Morphology and Inheritance of Wavy Flower Form in Periwinkle (Catharanthus roseus (L.) G. Don)

Periwinkle (Catharanthus roseus (L.) G. Don) is renowned for its diverse colors and resilience to harsh climates. Still, most commercial cultivars predominantly display flat petals. Using cultivars representing non-wavy, medium-wavy, and extreme-wavy flower forms, we examined morphological differences in both their mature leaves and floral organs. Phenotypes of self-pollinated (S₁) and cross-pollinated (F₁, F₂) populations further underscored their morphological distinctions. Specifically, the extreme-wavy type displayed elliptical leaves, broader than the non-wavy type, with a pronounced acute apex and a notably wrinkled blade surface. The non-wavy type also bore intensely wavy petal margins and exhibited a smaller flower diameter, with a notable absence of a functional pistil, indicating female sterility. The insights gained allowed for early differentiation during the seedling period. This study suggests that the inheritance of these flower forms is regulated by an allele WAVY (Wv), which exhibits incomplete dominance. Concretely, the non-wavy form arises from a recessive homozygous expression (wvwv), the extreme-wavy from a dominant homozygous expression (WvWv), and the medium-wavy from a heterozygous expression (Wvwv). This study provides clarity on morphological descriptions and inheritance patterns of wavy flower forms, facilitating strategic breeding of diverse flower forms in periwinkle.