Embryogenic Callus Induction in Fraser Fir

Abstract

Mass propagation of Fraser fir [Abies fraseri (Pursh) Poir], a valuable Christmas tree species in the United States, is problematic because methods currently used are inadequate. According to our results with somatic embryogenesis, the culturing methods used with other Abies species are applicable to Fraser fir. Stage 1 somatic embryogenic callus, characterized by suspensor cells and embryo heads, was obtained at low frequency using Schenk and Hildebrandt medium supplemented with 5 mm glutamine, 0.05% casein hydrolysate, 0.01% myoinositol, 2% sucrose, 5 μM benzyladenine, and 0.6% agar. The developmental stage of the embryo was important; embryogenic callus was obtained only with immature, precotyledonary embryos, not with fully formed embryos. Cold storage of cones containing immature embryos inhibited callus proliferation. Genotype was significant in that 35 of 44 families tested proliferated callus; however, only one embryo within one family continued proliferation to produce stage 1 embryogenic callus. Fully formed somatic embryos were not produced because the callus did not continue to proliferate. Although these experiments met with only limited success, they demonstrate the potential for somatic embryogenesis in Fraser fir and the general applicability of methods used with other Abies species.