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

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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.