The Initiation, Multiplication, and Cryopreservation of Fraser Fir (Abies fraseri [Pursh] Poir.) Embryogenic Tissue for Somatic Embryogenesis
Fischer, Susan Taylor
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Fraser fir (Abies fraseri [Pursh] Poir.) is a coniferous tree native to the southern Appalachian Mountains in the United States. Due to its restricted native range in a high-elevation habitat and long reproductive process, the forces of anthropogenic global climate change and invasive pests have made this species vulnerable to extinction (Conifer Specialist Group 1998). Research on ways to propagate mass numbers of conifers like the Fraser fir and restore forest productivity includes clonal propagation through somatic embryogenesis. Such research is critical to help ensure the survival of this species for both environmental and economic reasons. Fraser fir is the most popular Christmas tree in the United States and the primary Christmas tree species grown in North Carolina, where Christmas tree sales alone brought in a revenue of over $75 million dollars in 2011 (NCDA 2012). To explore potential methods of increasing embryogenic tissue initiation and growth, embryogenic tissue initiation and capture media were supplemented with the redox chemical sodium thiosulfate (158.09 mg/L) and were compared to control media. Although the redox medium yielded a higher average percent initiation (29.3% versus 26.9%), the results were not statistically significant (p > 0.05). To assess the effects of toxic carbohydrate hydrolysis products in autoclaved media, growth of embryogenic tissue was recorded for capture media with autoclaved sucrose and compared to the growth of tissue on media with filter-sterilized sucrose. The non-significant results suggest that filter-sterilization of sucrose is not necessary and does not inhibit embryonic tissue proliferation. High-mass initiations were selected for cryopreservation and were analyzed for new growth after removal from cryogenic storage. Ongoing research includes production of somatic embryos from designated high-yielding cultures removed from cryostorage, propagation of those cultures on maturation media, and germination of normal somatic embryos on germination media to effectively create highly efficient protocols for the somatic embryogenesis of Fraser fir.