Taro Fujii

Photoreactivation of mutations induced by ultraviolet radiation of maize pollen

Abstract A normal strain with genes of Yg 2 , c and Bz , and strain No. 641 with genes of yg 2 , C and bz were used as male and female parents, respectively. Pollen grains of the normal strain were exposed to ultraviolet radiation (UV). Half of the irradiated pollen grains were exposed to visible light for 30 min and then pollinated to the female stock in the field under sunlight whereas the other half were held for 30 min in dark and then pollinated to the female parent in a room illuminated by non-photoreactive sodium light. For purposes of comparison, γ-ray irradiated pollen grains were subjected to similar posttreatments. Total frequency of mutation from Bz to bz (sum of the frequencies of whole and partial mutations) increased with dose both for UV and γ-ray treatments. After the photoreactivation treatment, mutation frequency markedly decreased for the UV lots; photoreactivation occurred to the same order of extent both for wholes and partials. No significant photoreactivation was observed for γ-ray induced mutation. Photoreactivation was also observed for the UV mutation at Yg 2 locus though to a lesser extent than for the Bz locus whereas no significant photoreactivation occurred for γ-ray induced mutation at this locus. These results are briefly discussed in relation to the mechanism of photoreactivation, with particular reference to those obtained by other workers.

Diallel analysis of nitrogen fixation in the rhizosphere of rice

Abstract The genetics of nitrogen fixing ability in the rhizosphere of rice ( Oryza sativa L.) was investigated by diallel analysis. In an 11 × 11 diallel set, Wr-Vr graph analysis revealed the presence of a non-allelic interaction. Excluding the interacting parents, a 7 × 7 diallel set gave more uniform ( Wr - Vr ) values and regression of nearly unity, indicating the disappearance of non-allelic interaction. The regression line indicated partial dominance. Estimates of genetic components of variation were in close agreement with the results from Wr-Vr graph analysis; the average degree of dominance was in the range of partial dominance and an excess of dominant alleles over recessive alleles. Correlation between parental performance and ( Wr + Vr ) values suggested that nitrogen fixing activity in the rhizosphere of the highest parent was likely governed by recessive alleles.

Mutagenic effect of l-ethionine in soybean and maize

Abstract The mutagenic effect of l -ethionine in plants was examined using heterozygotic soybean and maize. Seeds were soaked in solutions of different concentration and the mutational frequency increment was measured by the increase of mutant sectors on the leaf. l -ethionine has a mutagenic effect in plants; a concentration of about 0.5 mg/ml or more in soybean and higher than 1.0 mg/ml in maize enhanced somatic mutation frequency.

Effect of TPA on the mutagenicity of caffeine in the soybean mutation test

12-O-Tetradecanoylphorbol-13-acetate (TPA) is a well-known tumor promoter in mouse-skin carcinogenesis. Its effects on mutagenesis in a soybean test system were examined, and the effects were judged from the appearance of spots of various colors on the leaves. When soybean seeds were treated with TPA plus 0.03% caffeine, the frequency of spots per leaf decreased significantly and in proportion to the concentration of TPA. TPA alone at concentrations of 1–20 μg/ml did not induce any mutations. Mutations induced by γ-rays were not affected by administration of TPA either before or after exposure to γ-rays. The mechanism of suppression by TPA of mutations induced by caffeine is discussed.

Mutagenic effect of a pesticide (Ekatin) in the soybean test system

Abstract The mutagenicity of several agricultural chemicals was examined with a soybean test system. Concentrations of the applied chemicals were similar to those used for pest control, viz., 500–2000 times dilution. Five chemicals (Antio, Baycid, Diazinon, EPN and Karphos) showed no mutagenic activity. An increase in mutant spots was observed with Ekatin (thiometon). Activation experiments with in vitro or in vivo methods using microbial test system were conducted. Systematic investigations in bacteria, however, yielded negative results in all cases, suggesting that the mutagenic activity of Ekatin or thiometon was specific for plants.

Mutagenic activities of EMS on somatic (M1) and recessive (M2) mutations in the soybean test system

Abstract The possibility of development of a system which can assess the extent of genetic damage by measuring somatic mutations in a treated or M 1 generation was studied by using the soybean test system. We investigated somatic mutation induced by EMS in M 1 soybean plants and the segregation of chlorophyll deficient mutants in the M 2 population. Dose vs mutation frequency relationships were not concomitant between somatic and recessive mutations. However, the scoring of somatic mutations could assist in the assessment of the extent of recessive mutation events.

Absence of mutagenic activity of benzo[a]pyrene in the soybean test system☆

Abstract The potential for benzo[a]pyrene to induce mutations in the soybean test system was studied. In spite of the reported high sensitivity of the soybean test system to other agents, no mutagenic effect of benzo[a]pyrene was detected even in the presence of S9 mixtures prepared from rat liver or plant tissue. Some abnormal seedling growth was observed with treatments of high concentration of the drug with rat liver S9 mixture.