Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2017
Publication Date: 4/30/2017
Citation: Thammina, C., Kidwell Slak, D.L., Lura, S.B., Pooler, M.R. 2017. SSR markers reveal the genetic diversity of Asian Cercis taxa at the U.S. National Arboretum. HortScience. 52(4):498-502.
Interpretive Summary: Redbuds are popular ornamental small trees or shrubs valued commercially for their showy early spring bloom, heart-shaped leaves, and adaptability to diverse environmental conditions. Each year, approximately one million redbud plants are sold in the United States, with a market value of $27 million. The U.S. National Arboretum has an active redbud breeding program that focuses on developing cultivars that are tolerant to biotic and abiotic stress, can be propagated readily from cuttings, and have superior ornamental traits. In support of the breeding program, the National Arboretum has amassed a diverse collection of redbud germplasm collected in North America and Asia, as well as representative redbud cultivars sold in the U.S. Because of their increasing popularity in cultivation in the U.S. and confusion over species distinctions, we used molecular markers to clarifying the identity and diversity of the Asian redbud accessions in our collection. This information has practical implications for the breeding program, as well as for efficient management of germplasm collections.
Technical Abstract: The redbud (Cercis L. species) is a popular landscape plant grown widely in the United States. There are more than twenty cultivars of eastern redbud (Cercis canadensis L.) and at least three cultivars of Asian taxa (primarily C. chinensis Bunge) in the trade. The U.S. National Arboretum (USNA) has a diverse collection of Cercis germplasm collected in North America and Asia. We used 14 genomic simple sequence repeat markers (genomic-SSRs) to analyze the genetic diversity of 53 accessions of Asian Cercis taxa from our collection, including C. chinensis, C. chingii Chun, C. gigantea ined., C. glabra Pamp., C. racemosa Oliv., and C. yunnanensis Hu & W. C. Cheng. SSR markers detected an average of 5.7 alleles per locus with a range of 2 to 9 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.