Analysis of Flower Color Diversity in Phalaenopsis Based on Anthocyanin Metabolism

Phalaenopsis hybrids are the most popular potted flowers in flower markets worldwide because they exhibit various flower colors, including yellow, green, white and red-purple. A thorough assessment of petal color polymorphism in Phalaenopsis enables the promotion of mechanistic studies on floral coloration regulation. In this study, we collected 156 Phalaenopsis germplasms to assess their chromativity value (L*, a* and b*), and then divided them into six groups according to their petal color: white (21), green (11), yellow-orange (37), pink (40), purplish-red (25) and dark red (22). Significant correlations were detected between petal color chromaticity indices and both the total concentration and the compositional ratio of the two primary anthocyanin components: cyanidin 3,5-O-diglucoside (Cy3G5G) and delphinidin 3,5-O-diglucoside (Dp3G5G). The red petal phenotype was largely determined by high accumulations of Cy3G5G and Dp3G5G, as well as a high Cy3G5G/Dp3G5G ratio. By integrating CIELab color parameters with anthocyanin composition and gene expression analyses, a quantitative regulatory model for Phalaenopsis flower color was established. We have revealed that the phenotypic traits of high a* and low L* values are directly associated with the high expression of key structural genes (PhF3′H, PhDFR, PhF3′5′H). These results provide molecular markers and a screening basis for screening, enabling directional flower color breeding, and significantly enhancing the predictability and accuracy of breeding programs.