The Development and Use of SSR Markers for Penstemon scariosus, a Species with Horticultural Potential

Penstemon scariosus var. scariosus is horticulturally interesting because of its rather large showy blossoms, and its attractive emerald to dark green and somewhat compact foliage found in plants from some accessions. Furthermore, this perennial plant has potential in xeric urban landscapes of the western US because it flourishes in arid and desolate environments at higher altitudes. Finally, P. scariosus var. albifluvis is being considered for listing under the Endangered Species Act of 1973 due to recovery of hydrocarbon deposits located at sites where this variety is almost exclusively found. Thus, the horticultural potential of var. scariosus and the rarity of var. albifluvis underlie the importance of understanding of the phylogenetic relationship within P. scariosus. To do so, we developed a set of ten new SSR (simple sequence repeat) markers specifically to study this species. These markers were identified using a genomic reduction protocol in combination with next-generation sequencing of P. scariosus. Besides these ten markers, we tested all previously reported Penstemon SSRs and identified six additional markers that were robust, reliable, and polymorphic across a subset of 27 accessions including all four varieties of P. scariosus and eight closely related taxa. Of these 16 markers we selected ten that combined well together when labeled with either NED (yellow), 6-FAM (blue), or HEX (green) utilizing the ABI 3730xl with Gene Scan 500 ROX Size Standard. We utilized those ten markers to test the individual samples of our collected 76 accessions. The results of this study indicate that one taxon (P. fremontii var. glabrescens) is genetically distinct from P. fremontii and was elevated to its own species. Additionally, our data suggests that P. scariosus var. albifluvis is genetically independent and unique compared to the rest of the P. scariosus varieties. The intraspecific phylogenetic relationships morphological distinction of three remaining varieties of P. scariosus (var. cyanomontanus, garrettii, and scariosus) are less clear.