Molecular and morphological evidences for the hybrid origin of Kushui Rose

Natural hybridization has played a significant role in the evolution of the genus Rosa . Kushui Rose ( R. sertata × R. rugosa ) is a natural hybrid of R. sertata and the cultivated rose R. rugosa . We conducted molecular sequence analysis and a morphological traits examination in the related taxa of the genus to test the hybrid origin of Kushui Rose. Although principal component analysis of the morphological characteristics revealed that Kushui Rose was intermediate between R. rugosa and R. willmottiae, and R. sertata , the unambiguous sequence additivities of the nuclear DNAs (ITS and GAPDH ), as well as the incongruence between the nuclear and chloroplast gene trees, revealed that the hybrid origin of Kushui Rose was R. rugosa and R. willmottiae rather than R. sertata . Furthermore, the cluster relationships in the concatenated chloroplast (cpDNA) trees ( psbA-trnH , trnL-F , and trnS-G ) implied that R. willmottiae and R. rugosa acted as the maternal parent and the paternal parent, respectively, during homoploidization speciation. Here, our research provides a more reasonable orientation for further tracing the origin of this hybrid species and research on its horticultural traits with heterosis.