Studies on modification of mutation response of barley seeds to ethyl methanesulfonate

Abstract

1. Diploid six rowed barley seeds were soaked in water for 4, 8, 12, 16, 20, 24 and 28 hours, before treatment with 0.3% and 0.6% aqueous solution of ethyl methanesulfonate for 4 hours. Morphological, cytological and genetical changes induced were studied. 2. For all criteria studied, 16 hours or 20 hours presoaking in water was found to increase the sensitivity of the seeds to the maximum. Highest mutation rate was obtained at this time of presoaking, when appropriate concentration was used. 3. The proportion of chlorophyll to viable mutations was found to vary with various times of presoaking. At longer presoaking times, relatively higher proportion of viable mutations were obtained. This, however, was not associated with an increase in viable mutation rate. 4. The chlorophyll mutation spectrum was also found to vary for a given dose of EMS following different presoaking times. 5. The possible factors for the increased sensitivity at 16 to 20 hours soaking are discussed in light of similar studies with radiations as well as available microautoradiographic data pertaining to the sequence of chromosome duplication in germinating barley seeds. It is concluded that a metabolic factor like DNA duplication in the cell initials may be involved in bestowing this increased sensitivity during this presoaking period.