Phenotype and ploidy analysis of the colchicine-induced M₁ generation of echeveria species

Mutation breeding is an important tool for developing new cultivars in horticulture. Among the many methods of mutation breeding, chemical mutation is highly effective and can be performed easily. Compared to natural breeding methods, higher mutation rates and the faster induction of desirable characteristics have been reported with the use of chemical mutagens. Succulents have recently gained popularity because of their unique geometrical shapes and their ability to survive with minimal watering. Succulents that have peculiar shapes and colors demand higher prices. In this study, we used colchicine, a chemical mutagen, and tested its application on three Echeveria succulent species. A phenotypic evaluation was conducted on the mutant succulents produced from the application of colchicine on propagated leaf cuttings. Phenotypic evaluation included plant parameters and morphological analysis. Ploidy analysis was conducted to confirm the effects of the mutagen treatments. In all selected Echeveria species, the use of colchicine produced mutant species that varied significantly from those of the control; however, treatment concentration and duration varied per species. The phenotypic evaluation revealed that colchicine-mutated plants exhibited compactness, with mutants being generally taller with a thicker but shorter plant diameter compared to that of the control. Mutated plants exhibited prominent changes in color for the a* and b* values. Similarly, changes in leaf shape were observed and were evident at their apexes. These morphological changes are attributed to the change in ploidy level, which was confirmed through stomata and ploidy analysis. Larger stomata size was accompanied by lower stomata density. Based on the flow cytometry analysis, mutated succulents exhibited a 2x-4x complex.