White spruce (Picea glauca) embryogenic callus was obtained using 3- to 11-year-old seeds as a source of zygotic embryos. They were cultured on half-strength Litvay's medium supplemented with 10 μM 2,4-dichlorophenoxyacetic acid, 5 μM benzylaminopurine, 1 g/L casein hydrolysate, 500 mg/L glutamine, and 1% sucrose. The frequency of induction of embryogenic callus was significantly improved by incubation at 25 °C and by a 4-h imbibition of the seeds. The yield of embryogenic callus was significantly affected by the geographic provenance of the seeds and by their number of years in storage. A significant correlation was also found between the yield of embryogénie callus and the percentage of germination of the seedlot used. Even after 11 years of storage, 40% of the zygotic embryos could produce an embryogenic callus when dissected from seeds with a high germination rate. Somatic embryos were matured after transfer onto an embryo development medium composed of the same medium but including 6% sucrose, 1 μM 2,4-dichlorophenoxyacetic acid, and 5 μM kinetin. The somatic embryos developed further under in vitro conditions and were then transplanted into soil. The somatic embryoderived plantlets established in the greenhouse were similar to control plantlets obtained from germinated seeds. Mature embryos from stored seeds were shown to constitute a valuable source for white spruce somatic embryogenesis.
Genetic control and evolutionary potential of a constitutive resistance mechanism against the spruce budworm (Choristoneura fumiferana) in white spruce (Picea glauca)
