Inheritance Patterns of Flower Color Traits in Self-Pollinated and Cross-Pollinated Progeny of Four Commercial Catharanthus roseus Cultivars

Periwinkle (Catharanthus roseus (L.) G. Don) has emerged as an important breeding crop in response to global warming due to its heat tolerance and diverse floral colors. In this study, four commercial cultivars of periwinkle were self-pollinated and cross-pollinated. Flower color phenotypes of progeny were classified by hierarchical clustering with RGB color parameters. Our genetic analysis elucidated a multi-locus inheritance model for floral pigmentation. Specifically, the W gene serves as a switch, where its homozygous recessive state produces white flowers and masks all other color genes. When pigmentation is present, the Hf gene dictates an apricot color in its recessive form. The basal colors of purple and magenta are governed by the dominant and recessive alleles of the Ma gene, respectively. The Or and An genes interact to produce pink flowers when both dominant alleles are present, whereas orange/orange-red colors emerge if either locus is homozygous recessive. Beyond these basal colors, the En and Li genes function as intensity regulators, intensifying and diluting the floral color, respectively, in their homozygous recessive genotype. Based on segregation ratios, genetic linkage was identified between the Li and Ma genes, as well as between the En and Or/An genes. By elucidating the inheritance models of periwinkle flower color through color parameter classification, this study provides a strategic framework for future parental selection, progeny trait prediction, and the development of novel flower colors in breeding projects.