Tissue cultures were initiated from root sections excised from 5∼7 day-old seedling, in 60 varieties including various ecospecies i.e. japonica, indica, japonica-iridica hybrids, and large grain varieties (assumed to be javanica type) in rice (Oryza sativa L.) on basal Murashige and Skoog's (1962) medium containing 3.0 mg/l 2, 4-dichlorophenoxyacetic acid (2, 4-D), 2.O g/l of casein hydrolysate, and 30 g/l sucrose. Cultures were maintained on the same medium with 2.O mg/l 2, 4-D. Plant regeneration was accomplished by subculturing for 2 to 3 passages to the same basal medium with 0.02mg/l 2, 4-D and 10mg/l kinetin. Remarkable variability in plant regeneration was observed among varieties tested. All the cultures of the japonica varieties had good capacity for regeneration, while some of the cultures of indica, japonica-indica hybrids, and large grain varieties were poor. It was observed that 11 of 28 cultures in japonica, 2 of 16 in indica, and 1 of 10 in large grain varieties had relatively high potential for regeneration at more than 30%. Besides normal plant regeneration, cultures showed various responses such as massive rooting without shoot formation, retention of green pigmented region without further development, and occurence of necrotic dead tissue. Two distinct types of plant regeneration were observed, one of which was organogenesis, and other was somatic embryogenesis. Most of the cultures from the indica varieties, Chyokoto and Gaiya Dhan Tosar, initiated plantlet through somatic embryogenesis.

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Experiments were carried out to determin the relationship between the style shortening observed shortly after pollination and the seed fertility (percent of fertile seeds to the total number of disc florets on each flower head). 1. It was found that the morphological difference existed between shortened style and unshortened style observed shortly after pollination was maintained until the seed maturation. 2. Where times of pollination were varied, both percentage of disc florets with shortened style to the total number of disc florets on each flower head and seed fertility increased with increased time of pollination. Moreover, in the disc florets without the shortened style, no seed was harvested. 3. In the case where self- and cross-pollination were made throughout the whle flowering period, it was observed that the percentage of disc florets with shortened style on each flower head and the seed fertility showed the various values, and the relationship between them was highly and positively correlated. Therefore, it was suggested that crossing for seed production could be done rapidly by observing whether the style shortened or otherwise after pollination. 4. To determine the status of the style shortening in the natural condition, observation on disc florets on each of flower head after open-pollination was carried out. In this case also, the relation between the paercentage of disc florets with shortened style to the total number of disc florets on each flower head and seed fertility was highly and positively correlated. This confirmed that the style shortening observed shortly after compatible pollination was the general phenomenon in the disc floret of chrysanthemum.

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We examined the variation of DNA content in six Glycine species. DNA amount was estimated through Feulgen microspectrophotometry and chemical extraction. Glycine soja, known as the wild ancestor of G.max, has higher DNA content than G.tnax, although some overlapping occurs. Therefore, cellular DNA content has been reduced during the course of soybean domestication. As G.tabacina and tomentella contain both diploid and tetraploid strains, the interspecific variation was examined based on DNA content per chromosome. Glycinc soja has more chromosomal DNA than G.tabacina and probably other wild species. Therefore, we can conclude that the wild species, G.soja which has relatively high chromosomal DNA amount among wild relatives, was domesticated to the cultivated soybean. We consider that the relatively high DNA content of G, soja has enabled the wide genetic variation resulting in the formation of soybean through the reduction of DNA. The reduction of DNA amount through domestication will be also expected in other crops than soybean and rice.

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Flowering response of 7 cultivars belonging to 3 different varieties of Brassica campestris were explored in their relation to vernalization, photoperiod and gibberellins (GAs) under controlled environment using growth cabinets. In 5 Japanese cultivars (Nozawana, Uzuki-Komatsuna, Shin-Santosai, Bansei-Mana and Shigatsu-Shirona) out of 7 ones tested, flowering did not occur under 8hour photoperiods even though they had been vernalized (20 days) and received GA3 although it induced stem elongation. In those cultivars GAs are likely to play a direct role in the bolting but probably are not directly functional in initiating flowering. Two Chinese cultivars tested here were unique for their flowering responses. Tsai Hsin was a day neutral cultivar wlth low vernalization requirement ; it flowered either under 24 and 8hour photoperiods in both of vernalized and nonvernalized plants. Hong Tsai Tai was a typical long-day plant and it did not require vernalization under 24hour photoperiod. On the other hand, vernalization substituted the long-day requirement since seed-vernalized plants flowered even under short-days. Application of GA3 induced the flowering in nonvernalized plants under 8hour photoperiod and that of Ancymidol, an inhibitor of GA biosynthesis, inhibited the flowering of vernalized plants. In this cultivar, GAS Seem to play some role not only in the bolting but also in the ffowering itself.

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Inheritance of quantitative resitance of IR28 was studied through the analysis of 6 populations, P₁, P₂, F₁, F₂, B₁ and B₂, derived from each of two crosses, Toyonishiki/IR28 and Todorokiwase/IR28. In both the crosses, F₂, B₁ and B₂ populations showed each a continuous variation in the resistance to each bacterial group. In some combinations of plant material and bacterial group, it was proved that transforming the original data into square roots was the most adequate for the analysis by additive-dominance model, and the major contribution to population mean was made by additive gene effects. There were some other cases where data were not fit for additive-dominance model through every kind of transformation attempted. In these cases, the effect of a digenic interaction remained yet in the total effect of all the genes controlling the resistance, though additive gene effects were also significant. Both heritabilities in a narrow sense and in a broad sense proved to be significantly different from zero and fairly high, suggesting that the selection for the resistance at an early generation of hybrid is effective. Quantitatlve resistances to bacterial groups II, III and IV highly correlated with each other both genetically and phenotypically. These high correlations probably make it possible to select the plants non-specifically resistant to all the three bacterial groups by the inoculation of only one of them.

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Early internode elongation of barley causes possible frost injury in spring. It needs for avoiding frost injury to begin internode elongation later. The effects of temperature and photoperiod on the beginning of internode elongation were investigated. When a total of about 100 varieties and breeding lines was grown in field conditions, a positive correlation was found between the beginning of internode elongation and the heading time. However, some varieties gave relatively late beginning of internode elongation together with early heading. Furthermore, five representative varieties were examined in the controlled conditions of temperature and photoperiod. Under long day condition, internode elongation was uniformly retarded with Lalling in temperature, regardless of varieties. There could be seen no appreciable differences in response to temperature. The varietal differences in internode elongation were given under short day condition, and enlarged with the rise of temperaure. Therefore, the sensitivity to short day was one of the main factors to control the beginning of internode elongation. It was discussed whether the breeding of early heading varieties with the late beginning of internode elongation would be feasible.

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Inheritance of resistance to Alternaria blotch caused by Alternaria mali Roberts in apple was studied. F₁ seedlings were inoculated at their four to six-leaf stage with spore suspension of an Alternaria strain AKI-3, and according to the criteria for the reaction, they were classified into R (resistant) and S (susceptible) groups (Figs. 1 and 2). A total of 27 F₁ cross combinations among eight varieties of known disease reaction were investigated in the first experiment. As the result, segregation ratios of 1R:3S and 1R:1S were found in the parental crosses of S×S and S×R or its reciprocals, respectively, while few susceptible plants were seen in the crosses between resistant varieties. This will be plausibly explained on the assumption that the resistance to Alternaria blotch is controlled by a single recessive gene, and the genic constitution of the susceptible varieties used in this experiment are all heterozygous for the gene pair. So, a gene symbol Alt alt is allotted for susceptible vs. resistant condition for this disease.

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Effects of radiation on the development of embryo in Brassica oleracea var. capitata L. (Varieties; Kinpai and Kairyofuji) were investigated to increase the survival rates of embryos by culture techniques after irradiation of doses which were sterile to seed formation, with the purpose of increasing mutation rates. Embryos at different developmental stages ranging from globular to early heart embryo were irradiated with 20kR of gamma rays at the daily rate of 5kR or 20kR (Fig.1 and Table 1). The embryos were excised from ovules 7 to 30 days after irradiation and were cultured on Bladeys' media. Seed fertility was higher in 5kR/day than 20kR/day. Seed germination exhibited 0% in all doses and dose rates except for control. Therefore, it w.as recognized that the doses used in the experiments were lethal ones.

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Sterility is one of the obstacles to rice breeding for introducing useful genes by wide crossing, and many studies have reported on the sterility in indica×japonica crosses of rice. However, very few reports have dealt with female sterility. Typical female sterility was found in the backcrossed progenies that were developed in the breeding program to incorporate the blast resistance of an Indonesian variety "Tjina" into a Japanese variety "Fujisaka 5". The Fl of the cross Fujisaka 5×Tjina was backcrossed with pollens of Fujisaka 5. Plants with very low spikelet fertility were found in the selfing lines following the fourth backcross. Each panicle bore a few seeds (Fig.1), although it headed at the same time as the recurrent parent Fujisaka 5 under favorable growing conditions in mid-August. Spikelets of sterile plants opened normally and had iodine-stainable and highly fertile pollen grains in anthers, as Fujisaka 5 did (Table 6). The emasculated spikelets of Fujisaka 5 bore seeds at a high rate when they were crossed with pollens of sterile plants, but the emasculated spikelets of sterile plants set no seeds even when normal pollens of Fujisaka 5 were sprinkled over their. stigmas (Table 5). Since the defect of embryo-sac development was observed in the ovules of sterile plants (Fig.2), the sterility in these materials was due to female sterility.

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This study was planned to know the effect of grain shape on the notching of rice grain which has already been shown to occur primarily due to the unbalance between floral glume size and growth of caryopsis. A total of nine crosses were prepared; six were the crosses between normal grained varieties and minute grained ones with the dwarf genes d-1 or d-7, and the remaining three were the crosses between normal type varieties. To measure the potential length of caryopsis (Tl), upper parts of floral glumes on one or two panicles of each plant were clipped off two or three days after anthesis. In this state the caryopsis elongated without restriction by the floral glumes (Fig.2). The natural length of caryopsis (Cl) was estimated by measuring the grain length encased by floral glumes. Because Tl is longer than Cl, the degree of unbalance between Tl and Cl will be expressed as the ratio of Tl against Cl. Grain shape index can be indicated as Cl divided by Cb, breadth of caryopsis.

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S alleles and respective S-glycoproteins in 29 F₁ hybrid varieties of Japanese radish were analysed to know practical problems that may lie in the S-glycoproteln analysis for S allele handling. One plant was taken at random from respective varieties and selfed progenies were observed. Out of 29 families, 20 showed segregation for incompatibility and were explained by assuming two S alleles with sporophytic action. The others showed no prominent segregation (7 families) or complex segregation (2 families). Thirty three homozygotes for S alleles were established. Diallel pollination test between the 33 homozygotes was carried out to examine the identity of the S alleles. Although the test has not been completed, they were classified into 20 different S alleles: 19 were comprised of 6 different S alleles and the rest 14 were assumed to be different each other.

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