Radiation Genetics in Wheat, VI

Abstract

Thermal and fast neutron irradiation was performed on dormant seeds of Triticum monococcum flavescens. The higher the dosage of thermal and fast neutrons, the more delayed the germination and growth of seedlings. The seeds were almost uniformly injured following each treatment. There was almost no germination at 37.5 X 1012 nth/cm2 of thermal neutrons and at 5 krad fast neutrons. Even at about 30 X 1012nth/cm2 and at 2.5 krad the seedlings did not grow and died in an early stage. Also the higher the dosage, the more reduced the survival rate, height of mature plants, and seed fertility. The frequency of chromosome aberrations and chlorophyll and other mutations increased with an increase of dosage. In comparison with the results obtained from X- and gamma-irradiations, 1 r equivalent effects of X-rays are produced by about 2 X 109 nth/cm2 of thermal neutrons for seedling length and seed fertility. Also the 1 r equivalent effects correspond roughly to those of the order of 109 nth/cm2 for chromosome aberrations and chlorophyll mutations. A relative biological effectiveness (RBE) of fast neutrons to X-rays was found to be for germination rate 4, for seedling length 10, for seed fertility 12, for chromosome aberrations 8 and for chlorophyll mutations 10.