Abstract
Floral morphology is a crucial trait that determines the commercial value of ornamental plants and pollinator preference. Scaevola aemula (Fan Flower) typically develops bilaterally symmetrical flowers, but a recessive mutant with a radially symmetrical flower (peloric) has been isolated from a breeding population. In the present study, we explored the molecular basis of the floral traits of S. aemula. We found a genetic-phenotypic association for the CYCLOIDEA (CYC) gene SaCYC2, which is known as a regulatory gene for floral symmetry in various plants. The peloric flower line had a nonsense mutation immediately downstream of the start codon of SaCYC2 causing a loss of function. RNA-sequencing analysis revealed three paralogous CYC genes in S. aemula, but only SaCYC2 was preferentially expressed in the dorsal side of the petals. Moreover, we developed a co-dominant cleaved amplified polymorphic sequence (CAPS) marker based on the nonsense mutation to verify floral traits, thereby accelerating the selection and breeding of Scaevola spp. Our findings support the conserved function of CYC genes that determine aspects of floral morphology in Asteraceae.