Enhancement of somatic embryogenesis from immature zygotic embryos of Pinus sylvestris

Somatic embryogenesis (SE) is considered the most promising vegetative propagation method for Scots pine (Pinus sylvestris L.), and the aim of the present work was to study ways to improve the individual steps of the technique. According to the results, donor genotype has a significant effect on SE initiation in Scots pine. Relatively good initiation frequencies of 20-30% can be achieved, but there are also recalcitrant families. To obtain high-quality somatic embryos that also perform well as emblings in the greenhouse, the SE cultures should be proliferated and matured as a thin layer spread on filter paper, with a high (80-90 µM) abscisic acid concentration applied during maturation. Filter proliferation was found to result in a slightly smaller number of embryos, but of higher quality, than proliferation as tissue clumps. From maturation, the somatic embryos should be harvested for germination only during a limited period, and their germination performed in vitro on tissue culture media. Specific attention has to be paid to the quality of the somatic embryos; slim-type embryos have the best germination and greenhouse performance. With optimized culture conditions and tight quality control, over 90% of the embryos germinate and develop into vigorously growing emblings.