Quantitative analysis of floral symmetry and tube dilation in an F2 cross of Sinningia speciosa

• We examine the floral shape variation on offspring of two S. speciosa cultivars.
• We depict shape as symmetry and dilation scores by geometric morphometrics (GM).
• Floral shape variation is associated to inheritance of floral symmetry.
• GM helps to reveal the association of floral traits and their genetic background.

Shape variation within a flower breeding line is a topic of considerable interest to horticulturalists. Sinningia speciosa (Florist's Gloxinia) is a species that presents diversified floral shapes. This study aimed to quantitatively assess floral shape variation in an F2 cross of S. speciosa between a zygomorphic wild variety and an actinomorphic peloric cultivar via geometric morphometrics. The result indicated symmetric variation and tube dilation accounted for the major variance of floral shape changes. We further tested whether these shape variations can be correlated to any inherited genetic variation. ANOVA analysis detected candidate CYCLOIDEA (SsCYC) marker allele that showed strong associations with variations of corolla symmetry and tube dilation. This study demonstrated that using geometric morphometrics might considerably enhance the detection of phenotypic and genetic association on complex floral shape variation.