Induction of somatic embryos from mature seed of melon (Cucumis melo. L.) was conducted on media solidified with gelrite. The most reproducible result was obtained with rhombic explant consisted of radicle, hypocotyl, and a promixal part of cytoledon. Somatic embryos were produced around the cut surface at the border of hypocotyl and cotyledon. Soaking sterilized seed in water for two hours or more promoted embryogenesis. Numbers of somatic embryos were increased by the supplementation of 2 mg/l NAA to modified MS media together with 1∼4mg/l 2, 4-D and 0.1 mg/l BA. Percentages of germination (rooting and shoot formation) were different among various shapes of somatic embryos. 'Thin cone' shaped embryo germinated in high percentage. Regenerated plants grew normally and set fruits.

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Extremely high concentration of pool type of gibberellins (GAs) which was detected by the Tan-ginbozu dwarf rice assay was found to be localized in the uppermost internodes of submerged and non-submerged floating rice plants. However, the level of the blologically active type of GAS which was detected by the Waito-C dwarf rice assay was higher in the internodes of the submerged plants than in those of the non-submerged ones. Amounts of GAS in leaves were also found to be higher in the submerged plants than in the non-submerged ones.

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Hitherto, there is little {nformation on species or line and organ specificity concerning callus and organ formation, plant regeneration from calli and proliferation from explants in yam species. To address, we examined variation in species/organ specificity for callus induction and organogenesis using three yam species, i.e. Dioscorea esculenta BURK., D. rotun.data POIR. and D. alata L. Axillary buds or shoot tips and single-node segments with one or two axillary buds were inoculated onto the culture media containing various combinations of plant hormones. Using axillary buds, D. esculenta acc. LE 030 produced calli on MS medium containing 2.0mg/l NAA in combination with 0.0, 0.2 and 0.5mg/l BA followed by green spot (45 to 75%), shoot (20 fo 30%) and root (20 to 90%) formation from calli. Similarly, D. alata L. cv. Farm Lisbon produced calli only on MS medium containing 1.0mg/l BA and 2.0mg/l NAA followed by high green spot (75%), shoot (50%) and root (10%) formation from the calli. On the other hand, two accessions of D, rotundata i.e. HR 018 and 020 produced calli followed by green spot (13 to 100%) and root (15 to 85%), but no shoot formatlon from the calli. Using single-node segments, two accessions of D. esculenta produced shoots at an average of 2.8 directly from nodal explant without callus formation on MS medium containing 0.1 mg/l NAA and 0.2 mg/l BA. Similarly, two accessions of D. rotundata produced shoots at an average of 3.2 to 4.8 on MS medium containing 1.0 to 2.0mg/l and 0.2 to 2.0mg/l BA. However, two cultlvars of D. alata and two accessions of D. rotuudata produced at an average of 4.0 and 6.0 shoots, respectively through the proliferation of bud on MS medium containing 15.0mg/l adenine sulfate. This proliferation was not affected by the additlon of NAAat 0.1, 0.5 and 1.0mg/l NAA. The present experiment showed species or line and organ specificity for callus and organ formation and plant regeneration from calli and direct proliferation from axillary buds. Particularly, It is important that D. alata with poor seed formatlon regenerated plants from calli and also directly from single-node segment through the proliferation of axillary buds.

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In vitro callus formation by mature embryo explants, and subsequent plant regeneration were investigated using 203 Japanese and introduced varieties of barley (Hordeum vulgare L.). These included 176 six-rowed and 27 two-rowed genotypes. Mature embryos detached from seeds were inoculated on the modified N6 medium containing 2 mg/l 2, 4-dichlorophenoxyacetic acid (2, 4-D). Callus was produced in 193 varieties, although most of the calli were soft, watery, translucent and poor in proliferation. Plants could be regenerated from secondary callus especially with some two-rowed genotypes. The growth of secondary callus was promoted by increasing 2, 4-D concentration to 5 mg/l. Plant regeneration was observed in 14 varieties including 6 six-rowed and 8 two-rowed ones. Some of the varieties used, especially the two-rowed ones: may be useful for developing the mature embryo culture system in barley.

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The isogenic lines of d-12(yukara dwarf )d-18^K(kotaketamanishiki dwarf)and d-47(t)(dee-geo-woo-gen dwarf), and their recurrent parent, Shiokari were used in this study. They are abbreviated to d-12 Iine, d-18^k line and d-47 Iine with their gene symbols. Cool air treatments with and without deep water were carried out by means of artificial light growih rooms, both of which were set at 12°C for 4 days. The former and the latter are abbreviated to "DW" and "CA" respectively The cool temperature tolerance itself was mvestigat ed through the CA; the tolerances of the lines at the bootlng stage seem to be in the order of d-18k line Shiokari d-12 line d-47 line. In the DW, each treated pot was filled with water to a depth of 14 cm. The water temperature rose to about 16°C owing to the illumination at about 50, 000 lux. In d-18^k line, the dropping of spikelet fertility (31.9%), which is shown in the CA, was not observed in the DW; the lowest value in the DW was as high as 58.3%. This difference between the DW and CA was caused by the fact that the developing panicle of d-18^k line was almost wholly under the water surface until 9 days before heading. The most serious sterility of d-12 Iine was also alleviated since a considerable part of its developing panicle was under the water surface. On the other hand, the most serious sterility of Shiokari was not alleviated since its developing panicle wholly protruded from the water surface. That of d-47 line was not alleviated owing to its high sensitivity to cool temperature. Furthermore, it is found that d-18^k line almost eluded the cool weather damage at the booting stage in Kitami, Hokkaido in 1980.

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Soybean calli with nodular characteristics (nodular calli) and high regeneration potential were found to be induced by cocultivated with strains of bacteria Pseudomonas maltophilia in vitro. Upon subculture of the nodular calli, somatic embryos were regenerated. Unfortunately no complete plants have been obtained from the cultures so far because the somatic embryos were malformed to various degrees. Histological analysis revealed that the nodules were well organized. Young nodules possessed mostly small cells with densely stained nuclei, which are considered to have high potential to yield somatic embryos under improved culture conditions. Besides the cocultivated bacteria, the age and physiological state of the calli and ingredients of culture mediurn were also important factors affecting nodular callus formation. The findings on this experiment suggest that the cocultivtion system may be developed to solve the serious problems in regenerating plants from callus culture of soybean.

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Sixty Asian varieties (Oryza sativa L.) which had been classified into Indica and Japonica types based on diagnostic characters (OKA 1958), were investigated for the genotypes of 10 isozyme species including 17 Ioci (Fig. 1 and 2, Table 1, 2 and 4). Genotypic frequencies at 11 loci, Acp-1. Amp-2. Cat-1. Est-2, Mal-1, Pgd-1. Pgi-1. Pboi-2, Pgi-3. Pox-2 and Sdh-1 were significantly different between Indica and Japonica types (Table 5). Discriminant scores (D scores) for Indica and Japonica varieties were calculated for the above eleven loci. However, the alleles at Pgd-1 and Sdh-1 Ioci were not enough to discriminate between Indica and Japonica types. D score averaged over the nine loci excluding Pgd-1 and Sdh-1, appeared to be more useful than that based on the eleven loci (Table 7). Thus, the Asian varieties were classified by using D scores averaged over the nine loci (Fig. 3A). Japonica varieties except for one and Indica varieties classified by OKA (1958) showed D scores ranging from 0.12 to 0.30 and from 0.69 to 0.94, respectively. Only one Japonica variety showed D scores with a value of 0.6. Because the variety carried alleles frequently found in Japonica type varieties, only at Acp-1, Mal-1 and Pgi-1 and alleles frequently found in Indica type varieties at other six loci, it appeared to be a 'recombinant type' between Indica and Japonica varieties. Based on these results, varieties with D scores ranging from 0.0 to 0.4 and from 0.6 to 1.0 were confirmed to be Japonica and Indica types, respectively, and newly used Pgi-3 and Mal-1 were also confirmed to be useful for discriminating the varieties.

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Seven types of monosomic addition lines of radish with single kale chromosome (a∼g) have been bred by successive crossings of synthetic arnphidiploid Raphanobrassica (2n=36, RRCC) with radish (Raphanus sativus L., 2n=18, RR) (KANEKO, et al. 1987). In this paper, the transrnission rate of each kale chromosome in these seven monosomic addition lines was estimated by studying their morphology, and chromosome number as well as pollen and seed fertility. The materials used in this paper were the progenies derived from the reciprocal crosses between the seven monosomic addition lines (B₁F₁) and radish, the intercrosses among different addition lines, the sibcrosses of each type and the intercrosses between different addition lines.

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The differentiation of physiological races in Fusarium graminearum SCHWABE, a causal fungus of barley scab was analyzed in this study. Twenty Fusarium strains collected from Japan and US from 1933 to 1985 (Table 1) were inoculated to 20 barley varieties sampled from about 5, 000 varieties of the world collection preserved in the Barley Germplasm Center, Okayama University (Table 2). "Cut-spike" inoculation method developed by the authors (TAKEDA and HETA 1989) was applied for evaluating the degree of virulence of the Fusarium strains and the degree of resistance of the barley varieties. At the flowering time, three spikes of each barley variety were cut and sprayed with the conidia suspension of each Fusarium strain, and they were kept in a phytotron where the temperature, humidity and light conditions were controlled. Thereafter the percentage of infected florets were recorded on the eighth day after inoculation. The experiment was replicated twice. For the statistical analyses, the percentage of infected florets was transformed into the degree of angle.

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Soybean seeds contain isoflavone compounds which are responsible for the undesirable flavor of soybean products, namely bitterness and astringency. The analysis of isoflavones of soybean cultivars using high performance liquid chromatography revealed that in some early maturing cultivars, so-called "summer-type soybeans", the isoflavone contents were remarkably low. The low isoflavone content in the soybean cultivars grown under standard culture conditions was found to be stable.

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In order to maintain alien chromosome addition lines, it is very important to increase the level of male transmisslon rate. By limited pollination with a small number of pollen grains, the rates of late-flowering plants which might be due to a cabbage chromosome increased significantly in alien chromosome addition plants (2n = 21) of Ch{nese cabbage with single cabbage chromosome

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A morphological marker locus was utilized to analyse the possible linkage with the ability of regeneration in barley. Callus formation and shoot differentiation were initiated from immature embryos of P₁, P₂, F_l and F₂ plant populations from a cross between a sixrowed cultivar × two-rowed cultivar. Broad sense heritability for the regeneratlon rate was 0.76, thus showing definite contributions of genetical factors to regeneration. Regeneration rate was associated with the character of kernel row number; plant regeneration was enhanced by gene(s) coupling with the V allele on chromosome 2 from the two-rowed parent.

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We have constructed a genetic map of the nuclear genome in rice (Oryza sativa L.), utilizing 322 restriction fragment length polymorphism (RFLP) DNA markers and nine morphologlcal and biochemical genetlc markers. The RFLP map is based on the segregation of 144 F₂ plants from a cross between Indica and Japonica varieties. The map covers a total of 1, 836 cM with 347 loci and exceeds the data recorded in the classical genetic map of rice by 58.5% and the current RFLP map (McCOUCH et al. 1988) by 32.2%. The RFLP linkage groups were assigned to the twelve chromosomes of rice using trisomic mutants andseveral genetic markers. This map should provide the basis for the mapping of genes controlling agronomic traits of rice.

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