Symphyotrichum georgianum (Asteraceae), commonly known as Georgia aster, is a candidate for listing under the Federal Endangered Species Act in the four southeastern U.S. states where it lives. Rarity of this species is thought to be attributable in part to small population sizes and limited seed production. Protocols for in vitro germination, sustainable shoot micropropagation, shoot establishment in soil, and seed cryopreservation are presented that will assist in the safeguarding and augmentation of dwindling natural populations. Germination in vitro on growth regulator-free half-strength Murashige and Skoog (MS) medium after sterilization in H2O2 initiated the development of shoot cultures. Shoot multiplication and elongation occurred on half-strength MS salts containing 0.1 mg·L–l benzylaminopurine and 0.2 mg·L–l gibberellic acid, producing an average of 18 new shoots over a 6- to 8-week subculture cycle. Shoots rooted easily when planted into cutting mix after treatment with rooting powder containing indole-3-butyric acid (IBA) or in vitro rooting in medium with or without N-acetyl-L-aspartic acid (NAA). Plant survival after 1 month was 90% or higher for all treatments. Cryopreservation tests with seeds from three populations averaged 46.7% germination compared with control seed (no cryostorage) germination of 43%; differences were not statistically significant. Fresh seeds and seeds equilibrated for 1 to 4 weeks at room temperature and 12% relative humidity did not differ significantly in germination post-cryopreservation. Initial observations suggest that Georgia aster rapidly loses seed viability over 1 to 2 years when stored at room temperature. The ability to increase seed longevity through cryopreservation storage may be a critical step in the conservation of this species.
Sullivan Lynch, Rachel K. Johnston, Ron O. Determann, Jennifer M. Cruse-Sanders and Gerald S. Pullman
Cameron Northcutt, Daniel Davies, Ron Gagliardo, Kylie Bucalo, Ron O. Determann, Jennifer M. Cruse-Sanders and Gerald S. Pullman
The genus Sarracenia forms a group of carnivorous pitcher plants native to North America. Habitat destruction and overcollection have caused pitcher plants to become rare, including U.S. federally endangered S. oreophila as well as S. leucophylla and S. purpurea spp. venosa (Raf.) Wherry, both listed as endangered in several states. Protocols for in vitro germination, sustainable shoot micropropagation, shoot establishment in soil, and seed cryopreservation are presented. Six-min sulfuric acid scarification treatments coupled with appropriate tissue culture media resulted in germination in vitro within 3 weeks, often reaching greater than 50%. Best germination for S. leucophylla and S. purpurea occurred on one-third strength Murashige and Skoog (MS) salts, whereas S. oreophila germinated best on one-sixth strength MS salts. Adjustment of pH to 4.5 to simulate a bog environment further increased germination for S. leucophylla. Shoot multiplication occurred at optimal levels when explants were placed on media in the presence of a cytokinin without auxin with greatest multiplication on 6-benzylaminopurine (BAP) or trans-zeatin and best shoot quality on trans-zeatin. Plant establishment in soil required both an in vitro rooting treatment and use of shoot clusters resulting in greater than 80% survival in soil. Seed cryopreservation tests with all three species suggest storage in liquid N2 followed by in vitro micropropagation and plant establishment can be used to preserve material long term.