SOMATIC EMBRYOGENESIS AND PLANT-REGENERATION FORM 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-mu-M 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. Long-term cultures were maintained on the above medium, but with 5-mu-M 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-mu-M 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.