SOMATIC EMBRYOGENESIS IN CONIFERS - A CASE-STUDY OF INDUCTION AND DEVELOPMENT OF SOMATIC EMBRYOS IN PICEA-ABIES

Vegetatively propagated material offers many advantages over seed mate rial in forest tree breeding research and in reforestation programmes. Evidence is accumulating to suggest that using somatic embryos in for estry is a viable option. However, before somatic embryos can be used optimally in forestry, basic research aimed at increasing the number o f responsive genotypes as well as the age of the primary explant is ne eded. This in turn requires the establishment of a basic understanding of the physiological and molecular processes that underlie the develo pment of somatic embryos. The functions of genes and their development al and tissue specific regulation are studied using transient and stab le transformation techniques. The process of somatic embryogenesis can be divided into different steps: (1) initiation of somatic embryos fr om the primary explant, (2) proliferation of somatic embryos, (3) matu ration of somatic embryos and (4) plant regeneration. Cortical cells i n the primary explant are stimulated to go through repeated divisions so that dense nodules are formed from which somatic embryos differenti ate. The first formed somatic embryos continue to proliferate and give rise to embryogenic cell lines. Embryogenic cell lines of Picea abies can be divided into two main groups A and B, based on morphology, gro wth pattern and secretion of proteins. Our results suggest that extrac ellular proteins play a crucial role in embryogenesis of Picea abies. Somatic embryos from group A can be stimulated to go through a maturat ion process when treated with abscisic acid. Mature somatic embryos ca n develop into plants.