Enhancement of chemically-induced mutatin frequency in barley through alteration in the duration of pre-soaking of seeds

Abstract

Treatment of barley seeds pre-soaked in water for different periods ranging from 8 to 40 h with ethyl methanesulphonate (EMS) and N-nitrosomethyl urea (NMU) showed that the seeds were most sensitive to mutagenic treatments at 16 h and 28 h from the beginning of pre-soaking. Autoradiographic studies revealed that the first incorporation of labelled thymidine occurs after 16 h of pre-soaking. Therefore, the first peak of sensitivity may be related with DNA synthesis. The second peak of sensitivity may be caused either by the release of certain metabolic products which have a sensitizing effect or because of a second wave of cells entering DNA synthesis in cases as asynchronous cell division. The plants in the M₁ generation showed a high frequency of chlorophyll chimeras. The frequency of appearance as well as the size of these sectors were significantly high after treatment with NMU. Multiple mutations also occurred more frequently in NMU-treated plants. There is great scope for increasingly both the frequency and spectrum of mutations in treatments with chemical mutagens through suitable modification of the treatment conditions.