PERTANIKA JOURNAL OF TROPICAL AGRICULTURAL SCIENCE

Chrysanthemum is a subtropical ornamental plant traditionally cultivated in highland regions. Increasing temperatures caused by climate change are causing a decrease in flower production and quality, thus encouraging the availability of chrysanthemum varieties adapted to warmer lowland environments. This study aimed to induce genetic and phenotypic variations in the Indonesian chrysanthemum variety 'Marina' for potential lowland adaptation using Ethyl Methanesulphonate (EMS) combined with Paclobutrazol (PBZ). EMS concentrations of 0 and 0.77% and PBZ concentrations of 100 and 200 ppm were used as treatment. Morphological parametres, including plant height, number of leaves, number of nodes, diametre of stem, number of flowers, metrediametre of flowers, and percentage change in flower colour, were evaluated under natural lowland heat stress. Genetic distance was confirmed using RAPD and SSR molecular markers. The results showed that the application of 0.77% EMS and 200 ppm PBZ successfully induced significant phenotypic and genetic variations in the 'Marina' chrysanthemum. Applying 0.77% EMS mutagen has produced several promising putative mutant lines, specifically KM11, KM20, and KM22, which have distinct leaf shapes, bright flower colours, and reduced the time of flowering compared to the parent. Molecular analysis showed significant genetic polymorphisms, with KM11 showing the highest genetic distances (56% similarity) from the parent, while KM22 showed the lowest. These results provide a valuable genetic background for developing lowland-tolerant chrysanthemums, although further analysis of the next generations is required to confirm the stability of these traits for commercial release.