Propagation for the Conservation of Pityopsis ruthii, an Endangered Species from the Southeastern United States

Abstract

<jats:p><jats:italic>Pityopsis ruthii</jats:italic> is an endangered species endemic to the Hiwassee and Ocoee Rivers in Tennessee. As part of a recovery effort focused on <jats:italic>P. ruthii</jats:italic>, vegetative propagation and in vitro multiplication and seed germination techniques were developed. Plants were vegetatively propagated using greenhouse stock plants and wild-collected stems. Rooting occurred with and without auxin treatments but was greatest when 0.1% indole-3-butyric acid (IBA) talc was applied to the vegetative cuttings; rooting was lowest when flowering stems were used. Pro-Mix BX substrate provided the most consistent rooting. In vitro multiplication was accomplished by the removal of lateral shoots from in vitro-grown plants that were rooted on Murashige and Skoog (MS0) basal medium with 270 clones produced from a single individual after 4 months. Nineteen clones were transplanted and secured with bonded fiber matrix into their natural habitat and 14 survived for 1 year. To avoid genetic swamping of native populations with the introduction of large numbers of genetically identical individuals through clonal propagation, seed-based propagation efforts were explored. Open-pollinated seeds were collected, disinfested and germinated, and seedlings established on MS medium. Seeds were submersed in 70% ethanol for 1 minute and briefly flamed. Seeds were surface-sterilized in a range [10% to 50% (v/v)] Clorox<jats:sup>®</jats:sup> bleach solutions with vigorous shaking for 20 minutes, rinsed three times in sterile water, and germinated on MS0. Removal of pappus from seeds was required for successful disinfestations, but the bleach concentration was not critical. Successful propagation is a step toward the conservation and recovery of <jats:italic>P. ruthii</jats:italic> and should allow future reintroduction projects.</jats:p>

Population Structure and Genetic Diversity Within the Endangered Species Pityopsis ruthii (Asteraceae)

“…Ongoing pollination studies and reintroduction efforts add to the effort base of knowledge on the ecology of this endangered species ( Wadl et al, 2014 , 2018 ; Moore et al, 2016 ). With the habitat and topography of P. ruthii , surrounded by high ridges and ineffective seed dispersal mechanisms, the species may not be able to migrate with warming climates.…”

“…Along with understanding the ecology of the species, a viable method of introducing diversity into the natural habitat is necessary. Cultivation of plants is possible through both stem cuttings and tissue culture, providing methods for reintroduction studies; it is feasible to grow P. ruthii seedlings in vitro and transplant seamlessly into the natural habitat ( Wadl et al, 2014 , 2018 ).…”

“…Studies on genetic diversity have been limited prior to the development of microsatellite markers for P. ruthii ( Wadl et al, 2011a ). Notably, in vitro ( Wadl et al, 2011b ) as well as vegetative ( Wadl et al, 2014 ) propagation methods for P. ruthii were developed to enable reintroduction and augmentation studies ( Wadl et al, 2018 ). The U.S.…”

“…This study is the first to use highly variable microsatellite loci to examine the genetic diversity and population structure of P. ruthii . The results of this study provide valuable genetic information that can be combined with the development of effective propagation and reintroduction techniques ( Wadl et al, 2011b , 2014 ), geospatial mapping of all known occurrences, and stressors affecting P. ruthii ( Moore et al, 2016 ) to guide conservation and management decisions for the species.…”

Phenotypic plasticity and genetic diversity elucidate rarity and vulnerability of an endangered riparian plant

“…We identified viable seeds as described by Wadl et al (2014) and sowed six to eight viable seeds representing half to full siblings per parent individual from each sampled population into each of four 7‐cm 2 × 8.5‐cm‐deep pots filled with a potting medium (Pro‐Mix Bx Biofungicide + Mycorrhizae, Premier Tech Horticulture, Quakertown, PA, USA). Although this growth environment differs from the boulder cracks in which P. ruthii is generally found, our use of potting mix in pots was informed by previously successful protocol for growing P. ruthii (Wadl et al, 2014) with the consideration of the endangered status of this species and our limited seed supply. Using a common potting medium for both P. ruthii and P. graminifolia also allowed us to control for the influence of soil type on measured outcomes.…”