Assessing the genetic diversity of the genus <i>Viburnum</i> using simple sequence repeats

The genus Viburnum was established in 1753 by Linnaeus and is the largest genus in the Adoxaceae and consists of approximately 160 species. Viburnum species are small trees which grow throughout the temperate regions of the Northern Hemisphere (Hoch, 1995). While this genus shares little variety in fruit and flower morphology, it is diverse in many other traits. As molecular studies advance, this large genus continues to undergo reclassification. Here three SSR libraries were constructed to discern additional molecular insight into this vast genus.

Microsatellite markers were developed to characterize Viburnum on several different levels. V. dilatatum is an introduced Asian species that has a wide range of desirable horticultural traits, but this is countered with a propensity for its seedlings to become invasive, therefore creating an interest in the genetics and breeding of this species. Eleven SSR markers were used to characterize V. dilatatum, and are expected to aid in breeding programs that are attempting to develop new cultivars and assist with early detection and screening of plants that have escaped cultivation.

Genetic diversity and population structure was examined in the native species V. rufidulum. The populations examined were found to have a low to moderate genetic differentiation and high level of gene flow. The greatest genetic variation was found to exist within populations. This coupled with the high cross transferability of the SSR markers to other Viburnum species are expected to be helpful in refining the phylogenetic relationship of Viburnum and other genera in Adoxaceae.

In the past the Viburnum has undergone various reclassifications based on morphological and molecular studies. Thirty-three microsatellite markers were developed from V. dilatatum, V. farreri, and V. rufidulum and utilized to characterize the relationships between various taxa. Cross transferability of the loci was analyzed and the polymorphic information content ranged from 0.42 to 0.97%. Three loci were used to construct a phylogenic tree. Sequence alignments indicated well preserved primer sites and resulted in cross transferability among many Viburnum species and to other genera. We expect this set of SSR markers to of utility in future genetic studies, marker assisted selection, and breeding programs.