The effect of ethyl methanesulfonate on the growth response, chromosome structure and mutation rate in barley

Abstract

Effects of ethyl methanesulfonate (EMS) and X-rays were compared by several biological measures in barley. The criteria studied included rate of growth, survival and fertility of M 1 plants, frequencies of chromosomal aberrations in mitosis of seedlings and meiosis of M 1 spikes, and the frequencies of chlorophyll deficient mutations among M 2 seedling progeny. The doses of EMS and X-ray treatments chosen reduced the rate of seedling growth and survival to a comparable degree. The reduction of fertility was directly related to the frequency of chromosome aberrations and mutations after X-ray treatment. After EMS treatment, the decrease of fertility was pronounced; however, there was little effect on seedling growth and survival. Also, the frequency of chromosome aberrations observed in EMS treatments was negligible, whereas a high rate of chlorophyll deficient mutations was induced in both M 1 plants and M 2 progenies. Preliminary results indicated that the efficiency of EMS treatments can be further increased when the treatment solutions are buffered and the delayed action of the mutagen is prevented. Physiological damage, e.g., reduced seedling growth and survival, increased with concentration of hydrolysis products in the treatment solutions, except when buffers were added. The damage caused by drying seeds after EMS treatment was reduced considerably by soaking the treated seeds in distilled water before drying. This delayed effect may be due to active agent and/or by-products retained in the tissue after the defined treatment time.