| Relation between polyploidy and effects of gamma- and neutron-radiation on wheat S. MATSUMURA National Institute of Genetics, Misima, Japan Exposure to 14 MeV neutrons obtained from (D, T) reaction was carried out in the Biology Division of Oak Ridge National Laboratory. For the calculation of given doses, based on Randolph's method, the analysed elemental compositions and the measured fast-neutron fluxes were used. The dose, applied to dormant seeds, ranged from 0.48 to 1.80 krad for Triticum monococcum and from 0.95 to 2.24 krad for T. durum and T. vulgare. At the same time gamma-radiations were used for comparison at 4.3-17.2 krad ORNL. After exposure to 1.80 krad of fast neutrons, the seeds of T. monococcum germinated but most of the seedlings died in an early stage, while in T. durum and T. vulgare slow growth of the seedlings continued even at 2.24 krad of fast neutrons. The higher was the dose of fast neutrons and gamma rays, the more delayed were germination and growth of seedlings, the more reduced were survival rate and seed fertility, and the more increased were chlorophyll mutations, with the exceptions of mutations in T. vulgare (Table 1). In general, T. monococcum is the most sensitive to fast neutrons and gamma-rays. There is no significant difference between T. durum and T. vulgare. Also the relative biological effectiveness (RBE) of fast neutrons to gamma-rays was found to be 10-15 for those properties in T. monococcum. The RBE values for these characters in polyploids were higher than in T. monococcum, respectively. |