Polyploidy induced by colchicine in Dendranthema indicum var. aromaticum, a scented chrysanthemum

Dendranthema indicum var. aromaticum from the genus Chrysanthemum is a rare species with a rich flavor. The aim of this study was to find a suitable treatment combination that would effectively induce polyploidy of diploid Dendranthema indicum var. aromaticum and to lay the foundation for the late cultivation of aromatic Chrysanthemum. In this study materials, colchicine concentration and treatment duration were examined for improving the induction of polyploidy. The combinations of three materials (shoot tips, pre-germinated seeds and grin), five colchicine concentrations (100, 200, 500, 1,000 and 2,000 mg L-1) and three treatment durations (12, 24 and 48 h) were tested in Dendranthema indicum var. aromaticum. A total of 7 tetraploids and 301 chimeras determined by chromosome number analysis were obtained. The treatment of grin seeds with 1,000 mg L-1 colchicine for 24 h (14.5%) and shoot tips with 1,000 mg L-1 colchicine for 7 d (40%) were suitable for induction of chromosome doubling. The tetraploid plants displayed much larger stomata with lower density, as well as a higher chloroplast count than the diploid paints. Moreover, tetraploid plants developed larger, thicker leaves, greater flower diameter, more epidermis hairs and shorter plant height than the diploid plants.