Molecular and morphological data reveal hybrid origin of wild Prunus yedoensis (Rosaceae) from Jeju Island, Korea: Implications for the origin of the flowering cherry

• Premise of the study: The subgenus Cerasus of the genus Prunus includes several popular ornamental flowering cherries. Of the hundreds of cultivars, P . × yedoensis (‘Somei‐yoshino’) is the most popular and familiar cultivar in Korea and Japan and is considered to be of hybrid origin. However, the hybrid origin of P . × yedoensis and its relationship to wild P. yedoensis , naturally occurring on Jeju Island, Korea, are highly controversial. • Methods: We extensively sampled wild P. yedoensis , cultivated P . × yedoensis , and numerous individuals from other species belonging to subgenus Cerasus on Jeju Island. Samples from 71 accessions, representing 13 species and one cultivar ( P . × yedoensis ), were sequenced for nrDNA ITS/ETS (952 characters) and seven noncoding cpDNA regions (5421 characters) and subjected to maximum parsimony and maximum likelihood analysis. Additive polymorphisms in the ITS/ETS regions were confirmed by cloning amplicons from representative species. • Key results: The nuclear (ITS/ETS and G3pdh ) and cpDNA data, along with several morphological characteristics, provide the first convincing evidence for the hybrid origin of wild P. yedoensis . The maternal parent was determined to be P. spachiana f. ascendens , while the paternal parent was unresolved from the taxonomically complex P. serrulata / P. sargentii clade. The presence of two kinds of ribotypes was confirmed by cloning, and the possible origin of cultivated P . × yedoensis from wild populations on Jeju Island was also suggested. • Conclusions: Bidirectional and multiple hybridization events were responsible for the origin of wild P. yedoensis . Extensive gene flow was documented in this study, suggesting an important role of reticulate evolution in subgenus Cerasus .