Molecular Markers Within and Beyond Viburnum: A Single Set of SSRs for an Immense Genus

Comprised of more than 160 species, Viburnum is the largest genus in the Viburnaceae (formerly Adoxaceae) alongside Adoxa and Sambucus. The native range of Viburnum species spans much of the Northern Hemisphere and extends into the mountains of South America and Southeastern Asia. Their wide geographic range has made Viburnum particularly interesting to phylogeographers and phylogeneticists. This diverse genus is also horticulturally valuable with varying traits such as fragrance, fruit color, and bud and inflorescence form. There is sufficient morphological diversity in the genus for there to be more than 70 species and intraspecific hybrids in cultivation, and in 2017, viburnums generated $23.2 million in wholesale and retail sales in the U.S. alone. Viburnums’ horticultural value is in large part due to their ornamental qualities varying throughout the year, but also lasting much of the year. Typically, molecular markers are developed only for single species when breeding and assessing genetic diversity. This is despite many markers displaying cross-transferability to other closely related species and genera. Microsatellite markers, also known as simple sequence repeats (SSRs), were previously developed from three of the four large clades of Viburnum (Valvatotinus, Laminotinus, and Porphyrotinus). For markers to span the entire genus, genomic SSRs (gSSRs) were developed from V. farreri, which is a member of the East Asian center of diversity, the fourth large clade (Crenotinus), and a popular ornamental in the United States. The four sets of markers (a total of 49) were then tested on 46 Viburnum species and five closely related species in the rest of the Viburnaceae and the Caprifoliaceae. The markers developed here in conjunction with previous markers eliminate the need to develop markers for each species in this massive genus and closely related taxa. These SSRs are suitable and ready to use for breeding, exploring genetic diversity, and delimiting species and cultivars in Viburnum and possibly select species in the rest of the Viburnaceae and the Caprifoliaceae.