To map earliness gene(s) on the 7 th chromosome of rice, Oryza sativa L., three earlyheading isogenic lines T65 ?? R-1, T65 ?? R-5 and T65 ?? R-6, were bred after 9 or 10 backcrosses with Taichung 65 (a cultivar from Taiwan) to two interchange homozygotes T3-7 and RT7-11, and a linkage tester HO 775, respectively. Each early-heading isogenic line carried a dominant earliness gene. The earliness gene was one of the allele of Ef₁ locus (early flowering), which is identical with or isoallelic to Ef₁^b. Ef₁ was linked with seven breakpoints involving the 7 th chromosome, 7-11, 6-7, 3-7, 7-8b, 7-9, 7-8a, and 2-7a, and two genes an the chromasome, fgl (faded green leaves) and pgl (pale green leaves), recombination values being 2. 2, 3. O, 7. 8, 11. g, 23. 3, 25. 9, 28. 5, 15. 3 and 29.0%, respectively. Ef₁ was estimated not to be located on the 9 th chromosome, but on the 7th, and the early observation of a linkage between Ef₁^b and the lazy growthhabit gene la on the 9th chromosome was not correct. The arrangement of four linked genes and seven breakpoints on the 7 th chromosome were estimated as pgl-7-8 b-Rf₁-fgl-7-11-Ef₁-6-7-3-7-7-9-7-8 a-2-7 a.

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To analyse the genetic aspects of C₃ and C₄ photosynthetic systems, the photosynthetic charcacteristics of the progenies derived from a backcross, (Atriplex rosea (C₄, 2 n=18, 2x)xA.patula (C₃, 2n=36, 4x))xA, rosea, were investigated. Out of three plants derived from the backcross, two showed C4-Iike traits based on the C0₂ compensation point and δ¹³C values as well as enzyme analysis and leaf anatomy. Another plant showed C₃-like characteristics. The descendants of these plants were segregated into three discrete morphofogical types ; p-type plants which were similar to A. patula ; d-type plants which were dwarf with dark green leaves ; and r-type plants which resembled A.rosea but exhibited a highly branching habit. The isozyme patterns of the leaves of the pand d-types were similar to those of A.patula, while th.e isozyme patterns of the r-type were either similar to those of A.rosea or different from the parental patterns. Based on anatomical, photosynthetic and enzymological observations, the p- and d-types showed C₃-like traits, whereas the r-type C₄-like ones. Chromosome analysis from the root tips revealed a 2n=36 number in the p- and d-types and a 2n=18 one in the r-type. It is suggested that the expression of C₄ photosynthesis is affected by the dose of the genome of the C₄ species and that the genes related to C₄ photosynthesis tend to be inherited as a group in the interspecific hybrids.

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Maintenance of valuable genotypes of common buckwheat is difiicult owing to heterostylic self-incompatibility. To establish vegetative propagation system, a procedure for plant regeneration from immature inflorescence culture was developed. Immature inflorescences of common buckwheat and perennial buckwheat were cultured on B5 media supplemented with NAA, 2, 4-D and BA at various concentrations. Direct shoot production from the inflorescence of common buckwheat was promoted by the addition of 0-2.0 mg/l NAA+0-2.0mg/l BA (optimum. 0.2 mg/l NAA+1. 0 mg/l BA). In perennial buckwheat, direct shoot was induced only on the medium containing 1.0mg/l NAA and l.0mg/l BA with lower frequency. than common buckwheat. In the presence of more than 1.0mg/l 2, 4-D or more than 2.0mg/l NAA, callus was well formed in both species. Shoots were induced from common. buckwheat callus on B5 medium containing 0.2 mg/l NAA and 1.0mg/l BA and lacking plant growth regulators, but not from perennial buckwheat. The shoots obtained by the two different pathways developed a root system on MS medium containing 1.0 mg/l IBA. Chromosomal analysis of the directly induced regenerants showed that they had diploid chromosome numbers (2 n=16).

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Cultivars of four crop species, rice, soybean, eggplant and tobacco, their ancestral species and their wild relatives were cultivated in pot and field under presently employed conventional methods. Their products were measured in order to compare the yields between the current cultivar, its wild ancestor and the related wild species. In rice, grain yield was higher in the ancestral species than the other three Oryza species in both pot and field experiments. This was also the case for tobacco, in whlch leaf weight of one of the ancestors was larger in pot and field than the cultivated species. Soybean presented a little different situation. In the pot experiment, ancestral species showed higher grain yield than the cultivated species, but the order of species in grain weight was reversed in the field experiment. However, the difference in grain yield was not very large in either experiment. In the case of eggplant, the cultivated species outyielded the wild species in both pot and field experiments. In the fleld experiment, however, the fruit yield of one ancestor was 90% of cultivated species. These results show that under the present conditions, yield of wild ancestor does not largely differ from that of the cultivated species in these crops. Wild ancestors are characterized by the relatively high yield among wild species. The results may show that the domestication is not the process of increasing the yield.

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Cultivars or mutant lines which contain glutinous endosperm starch have been developed in seven crops, including rice, maize, barley, etc. However, reports on Triticum species with glutinous endosperm are not available. Attempts were made to induce the mutation of endosperm glutinousness in Triticum monococcum L. by treatment with EMS. Four hundred seeds of T. Inonococcum were pre-soaked for 20h and treated with 0.4% (v/v) EMS for 24h at room temperataure. Germination percentage was 42.0%After transplanting of the M₁ seedlings to a field, 99M₁ plants died partly due to late transplanting and severe winter weather conditions. However, 2, 016 M₂ seeds were harvested from the fertile 59M₁ plants which survived. By staining the endosperm starch of the distal part of the seeds with a KI-I₂ solution, six out of 2, 016 seeds showed a red brown color, which is the typical reaction of glutinous endosperm starch to KI-I₂. Consequently, these six M₂ seeds were considered to be glutinous endosperm mutants. The appearance of these seeds was not different from that of the seeds of normal T. monococcum. Two M₂ seeds were also obtained, in which the endosperm starch showed a reddish purple color rather than the typical purple color of non-glutinous starch. The present results indicate that glutinous endosperm mutants can be obtained in Triticum species.

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The rates of germination and seedling growth of the maize F₁ hybrid (Oh 545xW22) exceeded those of the parental lines in the later period of germination. The content of free fatty acids (FFA) in the scutellum of the F₁ hybrid increased faster than in either parental lines. On the other hand, the decrease in the concentration of two protein fractions detected by electrophoresis in the embryo was greater in the F₁ hybrid than in the parents. The enzymatic activities concerned with the lipid metabolism (lipase, catalase, isocitrate lyase and malate synthetase) and protein decomposition (proteinase) were higher in the F₁ hybrid than in the parental lines. Embryo of F₁ hybrid contained a larger amount of ribosomal ribonucleic acid (rRNA) than the parental lines, and the amount of ³H-leucine incorporation into the embryo was the largest in the F₁ hybrid. The results of the present experiments suggest that the higher activity of the lipid and protein metabolism in the embryo was related to the more vigorous cell growth of the embryonic axis, and induced faster germination of the F₁ hybrid kernels.

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Ginger has a low propagation rate and pathogens can be transmitted through the rhizomes to the next generation, as it is a vegetatively propagated crop. The purpose of this study was to develop a technique of efficient clonal propagation of g;nger by tissue culture. In the apical meristem culture on, agar media, treatment with high BA concentrations induced the increase of the number of buds and inhibited rooting. There was no clear relationship between the NAA concentration and the number of regenerated buds and the development of roots. Many plants with normal shoots and roots were obtained on modified MS medium with low BA concentrations, and at the maximum 6.3 plants were obtained at I mg/l BA without NAA supplementation(Table 1). In the culture of stem discs with axillary buds on agar media, the modified MS medium was more suitable than the B5 medium in relation to the rate of shooting or rooting. There was no relationship between the growth regulator concentration and the rate of shooting or rooting. However, the modified MS medium containing 3 mg/l BA and 5mg/l NAA was the most suitable medium for plant regeneration from stem discs (Table 2). In the rollel- tube culture of stem discs in liquid media, 2, 4-D induced either callus formation or tissue expansion. Multiple bud clumps were obtained in the modlfied MS medium with high BA concentrations, and the BA concentration was positively correlated with the number of buds (Table 3, Fig. 1). The mean bud number of a multiple bud clump was 44.5 and the maximum was 61. The multiple bud clumps could be subcultured and propag.ated by cutting the clumps into pieces in the liquid medium containing 10 mg/l BA. When the cut buds were cultured on agar medium with 3mg/l BA they began to grow quickly up to on intact plant, and acclimation of the regenerated plant was easy. It is concluded that multiple bud clumps obtained by roller tube culture are useful for the micropropagation of ginger.

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Grain ripening was examined in the rice cultivar, Hokuriku 130, which has very large grains and is high yielding. In the eight genotypes with a wide range of grain size. width of brown rice grain showed a plateau at 3.6mm. after the hull width exceeded 4.3 mm. Hence in the genotypes with a hull width exceeding 4.4 mm, the grain ripening was unsatisfactory leading to a decrease in grain ripening (lower husking ratio). In the Hokuriku 130, the hull was 4. 1 mm wide and the cultivar exhibited the highest husking ratio. When Hokuriku 130 was compared with a standard cultivar Koganebare, it gave a considerably higher yield because the 1-grain weight was 85-89% larger with a comparable percentage of ripened grains although the number of spikelets per m² was 34-40% lower. In addition, the percentage of the grains on the primary rachis-branches was remarkably higher which obviously contributed to the higher percentage of ripened grains. It is suggested that the good ripening characteristics of the Hokuriku 130 were due to the higher percentage of grains on the primary rachis-branches resulting from the smaller number of spikelets per panicle and the suitable hull width which offers good grain ripening.

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Using a computer image analysis, we tried to characterize the plant type of four rice cultivars, Koshihikari, Sasanishiki, Akihikari and Milyang 23. A color photograph of a plant profile of a single plant growing in a pot was taken at five stages from the maximum tillering stage to 12 days after heading. The photographic images were transferred to the image processing system. Each cultivar was visually characterized by the contour lines of leaf-density and the arrows representing leaf angles in each sub-area on a computer display. Comparison of the numerical factors associated with the plrant type showed clear intervarietal differences. The characteristics of each cultivar were not prominent at the early stages but became clearer at and after the heading time. It is considered that the computer image analysis used in the present study is useful for objectively and numerically describing a plant type which is closely connected with the light-receiving efficiency of cultivars, without any destruction of plant material.

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The nature of the resistance to inLestation with the azuki bean weevil was investigated in the progeny of crosses between two susceptible mung bean (Vigna radiata) cultivars, Osaka-ryokutou and No. 3-ryokutou, and a resistant wild mung bean (V. sublobata) strain, TC 1966. The F₁ and, F₂ seeds from the crosses were subjected to test for the detection of the weevil resistance. Segregation of the F₂ plant populations derived from the crossesfor the resistance was examined by subjecting the F₃ seeds obtained from individual F₂ plants to the same test. The results indicated that the weevil resistance of TC 1966 was controlled by a single dominant gene for which the gene symbol R was proposed. Two backcrosses were made to Osaka-ryokutou with selection for the weevil resistance. In the BC₂F₂ generation, mungbean type-resistant plants whose seeds showed similar morphological traits such as seed size and seed coat color to those of Osaka-ryokutou were obtained.

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Indirect somatic embryogenesis occurred in Japanese persimmon 'Fuyu' Ieaf segments which were cut from shoots one year plus four or five weeks after the beginning of subculturing on Murashige and Skoog's medium which contained half strength nitrogen (1/2 NMS) supplemented with 10^-5M zeatin. Embryo formation was increased by the addition of 10-6M BAP and 10-5 M NAA to the same 1/2NMS medium in which the shoots had been cultured. Leaf segments planted with their obverse sides in contact with the medium showed a higher percentage of embryo formation than those planted with their reverse sides in contact.

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Populations of artificial autotetraploids of rice (Oryza sativa L, cvs. Nipponbare and Fukunishiki) were repeatedly irradiated with gamma-rays through several generations. Plants which did not differ in appearance from the original diploid plants occurred occasionally in the populations. These plants were designated as diploid-like plants. Eight diploid-like plants were obtained so far, and their generations were advanced without irradiation in order to examine the mode of segregation of visible characters in their progeny. The results indicated that plants showing several kinds of mutant characters could be obtained and were fully fertile. Usefulness of the tetraploid-irradiation technique for developing fertile rice plants which exhibit gross phenotypic changes is discussed.

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