Radiosensitivity of California Mariout barley seeds and determination of the optimal doses for mutation breeding

Abstract

The locally adapted barley variety California Mariout (C.M) was used to investigate the effect of different gamma ray doses (0, 50, 100, 150, 200, 250, 300, 350 and 400 Gy) from a colbat-60 source on emergence and seedling height and to determine the optimal mutagenic doses required for mutation breeding for improving this barley variety. Prior to irradiation, dry C.M. seeds were equilibrated to a 13% moisture content for higher mutagenic efficiency. The irradiation with gamma ray produced a significant effect on emergence and seedling height compared to the control (0 Gy). At the lower doses up to 200 Gy, emergence % was slightly but not significantly increased. At the higher doses 250, 300, 350 and 400 Gy. emergence % was significantly delayed and reduced scoring 68.9%, 70%, 34.4% and 25.5%, respectively, the control being 90%. The lower doses 50 Gy and 100 Gy produced a radiostimulant effect on seedling height and gave a significant increase in the length of the first leaf of approximately 10.4%. The doses 150 Gy and 200 Gy slightly reduced the seedling height and the high doses 250-400 Gy reduced the seedling height significantly. The correlation coefficient for seedling height was very high (-0.906) indicating an inverse relationship with dose with a regression coefficient of -0.0181. Using the regression equation, the GR10 and GR15 were extrapolated to be 182 Gy and 218 Gy, respectively, and were selected as the optimal mutagenic doses for use in mutation breeding programmes for improving C.M.