The experiments were carried out to study the effect of different doses of gamma-rays on some morphological traits in the M1 and M2 - generations of Centaurea cyanus. Seeds were irradiated with different doses of gamma- rays (0,5,10,15,20 and 25 kr.). Observations on germination percentage, plant height, number of branches, leaf chlorophyll content, flowering date, number of inflorescences, inflorescence diameter, morphological changes and mutation aberrations were recorded.
      In the M1 and M2 -generations all doses of gamma radiation decreased the seed germination percentage. The plant height was reduced in all gamma radiation treatments in the M1 -generation of both seasons. The higher the dose the higher growth reduction obtained. In the M2 –generation the differences in plant height were not significant in both seasons. Thenumber of branches was not affected by gamma-radiation treatments in all generations for both seasons.  The effect of gamma-rays on theleaves chlorophyll content was not significant in both seasons. The flowering date was significantly affected by the different doses of gamma-rays in all generations in both seasons. There was an increase in the number of days to flowering with an increase in the gamma-radiation doses as compared with the control. The dose of 5Kr. produced  the largest average number of inflorescences in the M1-generation of both seasons, however, in the M2-generation of both season, gamma-rays did not significantly affect the number of inflorescences. As for the inflorescence diameter, gamma-rays did not significantly affect the inflorescence diameter in all generations in both seasons. In the M2-generation, the results showed that there were slight change in the flower colour at the treatments of 15 and 25 Kr. in the first season and at 5 and 25 kr in the second one. The colour was lighter than normal in 4 plants. The doses of 25 and 20 kr in the first and second seasons respectivelycaused some changes in
the shape of the floral organs in the M2 -generationintwo plants.