Objective  Color is the major ornamental characteristics of plants, anthocyanins are the key compounds of flower colors. The types and contents of anthocyanins can provide insight into the mechanism of petal color.

  Method  In this study, 36 samples of three pairs of Rhododendron subgenus Tsutsusi parents and their hybrids were subjected to anthocyanins profiling in petals and their separation characteristics using UPLC –Q –TOF –MS.

  Result  This study identified 17 compounds, including peonindin 3-O-galactoside, delphinidin 3-galactoside, malvidin 3-O-galactoside, and petunidin 3-galactoside, which were detected for the first time in Rhododendron subgenus Tsutsusi. A majority of anthocyanins in Rhododendron subgenus Tsutsusi are cyanidin, peonidin, and petunidin in the form of arabinosides. Cyanidin 3-arabinoside, cyanidin 3-O-glucoside and peonidin are responsible for the red-colored petals in Rhododendron subgenus Tsutsusi. Delphinidin 3-arabinoside, delphinidin 3-O-glucoside, malvidin 3-arabinoside, and malvidin 3-O-glucoside contribute to the petal’s purple color, while petunidin 3-O-arabinoside contributes to their purplish red color. The anthocyanin segregation analysis revealed that peonidin and cyanidin had transgressive inheritance, whereas malvidin 3-arabinoside, malvidin 3-O-glucoside, and petunidin 3-O-arabinoside had paternal inheritance.

  Conclusion  In this study, we demonstrate the coloring mechanism of Rhododendron subgenus Tsutsusi, which provides a reference for parent selection in breeding.