Propagation of Ruth's Golden Aster (Pityopsis ruthii), An Endangered Herbaceous Perennial

Ruth’s golden aster (Pityopsis ruthii) is a federally endangered plant that occurs along the Hiwassee and Ocoee Rivers in Polk County, Tennessee. This narrowly- distributed herbaceous perennial grows in crevices on exposed phyllite and graywacke rocks that are situated in and between the river channel and the adjacent forested slopes. The known populations occur on river systems that are managed by the Tennessee Valley Authority (TVA). A long-term monitoring program began in 1986 for Ruth’s golden aster. The Ocoee River population is considered stable, but the Hiwassee River population has experienced substantial declines in the total number of plants since monitoring began. The capability to successfully reintroduce individual Ruth’s golden aster plants into suitable habitat will be an essential part of a long-term conservation strategy for the species, but efforts to establish plants in the wild have been unsuccessful. Propagation of Ruth’s golden aster is critical for conservation of existing populations and provides back-up collections of plants for restoration should wild plants perish. For ex situ preservation of rare plant species seed based methods are generally the most efficient. However, growing Ruth’s golden aster from wild-harvested seed has proven unreliable because seed set and germination rates vary widely with the timing and location of collection. In addition, collecting large numbers of seed from wild populations to compensate for this variability may not be sustainable given the imperiled status of the species and the remote locations where it grows. Successful mircorpropagation of the species has been documented recently. Plants of Ruth’s golden aster have been cloned via in vitro culture of axillary buds, flower receptacles, leaf explants, and stem cuttings and in vivo through stem cuttings. Flower receptacles and leaf explants were cultured on Murashige and Skoog medium (MS) supplemented with 11.4 µM indole-3-acetic acid (IAA) in combination with 2.2, 4.4 or 8.8 µM 6-benzyladenine (BA) and for both explant sources, shoot regeneration on MS medium amended with 11.4 µM IAA and 2.2 µM BA was significantly higher (P<0.05) than on other treatments. Additionally, rooted plants were obtained from axillary buds and stems cuttings that were cultured on MS medium without plant growth regulators. Terminal stem cuttings about 6.4 cm (2.5 in) long treated with 3000 ppm indole-3-butyric acid (IBA) rooted within 2 weeks under intermittent mist. These propagation methods will allow fast and cost effective large scale production Ruth’s golden aster for use in reintroduction or supplementing wild populations.