Development of Penstemon scariosus (Plantaginaceae) Microsatellite Markers

Penstemon scariosus Pennell is one of many Penstemon species located in the northeastern corner of Utah and a short distance across the adjacent boarders of Colorado and Wyoming. This perennial plant thrives in arid, almost desolate landscapes to higher altitude forested areas. One distinct variety of P. scariosus, P. scariosus var. albifluvis, is being considered for listing under the Endangered Species Act of 1973 due to hydrocarbon deposits geographically located at sites where this variety is almost solely found. Thus, it is important to understand the phylogenetic relationship within P. scariosus. In order to do so, we needed to develop DNA SSRs (simple sequence repeats or microsatellites). These markers are specifically designed to be robust and reliable when used on P. scariosus and closely related taxa. Although SSR markers have been developed for Penstemon, we needed to redesign four of the six markers previously reported so that they would function appropriately on P. scariosus and closely related species. New SSR marker development was made possible using genomic reduction in combination with next-generation sequencing on samples of the four varieties of P. scariosus. From the sequence of the genomic reduction data, 240 candidate SSRs were randomly selected and designed into primers to determine viability.  Of the 240 markers, 16 displayed reliable and robust polymorphic characteristics across 12 taxa of Penstemon. These 16 microsatellite markers are now being used to do phylogenetic studies on the four varieties of P. scariosus and the two varieties of P. fremontii.