The molecular basis underlying phenotypic diversity in Camellia flower coloration and the evolution of research paradigms

• Flavonoid composition and content determine Camellia petal coloration. • Red pigments (cyanidin derivatives) dominate over 95 % of cultivars. • Yellow coloration is mainly driven by flavonols (Qu3G, Qu7G) rather than carotenoids. • Modulating DFR/FLS competition and MBW factors can redirect color phenotypes. • Breeding approaches (hybridization, MAS, gene editing) accelerate color improvement. Camellia, recognized as one of China's Top Ten Traditional Famous Flowers, holds global significance as a premier ornamental plant in horticulture. Flower coloration stands as one of the most critical ornamental traits in Camellias. However, current Camellia cultivars exhibit limited color diversity, predominantly featuring red-dominated spectrum with rare yellow and multicolored cultivars. Although genes associated with flavonoid biosynthesis have been partially characterized, the genetic and transcriptional regulatory mechanisms underlying Camellia flower coloration remain incompletely elucidated. Furthermore, structural genes along the flavonoid biosynthetic pathway have not been fully characterized. This knowledge gap underscores the necessity to systematically decipher the genetic architecture and molecular regulatory networks governing floral pigmentation, which will establish theoretical foundations for breeding novel color cultivars. This comprehensive review examines the pivotal role of flavonoids in Camellia coloration, analyzes the impacts of physicochemical factors on pigmentation dynamics, and explores molecular regulatory mechanisms underlying flavonoid biosynthesis. It further synthesizes recent advancements in breeding strategies for Camellia color improvement. This synthesis aims to provide valuable references for developing novel Camellia cultivars with enhanced color phenotypes through targeted genetic manipulation and precision breeding approaches.