Insights into historic and genetic relationships of diverse common lilac (Syringa vulgaris) genotypes based on whole-genome profiling

Common lilac (Syringa vulgaris L.) is a popular landscaping plant. Our aim was to obtain a large set of single nucleotide polymorphism (SNP) markers, to reveal the precise identities of the investigated S. vulgaris accessions, and to discover genetic relationships among them. The studied plant material included local Finnish, previously unidentified accessions, known reference cultivars, and so-called historical accessions i.e., old shrubs growing in historic cultural landscapes. We intended to verify cultivar names for some valuable local common lilac accessions and to provide insights into the history of common lilac cultivation in Finland. In the analyses, we used a set of 15,007 SNP markers. First, polymorphic information contents were calculated (mean 0.190, range 0.012–0.500 per marker). Then, to investigate genetic relationships among genotypes, a phylogenetic tree was constructed, and a principal coordinate analysis was conducted. A Bayesian analysis of population structure was performed to determine the number and distribution of genetic clusters among samples. Genetic marker data combined with existing historical and phenotypic knowledge revealed novel information on the unidentified cultivars and on the genetic relationships among studied accessions and solved the arrival and early history of common lilac in Finland. Overall, such comprehensive genomic characterization and deep understanding of genetic relationships of S. vulgaris can be used when utilizing present cultivars and developing new ones in future breeding programs.