Effect of gamma irradiation on the expression of structural genes involved in anthocyanin biosynthesis pathway in chrysanthemum

Chrysanthemums (Chrysanthemum morifolium) are an important ornamental plants in Iran and the world with a high commercial value. Among different doses of gamma irradiation, the irradiation at 40 Gy by a Cobalt-60 source to four-week-old seedlings of a purple commercial cultivar of chrysanthemum, i.e. ‘Rambla’ produced three mutants with dark purple, pale purple, and Indian red colors. To explore the effect of variations in the expression levels of the structural genes involved in the anthocyanin biosynthesis pathway on the color of the mutants, the RNA of the mutants and control plants was extracted from the petals of the M1V3 generation and studied by the RT-qPCR method. The significant changes in the relative expression levels of F3'H, DFR, ANS, and 3GT in the mutants versus the control showed the role of these genes in the petal color change. The total anthocyanin content had significant correlation with the relative expression levels of DFR, ANS, and 3GT. Stepwise regression for the total anthocyanin content as the dependent variable and the relative expression level of the structural genes involved in the anthocyanin biosynthesis pathway as independent variables showed that 3GT had the strongest impact on dependent variable. F3'H relative expression caused significant changes in the mutants versus the control and it was introduced as an appropriate key gene for genetic manipulations to create color diversity in chrysanthemums.