Certain aspects of the sensitivity and mutability of two beans varieties under the influence of gamma-irradiation and EMS treatment

The relation between sensitivity and mutability of some beans varieties after treatment of their seeds with different gamma-ray doses and ethyl methanesulphonate (EMS) and the changes in their mutagenic effect with increasing the dose were studied. Seleccion 11 and Bolita 41 varieties were used. Seed irradiation (humidity 8,5%) was carried out with doses of 7500, 12500 and 17500 rad gamma-rays. EMS solutions of 0.05, 0,10 and 0,15% at 200C for 12 hours were applied. Records of the percentages of germination and survival were kept in M1 generation. All seeds from survived plants were sown, and in M2 the type and number of chlorophyll mutations were reported. Survival of either variety decreased with increasing the case of gamma rays or of EMS. Gamma radiation injury was more severe and occurred even with lower doses. Seleccion 11 variety proved to be more sensitive. The comparison between plant survival in M1 and the percentage of chlorophyll mutations in M2 shows an inverse relation between them, i.e. the decrease in the percentage of survived plants was accompanied by an increase in the percentage of chlorophyll mutations. At a certain survival percentage the percentage of induced chlorophyll mutations was of the same order, regardless of the mutagen factor used. When hybrid forms were treated the mutation frequency was higher than the one following treatment of parent forms. A study of the mutation frequency, depending on the dose of the mutagenic factor shows that there is only a limited possibility to raise the percentage of induced mutations by the effects of higher doses. (A.B.)