Isolation of flower color and shape mutations by gamma radiation of Chrysanthemum morifolium Ramat cv. Youka

We investigated the effect of radiation damage on in vitro mutation induction in chrysanthemum. White petals of chrysanthemum (Chrysanthemum morifolium Ramat cv. Youka) were selected to induce mutation by gamma radiation. Calli produced were irradiated with gamma rays at 0, 10, 15 and 20 Gy. We found that the plants from the irradiated calli were different from control plants in number of leaves, leaf length & width, number of flowers, flower diameter, petiole diameter and petiole length after transplanting into the greenhouse for almost 70 days. Three mutants in flower color and shape were found in 15 Gy-treated plants. First type of mutant (M.1) has tubular petals. The second (M.2) and third (M.3) ones both have yellow flowers, while one of them has spooned shaped ray florets similar to the original cultivar and the other one has flat shaped florets. Semi-quantitative RT-PCR showed that most of carotenoid-biosynthesis related genes, except for violaxanthin deepoxidase (VDE) and lycopene ε-cyclase (LCYE), showed similar expression patterns in petals of the original ‘Youka’ and its mutants (M2 & M3). VDE and LCYE results showed high expression levels in M3 and M2 & M3 respectively, comparing with the control. On the other hand, expression patterns for VDE were similar in control and M2. These yellow mutants were maintained vegetatively and proved to be true-to-type in one successive generation. It can be concluded that gamma radiation with 15 Gy dose can be used for in vitro induction of flower color and shape mutations of chrysanthemum cv. Youka.