Somatic Embryogenesis and Plant Regeneration from Mature Zygotic Embryos of Red Spruce

Somatic embryogenesis and plantlet regeneration were obtained from mature embryos of red spruce, Picea rubens Sarg. Embryogenic tissues were produced from both 5- and 20-yr-old seed collections. The basal medium used was von Arnold and Eriksson's (AE) salt formulation supplemented with 1,000 mg/L casein hydrolysate, 250 mg/L L-glutamine, 10 μM each of naphthalene acetic acid and N6-benzyladenine (BA), 2% sucrose, and 0.3% Gelrite Gellan gum. Tissues were incubated in the dark at 26 C. Longterm cultures were maintained on the above medium, but with 5 μM BA. Tissues were cultured on phytohormone-free basal medium containing 1% activated charcoal for 7 d, and for maturation were transferred to basal medium containing 20-50 μM abscisic acid. When embryos appeared to be morphologically similar to fully imbibed zygotic embryos, they were removed for germination. They were partially dried and germinated on 1/2 AE at 24 C under reduced light. Plantlets were transferred to sterile peat moistened with 1/4 AE for further growth.