LAUSR

Abstract γ-rays have been used to develop many mutations in diverse ornamental plants, including chrysanthemum, of which most changes have been flower color. Flower color is determined by plant pigments, including anthocyanins, which are affected by mutation of genes in the anthocyanin biosynthesis pathway. Sucrose and plant hormones also crosstalk in complex signaling pathways and modulate anthocyanin biosynthesis. In this study, we determined the optimal sucrose and plant hormone treatments for expression of anthocyanin biosynthesis genes and compared the mutation frequency among sucrose, methyl jasmonate (MeJA), and/or γ-ray treatments in chrysanthemum. Anthocyanin biosynthesis genes were highly expressed with 50 mM sucrose treatment for 18 h. The highest expression levels of anthocyanin biosynthesis genes were observed under sucrose with MeJA treatment followed by MeJA treatment alone. Sucrose with abscisic acid (ABA) treatment, and ABA or GA3 treatment alone, had no effect on expression of anthocyanin biosynthesis genes. Sucrose with MeJA pre-treatment followed by γ-irradiation resulted in the highest mutation frequency (14.5%) among all treatments and a 1.5-fold increase in mutation frequency compared with γ-ray treatment alone. The ratio of anthocyanin-related flower-color mutants with sucrose and/or MeJA pre-treatments followed by γ-irradiation was higher than that with γ-ray treatment alone. Sucrose and/or MeJA modulated the expression of anthocyanin biosynthesis genes and highly expressed genes may be affected more readily by γ-rays, thus resulting in an increased frequency of anthocyanin-related flower-color mutants in chrysanthemum.