Variation in the phenotypic features and transcripts of color mutants of chrysanthemum (Dendranthema grandiflorum) derived from gamma ray mutagenesis

We investigated the structural genes and their transcripts for anthocyanin synthesis inDendranthema grandiflorum ‘Argus’. Color variations in chrysanthemum mutants were obtained through gamm ray irradiation to regenerated plants from anin vitro. Normal florets were pinkish, but the mutants had white or purple ray florets and white, purple, or yellow-green disc florets. Irradiation modified both flower size and the number of ray florets. Compared with the control, levels of total anthocyanins in the mutants ranged from 4 times lower to 6 times higher for the disc florets. This disparity was even more evident, up to 14-fold greater, in the ray florets. Expression of the CHI, F3′H, F3′5′H, DFR, and LDOX genes varied among the mutants, but no dramatic changes were detected in CHS and F3H transcripts in either leaf or floret tissues. Sequence homology to known anthocyanin genes from other plant species was 61 to 84%, 62 to 74%, and 71 to 76% for CHI, F3′H, and LDOX, respectively. Our results support the proposal that such radiation-induced mutations in genes within the anthocyanin pathway are associated with variations in chrysanthemum flower color.