Induction of flower-colour mutation by synchrotron-light irradiation in spray chrysanthemum

Abstract

Chrysanthemum is one of the most important ornamental plants. Mutation breeding is an important tool in breeding of chrysanthemum, and many cultivars have been produced through mutation breeding by using radiation such as gamma ray, etc. Although ion-beam irradiation is now widely used as a mutagen in the mutation breeding of plants, synchrotron light, another form of radiation, has not been used as a mutagen. Therefore, this study was conducted to clarify whether synchrotron light can be used as a new mutagen in chrysanthemum breeding. Five cultivars of spray chrysanthemum were subjected to synchrotron-light irradiation. As a result of the irradiation, the survival rate decreased as the absorbed dose increased. Flower-colour mutations were observed in three cultivars. There were varietal differences in survival rates and the frequencies of flower-colour mutation. Flowers of the mutants showed various colour patterns such as a deeper and paler colour than the original flowers. In the mutant of a cultivar with a marginal picotee, the proportions of picotee changed. A moderate absorbed dose of synchrotron-light irradiation for flower-colour mutation was found to be 11 to 23 Gy. These results indicate that synchrotron light can be used as a new mutagen in the mutation breeding of chrysanthemum.