MUTATION FREQUENCIES IN BARLEY AFTER TREATMENT WITH γ-RADIATION, ETHYLENE IMINE, ETHYL METHANESULFONATE AND MALEIC HYDRAZIDE

Abstract

Mutagens were applied to grains of barley (Hordeum vulgare L.) and the induced chlorophyll mutations were scored in the spike progenies (M2) of treated plants. Gamma-radiation doses in the 27r to 10,000r range induced spike mutations of frequencies rising from 0.17% after a 27r dose to 6.1% after a 10,800r dose. The spontaneous mutation frequency was 0.07%. The doubling-dose of gamma-radiation is estimated at 25r -lOOr. Per r, the radiation declined in efficiency in the 27r - 2160r range from 3.263 x 10-5 to 0.463 x 10-5 induced mutations per spike. Peak mutation frequencies observed after treatment with solutions of ethylene imine and ethyl methanesulfonate were 20.5% and 39.8% respectively. Maleic hydrazide was ineffective as a mutagen. When seeds were presoaked in an adenine-thymine mixture before treating with ethylene imine the mutation frequency rose to 23.8%. In many segregating spike progenies of treated plants the proportion of mutants was much less than one-fourth of the seedlings indicating that the mutation had been confined to a sector of the spike.