The genus Magnolia (Magnoliaceae) comprises more than 130 species distributed predominantly in temperate and tropical regions in Southeast Asia and is valued worldwide for its ornamental traits as well as for timber and medicinal products, and in trade. Despite their favored status, many species of Magnolia are faced with threats from logging, agricultural land use, development, and collection, and are at risk of extinction. Conservation of these species through habitat preservation and in ex situ collections is needed to prevent extinction. To provide a tool for conservation of Magnolia species, microsatellite markers developed previously for Magnolia ashei were tested in 10 other species of Magnolia to determine their transferability across species. Of the 64 primer pairs tested, 21 amplified alleles in the expected size range in all samples; 11 primer pairs amplified clean products in most, but not all, species; 18 primer pairs consistently amplified a polymerase chain reaction (PCR) product in most species, but had either low peak height or other amplification issues; and 14 primers showed excessive stutter, nonspecific amplification, or no amplification. Cluster analysis using the 129 alleles amplified by these 21 simple sequence repeat (SSR) primer pairs generated groups that corresponded to the known taxonomic relationships in this genus.
Chandra S. Thammina, Christopher von Kohn and Margaret R. Pooler
Chandra S. Thammina, David L. Kidwell-Slak, Stefan Lura and Margaret R. Pooler
The redbud (Cercis L. species) is a popular landscape plant grown widely in the United States. There are more than 20 cultivars of eastern redbud (Cercis canadensis L.) and at least three cultivars of Asian taxa (primarily Cercis chinensis Bunge) in the trade. The U.S. National Arboretum (USNA) has a diverse collection of Cercis germplasm collected in North America and Asia. Fourteen genomic simple sequence repeat (genomic-SSR) markers were used to analyze the genetic diversity of 53 accessions of Asian Cercis taxa from our collection, including C. chinensis, Cercis chingii Chun, Cercis gigantea ined., Cercis glabra Pamp., Cercis racemosa Oliv., and Cercis yunnanensis Hu and W. C. Cheng. SSR markers detected an average of 5.7 alleles per locus with a range of two to nine alleles. A dendrogram was generated by unweighted pair group method with arithmetic mean (UPGMA) cluster analysis using the Jaccard similarity coefficient. Four major clusters were identified. Accessions tended to group by taxa or provenance, but with some notable exceptions caused either by misidentification or nomenclatural confusion in the species. This information will be used for collection management and for making decisions in the breeding program to maximize genetic diversity of cultivated Cercis.