Through genetic studies of the vernalization requirements of winter wheats, it was made clear that the varietal differences of vernalization requirements in winter wheat are gener-ally controlled by alleles of major genes which have mainly an additive effect. Two such genes were discovered to be involved in the expression of the varietal differences of the vernalization requirements of winter wheat. The gene tentatively named Aa is responsiblp for the difference in the vernalization requirements between cultivars with 20 days' requi-rement and cultivars with 40 days' requirement. A Iow level of vernalization requirement is incompletely dominant over a high level of requirement. The Bb gene is responsible for the difference between a vernalization requirement of 40 days and that of 60 days, where a low level of requirement is dominant over a high level of requirement, although the domi-nance effect is weaker than the former case. Because of the experimental procedure, the allelic relation between Aa andBb is unknown at present. In addition, the allelic relation of these alleles to the Vrn genes is a matter of future investigation. Besides major genes, minor genes were found to be responsible for the varietal differences in ver-nalization requirement. Namely, the difference between Akasabi Shirazu 1, which has a vernalization requirement of 60 days, and cultivars with a vernalization requirement of 40 days was found to be attributable to the curnulative effect of minor genes.

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In order to obtain new hybrids (Brassicoraphaleus) and to examine the genetic traits of matromorphs on a cytological basis, triploids of Brassica japoeeica were crossed with diploids of Raphanus sativus. Matromorphs could not be obtained, but some F₁ hybrids were produced. The chromosome numbers of the F₁ plants were 2n=19 (4 plants), 21 (1 plant) and 23 (2 plants). These plants showed some bivalents and trivalents in addition to univalents. They were almost completely sterile. One 2n=19 plant produced only one seed by open-pollination. An F₂ plant (2n=38) was grown from this seed. The chromosome pairing of this plant was shown to be (1-0)_IV+(2-O)_lll+(19-16)_ll+ (3-0)_l. F₃ plants were derived from selfed or open-pollinated seeds of the F₂ plant. Some of the selfed progeny had 36, 37 or 38 chromosomes. The fertilities of the selfed and open-pollinated progenies averaged 2.50 and 2.62 seeds per silique under open-pollinated conditions, respectively. The F₁ to F₃ plants in the present study were similar to the already reported F₁ hybrids and amphidiploids in cytological behaviour. However, the plants in the present study showed several characteristics: (1) some of the F₁ and F₂ plants had pale yellow flowers, (2) almost all the F₃ plants had yellow flowers, and (3) the F₃ plants showed a good seed fertility. The pale yellow of flowers in F₁ and F₂ generations was probably due to the incomplete dominance of a flower colour gene or the existence of modifying genes. The occurrence of the yellow flowers in F₃ greneration was explained as the result of fertilization with a pollen grain carrying yellovr colour genes from a foreign strain. The good fertility of the F₃ plants was possibly caused by a linkage relation between the flower colour gene and a fertility gene. Nevertheless, it was further surmised that there were still other genes affecting fertility. The cause of difference in fertility amongr amphidiploids (Brassicoraphanus) from different sources is now being under investigation.

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The mutagenic effect of sodiurn azide was studied under several treatment conditions in dry and pre-soaked seeds of barley. In dry seeds, the germination rate and seedling growth were reduced in proportion to the increase in concentration of sodium azide. The highest limit of chlorophyll mutation frequency was about 3xlO^-1 per M₁ spike and lxl0^-1 per M₂ seedling. The percentages of various types of chlorophyll mutation under all these treatment conditions were 47.8, 36.6 and 15.6 for albina, viridis and others (xantha, striata etc.) respectively. In presoaked seeds, the growth inhibiting effects of sodium azide did not increase with the prolongation of pre-soaking time. The highest value of chlorophyll mutation frequency was observed when sodium azide was applied at the S-phase in the first postdormant mitotic cycle. The frequency of visible mutants followed the same pattern. From these results, it is concluded that sodium azide is an effective mutagen and also that this agent is most effective in inducing mutation when applied at the S-phase.

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Effects of radiation on the embryonic development of Brassica pekinensis were inves-tigated quarititatively in relation to sizes of embryo, cell number of embryo and endosperm, mean cell size and difference between embryo and endosperm after irradiation. Embryos at different embryonic stages ranging from zygotes to small globular embryos were irradiated with 10 and 20KR of gamma rays for one day (Fig. 2). Pods were sampled for the observation of histological development of embryonic tissues. i. e., sizes of embryo, cell number of embryos and number of endosperm nuclei (apical and basal endosperm nuclei). A central size of continuous paraffin sections was selected as a part for measuring each tissue. The size of embryo expressed with transverse and longitudinal diameters of embryo tended to decrease when the plant was irradiated at more advanced stages. Cell number of embryos and the number of endosperm nuclei were seriously decreased by irradiation through entire stages tested, i, e. zygote through small globular at 6 days after irradia-tion.

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Ninety-seven Andean races of maize (Zea mays L.) native to Perti and Bolivia were grown in 1969 in the Experiment Farm of the University of Osaka PreLecture (34°35'N., 135°30'E.). The plants were exclusively delaying to mature in Osaka, especially in the races from 10wer latitudes and altitudes of the native countries. It was often difH:cult to do selfing in some races, especially frorn higher altitudes, because the silking delayed so long time that the ffowering of the tassel did not overlap with the former. Prolonged maturation had made the plants taller with greater number of nodes of the stalk. The longest leaf and the uppermost ear attached at quite high nodal positions, influenced by the altitude of the native cultivation site. Thus, the races were classifed into two grbups: (1) Races from lower altitudes (>1, 000m); The uppermost ear attached at an axil several leaves above the longest leaf. (2) Races from higher altitudes (>1, OOOm); The ear attached at the direct or near node of the longest leaf.

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Four early maturing barley varieties were sown in late summer at Kyushu Natl. Agric. Exp. Stn. and grown undet irrigated and non-irrigated conditions. Grain was harvested in Dec.-Jan. The results are shown in Tables I and 2. Experiments in the irrigated field : Water was led along channels between ridges occasion-ally. Seed was drilled by seeding rate of 400 kernels/m₂. The distance between the rows was 18 cm. One plot consisted of 5 rows which were 5 m long. Inner 3 rows were harvested in length of 3m.Sowing date was Aug. 26 Sep. 4 and Sep. 11, 1978. Basal dressing was l. O kg nitrogen/a and top dressing was O.5 kg nitrogen/a. Top dressing was applied when 3 Ieaves appeared. Enrergence and establishment of seedling were good. Saikai-kawa 24 (2-rowed) headed 42-46 days after sowing and grain matured in late Dec.-early Jan. Its growing period was about 4 months. Its grain yield was 32.0-39.5 kg/a. The high yield of this variety resulted from many ears. Hakei S 104 (6-rowed, introduced from CIMMYT as 4 th International Barley Observation Nursery No. 226) headed 34-37 days after sowing and matured in mid Dec. Its growing period was about 3 months. Its grain wa clarge and grain yield was 22. 6-34. 7 kg/a. Hakei S 104 had no tiller's ear and only ear of main stem bore seeds, whereas maturity of tiller's ear of Saikai-kawa 24 delayed under low temperature. Therefore, ripening period of Hakei S 104 became shorter than Saikai-kawa 24. Kawahonami (2-rowed) headed later than Saikai-kawa 24. It showed the highest total dry weight, so Kawahonami was assumed to be better than Saikai-kawa 24 for hay-making.

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Cooked rice grains were fxed with liquid air, then freeze-dried, and their surface and cross-sectional structures were observed by a scanning electron microscope. The surface of the cooked rice grain was consisted of two parts; the smooth areas and the rough areas. The smooth areas were liable to be positioned on the top of a grain and at the conjunction of two grains, and supposed to be evenly coated with some gel substances. Differences were observed among five tested varieties in the ratio of the smooth and rough areas (Fig. 1). Grains from high palatable varieties tended to show a higher ratio of the smooth to rough areas accompanied with a higher luster evaluation (Table 1). The height of the protuberances in the rough part tended to be lower in grains from high palatable varieties (Fig. 2). Besides the ratio of the smooth to rough areas, the height of the protuberances may affect the degree of luster of the grain surface. Varietal differences were also observed in the cross-sectional structures of the cooked grain. Storage cells in the endosperm from high palatable varieties such as Sasanishiki (Fig. 3-1eft) were more completely broken down as compared with those from lower palatable varieties such as Toyonishiki (Fig. 3-right). The degree of breakdown of the endosperm cells seems to have a relation to the degree of evenness of the grain surface.

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Extremely early cultivars of turnip, Brassica rapa L., with a rapid growth in younger stages to allow harvesting about 50 days after sowing, are in great demand in Jpan. A diallel-cross experiment was conducted to find to what extend the heterosis could participate in the early growth of turni, ps. Seven varieties differing from each other with regard to root size were used to yield 42 cross-combinations including reciprocals. Those forty-two F₁ hybrids and seven parental lines were planted in randomized blocks with two replications, and a diallel-cross analysis was performed. Plants were harvested 50 days after sowing, and measurement was made on diameter and length of plump root, diameter of tap root, and leaf length. The diameter of plump root at 50 days is taken as an indicator of the degree of earliness.

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The Korean rice variety, Tongil, was studied to know the inheritance of blast resistance. An F₃ population of the cross of PalkwengxTongil showed segregations which were able to be explained by two or more genes against seven fungus strains which had been used as differential fungus strains in Japan. The tests of hybrids of Tongil with KlYOSAWA'S differential varieties for classifying varieties based on blast resistance indicates that af least two of these genes for resistance in Tongil are Pi-a and Pi-b. Tests of Tongil with fungus mutants support the presence of the two genes. Tongil was susceptible to some Philippine fungus strains. The reactions of KIYOSAWA'S differential varieties to the Philippine fungus strains indicated that Kusabue has a gene or genes controlling moderate resistance to the strains. This resistance gene(s) is not carried by Tsuyuake.

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Progressive grafting experiments with two eggplant cultivars, Shinkuronasu and Shiro-nasu, in Solanum melongena L. were carried out to obtain graft-induced changes by two grafting methods. The so-called "Mentor method" were applied. The changes in fruit color (skin color-flesh color) and in Lruit shape (shape index= length/maximum diameter) were observed in the reciprocal graft combinations by seedling and fruit graftings. Based on the gene analysis of the fruit color by the crossings between Shinkuronasu and Shironasu, the gene changes in the grafted scions and their progenies were inferred as follows: from ddgg (white skin-white flesh, Shironasu type) or DDGG (dark purple-green, Shinkuronasu type) to DdGg (purple-green), from ddgg to ddGg (green-green), from ddgg to D-G-(purple to dark purple-green) +ddG-(green-green), from ddgg to D-G-+D-gg (purple to dark purple-white)+ddG-, from ddgg to D-G-+D-gg, from ddG- to D-G-, from ddG- to D-G-+D-gg, from D-gg to D-G- and from D-gg to D-G-+ddG-. It was discussed that the genotypic changes inferred fpr the fruit color in the grafted scions and their progenies were sirnilar to those in transformation phenomena in higher plants such as Petunia and Arabidopsis.

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