Under the condition of pool raising in Gunma Prefecture, we reduced the amount of soil in the nursery box to reduce the whole weight of the nursery box and to reduce the cost for raising paddy rice seedlings. The depth of covering soil was maintained at 7 mm in all plots, and the depth of basing soil was adjusted to 17, 13, 11, 7, and 0 mm. They were compared with the standard depth of 17 mm. We found that the 7 mm depth of basing soil and even no basing soil with 7 mm covering soil were able to raise seedlings having little effect on the accuracy of transplanting. However, in the bed without basing, it raised many seeds over covering soil and also the method of preventing seed-scattering out of nursery box was necessary for seeding. Moreover, for transplanting we must handle the thin mat much more carefully because the mat was too thin. Thus, we judged that the use of zero or 7 mm depth basing soil was unpractical. Considering the handling of mat and the accuracy of transplanting, we judged that the practical depth of the soil in a nursery box was 18 mm which was composed of 11 mm-depth basing soil and 7 mm covering soil. By this method, the weight of nursery box was reduced to about 20%, and the cost of the soil to about 25% compared with the conventional method.

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Winter wheat, usually seeded in autumn, was seeded before continuous snow cover to avoid the overlap between work for wheat sowing and rice harvesting. Then, the optimum seeding date and seeding density were determined. Winter wheat cultivar “Nanbukomugi” was seeded at intervals from early October to late November in 2000 ndash; 2002. The seedlings emerged when accumulative mean temperature above 0°C after seeding reached 95 ndash; 115°C. When the seeding date was early and accumulative mean temperature reached 95 ndash; 115°C before continuous snow cover, frost damage of the seedlings was serious. On the other hand, when seeding date was as late as early to late December, seedlings emerged after overwintering at a high rate, and grew and matured normally. We consider that the suitable seeding date for winter-seeding cultivation in Iwate Prefecture is early to late December. The winter-seeded wheat was inferior to the nomal autumn-seeded wheat in top growth, but had a large number of ears, low lodging frequency and a high grain yield of 379 g/m2, which was 95% of that in autumn-seeded wheat. The appearance quality of the grain was also nearly the same as that in autumn-seeded wheat, and the protein content of the grain was 14.4%, which was 1.4 point (%) higher than that in autumn-seeded wheat. The number of ears increased linearly with increasing seeding density. Grain yield also increased with increasing seeding density, but the maximum yield was 350 grains/m2.

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The re-accumulation of starch in the stem (culm and leaf sheath) of rice cultivars at harvest was examined from the viewpoint of the sink-source relationship as one of the characteristics of rice whole crop silage. Although stem starch content at harvest was high in some japonica cultivars, it was low in semi-dwarf indica cultivars. Some traits related to sink or source organ, especially in japonica cultivars, correlated with stem starch content at harvest. Spikelet number and the rate of increase in panicle dry weight per spikelet during the early-middle stage of ripening showed a significant negative and positive correlation with stem starch content at harvest respectively. Stem dry weight and leaf dry weight per spikelet at the middle stage of ripening also showed a significant positive correlation with stem starch content at harvest. These results suggested that the difference among japonica rice cultivars in their stem starch content at harvest could be determined from the size of their sink (grain and stem) and source (leaf) organs and the growth rate of the grain during the ripening period.

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Genetic relationships between cultivars are estimated either by coefficient of parentage, which is calculated using the database of cultivars lineage, or from genetic distance, which is calculated based on DNA polymorphism using the molecular markers. In this study, Euclidean distances and Nei's genetic distances among 22 barley cultivars were calculated using moleculer markers. The result of cluster analysis based on Eucedian distances was well explained by lineages of respective cultivars. A significant correlation (-0.526 ndash; -0.650) between the coefficients of parentage and the Nei's genetic distances was found among 22 modern cultivars grown in Japan. Thus, the validity of the coefficients of parentage between two cultivars, which are calculated assuming that cultivars derived from the crossing have half of the genetic materials of each parent, was supported by the genetic distance estimated from DNA polymorphism. On the other hand, the alleles detected by the molecular markers in this study were supposed to be nearly equally distributed to the offspring in the breeding process.

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To clarify the translocation pattern of photosynthetic products, and the effects of crop growth rate (CGR) and reserve substances before heading on the dry matter accumulation in the panicle during the grain filling stage, we examined the dynamics of dry matter in Nipponbare (japonica), Zhongyou No. 3 (indica) and Shanyou 63 (hybrid rice variety) grown at the paddy field of Shinshu Univ. in Central Japan. The dry matter in the stover and panicle was divided into two fractions: 1) cellular contents (CC) that could be degraded by crude enzymes (a-amylase and protease) and, 2) cell wall materials (CW) that could not be degraded. The dry matter accumulation rate in the panicle part was related to CGR in the Nipponbare and Zhongyou No. 3, but to the rate of dry matter translocation from stover to panicle in Shanyou 63. The accumulation rate of CW in a stover was related to CGR in every variety. The time when the rate of translocation from stover to panicle was maximal was earliest in Nipponbare followed by Zhongyou No. 3 and Shanyou 63. The dominant stage of translocation from stover to panicle was later in Shanyou 63 and Zhongyou No. 3 than in Nipponbare. The dates when the panicle growth rate was maximal were earliest in Zhongyou No. 3, followed by Nipponbare and Shanyou 63. The rate of dry matter accumulation in the panicle during the early grain filling stage was lowest in Shanyou 63 among the varieties, and the dry matter accumulation rate in the panicle was higher in the late grain filling stage than in the early grain filling stage. Thus, Shanyou 63 was suggested to have a lower ability to degrade stored compounds in the stover or have a higher content of water soluble materials.

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Pot experiments were conducted to observe the effects of incorporation timing and the amount of Chinese milk vetch (Astragalus sinicus L.) on the flowering and ripening of summer buckwheat (Fagopylum esculentum Moench, cv. Kitawasesoba). Chinese milk vetch as green manure was incorporated into the soil at rates of 50 g, 100 g, 200 g and 300 g fresh weight per pot of 5 liters in 1999, and at 50 g, 150 g and 300 g per pot in 2000. Early incorporation of larger amounts of Chinese milk vetch resulted in a higher seed yield in both years. A higher seed yield was obtained due to a larger number of flowers per plant. This early incorporation also increased the inorganic nitrogen content of the soil, promoting plant growth, and increasing the number of flowers. In addition, in spite of the greater number of flowers, the seed-setting rate did not decrease, possibly due to the high photosynthetic rate per plant brought by increase of leaf area during the middle ripening period. It is assumed that a sufficient amount of photosynthate was supplied to each flower under such conditions. It can be concluded that the early incorporation of 300g Chinese milk vetch into 5L pot was the best for the cultivation of summer buckwheat.

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The bleeding rate from the stem cut end is considered to reflect the root physiological activity since the bleeding is caused by the active water absorption by root. We analyzed factors affecting the bleeding rate using soybean seedlings in order to elucidate the relationship between the root respiration and bleeding rate in soybean plants. The bleeding rate was (1) exponentially decreased when the soil moisture percentage (w/w) dropped from 40% to 30%, (2) higher around 10 a.m. than in the early morning and evening, (3) rapidly declined after stem cutting for 6 hours and was constant thereafter, (4) affected by soil temperature and showed a nearly constant rate at 25 to 30°C, and (5) varied with the plant growth period corresponding to the variation of the root respiration rate showing the maximum level around 45 days after emergence, which is the flower bud initiation stage. When the above variable factors were set constant, the bleeding rate closely correlated with the root respiration rate, which can be expressed as the product of whole root weight and the respiration rate per root weight. Even though the bleeding rate was correlated with the whole root weight more closely than with the respiration rate per root weight, we could demonstrate that a higher respiration rate per root weight resulted in higher bleeding rate when the whole root weight was the same.

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To estimate the nitrogen competition between crops and living mulch plants, we compared the nitrogen flow in the sweet corn (Zea mays L.) - white clover (Trifolium repens L.) living mulch system (LM) with that in the conventional cultivation (CV). The field experiments were conducted in 2000 - 2002. Yield and total nitrogen content of sweet corn in LM were the same as that in CV. During the sweet corn growing period, the amount of nitrogen supplied from white clover residue to soil was estimated to be 11.72 gm-2. On the other hand, nitrogen taken up by white clover was 7.11 gm-2, and 1.55 gm-2 of which was from soil and fertilizer. The amount of nitrate leached out in LM was about 2.0 gm-2, which was lower than that in CV. The experiment using 15N showed that 27.3 % (2.48 gm-2) of nitrogen taken up by sweet corn was from the white clover residue and 6.62 gm-2 was from soil and fertilizer. The estimation of nitrogen flow showed that the nitrogen removal from soil in LM was about 2 gm-2 less than that in CV. These results suggest that nitrogen competition between sweet corn and white clover would be small. We consider that the rate of nitrogen fertilizer application could be reduced by using this living mulch system.

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To clarify the factors responsible for the changes in yield and brown rice quality due to the premature heading in rice, we grew two kinds of seedling of extremely early rice cultivars, ‘Tosapika’ and ‘Kitaake’ , under two temperature conditions different in the effective cumulative temperature (base temp. 10°C). Then, the seedlings with differentiated young panicles and those without differentiated panicles were transplanted to a paddy field. Similar results were obtained in the two cultivars. In the plants developed from the seedlings with differentiated young panicles, heading from the main culms was observed 30-32 days after transplanting (DAT), and that from the tillers 19-20 days later (donoted as premature-heading group). On the other hand, in the plants developed from the seedlings without differentiated panicles, the main culms headed at 57-58 DAT and the tillers two days later (control group). The heading duration of tillers in the premature-heading group (30-32 days) was longer than that in the control (13 days). In the premature-heading group, the final leaf number on the main culm was about 4 leaves lower than that in the control group (7.6-8.0 leaves) , but the numbers of tillers and panicles were higher. Yield in the premature-heading group was 9-15% lower than that in the control group. In the premature-heading group, although the number of panicles per unit area was higher, the number of spikelets per unit area was lower than in the control group, due to the markedly lower number of spikelets per panicle. The decrease in the number of spikelets, together with the lower percentage of filled grains on the tillers, was considered to be the reason for the lower yield in the premature-heading group. Furthermore, the apparent quality of the brown rice was low in the premature- heading group because of the presence of a lot of green rice kernels.

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Rice lines with a high seedling emergence rate were screened by sowing the seed 20 or 30 mm deep from the soil surface at 20°C or 25°C in a growth chamber, or placing the seeder-tape 20 mm deep from the soil surface in the field. As the gene sources of a high seedling emergence rate, we used Akamai from Japan, Arroz da Terra from Portugal, Dunghan Shali from Hungary, and Ta Hung Ku from China. However, these varieties had many inferior characters. To breed a practical cultivar with good agronomic characters in addition to a high seedling emergence rate, the Dontokoi or Kinuhikari were crossed with these varieties. From the hybrid progenies of Akamai and those of Ta Hung Ku, the lines with a high seedling emergence rate were selected by repeating the selection from early generations. From the hybrid progenies of Arroz da Terra and the those of Dunghan Shali, any lines with a high seedling emergence rate were not selected due to much trouble such as the frequent occurrence of leaf blast. For selecting the lines with a high seedling emergence rate, selection should be repeated from early generations. However, the lines selected for a high seedling emergence rate had inferior grain yield and quality, and further attempts of selecting the lines with high brown rice yield and good grain appearance are necessary.

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Viability of seeds in-shell of 198 cultivars of groundnut (Arachis hypogaea L.) stored at ambient temperature (5.5- 27.2°C, monthly mean for 1961-1990) since 1964, was examined in 1986, 1992 and 1993. Fifty to 100 air-dried pods of each cultivar were packed in kraft paper- or cheesecloth-bags, and 16-20 kg of them, were stored in a semi-hermetic tin-can (capacity 144 L) until 1972 and in a plastic hermetic container (75 L) after 1973, together with 5 and 2 kg calcium oxide cakes as desiccant (renewed once a year), respectively. In the two types of containers, relative humidity was 23 and 14%, respectively, and seed moisture was about 6 and 3%, respectively. Thirteen Spanish cultivars, two Virginia cultivars, and one inter-subspecific hybrid cultivar retained high germinability (&lsaquo80%) for 15-28 years of storage. Further studies on the reason of long seed viability of these cultivars, especially Spanish cultivars, and on the role of shell in retaining viability for a long period are necessary. Storage under the above conditions at ambient temperatures would be feasible as a small-scale conservation method of groundnut germplasm,especially that of Spanish cultivars, in the temperate and tropical regions.

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