The long-term nonfertilized paddy fields managed by NPO Nonorganic, Nonchemical Crop Production Research have maintained the grain yields of approximately 3 t ha^-1. However, the nutritional evaluation for the maintenance are still limited. This study aimed to characterize the nutritional dynamics in long-term nonfertilized paddy fields on the basis of measurements in 2014. The nutrients concentrations in soil solution showed consistency with those in a liquid layer after anaerobic incubation of soil, suggesting that the dynamics of nutrients concentration in soil solution were reflected by the supply ability of nutrients from soil. The concentrations of PO₄^3-，K⁺，Mg²⁺，Ca²⁺，SiO₂ in irrigated water higher than those in drained water, respectively, suggesting some amount of these nutrients were supplied by irrigation. The nutrients concentration of rice showed that nutrients deficiency were not observed except K⁺. The nutrients concentrations in soil solution did not always indicate rice productivity, recommending dynamic analysis for the relationship between nutrients concentrations in soil solution and nutrients uptakes.

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We conducted field experiments to select rice cultivars that are resistant to "multiple environmental stress", i.e., drought, flood and salinity for two years. We used Oryza sativa, O. glaberrima and NERICA cultivars that showed both flood and salinity tolerance, and compared drought resistance and recovery among these cultivars. Drought treatment was imposed by rain shelter, and after the treatment plants were rewatered to evaluate recovery for 10 days. During drought and recovery period, shoot dry weight, photosynthesis and transpiration were measured. Further, root research and growth analysis was conducted in the first and second year, respectively. Among the cultivars with drought resistance selected with relative shoot weight of drought treatment to control, O. glaberrima cultivars have a property as deep water rice, hence they may be candidate cultivars for regions prone to both drought and flood. In comparison of the recovery, only O. glaberrima showed negative correlation between the physiological parameters in drought period and those in recovery period. Moreover, two O. glaberrima cultivars showed greater relative growth ratio during recovery period in drought treatment than in control, suggesting that their high ability in the recovery is one of the important strategies for drought resistance.

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Annual and perennial differentiation in rice has been one of the major concerns for rice geneticists and ecologists. Among the traits related to reproductive systems, shooting and rooting ability from the nodes and ratooning ability were focused in this study. They were evaluated using backcross recombinant inbred lines (BRILs) between a perennial cultivar of Oryza sativa Nipponbare and an annual accession of O. rufipogon W630. Firstly, five pairs of first and second nodes from the top were collected from each BRIL plant before and after maturing stages. They were half-dipped in water for three weeks and shoot and root generation was observed. From the first nodes, few BRIL plants produced shoots at both stages, whereas most of them generated shoots from the second nodes. Rooting ability was not well observed for the first nodes of the BRILs after maturing, but almost half of their first nodes produced roots before maturing. From the second nodes, many BRILs generated roots at both stages. Continuous frequency distributions in the BRILs were observed for the shooting and rooting ability from the second nodes after maturing. Based on these data, QTL analysis was carried out, however, no significant loci were detected. Environmental factors such as water temperature might affect the evaluation of the traits. Secondly, ratooning ability was examined with another set of BRILs. About 60 days after heading, the percentages of ratoon numbers relative to total number of productive tillers were examined in the field. They were used for QTL analysis for ratooning ability, and one QTL was detected in the region of RM25-RM44 on chromosome 8 with LOD score of 4.2. Chromosome segment substitution analysis on the putative region will be needed to confirm the QTL location.

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Early flowering 1 (Ehd1), which is one of the most important genes controlling basic vegetative growth (BVG), plays critical roles in regulation of heading time. Therefore, it is important to analyze the interaction among Ehd1 and other heading-time genes. However, studies on the interaction of Ehd1 and other heading-time genes have been conducted with the different genetic background. In this study, single mutant lines induced by gamma-ray irradiation of the japonica rice cultivar "Gimbozu" were used with multiple mutant lines raised from the intercrossing of those single mutant lines. Thus, we could evaluate the interaction of Ehd1 and other heading-time genes under the same genetic background. Days to heading under short day (DTH_SD) was regarded as the BVG and the difference between days to heading under long day and short day (PSP_L-S) was regarded as photoperiod sensitivity (PS). In lines with Ehd1 allele, DTH_SD was constant regardless of PSP_L-S. In lines with ehd1 allele, DTH_SD was getting smaller as PSP_L-S become large. Ehd1 functions as the promoter of heading-time under short day condition, any effects of PS alleles on BVP might be masked by Ehd1 allele. Thus, the loss of function of Ehd1 allele can enable to exhibit the potential function of PS allele on BVG.

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Rice (Oryza sativa L.) is derived from the Asian common wild rice, O. rufipogon. In the early stage of domestication, panicle shape may be a key trait before the emergence of plants with non-seed shattering, because wild plants with cultivated-like type of closed panicles were observed to reduce seed shattering through seed retention. Previously, we identified a major locus for this trait to be SPR3 on chromosome 4, controlling gene expression of OsLG1. However, we also found some experimental lines, i.e., BC₂F₈ backcross recombinant inbred lines between O. sativa Nipponbare and O. rufipogon W630, that showed open panicles without wild alleles at SPR3. In this study, a line of AsN136 was selected from them in order to survey new genomic regions responsible for panicle spreading in wild rice. The AsN136 had wild homozygous alleles at 27 out of 180 SSR marker loci, showing nine wild chromosomal segments in the genetic background of Nipponbare. This line was crossed with Nipponbare, and the segregating population consisted of 150 BC₃F₂ plants were produced. They were planted in the paddy field, and their panicle shape was examined based on the observation of the rachisbranch junctions. QTL analysis for panicle shape was carried out with their marker genotype data at 27 SSR loci. As a result, two putative loci were detected on chromosomes 5 and 11, explaining 37.6% and 4.9% of the total phenotypic variance, respectively. The putative locus on chromosome 5 with stronger effect was further examined by the progeny test using BC₃F₃ plants. The results indicated that a new factor for panicle shape was located in the region of RM421-RM274. Expression analysis on OsLG1 and fine mapping of the new locus on chromosome 5 may give good clues to clarify the gene mechanism of panicle spreading.

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The high-resolution X-ray CT measuring was carried out in SPring-8 for the judgment of the shattering habit of unhulled rice in an aggregate of spikelet and part of panicle excavated from the remains in the early Yayoi Period (cal BC480±30). The shattering habit was estimated by analysis of the X-ray CT image of pixel size 25 μm of the base microstructure of unhulled rice in the aggregate. The shattering proportion was 35%. Since the shattering part of the unhulled rice was abscission layer at the base of rachilla, it was suggested in this case that the grade of shattering habit of unhulled rice in the aggregate was equivalent to very easy shattering of current cultivar. The unhulled rice in the aggregate judged as shattering or non-shattering was classified into japonica type instead of indica type with high shattering habit from the spikelet shape (length-to-width ratio). Furthermore, it was shown that the harvesting time of the unhulled rice, whose shattering habit was judged, would be presumed from evaluating the grain filling level of the unhulled rice by the thickness of brown rice latest determined in a growth of spikelet.

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It is important to understand the shear strength of rooted soil to estimate root lodging of crop plants. The shear strength of soil is expressed by the cohesion and friction coefficients, which are called the strength coefficients. The direct shear test is one of the simple procedures for measuring the strength coefficients. Strength coefficients are understood as the sum of the strength coefficients of the soil and the reinforcement of the roots. There have been few studies done on the strength coefficients of rooted soil which includes the roots of cereals and the reinforcement of the roots of cereals. In this paper, we attempted to conduct direct shear tests using rooted soils which comprise the roots of wheat under different water contents and different mixing amounts of roots in order to understand the shear strength of rooted soils which contain the roots of cereals. In the measurements, the rooted soils and the soils without stump were sampled from the same cultivated field. The water content of the samples was adjusted before conducting the direct shear tests. As a result, the accuracy of the strength coefficients was low for the samples which included pieces of wheat stumps. In contrast, the accuracy of the strength coefficients was high for the samples absent of any pieces of stump under any water or root content conditions. In addition, the effect of shear reinforcement against cohesion was mainly confirmed. It was confirmed at 10~25 kPa under a moisture weight percentage of 18%; however, it was hardly confirmed under a percentage of 24~28%.

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We investigated the effects of soil incorporation of hairy vetch (Vicia villosa Roth） on the yield, yield component, inspection grade and protein content of lowland rice plants in Hyogo Prefecture, western Japan. The effect of the soil incorporation of hairy vetch was observed throughout the growth period. For the stable securing of yield, it was thought that the combination with the weeding system from the early days was necessary.

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Plant breeding is to select agronomically valuable genotypes from a diverse set of gene combinations established through hybridizations and subsequent genetic recombinations. Therefore, it is important for the breeding science to understand how to control the recombination frequency. In the present study, we developed a new high-throughput method for analyzing the recombination frequency within wx locus in rice using an image processing software(ImageJ) and analyzed the effect of a retrotransposon(RT) on the recombination frequency around it. To develop the method, we used two near-isogenic rice lines, T65wx and 73wx1. These lines have different mutations on Wx gene, which controls starch synthesis in rice. Although these two lines produce only wx type pollen, F₁ plants developed from a cross between them produce Wx type pollen in a low frequency because of an intra-genic recombination between the two mutations on Wx locus. Therefore, it is possible to analyze the recombination frequency from a frequency of Wx type pollen. In this study, we used an image processing techniques for counting the total number of pollen grains. This enabled us to count the number of pollen grains more efficiently and precisely. By using the method described in this report, we also examined the effect of RT-insertion and found that an RT insertion on Wx gene reduces the intra-genic recombination frequency around the insertion.

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Supply of excellent seeds is indispensable to stable production of wheat. "Norin 61", which is a main wheat breed in Shiga prefecture, is usually harvest in rainy season of June. Therefore it is hard to judge seed harvest, and produced seeds are frequently under standard for germination examination. In this study, we investigated factors to affect germination on seed production. As a result, it was revealed that the germination rate decreased when harvesting high grain moisture above 30%. And seedling rate in field is lower than germination rate in laboratory. It is necessary for seeds with stable seedling in field to harvest wheat below 25% of grain moisture.

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A work of a new breed has been performed by crossbreeding or mutation induction by radiation or chemical, but use of the mutant by the ion beam irradiation is watched in recent years. An ion beam breeding which has higher mutation rate than other mutation breeding, doesn't decline fertility, and is available by vegetative propagation plants. In Hyogo prefecture, we induced mutants by ion beam irradiation in a chrysanthemum and an ornamental kale plant. We selected mainly by a flower color mutation in chrysanthemum, and made it clear that the tendency different from the part which appears of the mutation is seen at large mum and small mum. In ornamental kale plant, we selected the early coloring mutants whose coloring also becomes early in the climate that is too hot to color in late summer. Ion beam breeding was performed in various kinds of flowering plants, such as verbena, dahlia, rose, torenia, dianthus, toad lily, cymbidium and cherry tree. Some of those were registered and marketed. And now, ion beam breeding is also performed by the various lists of articles, and we think that various new breeds will be born increasingly from now on.

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Soybean［Glycine max (L.） Merr.］ is one of the important legume crops for food and feed supply, and its seed contains about 40% protein and 20% oil of dry weight. In recent years, consumers have great attention in functional components of healthy food, and also desire health-oriented new cultivars. In addition, soybean genome was sequenced in 2010, and approximately 54,000 predicted genes were published on a database, which were predicted from their nucleotide sequences. Since the function about most of the predicted genes are still unknown, researchers desire efficient tools to explore their function. Here, I present an overview of our soybean mutant resource and mutant screening system, which have a potential to develop novel breeding materials.

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Heavy-ion beams effectively induce DNA double strand breaks by their dense ionization effect on the irradiated cells. The degree of locally deposited energy is represented by the linear energy transfer（LET; the energy transferred per unit length, keV μm^-1). The value of the LET can be controlled by selecting ion-species or controlling the velocity of the ions. We found the most effective LET on mutation induction in Arabidopsis thaliana, and that the size of deletions induced by heavyion irradiation increases as increasing the value of LET. Based on these results, we proposed "on demand mutagenesis", in which the value of LET is selected for individual research purposes. Here, we presented the detail of the LET effect in heavyion irradiation together with the recently produced beneficial mutants of einkorn wheat, chlorella, and brown seaweed, which will be seeds of green innovation.

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A research progress in the gene accounting for the important breeding trait in crops allows to know that the useful trait has been generated by a mutation in the original gene. Recently, a genome editing technology has been developed and there has been a growing interest to apply it to create useful mutations in crops. Here, the tomato as a case study, I introduce an example of crop design research using the genome editing technology and issues towards implementation of the products.

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The word "Epigenome" refers to functional dynamics of the genome defined by covalent chemical modifications of nuclear DNA and histones. Regulation of epigenome state is important for maintenance of genome integrity through determining positions of meiotic recombination and mutation frequency that are key factors for efficient crop breeding. Recent progresses in cross breeding utilizing DNA markers and genomic selection have markedly accelerated efficiency in selection of individuals carrying appropriate genome compositions. However, approaches for active regulation of positions of meiotic recombination and frequency of mutation have been tried only poorly. Here I introduce several recent studies towards establishing active and novel approaches for genome engineering through epigenome regulation.

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