The effects of gamma irradiation on the growth and cytology of carrot (Dacus Carota L.) tissue culture

Carrot (Dacus Carota L.) tissue suspension cultures were subjected to 0.5-40 krad of gamma irradiation. Callus fresh weight was significantly increased and dry weight slightly increased by low doses (0.5 and 1 krad). Cells size increased at all doses. Cell number and colony-forming ability decreased. There was a negative correlation between radiation dose and mitotic index, and a positive correlation between dose and mitotic abnormalities (multipolar separations, lagging chromosomes, and bridges). Frequency of prophase was increased, and ana phase and telophase were reduced. Tissue culture conditions increased the incidence of aneuploidy and polyploidy in comparison to carrot root tips. Aneuploidy in tissue cultures was decreased and polyploidy was increased by gamma irradiation. Gamma irradiation stimulated shoot formation at 1 krad, and inhibited shoot formation at high doses (20-40 krads). The frequency of abnormal plants (albinos, and plants with no roots or deformation of leaves) regenerated from carrot cell cultures was increased by gamma irradiation. (authors). 30 refs., 3 figs