Somatic embryo maturation, germination, and soil establishment frequencies were compared for two conifer species, white and black spruce (Picea glauca and Picea mariana). The comparison of the two species regenerated and established in soil under the same conditions showed black spruce to be the most responsive. Shorter exposure times to 32 μM abscisic acid were not as effective as maturation on a medium containing 16 μM abscisic acid for 28 days. This gave similar maturation frequencies for the two species (6–8%), and germination frequencies of 64% for white spruce and over 73% for black spruce. Over 1800 black and white spruce plantlets were recovered, and more than 400 were transferred from in vitro to nonsterile conditions. Sixty percent (160) of the black spruce plantlets survived transfer and continued to grow vigorously. By comparison only 18% (29) of the white spruce plantlets survived, and half of these rapidly produced dormant buds and underwent no further shoot growth. White spruce plants that did not produce dormant buds grew vigorously. These results indicate that there are large differences in the ability of these closely related species to respond to plantlet establishment following regeneration from somatic embryos, and that black spruce is highly responsive to micropropagation by this method. Key words: Picea glauca, Picea mariana, somatic embryogenesis, maturation, germination, soil establishment.
