|
Comparison of mutagenic efficiency between EMS and
radiations in diploid wheat Taro FUJII and Seiji MATSUMURA Natianal Institute of Genetics, Misima, Japan Triticum monococcum flavescens was used in this study. Seeds were soaked in water for two hours and then treated with 0.1, 0.3 and 0.5% EMS solutions for 22 hours. For comparison, the seeds soaked for 24 hours were subjected to 0.5, 1.0 and 1.5 kR of gamma-rays at I kR/hr intensity. Moreover, EMS and gamma-ray treatments were combined to examine the synergistic effect of both treatments. The treatments were so combined that for two hours steeped seeds were placed in EMS solution for 22 hours and gamma-ray exposures were applied after five minutes washing in tap water. EMS solution was made with distilled water without buffer, and steeping and treatment were carried out under the constant temperature of 20C. Germination rates were fairly good as nearly 90 percent in gamma-ray 0.5, 1.0 and 1.5 kR lots germinated, but the seedling height and survival rate decreased with increasing dosage. EMS treated lots were severely impaired in germination, seedling growth and survival rate which was about 60 percent in 0.3% lot. About 70 percent of treated seeds emerged in 0.5% lot, but all youug seedlings died in early stage. Therefore, very low germination rate and no survivals were observed in 0.5% EMS treatment combined with 1.0 kR of gamma-rays. Chlorophyll mutations induced by EMS and gamma-rays were scored in the X2 generation, as shown in Table 1. Chlorophyll mutation rate was similar in EMS 0.1% and gamma-ray 1.0kR lots, but that in EMS 0.3% lot was very high. Mutagenic efficiency between gamma-rays and EMS could not be compared directly from the data presented in the table, since the former is an ionizing radiation and the latter is an alkylating agent. So the decrease of survival rates in the gamma-ray lot was plotted, and survival rates in EMS treated lots were adjusted at the appropriate points of the line representing gamma-ray treatment. According to the procedure, survival rates in 0.1 and 0.3% EMS treatments were almost similar to those of 1.0 and 1.5 kR lots of gamma-rays, respectively. Chlorophyll mutation frequency was nearly equal in gamma-ray 1.0 kR and EMS 0.1% lots. The rate of EMS 0.3% lot was about three times higher against that of gamma-ray 1.5kR lot, while they showed similar survival rates. (Received Jan.3,1968) |