Phenotypic Evaluation and Nuclear DNA Content Analysis of Oryzalin-Induced Echeveria Mutant Cultivars

Succulent plants are in high demand in the floriculture industry owing to their peculiar leaf arran-gement, water-efficient characteristics, and wide color variation. In particular, the succulent genus Echeveria is preferred by many plant collectors and hobbyists. Therefore, continuous breeding programs for these succulents are underway to produce novel cultivars with new features, leading to higher market prices. As opposed to conventional breeding, chemical mutagenesis can achieve this goal. The use of oryzalin, an anti-microtubule drug, is effective to induce plant mutations and less hazardous to human health. Thus, in earlier work, we explored the use of oryzalin to induce mutant Echeveria cultivars, specifically the ‘Brave’, ‘Momotarou’, and ‘Sistar’. Briefly, different concentrations (0.2%, 0.4%, 0.6%, 0.8%, and 1.0%) and dipping durations (3, 6, 9, and 12 h) of oryzalin were employed for chemical mutagenesis. Oryzalin produced Echeveria mutants with fewer, larger, darker, and thicker leaves compared to control plants. A stomatal analysis revealed that the mutants exhibited larger but fewer stomata and a lower epidermal cell density, consistent with polyploidization. Future studies involving chromosome counting and flow cytometry of putative oryzalin-induced mutants and their next generations are warranted to identify whether these alternations are reversible. Our findings will be useful for the mutation breeding of closely related ornamentals or other potted plants and development of new cultivars with novel traits.