Somatic embryogenesis and embryo encapsulation in Fraxinus angustifolia Vhal.

Summary

This is the first paper on somatic embryogenesis in F. angustifolia, an important tree in the Mediterranean Basin for landscaping and wood production. The induction of somatic embryogenesis from immature zygotic embyros and the subsequent development, maturation, encapsulation and conversion of somatic embryos into plantlets, as well as the long-term maintenance of embryogénie capacity, are reported. The developmental stage of immature zygotic embryos affected morphogenic response. An auxin-cytokinin ratio of 2:1 (2,4-dichlorophenoxyacetic acid: benzyladenine) was essential for induction. A combination of 2,4-dichlorphenoxyacetic acid (0.44 |j,M) and benzyladenine (4.4 |j,M) has made it possible to maintain embryogénie capacity for over three years. Mannitol (30 g 1^_1) and activated charcoal (2 g l”¹) positively affected somatic embryo maturation. The encapsulation of somatic embryos in sodium-alginate beads adversely affected plant conversion, regardless of nutrient additions to the alginate. Sixty-five per cent of non-encapsulated somatic embryos were successfully converted into whole plantlets on hormone-free MS medium in comparison to 23% of the encapsulated ones.