Seed cryopreservation and micropropagation of the critically endangered species swamp pink (Helonias bullata L.)

摘要

Helonias bullata, commonly known as swamp pink, is a perennial rhizomatous herb native to the eastern coast of the United States that is found mainly in forested wetlands, swamps, and mountain bogs. Habitat destruction has caused H. bullata to become rare, and it is federally listed as threatened. Protocols were developed for in vitro germination, shoot micropropagation, shoot establishment in soil, and seed cryopreservation that will assist in the safeguarding and conservation of dwindling natural populations. Seeds were germinated in vitro on plant growth regulator (PGR)-free 1/3-strength Murashige and Skoog (MS) medium after seed sterilization in H2O2 and used for establishment of shoot cultures. Shoot multiplication and elongation occurred on 1/3-strength MS medium containing 0.25-1 mg/l kinetin or 1-2 mg/l trans-zeatin followed by growth on PGR-free medium. All shoots (100%) rooted when planted directly into potting media. Rapid-immersion seed cryopreservation resulted in statistically significant increases in germination in vitro or in potting mix compared to control treatments. H. bullata seeds share characteristics of both orthodox and recalcitrant seeds including rapid loss of viability over time, survival at 5A degrees C, and survival after cryopreservation. Therefore, they are most accurately classified as intermediate-type seed.