The anther culture technique was applied on three Japanese rice varieties, Koshihikari, Kagahikari and Notohikari, to obtain useful mutants for breeding. After cold pretreatment (5℃) for 7-10 days, anthers were inoculated on the callus-inducing media at the stage that the distances between auricles of the last two leaves were 5-10cm. For callus formation, two kinds of media were used : Ne basic medium supplemented with 2, 4-D 0.2mg/l, NAA 1mg/l and sucrose 70g/l (N_6-1 medium) and N_6 basic medium supplemented with 2, 4-D 2mg/l, yeast extract 1g/l and sucrose 70g/l(N_6-2 medium). For plantlet induction, the N_6 basic medium supplemented with NAA 0.5mg/l, kinetin 1mg/l and sucrose 50g/l was used. Chromosome number was counted by the Giemsa staining method in root-tip cells of A_1 plant (1st generation of regenerated plants). A_2 lines were cultured in paddy field separately as panicle-row lined from all panicles of A_1 plants. The frequency of callus formation was higher on N_6-2 medium than on N_6-1 medium, though they were very low (2.8% on average) (Table 1). The plantlet induction was higher from the pollen calluses formed on N_6-2 medium than those formed on N_6-1 medium (Table 2). A half number of regenerated plants were albinos. Chromosome counts of regenerated plants showed x (30.3%), 2x (64.8%), 3x (3.5%) and 4x (1.4%) (Table 3). In Koshihikari, the occurrence of mutation in A_1 plant level was estimated to be 32.2%. 1242 lines of A_2 generation as the panicle-row lines from 90 A_1 plants were cultured in paddy field. Among them, 81 mutant lines were discovered. Various mutants in connection with heading date, culm length, leaf shape, leaf color, ear shape or sterility were also found (Table 4). Useful mutants having characters of early maturity and/or short culm were obtained (Table 5). In Kagahikari and Notohikari, mutants with delayed maturity (7 days later than control) and non-white beliverering grains were obtained, respectively. The behaviour of occurrence of these mutations in A_1 plant was discussed. Above mentioned results show that the anther culture technique is an useful means of mutation breeding in rice.

View full abstract

One-step procedure of anther culture by which plantlets are regenerated on anther culture media wothout transferring the embryos to a regeneration medium was studied in 6 wheat cultivars including Japanese wheat cultivars (strains), and compared with usual two-step procedure. Two kinds of media for one-step procedure were used ; C_<17> and N_6 basal media supplemented with 1.0mg/l of NAA and 1.5mg/l of kinetin (C_<17>-1 and N_6-1, respectively). For two-step procedure, C_<17> basal medium supplemented with 2.0mg/l of 2, 4-D and 0.5mg/l of kinetin (C_<17>-2) was used as an anther culture medium, and modified LS medium supplemented with 0.5mg/l of NAA and 0.5mg/l of kinetin as a regeneration medium. The frequencies of anthers which produced pollen embryos and regenerated plantlets varied with genotypes in both procedures. Kitakamikomugi showed the lowest frequency of embryo formation. Norin 61 showed the lower frequency of regenerated plantlets though it showed the higher frequency of embryo formation. The frequencies of green plantlet regeneration in Norin 12 and Orofen were 1.2% and 0.8%, respectively, in one-step procedure on the C_<17>-1 medium, while 0.2% in two-step procedure. This one-step procedure would be useful method for saving time, material and space in using anther culture technique at practical breeding.

View full abstract

Among the three genomes of common wheat (2n=6x=42, AABBDD), only the B genome donor has not been identified yet. This work was planned to extract B genome plants from durum wheat (2n=4x=28, AABB), which has common B genome chromosomes, by means of PFP (para-fluorophenylalanine) treatment. PFP was treated on the stigmas of durum wheat at 6 or 24h after self-pollination. The seeds were harvested and the chromosome number was observed in root tip cells. Among 573 plants observed, only three plants showed chromosomal aberrations, namely, one plant having fourteen chromosomes, one plant having one dicentric chromosome, and one plant having 29 chromosomes. The plant having fourteen chromosomes was found to be haploid, genome constitution being AB, by observation of meiosis. Calluses were then induced from immature inflorescences of the haploid plant. They were subcultured for nine months with the medium containing PFP. Chromosome aberrations were significantly induced in the cultured cells treated with PFP, though the effect on chromosome number reduction by PFP treatment was not clear. Thus, plants having only B genome chromosomes were not obtained in the present experiment.

View full abstract

Soybeans are the main crop in rotational paddy fields in Ishikawa prefecture, and the symbiotic nitrogen fixation activity of soybeans (Glycine max L. MERRILL) was compared for the three main soil types in Kaga district. To estimate the amount of fixed nitrogen, two pairs of nodulating and nonnodulating isolines (A62-1, A62-2 ; T201, T202) were employed and the recommended variety "Enrei" was also used for comparison with the nodulating isolines. To determine factors affecting the activity, the symbiotic nitrogen fixation of the soybean rhizobia group in each soil was examined under conditions that exclude the effect of physical and chemical properties of the soils. The symbiotic nitrogen fixation capability of pure cultures of isolated soybean rhizobia were also determined for each soil. The results may be summarized as follows. The ranking of the three soils (Gray Lowland soil, Andosol, and Yellow soil) in symbiotic nitrogen fixation activity of soybeans in case of the isolines was different from that in case of the "Enrei". With "Enrei", it was Gray Lowland soil &gt; Andosol ≧ Yellow soil. In. addition, the amount of fixed nitrogen of "Enrei" was much higher than that of the isolines. This showed that isoline with the same growth period and plant type as "Enrei" is necessary for selection. Symbiotic nitrogen fixation with the soybean rhizobia group was almost the same for Gray Lowland soil and Andosol, and in Yellow soil, it was inferior to the other two soils. There was no difference in the nitrogen fixation capability of isolated soybean rhizobia strains in these three soils. However, one isolated strain in Yellow soil had a high specific nitrogen fixation capability. From the above results, it was evident that the effects of soil conditions on the symbiotic nitrogen fixation activity of soybeans in the soils were stronger than that of the nitrogen fixation capability of rhizobia itself. A detailed determination of the biological factors among the soil conditions will be required.

View full abstract

In natural infection of bacterial blossom blight of kiwifruit, symptoms of infected buds and flowers are classified into five types. Initial infection of flower buds occurs on burst sepals of young buds. In this case, pathogenic bacteria invade through the wound of sepals causing a necrotic symptom on the sepals (S type). However, interior organs of the flower buds showed no symptom at this stage. After 3-4 days of rainfall, swelled buds showed most severe symptoms, all interior organs being rotted with dark brown rot color. Swelled buds were highly susceptible to the disease, and all the infected buds exhibited the most severe symptoms such as dark brown rot of stamens, stigmata and styles, and yellowish browning of petals (F-I and F-II types). If the infection had occurred in open or opening flower buds at the blossom stages, symptoms were mild and only limited number of anthers, and some of the stigma became faint brown color. Generally, infection of swelled buds resulted in remarkable infection of stigmata. When efflorescence followed soon after infection, light-symptoms were observed of the flowers. The stigma infection is related directly to falling of buds and fruits (Fr-I and II), and the production of various deformed fruits (Fr-III-A, B and C) of no commercial value. High concentration of the inoculum is essential for the occurrence of severe symptom of swelling buds. When high concentration of bacterial suspension that had been prepared from colonies of the pathogenic bacteria on nutrient agar medium were inoculated by spraying on the surface of swelling buds, necrosis of the bud were not observed for 3-4 days. When the same suspension was injected into interior of buds, however, the typical severe symptom appeared 2-3 days after injection. These results indicate that the bacteria cannot invade directly into buds from the outside in a short period of time. Even if many bacteria were spread from infected leaves and stems, they are most likely unable to invade quickly into swelled buds to cause severe infection. Infection of the interior organs of floral buds seems to occur in such a way that the bacterial ooze effused on inner surface of infected sepals are directly carried into interior organs with rainwater through interspace between the sepals and petals of swelled buds.

View full abstract

In order to investigate changes in composting process of the mixture of cow dung and rice husk (1 : 1, v/v), several maturity measuring methods were applied and their applicabilities were examined. Maturity measuring methods used in the study were the following six ones ; (1) C/N ratio of air-dry samples and C/organic N ratio of water extracts, (2) gel chromatograms of water extracts, (3) humic acid content, (4) thermograms by microthermometer, (5) bioassay with Lemna paucicostata under sterile condition, (6) tomato seedling test in a small pot. C/N ratio could be used as an simple index of the maturity of the compost of cow dung and rice husk. C/organic N of water extracts that had been proved to be effective in sewage sludge compost, however, showed no obvious change during the composting process. Gel chromatograms of water extracts showed the increase of high molecular comounds of dark brown color as expected to be humic substances, but the decrease of low molecular compounds was not so apparent. The content of humic acid was found to have a good correlation with C/N ratio and can be used as a simpler and better index of the comosting process than gel chromatogram. Thermograms measured by microthermometer showed that total heat generation became lower and the time of the maximum heat generation became earlier as the composting stage proceeded, which suggested the decrease of easily decomposed compounds and the increase of microbial density, respectively. In both bioassays using L. paucicostata or tomato seedling, the existence of plant growth inhibitor was shown in the first composting stage and it disappeared during the second composting stage. Some different results between Lemna assay and tomato assay suggested a possibility of the production of plant growth inhibitors during the decomposition of the compost in soil.

View full abstract