Flower morphology and biometrical aspects in rolB and ORF13a Kalanchoë blossfeldiana ‘Molly’ lines

Kalanchoë blossfeldiana and its derived hybrids comprise one of the most important potted plants in Europe and ranks first in Denmark’s best-selling ornamental species. There is a strong market for Kalanchoë and consumers have an increasing demand for novelty and high quality of Kalanchoë products. At the same time, the flower morphology plays a crucial role in the breeding of new varieties. Breeding new traits using natural transformation with Rhizobium rhizogenes successfully introduced compact growth in Kalanchoë by introgression of transfer-DNA fragments of the root-inducing (Ri) plasmid into plants during bacterial infection. However, the role and function of individual root oncogenic loci (rol)-genes and open reading frames (ORFs) from R. rhizogenes basically remains unclear. This work aimed at investigating the effect of individual constructs overexpressing rolB and ORF13a in K. blossfeldiana ‘Molly’ by assessing biometrical and flower morphology features. Plants transformed with rolB and ORF13a had 30 and 37% lower height compared to wild type (WT), respectively 90 days after propagation. The rolB line plant diameter exhibited a reduction of 25% while ORF13a was 34% reduced in comparison to WT. Additionally, the leaf number of rolB and ORF13a was reduced to 40% less in comparison to WT. Moreover, the flower morphology of rolB and ORF13a showed markedly distinct flower shape compared to the WT. The transgenic lines exhibited lobose corollas, where the four petals were fan-shaped. In addition, the edges of petals from transgenic lines were not smooth as WT, presenting curly and irregular edges. Therefore, transformation with the single constructs of rolB and ORF13a resulted in different compactness levels between the transgenic lines of K. blossfeldiana ‘Molly’, demonstrating that unexplored ORFs could also present a novel genetic pool in terms of dwarfed phenotypes.