2019 ASHS Annual Conference

Big-bracted dogwoods (Cornus ssp.) are small, spring-flowering ornamental trees prized for their beautiful blooms with showy bracts, attractive fruit, and fall color. Cornus florida and C. kousa are two of the most popular species for cultivated landscapes. Cornus florida is native to the eastern United States and blooms early in the spring before its leaves appear. The Asian native C. kousa blooms about a month later and has gained popularity in recent years due to its improved disease and pest tolerance. Hybrids between the two species can also be found in cultivation. In this study, we used the genotyping-by-sequencing (GBS) approach to discover single nucleotide polymorphism (SNP) and insertion and deletion (indel) markers in the Rutgers University Cornus cultivar collection (n=108) and in wild-collected Cornus from several arboretums’ collections (n=30). This marker data was used to examine relationships, clonal identities, genetic diversity, and population structure. DNA was extracted using the Qiagen DNeasy Plant Kit and quality controlled with a spectrophotometer. To prepare the GBS libraries, DNA samples were double digested with PstI-HF and MspI restriction enzymes, barcoded, and multiplexed. The libraries were sequenced by Genewiz labs in South Plainfield, NJ using paired-end Illumina sequencing. SNPs and indels were called by the bioinformatics pipeline GBS-SNP-CROP and the 1,250 most informative markers were used in downstream analysis. A cluster dendrogram was made with the R package pvclust, population structure was investigated with STRUCTURE, and diversity indices and relationships between and among the cultivars and wild-origin accessions were calculated. The results provide valuable insight into the genetic diversity and population structure of these important landscape plants. They can guide future germplasm collection efforts and aid parental selection in breeding by helping to avoid choices that may narrow the gene pool.