Mutational response of rice seeds to ethyl methanesulfonate and busulfan in relation to chromosome duplication

Abstract

At various times after soaking of rice seeds they were treated with ethyl methanesulfonate (EMS) and its bifunctional agent 1,4-di(methanesulfonoxy)butane (busulfan). After 60-h soaked seeds had been treated for 2 h with EMS and busulfan, the LD 50 was estimated as 4·10 −4 M for the former, and 1.3·10 −5 M for the latter. In EMS- or busulfan-treated materials field survival was reduced to a marked extent at the S stage, and the maximal lethality was attained at the late S and/or early G 2 phase. After EMS treatment the mutation frequency was very high in late G 1, decreased suddenly at middle S, increased again markedly at late S and/or early G 2 and subsequently decreased. On the other hand, busulfan produced the mutation only in the cells that were in the process of DNA synthesis. Concerning the mutation spectrum the tigrina mutant appeared only in treatments made in the G 1 phase. In the light of these results, the mutagenesis of EMS and busulfan is discussed.