Studies on genetic effects of mutagenic treatments of germinating seeds in barley

It is known that presoaked seeds are more sensitive to radiations than dry seeds. This report deals with the genetic effects of mutagenic treatments in germinating seeds of barley after various periods of presoaking. Germinating seeds were treated with ethyleneimine or gamma-rays after various periods of presoaking in distilled water up to 30 hours, while redried seeds were irradiated with gamma-rays and thermal neutron radiation. Effects of these treatments on induction of chlorophyll mutation were examined. An investigation on field character mutations was also carried out. It was revealed that, in addition to S phase, three stages showing high mutation frequency existed in G1 stage. Mutagenic treatments of these sensitive stages of G1 in germinating seeds would be effective for induction of mutation, because high mutation frequency could be observed without decreasing seed fertility. The fact that the sensitivity of these stages remained the same after redrying of seeds, may give a clue to study the mechanisms of mutation induction in these stages. Irradiation of redried seeds will be effective also as mutagenic treatment, especially in combination with other mutagen treatments. (Nogami, K.)