Flower type is the most valuable ornamental trait in floricultural plants, for which the ABCDE model was proposed to explain the identity of each floral organ in flowering plants. The C-class gene AGAMOUS (AG) is responsible for stamen formation and plays an essential role in the double flower phenotype. A previous study in carnation revealed that the mutation in the miR172 binding site of the A-class gene APETALA2 (AP2) leads to petal accumulation. And the expression level of AG was reduced significantly in the double flowers compared with that in the single flowers. However, there was no sequence polymorphism detected between AGs isolated from the double flowers and single flowers. Here, we performed AG analysis using single and semi-double flower carnations, and detected several mutations located in the crucial position like the MADS-box domain in the AGs of semi-double flower carnations while no changes were found at the miR172 binding site of AP2. As a result, the expression levels of AGs are reduced in the semi-double flower carnation, which could be caught by the loss function of AGs. Our data proves that AGs mutations are also associated with the semi-double flower formation in carnation, complementing the lack of research about AG-mutation-associated double flower formation in carnation.

Gypsophila paniculata is one of the most popular cut flowers in the world whose major cultivars are blooming white. As is well known, blue flowers could be generated via the overexpression of the gene encoding flavonoid 3′5′-hydroxylase (F3′5′H) in species that naturally lack it. In this study, we established the regeneration and a genetic transformation system for the commercial cultivar ‘YX4’ of G. paniculata and introduced the F3′5′H of Platycodon grandiflorus (PgF3′5′H) successfully into ‘YX4’ using the established protocol. A total of 281 hygromycin (Hyg)-resistant plantlets were obtained, and 38 of them were polymerase chain reaction (PCR) positive, indicating a 13.5% transformation efficiency. Shoot apex without meristem was more suitable for explant due to its high regeneration capacity, and the supplement of thidiazuron (TDZ) provided the most efficient promotion of adventitious bud induction, whereas the supplement of 6-Benzyladenine (6-BA) and 1-naphthaleneacetic acid (NAA) did not affect much. Additionally, the combination of 1 day (d) pre-culture, 5 d co-culture, 10 min infection, 30 mg·L⁻¹ additional acetosyringone (AS) supplement, and 10 mg·L⁻¹ Hyg selection formed the optimized system for ‘YX4’ transformation. This reliable and efficient agrobacterium-mediated transformation of the valuable commercial cultivar ‘YX4’ will contribute not only to the creation and improvement of G. paniculata cultivars, but also to the function research of genes associated with important ornamental traits.