This study was conducted to examine the effects of tilling and seeding methods on the growth of rice direct-seeded in well-drained paddy field. The tilling methods used were plowing, non-tilling, and non-tilling-V-shape furrowing. The seeding methods used were dibbling at 1, 3 and 5 cm depth under the plowing condition, dibbling at 1 and 3 cm depth under non-tilling condition, and shallow and deep soil covering under the non-tilling-V-shape furrowing condition. Cultivar Koshihikari was used in this study. The percentage of emergence in most plots was higher than 70%, except for dibbling at 5 cm depth under plowing condition. Mesocotyl and the second internode elongated in some plots. In all plots, non-productive tillers rarely appeared. Many panicles differentiated on the tillers at nodal positions higher than the fourth node from the neck node of panicle, except for the plants seeded by dibbling at a 1 and 3 cm depth under a plowing condition. Dry matter weights of leaves and culms in direct-seeded plants were biased to the lower part of the plants compared with the transplanted plants. As a whole, the plants seeded by soil covering under non-tilling-V-shape furrowing condition showed the best growth, although there is a possibility of lodging in the field. When seeded by dibbling at a 3 cm depth under a non-tilling condition, the emergence was good and the lodging was not observed, but the panicle number was somewhat low.

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We investigated the effects of the drainage day after submerged direct seeding on the emergence and establishment of rice seedlings in pot experiments for the application of the new direct seeding method with a “shooting hill-seeder”. Draining flooded water after sowing rice seeds coated with calcium peroxide into puddled soil caused soil contract in due to the decrease of soil water (liquid phase) increased solid phase and change of soil structure. Draining immediately after seeding produced an air phase in the soil due to increase of air permeability in the soil. In contrast, no air phase was found in the soil flooded or drained five days after seeding. Furthermore, in the pots drained immediately after seeding the days to the second leaf emergence was decreased, and the dry weights of shoots and roots of the seedlings were increased compared with the pots with flooded and those drained on the fifth day after seeding. These results suggest that drainage immediately after seeding improves the rates of emergence and establishment of submerged direct-seeded rice seedlings.

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Tiller production of rice plants (cv. Kinuhikari) transplanted at different seedling numbers per hill (1, 3, 5, 7 and 9 seedlings per hill) was examined in 1994, a hot and sunny year. Tillering duration decreased with increasing number of seedlings per hill (density), and that in the 9-seedling hills was two weeks shorter than that in the 1-seedling hills. The higher the seedling density, the earlier was the time of tillering. In 1 to 5-seedling hills, the tiller production rate increased with increasing seedling density, but the rate decreased in the hills with higher seedling densities. Primary tillers emerged at the third (T3) to the ninth node (T9) of the main stem in 1-seedling hills, at T3 to T9 nodes in 3-seedling hills, and at T3 to T7 nodes in 5, 7and 9-seedling hills. Heading duration was 8—9 days in 5, 7and 9-seedling hills and 10—12 days in 1 and 3-seedling hills. The number of spikelets per panicle decreased with increasing seedling density, and the largest panicles on primary tillers were formed on the tillers at T7, T6, T5 and T4 nodes in 1, 3, 5, 7 and 9-seedling hills, respectively. These results suggest that, in hot and sunny years, seedling number per hill affects the tillering time, tiller number, heading time and panicle size on each nodal tiller.

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For stable production of rice with high grain quality and good eating quality, we investigated the weight of brown rice, the rate of whole grains and protein content of milled grains formed on the main stem, and on the tillers at each nodal position and nodal order in rice cultivar Akitakomachi transplanted at the 4th leaf stage. The tillering rate and productive rate were stably higher on the main stem and primary tillers at the 4-7th nodal positions than on other primary tillers or secondary tillers. The weight of brown rice per panicle was stably heavier on the main stem and primary tillers at the 4-7th nodal positions than on the secondary tillers. Moreover the rate of whole grain was higher on the main stem and primary tillers at the 4-7th nodal positions than on the secondary tillers. Protein content of milled grains was lowest on the main stem and primary tillers at the 4-5th nodal positions, followed by the primary tillers at the 6th nodal positions and other tillers in this order. These results confirm that the main stem and primary tillers at the 4-7th nodal positions are useful for achieving stable production of rice with high grain quality and good eating quality.

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The soybean breeding program for high isoflavone content started in 1996 at the Kariwano Branch of the National Agriculture Research Center for Tohoku Region. The isoflavone content of seeds of more than 2,000 soybean [Glycine max (L.) Merr.] and wild soybean (Glycine soja Sieb. et Zucc.) were evaluated using high-performance liquid chromatography (HPLC) from 1996 to 2002 to select parents for cross-breeding and to investigate the yearly change of isoflavone content. Isofavone content ranged from 23.5 to 848.5 mg/100gDW and was generally lower in early maturing than in medium and late maturing groups. Moreover, the difference in isoflavone content among varieties and lines was small in the early maturing group but was large in the medium and late maturing groups. The ratio of the content of daidzein to that of the total isoflavones ranged from 18.6 to 81.7% and stable in each germplasm. Moreover, the yearly coefficient of variation of total isoflavone content investigated for six years by using 18 varieties was 13.1-60.7%, and did not correlate with isoflavone content. In addition, it did not correlate with the seed coat color, the cotyledon color, the weight of 100 seeds and the crude protein content in all germplasms used. The seeding time, i. e., regular or late season culture, was significantly correlated with isoflavone content in 15 varieties. These results suggest the possibility of the breeding and cultivation of soybean with a high isoflavone content soybean.

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Evaluation of sesamin and sesamolin contents of sesame seeds is necessary for breeding lignan-rich sesame varieties. Maturity of individual capsules is not uniform in a sesame plant and the size and the sesamin and sesamolin contents of seeds also vary with the capsule. Seed weight is lighter in upper capsules which flowered later and is stable in the capsules more than 30-40 days after flowering. Sesamin and sesamolin contents of seed were highest in the capsules at 30 days after flowering, and decreased thereafter. Sesamin and sesamolin contents of seeds in the capsules, which flowered on the same date and were harvested on different dates, showed a similar trend related to the days after flowering. Sesamin and sesamolin contents of seeds changed with the seed maturity. Therefore, it is necessary to use the capsules at an accurate maturity stage to examine the varietal difference of the contents. Analyzing sesamin and sesamorin contents of seeds from the capsules which flowered and were harvested on the same dates is necessary for the selection of lignan rich sesame varieties. Especially the capsules around 30 days after flowering showed a large varietal difference in sesamin and sesamolin contents of seeds.

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For breeding rice with a high root-lodging resistance, which is important for direct seeding in subnerged paddy fields, selection of cultivars at the seedling stage is preferable. Twenty typical Indica and Japonica rice varieties were tested for root-lodging resistance and breaking resistance of the basal stem. Breaking resistance at the basal part of the seedling in the 20 varieties was measured using a push pull gauge at 23 days after sowing. It varied from 12.9 N to 27.9 N and lodging resistance highly correlated with the breaking resistance. Next, we selected eight varieties and examined the change in pushing resistance and breaking resistance of basal stem after heading. None of the varieties showed any significant change pushing resistance. Breaking resistance was significantly reduced in three varieties, but it did not change in five varieties. Pushing resistance at any time after heading was highly correlated with breaking resistance of the basal stem in eight varieties. Thus, it is concluded that the lodging resistance at the ripening stage of the rice varieties can be evaluated by the breaking resistance at the basal part of the seedlings.

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The hydraulic resistances of each organ in napiergrass and maize shoots were measured with a pressure flow meter. The results obtained were as follows: 1) Hydraulic resistances of the shoot, leaf and stem, R_shoot, R_leaf and R_stem, respectively, in napiergrass were significantly higher than those in maize. Particularly, R_stem in napiergrass was about four-fold larger than that in maize. 2) The cross sectional area of a stem (SA) was smaller in napiergrass than in maize, and the difference between napiergrass and maize in R_stem normalized by SA (R^S_stem) was smaller than that in R_stem. However, R^S_stem in napiergrass was still about two-fold larger than that in maize, indicating that napiergrass has a higher hydraulic resistance in the stem due to the synergistic effect of these two factors. 3) The hydraulic resistance of a stem was divided into three components, the resistance toward the leaf sheath of the nodal stem (γ_γ), the resistance toward the stem apex of the nodal stem (γ_a) and the resistance of the inter-nodal stem (γ_in). Both γ_γ and γ_a were high in napiergrass and the difference between napiergrass and maize was particularly large in γ_γ. These results suggested that a high R^S_stem in napiergrass was related with the water transport through the nodal stem. It was considered that a small stem diameter and high hydraulic resistance of nodal stem would result in a high resistance to water flow in napiergrass stem.

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The effects of root pruning on formation of crown root primordia (CRP) in young rice seedlings was examined morphologically in consideration of the size and running of a peripheral cylinder of longitudinal vascular bundles (PV). Seedlings at the 3.2 leaf stage were transplanted to a paddy field after pruning all roots. Main stems were sampled four times until the 7.2 leaf stage; then serial cross-sections were observed under a light microscope. Root pruning decreased the PV area (side area of PV) throughout the stem (from the coleoptile ‘unit’ to the 5th ‘unit’), especially apical part of the stem (from the third ‘unit’ and to apex), but did not affect the CRP number. On the other hand, the diameter of the basal portion of CRP decreased once (4.2 and 5.2 leaf stages) in the third ‘unit’, but it subsequently recovered. Consequently, the number of CRP per PV area and the ratio of the sum of basal area of CRP to PV area were increased by root pruning, especially in the apical part of the stem (from the third ‘unit’ to apex). These results suggested that the number of CRP in young seedlings was unaffected by root pruning at transplantation, although the PV shrank and the CRP diameter decreased temporarily. Moreover, activities of differentiation of CRP and/or formation of the crown root tissues, which originated in PV, seem to be increased by root pruning, promoting recovery from transplantation injury.

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In recent years, the early season culture using the early cultivars has been commonly practiced in early season rice culture on the coastal areas in Kochi Prefecture. In order to clarify the yield-determining factors in this cropping type, we compared the characteristics of dry matter production and the yielding abilities of the early cultivars, ‘Tosapika’, ‘Natsuhikari’ and ‘Koshihikari’ with those of a medium cultivar, ‘Koganenishiki’. The period from the transplanting to the panicle formation stage was the shortest in ‘Tosapika’ among the early cultivars and followed by ‘Natsuhikari’ and ‘Koshihikari’. The period was shorter when the middle seedlings at the 4.1—4.6 leaf age were transplanted when young seedling at the 3.0—3.3 leaf age were transplanted in all the cultivars. The yield did not differ between the plants transplanted at the middle and young seedling stage in all the early cultivars. The highest brown rice yield was observed in ‘Koshihikari’ due to a higher percentage of ripened grains and higher number of spikelets per m². Significant differences in the brown rice yield were not observed among the other three cultivars. ‘Tosapika’ was comparable with ‘Koshihikari’ in the number of spikelets, but had a lower percentage of ripened grains and 1000-grain weight. The top dry weights of early cultivars were lighter than that of ‘Koganenishiki’ through the whole growth duration. However, early cultivars showed the higher crop growth rate due to the higher net assimilation rates and the higher dry matter partitioning ratios to the panicle during ripening period. On the other hand, the sink/source ratio (number of spikelets per m²/leaf area index at full heading stage) was the highest in ‘Tosapika’ among the cultivars and which might be closely related with the lower degree of grain filling (percentage of ripened grains×1000-grain weight). It was suggested that the increase of grain filling by controlling source size is necessary for attaining the higher stable yield of ‘Tosapika’, an extremely early cultivar, in the warm southwestern district of Japan.

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A japonica rice (cv.Koshihikari) was used to test the effects on blooming and ripening of UV-B radiation treatment combined with high temperature treatments (day/night, 35 / 30°C). Strong UV-B radiation (60.4 kJ/m² · day) slightly increased sterility. High temperatures and weak UV-B radiation (18.1 kJ/m² · day) applied together from two weeks before heading and from the heading day increased sterility and those applied from two weeks after heading decreased sterility. High temperature combined with strong UV-B radiation applied from two weeks before heading increased sterility and decreased the size of unhulled grain and anther length. The same treatment given from the heading stage greatly increased sterility and decreased anther length and pollen production, and that given two weeks after heading decreased unhulled grain weight. It also decreaed photosynthetic rate in Flag leaves. A high temperature applied together with strong UV-B radiation had a synergistic effect causing poor growth; it increased the harmful effects of a high temperature and sttong UV-B given separately, on the sterility and pollen formation.

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The objective of this study was to establish the technology to identify paddy rice cultivars by Ramdom Amplified Polymorphic DNA (RAPD) analysis to raise the quality of rice in Tochigi prefecture and to prevent seed contamination in the foundation seed and the stock seed. A total of 20 paddy rice cultivars including 9 recommended and promising cultivars in Tochigi prefecture, were studied. They could be identified individually by the electrophoresis of the DNA fragments amplified by PCR using 7 random primers, on 1.5% agarose gels and by staining with ethidium bromide.

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This study investigated the effects of puddling and drainage on seedling emergence and establishment of rice direct seeded with a “shooting hill-seeder” in submerged paddy fields. Water content (oxygen diffusion rate) of puddled soil was higher (lower) in the plots where puddling was conducted twice with a paddy harrow than in the plots puddled only once. Water content and the oxygen diffusion rate of puddled soil varied somewhat with the degree of drainage after sowing even within the same plot due to irregular leveling there. The water content (oxygen diffusion rate) of soil was lower (higher) in the well-drained part than in the poorly drained part. The number of established rice seedlings per square meter in the twice-puddled plot was lower than that in the once-puddled plot. The number of established rice seedlings per square meter was the lowest in the poorly drained part of the once-puddled plot, and seedling growth there was the worst. These suggest that in rice seeding with a shooting hill-seeder followed by drainage less puddling (avoiding over-puddling) and proper draining with uniform leveling are necessary for both stable seedling emergence and establishment.

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In 1986, a new-type transplanting machine for the 6th leaf-emerging seedlings was introduced to two innovative farmers' groups at Kikuchi district in Kumamoto Prefecture where transplanting machines for the 4th or 5th leaf-emerging seedlings were used since around 1975 to increase grain yield. One of the agricultural practices used in Yamagata Prefecture for the new-type transplanting machine, is a so-called "multiple row planting" method in which every 6 or 8 rows with 30-33cm row spacing were separated by 60cm. A yield survey was conducted in two paddy fields for Koshihikari an early variety and seven paddy fields for Minaminishiki that is late variety. Grain yield per unit land area at the outermost row with 60cm distance between the units of multiple rows for Koshihikari was 82% and 87% to that in the inner rows. For Minaminishiki, grain yield per unit land area in the outermost row was almost the same as that in the inner rows when the distance between the units of multiple rows was 45cm. When the distance was 60cm, grain yield in the outermost row ranged from 78% to 91% of that in the inter rows with one exception where 20-50 t/ha of swine fully fermented compost was applied every year and the grain yield was 109%. Rice plants grown in the outermost row could not increase the number of panicles and grain yield per panicles to compensate for the enlarged occupied land area.

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