breeding programmes and for connecting breed ing 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 s omatic embryo plants is under a cumulative influence of a number of treatme nts given during the in vitro phase and during the cx vitro establishment p hase. The aim of this study was to identify treatments with a negative infl uence on the subsequent growth of somatic embryo plants of Norway spruce (P icea abies L. Karst.). Based on the results, the time of contact with absci sic acid during somatic embryo maturation and the length of continuous ligh t treatment (CLT) during the first growth period strongly affect the height growth during two successive growth periods. In both cases longer treatmen ts exerted negative effects. Based on these results a new method was set up , which includes: (1) prematuration treatment or the suspension culture in a growth regulator-free medium, by which the maturation step is synchronize d and contracted. and (2) a two-phase germination treatment, first on a sol idified medium and then in a liquid medium. This treatment avoids extended CLT during the first growth period. Another advantage of the two-phase germ ination treatment is a better root-system development. Somatic embryo plant s produced according to this method can be transferred directly from in vit ro conditions to the greenhouse.