| RBE value 14 MeV fast neutrons to 60Co gamma-rays
in T. monococcum T. FUJII National Institute of Genetics. Misima, Japan RBE value of 14 MeV neutrons to gamma-rays in einkorn wheat was studied by using the specific loci method. Dry dormant normal seeds and F1 seeds from the cross between normal-5001 and chlorina-5040 were subjected to 4.3-12.9 krad of gamma-rays and 0.48-1.43 krad of neutrons. Mutations from dominant normal green to chlorina occurred by both irradiations and appeared in the leaves and stems of the heterozygotic X1 plants as longitudinal stripes. Around 80 per cent of seeds germinated in the control lot and in the lowest dosage lots from both neutron and gamma-ray irradiation, and germination percentages were gradually decreasing with increasing dosage of both kinds of radiation. Moreover, a similar tendency was observed in early stages as to seedling growth which was gradually inhibited with increasing dosage. According to these results, neutron irradiation was about 13 times as effective as that of gamma-rays. Survival rate in the non-irradiated control was about 90 per cent and about 50-80 per cent of germinated seedlings survived in 0.45 and 0.95 krad lots from neutron irradiation from all lots irradiated by gamma-rays. On the other hand, only about 4 per cent of germinated seedling survived in the highest neutron lot. No mutation was observed in the control lot, and the number of plants which contained striped tillers increased with increasing dosage of both kinds of radiation as shown in Table 1. The rates for striping were calculated per spike and 0.19, 0.35 and 0.48 x 10-6 per krad were obtained from 4.3, 8.6 and 12.9 krad gamma-ray irradiation, respectively. 0.95 and 7.12 x 10-6 per krad were obtained from 0.48 and 0.95 krad neutron irradiation. 1.43 krad neutron irradiation is too high for einkorn wheat. From the results, RBE value of 14 MeV fast neutrons to 60Co gamma-rays was about 13. |