The genus Pityopsis is comprised of seven perennial species and can be found in the eastern United States, southeast Mexico, Bahamas, and Central America (Belize, Guatemala, and Honduras) (Semple, 2006). Pityopsis ruthii (Ruth’s golden aster) is listed under the Endangered Species Act (ESA) and occurs only along two small reaches of the Ocoee and Hiwassee Rivers in Polk County, TN. It grows in crevices on exposed phyllite and graywacke rocks that are in and between the river channel and the adjacent forested slopes. The most recent census of Ruth’s golden aster populations counted ≈11,150 plants; more than 90% occur along the Hiwassee River (Tennessee Valley Authority, unpublished data).
Despite its critically imperiled status, as evidenced by its small overall population and narrow geographical range, there has been relatively little applied research focused specifically on species recovery. However, the U.S. Fish and Wildlife Service, which is the federal agency charged with safeguarding species listed under the ESA, has outlined recovery criteria for Ruth’s golden aster that highlight the most critical data gaps and research needs [U.S. Fish and Wildlife Service (USFWS), 1992]. The most recent review of the species status cites a continuing need for better ex situ conservation efforts and additional research focused on restoration of Ruth’s golden aster in suitable habitat (USFWS, 2012).
Previous ex situ conservation efforts for Ruth’s golden aster have been focused entirely on long-term seed storage (USFWS, 2012). Provided seeds are available and germinate readily, seed-based methods are often the most efficient means for ex situ conservation (Pence, 2011). However, wild-collected Ruth’s golden aster seeds often exhibit poor germination and produce seedlings with low vigor (Clebsch and Sloan, 1993; Cruzan, 2001; Farmer, 1977; White, 1977). To overcome the limitations of propagating solely with seed and to provide increased flexibility in ex situ conservation efforts, an in vitro propagation protocol was developed (Wadl et al., 2011). Whereas Wadl et al. (2011) demonstrated the capability to produce plants in vitro, further refinement of current techniques is needed to ensure reliable propagation. Although propagating Ruth’s golden aster from seed can be problematic, using seed has the advantage of producing genetically diverse propagules instead of clonal plants, which is essential to minimizing the potential for genetic swamping when producing plants for ex situ conservation and restoration.
Previous efforts to restore Ruth’s golden aster in a suitable, unoccupied habitat were unsuccessful. Cruzan and Beaty (1998) performed several experimental plantings, but after two growing seasons, almost 100% of the transplants had died. The reasons for the experimental failures were not entirely clear, but the investigators recognized the potential for drought stress and soil disturbance to negatively impact reintroduced plants. Although the relative importance of these two factors in the survival of transplanted Ruth’s golden aster is unknown, some attempt to mitigate for drought stress and soil disturbance will be integral to restoring the species into a suitable habitat.
The goal of this study was to refine the standard seed germination protocol, in vitro seed germination methodology, and vegetative propagation techniques, including in vitro multiplication of cloned plantlets, to facilitate ex situ conservation and development of a new methodology for restoring Ruth’s golden aster into suitable habitat.
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