Abstract: In vitro plantlets of two cut chrysanthemum cultivars were irradiated with 0，10，15 and 20 Gy of 60Co-gamma rays，respectively. The stems and leaves from irradiated plantlets were used as explants for further in vitro culture. The effects of radiation on the rate of produced axillary buds，induced callus and differentiated adventitious buds were analysed. Variations of the main morphological characters in M1 plants were documented. The results showed that 60Co-gamma rays dramatically inhibited the callus induction and differentiation from either leaves or stems explants，the inhibition effect increased with the increase in the dose of irradiation. The sensitivity to irradiation was upon to different cultivars and different types of explants. The irradiated stem was more suitable to be used as explants than the irradiated leaves. The plant height and flower diameter decreased in the M1 of‘Changzi’while increased slightly in M1 of‘Jinba’. The variation rate of morphological characters in plants regenerated from stems and leaves was higher than that regenerated from axillary buds. Rates of variation of flower color and petal type in ‘Changzi’were higher than that in‘Jinba’.

Key words: Chrysanthemum × morifolium, cut chrysanthemum, gamma ray, effects of irradiation, morphological characters variation