Induction of Mutations in Veronica Species by Colchicine Treatment

Veronica nakaiana Ohwi and Veronica pusanensis Y.N.Lee are rare and endemic plants native to Korea, with increasing interest in their cultivation and breeding for industrial applications. Mutation breeding is important for developing horticultural cultivars. Among mutation breeding techniques, chemical mutagenesis is particularly accessible and effective. Colchicine-induced mutagenesis was performed in vivo at various concentrations (0.2%, 0.4%, 0.6%, 0.8%, and 1.0%) and treatment durations (1, 2, 3, 4, and 5 h). Both V. nakaiana Ohwi and V. pusanensis Y.N.Lee showed the highest survival (23.4% and 34.8%, respectively) and mutation (1.6% and 0.5%, respectively) rates with 0.2% colchicine. Flow cytometry and chromosome number analyses revealed mutants as tetraploid, with chromosome numbers ranging from 2n = 66 to 2n = 68. Stomatal analysis indicated increased stomatal length and width and decreased stomatal density. Morphological analysis of the mutants revealed that the leaves of V. nakaiana Ohwi and V. pusanensis Y.N.Lee were significantly larger and had different shapes compared to the control. This study successfully generated new mutant plants of two Veronica species using chemical mutagen treatment, which could be utilized as new genetic resources for various Veronica species breeding programs in the future.