Relationship between Anthocyanin Composition and Floral Color of Hibiscus syriacus

Hibiscus syriacus is a highly ornamental flowering shrub widely grown in East Asia. Its abundant flower colors mainly reflect the accumulation of anthocyanins. Classifying H. syriacus petals and identifying the relationship between flower color and anthocyanins can provide references for flower color breeding. With eight cultivars of H. syriacus as experimental materials, the floral color was described using the Royal Horticultural Society Color Chart and the CIEL*a*b* coordinate. The anthocyanin in petals was qualitatively and quantitatively analyzed by using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and the relationships between flower color and anthocyanin were analyzed by using stepwise regression analysis. We divided eight cultivars of H. syriacus into five color lines: red-purple, white, violet, purple, and blue-purple, and then into two groups: purple and red-purple. The results showed that the L* had a significant negative correlation with a* and C*. A total of 52 anthocyanin components were detected in the petals of H. syriacus, including cyanidin, delphinidin, malvidin, petunidin, peonidin, and pelargonidin derivatives. Cyanidin derivatives accounted for the highest proportion, and pelargonidin derivatives accounted for the lowest proportion of the total anthocyanins. Petals of 'Pink Giant' contained the largest number of types of anthocyanin components and the highest total anthocyanin content, while the petals of 'Albus Single' contained the smallest. Petunidin-3-O-glucoside showed a significant negative correlation with L* in the red-purple group and in all cultivars, whereas it showed a significant negative correlation with b* in the purple group. Delphinidin-3-O-(6-O-Malonyl-beta-D-glucoside) exhibited a significant positive correlation with a* in the red-purple group, and delphinidin-3-O-glucoside showed a significant negative correlation with L* in the purple group. Therefore, our results suggest that changing the content of these three anthocyanin components may have the potential to alter the flower color. This research provides scientific guidance and a foundation for the molecular breeding of H. syriacus cultivars with new floral colors.