Growth Characteristics and Biological Responses of Korean Elite Soybean (Glycine max L. Merr.) Cultivars Exposed to Gamma-Rays

The present study was conducted to evaluate the biological responses of soybean irradiated by gamma-rays. Four elite Korean soybean cultivars, Kwangankong, Shinpaldal-2, Shinhwakong, and Ilmikong, were irradiated with 100-400 Gy of gamma-rays. All cultivars showed significant reductions in morphological parameters. Seedling emergence rates of Kwangankong, Shinpaldal-2, Shinhwakong, and Ilmikong decreased by 46%, 31%, 44%, and 43% at 400 Gy, respectively. Plant height and fresh weight decreased with increasing dose. The median reduction dose (RD50) for plant height ranged from 184 to 278 Gy with an average of 212 Gy.The optimal dose of gamma irradiation for inducing mutation in the four elite soybean cultivars was in the range 200-300 Gy. Contents of malonaldehyde (MDA) in the gamma-ray irradiated plants were higher than those in the controls. With the exception of Kwangankong, activities of ascorbate peroxidase (APX) in other cultivars decreased at 100 Gy and started to increase significantly at 200 Gy and Shinhwakong cultivar had highest APX value observed at 300 Gy. No significant changes in peroxidase (POD) activity were observed inthe Kwangankong, Shinpaldal-2, and Shinhwakong, while, POD activity increased with increasing dose in Ilmikong. In addition, gamma-ray treatments elicited a marked reduction in chlorophyll a contents compared to chlorophyll b contents in Kwangankong, Shinpaldal-2, and Ilmikong. Growth characteristics (plant height and fresh weight) were highly negatively (P ＜ 0.01) correlated with the dose of gamma-rays, while the MDA content and APX activities were positively (P ＜ 0.05) correlated with dose.