Chrysanthemum In general, it is very difficult to isolate mutants from mutation sectors in vegetatively propagated crops although the maintenance of mutant genotypes is easier than the seed-propagated species. It has been shown that the combined method of chronic Gamma-ray irradiation and tissue culture is very effective in solving this problem. By tissue culturing the floral organs of chrysanthemum ( Chrysanthemum morifolium Ramat.) plants chronically irradiated in the Gamma Field from the seedling to the flowering stages, many non-chimeric mutants, with various flower colors and shapes, are obtained [22]. From these mutant lines, 10 cultivars were registered. The technology, given the term “radiobiotechnology,” is not only effective in obtaining non-chimeric mutants but also effective in producing high mutation frequencies. The method has been utilized to induce mutations in various vegetatively propagated crops and many mutant cultivars have been registered.