2018 ASHS Annual Conference

Big-bracted dogwoods (Cornus spp.) are small trees that are prized as ornamentals in managed landscapes because of their beautiful spring blooms with showy bracts, striking red fruits, and attractive fall color. Two of the most popular species are C. florida and C. kousa. Cornus florida is native to the eastern United States and blooms early in the spring before its leaves appear. Cornus kousa, from Asia, blooms later than C. florida and is more resistant to powdery mildew and dogwood anthracnose. Vigorous, disease-resistant hybrids between the two species can also be found in cultivation. A performance trial holding 96 different accessions of big-bracted dogwoods was established in 2016 at Rutgers University in New Jersey. In this study, we are using the genotype by sequencing (GBS) approach to discover single nucleotide polymorphisms (SNPs) within our Cornus accessions and use them to examine relationships, clonal identities, genetic diversity, and population structure. As a preliminary trial before including the entire collection, we focused on a subset of 48 accessions: 20 C. florida, 20 C. kousa, and 8 interspecific hybrids. DNA was extracted from dormant flower buds using Qiagen DNeasy Plant Kit, and quality and concentration was quantified with a spectrophotometer. DNA was double digested with PstI-HF and MspI, barcoded, multiplexed, and sent to Genewiz labs for sequencing. The raw data will be analyzed with Stacks, JoinMap, and STRUCTURE. Results, including the number of high quality SNPs as well as indices of diversity and relationships between the preliminary subset of Cornus cultivars, will be presented. These data will support a larger study and provide valuable insight into the genetic diversity and population structure of these important landscape plants, as well as guide future germplasm collection efforts for the development of improved cultivars.