A set of SSR markers to characterize genetic diversity in all Viburnum species

About 160 species are classified within the Viburnum genus and many of these are cultivated for horticultural purposes. The vast dispersal of Viburnum makes the genus a useful model for studying evolutionary history and inferring how species expanded into their current distributions. Simple sequence repeat (SSR) markers were previously developed for five Viburnum species that were classified within the four major clades (Laminotinus, Crenotinus, Valvatotinus, and Porphyrotinus). The ability of some of these markers to cross-amplify in Viburnum species has been scantly evaluated, but there has not been any genus-wide assessment for the markers. We evaluated a collection of 49 SSR markers for the ability to cross-amplify in 224 samples, including 46 Viburnum species, representing all 16 subclades, and five additional species in the Viburnaceae and Caprifoliaceae. A subset of 14 potentially comprehensive markers for Viburnum species was identified and evaluated for the ability to detect polymorphisms in species outside of their respective clades. The 49 markers had overall amplification success in 52% of the samples, including a 60% success rate within the Viburnum genus and 14% in other genera. The comprehensive marker set amplified alleles in 74% of all samples tested, including 85% of Viburnum samples and 19% of outgroup samples. To the best of our knowledge, this is the first comprehensive set of markers able to characterize species across an entire genus. This set of markers can be used to assess the genetic diversity and population structure of most Viburnum species and closely allied species.

Development and Characterization of 20 Genomic SSR Markers for Ornamental Cultivars of Weigela

Weigela (Caprifoliaceae) is a genus of ornamental plants popular for its phenotypic variation and hardiness, that includes species hybridized to produce the commercially available cultivars. Despite its popularity, limited genetic resources exist for the genus. Twenty genomic simple sequence repeat (gSSR) markers distributed across the genome were developed using low coverage whole-genome sequencing data of Weigela Spilled Wine^®. A cross-amplification evaluation with these 20 gSSR markers on a collection of 18 Weigela cultivars revealed a total of 111 unique alleles, including 36 private alleles. A diagrammatic key was constructed to identify cultivars using only six of the gSSR markers, demonstrating the newly developed gSSR markers are immediately useful for cultivar identification. Future uses could include breeding with marker-assisted selection, determining the history of hybridization of the current cultivated lines, aiding in the construction of genetic maps, and assessing the patterns of population genetic structure of Weigela spp.