EFFECTS OF 14MeV NEUTRONS IN HETEROZYGOTIC EINKORN WHEAT

Abstract

Heterozygotic einkorn wheat seeds were subjected to γ-rays and 14MeV neutrons and the effect of neutrons on the frequency of somatic mutation and fertility in X1 were examined. Up to 900rad of neutrons had no apparent effect on germination rate. Survival rates were slowly decreasing with increasing dosage. A similar tendency was also observed in the average number of tillers, but it was not marked.Somatic mutation rate was calculated on spike basis. An almost linear relation of the mutation curve was observed between mutation frequency and neutron dosage.Very high mutation rate or high RBE values in 14MeV neutrons was obtained in this experiment like in the previous experiment, for instance somatic mutation rate in the γ-ray 8600rad lot was 0.18 and that of neutron 324rad lot was 0.39. RBE value of neutron was very high in higher plants in general.Decrease of fertility was marked with increasing dosage. When the fertility was compared between mutated and non-mutated tillers (including the main stalk) within each individual, average fertility in the former was lower than in the latter. These facts support the view that most of somatic mutation arises from chromosome aberrations.Average number of mutated tillers per individual roughly increased with increasing dosage, as the result of repeated occurrence of the same kind of mutation within the same individual.