| Genetic effects of Beta- and gamma-radiations on Einkorn
wheat S. MATSUMURA National Institute of Genetics, Misima, Japan To compare the genetic effects of Beta-radiation with those of gamma-radiation, seeds of Triticum monococcum flavescens were soaked in 32P and 131I solutions for 2 days just before sowing. Radioactive solutions of pH 6 to 7 contained 0.05-0.4 mc/gm of 32P and 0.2-0.8 mc/gm of 131I. Also gamma-irradiation with 60Co was applied at the dosages 2.5, 5, 10 and 20 kr immediately after soaking seeds in water for 2 days. The growth of seedlings, single-spike fertility and chromosome aberrations of treated plants (X1) and the chlorophyll mutations in X2 were compared for Beta- and gamma-irradiations. The data are shown in Table 1. The seedlings were measured 18 days after sowing. The relation between the inhibition of seedling growth and dosage of Beta- and gamma-radiations coincides roughly with that between the decrease of fertility and dosage. gamma-rays at 2.5 kr slightly inhibited the growth of seedlings and reduced the fertility, those effects correspond roughly to those of Beta-radiation from 0.2 mc/gm 32P solution and 0.8 mc/gm 131I solution. gamma-irradiation at 10 kr was markedly effective. There was no germination at 20 kr with gamma-irradiation. In the treated plants (X1) white and yellow stripes were often found, especially in 32P. The frequency of ears with chromosome aberrations in X1-plants was strikingly high with gamma-irradiation. The majority of induced chromosome aberrations were: (4)+5II, often (4)+(4)+3II or (6)+4II and seldom (8)+3II or asynaptic 14I. The frequency of head progenies with chlorophyll mutations in the X2-generation increased with the increase of radiation dosage. The effects of Beta-radiation from 0.4 mc/gm 32P solution correspond roughly to those of 5.0 kr gamma-radiation. The majority of chlorophyll mutations with Beta-irradiation were albina, xantha and viridis, while with gamma-irradiation albo-viridis, virido-albina and basi-viridis were also often observed. In conclusion the effects of Beta-radiation from 0.2 mc/gm 32P solution and 0.8 mc/gm 131I solution correspond to those of 2.5 kr gamma-radiation. If we assume that the effects of Beta-radiation are confined only to embryo, from calculation we find that the 0.2 mc/gm 32P solution equals about 2.4 krad. This will account for the present data. |