[in Japanese]

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To cultivate waxy rice instead of transplanting by direct sowing in Hokkaido, we investigated the germination, emergence and establishment of waxy rice (cv. Hakuchou-mochi and cv. Kazenoko-mochi) under artificial or natural conditions, and also investigated the growth and yield of waxy rice (cv. Hakuchou-mochi) by machinery direct sowing in a well-drained paddy field from 1998 to 2001. The rates of germination and emergence of the two cultivars of waxy rice under artificial conditions were higher than those of nonwaxy rice (cv. Yukimaru) that was used for direct sowing. In the paddy field, the establishment percentages of the waxy rice were slightly inferior to or nearly the same as those of the nonwaxy rice under shallow seeding depth conditions. In the case of deep seeding conditions, the establishment percentages of the waxy rice were higher than those of the nonwaxy rice. The establishment of the waxy cultivar sown with a up-cut rotary seeder in a well-drained paddy field was 32 to 56%, and the number of establishment was 159 to 234 seedlings per m². When the seeds not coated with oxygen supplier (calcium peroxide) were used, the number of established seedlings decreased. The heading and maturity stage of the waxy rice directly sown at a suitable seeding time were 2 to 6 days and 0 to 2 days later, respectively, than those of transplanted waxy rice. The yield of directly sown plants was 86 to 115% of that of transplanted plants, and late sowing greatly decreased the yield except in 1999. The number of established seedlings was correlated with that of panicles, and the panicle number was higher in the directly sown plants than in the transplanted plants. Because yield increased as the panicle number increased, it is important to increase the number of established seedlings for increase of the yield. However, the yield was also affected by meteorological conditions. For the introduction of direct sowing of waxy rice to Hokkaido instead of transplanting, it is necessary to consider the delay of heading and maturity stage.

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A new nursery box (trade name : Karukaru-new-line) for rice seedlings was developed jointly by the Tochigi Prefecture Agricultural Experiment Station and a material manufacturer (Marusan Sangyo Corp.). It has a depth of about 2/3 of the ordinary nursery box, and the soil used is also reduced to about 2/3. However, the new nursery box is not only light but also good for raising seedlings. In this study, we examined the possibility of using the new nursery box for pool raising of seedlings under the conditions, widely used in Gunma prefecture, for 3 years. Aithough more roots extended from the bottom of the new nursery box when the nursing period was prolonged, the rooting pattern was different and, it was not necessary to cut the roots or to prevent root extension, which was usually necessary with the ordinary nursery box at the time of transplanting. Because of the smaller amount of soil, the amount of fertilizer was also reduced, and the growth in the new nursery box was sometimes inferior without additional fertilizer. However, transplant precision, rooting and early growth were not significantly different from those in the ordinary box, and it is there were no problems for utilizing the new method.

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In order to investigate the possibility of cultivating soybeans in a flooded paddy field, we examined the secondary aerenchyma formation, growth and yield of soybean variety ‘Aso aogari’, which forms secondary aerenchyma well, under flooded conditions. Plants were irrigated as occasion demanded or continuously flooded up to 3 cm above the soil surface after the primary leaf expanded. The flooded plants could grow until harvest. The secondary aerenchyma was observed in the hypocotyl, tap root, adventitious roots and nodules of flooded plants in the early growth stage, and its volume increased as plants grew older, although it was rare in the irrigated plants. Hypocotyl porosity of flooded plants was higher than that of irrigated plants throughout the growth period. In the pot experiment, flooding decreased the growth and grain yield per plant. In the field experiment, however, flooded plants under dense planting had the same number of ripening pods and seeds per unit area as irrigated plants had, and grain yield was over 300 g/m². These results suggested that the variety grew until harvest under flooding forming secondary aerenchyma quickly and maintaining the ventilation system until the late growth stage. Soybean cultivation in the flooded paddy field would be feasible.

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Job’s-tears (Coix lacryma-jobi L. var frumentacea Makino), cv. Hatochikara was sown in an upland field converted from a paddy field at the densities of 2.8, 5.6, 6.3, 8.3, 11.1, 16.0 and 25.0 hill per m². The dry weights of the stems and leaves and grain yield increased as the planting density increased up to 11.1 hill per m². As the planting density increased further the dry weights of stems and leaves gradually increased but that of the grains decreased, and thus their sum remained at the same level. The dry weights of stems and leaves highly correlated with the number of stems (r=0.884^**) and total number stem nodes (r=0.829^**). The number of stems per plant was decreased by dense planting due to the reduced stem emergence and decreased survival rate of the stems. The number of bracts increased as the planting density increased up to 11.1 hill per m², but slightly decreased at the higher density. The higher the planting density, the smaller the stem diameter, the lower the number of bracts. These results suggested that the number of bracts was reduced by dense planting through the reduced growth of stems. The number of kernels and grain yield highly correlated with the number of bracts, though the sterile kernels slightly increased as the planting density increased. From these results it was suggested that the decrease in grain yield caused by dense planting would be attributable mainly to the suppression of the emergence and growth of stems.

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The accuracy of the results of a sensory test for highly palatable rice cultivars comparable to Koshihikari by a small panel was evaluated statistically by analysis of variance. Concerning the overall eating quality, differences among cultivars and panel members were significant. However, the interaction between cultivars and panel members was not significant, showing that the evaluation of cultivars by panel members as a whole is meaningful. The taste preference of the panel members with a reputation for high tasting ability generally coincided with the mean value of the palatability of all panel members. The number of panel members who had high differentiating ability for overall eating quality was 5 out of 17 members (30%), and the least significant difference (LSD (0.05)) for cultivar difference in overall eating quality was 0.27. Thus, it was concluded that the sensory test for highly palatable rice cultivars by a small panel is reasonable. The reliability of the panel as a whole seems to be more important than that of each panel member singly in the sensory test for highly palatable rice cultivars comparable to Koshihikari.

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This study was aimed to obtain stable and high flour quality wheat by planting earlier than usual by using several cultivars differing in winter habit. The protein content, maximum viscosity and flour color varied with the sowing time, but flour yield, ash content and amylose content did not. Sowing at the end of October increased grain protein content due to less starch accumulation by decreased grain yield owing to less grains per ear and lodging. Gluten index and maximum visocity were lowered by early sowing. Flour color deteriorated by early sowing owing to the high protein content due to the low grain filling and rain damage during the grain filling period. It is concluded that the limit of the earliest sowing time in Fukuoka prefecture to obtain marketable high quality flour is 5 of November judging from the data of growth, yield, grain quality and flour quality of wheat sown at various times.

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The seedling emergence of rice in direct seeding in submerged soil was investigated with respect to the degree of the forced sprouting, temperature and seedling depth. As a preliminary test, eight representative rice cultivars of various origin, i.e, Akihikari, Koshihikari, Kinuhikari, Akage, Akamai, Arborio, Lemont, and Habataki, were tested for emergence. The optimum condition for germination in the submerged soil was exposure to 25°C for 2∼3 days. Germinated seeds with 0.4∼1.4 mm coleoptiles were placed at 1cm, 2 cm and 3 cm depth under the submerged soil surface in a growth chamber kept at 15°C and 25°C. The seedling emergence widely varied genotypes when seeded at a 2 cm or 3 cm depth at 25°C and 1cm depth at 15°C. Then the emergence of 302 rice cultivars seeded at a 2 cm depth at 25°C was compared. Among them 59 (modern) and 104 (native) cultivars from Japan, 40 from China, 39 from Korea, 23 from Italy, 13 from America, 9 from India, 4 from Russia, and 11 from other countries. The rice cultivars from India, Sri Lanka, and Bangladesh showed a significantly lower percentage of emergence than those from Japan. These findings suggested that Indica type varieties had poor seedling emergence under a submerged soil condition.

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Twenty typical Indica and Japonica rice varieties were tested for resistance to root lodging using a push-pull gauge for two years. Pushing resistance varied from 0.56 N to 2.57 N among the 20 varieties. Kanto PL12 was selected as a lodging-resistant variety, M401 as a moderately resistant variety, and Kinuhikari as a sensitive variety. The growth angle of the crown roots of the three varieties was measured as 10 days after heading, and we found that the number of roots growing in a shallower direction (0∼18°) was highest in Kanto PL12, followed by M401 and Kinuhikari. Next, the growth angle of crown roots in the 20 varieties was measured by basket-method. We divided the growth angle of crown roots, from 0° (horizontal) to 90° (vertical) at 23 days after sowing, into five equal ranges and found that the lodging-resistant varieties had many crown roots growing at an angle between 36° and 54°. We also found that lodging resistance was highly correlated with the pulling strength of the crown roots of the seedlings. Thus, it is concidered that the lodging-resistance of varieties can be evaluated by the number of crown roots growing at an angle between 36° and 54° or pulling strength of the thick roots of the seedlings.

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The total number of leaves on the main stem was 9 in Norin 11, and 10 in Norin 9 and Norin 15 under normal-season culture. The last primary tillers developed from the 8th node of the main stems in the three varieties. However, the system of tillering was ordinary and many upper nodal tillers appeared in the three varieties. The lowest nodal position developing the primary upper nodal tillers was judged to be the node where a protuberance of tiller primordium or a young bud having 1 to 2 leaf primordia were observed at the panicle-neck-node differentiation stage (referred to as PND) of the main shoot. This nodal position was 7th, 6th and 5th node in Norin 9, Norin 15 and Norin 11, respectively. The last upper nodal tillers had 3 or 4 leaves. The reason for this system was considered as follows : After PND of the main shoot, the protuberance of the primary tiller primordia can reach its PND only after the main shoot developed additional 2.5 leaves. On the other hand, the result of the developmental anatomy showed that, during the above-mentioned development of the main shoot, tiller primordia developed propyll and 2 or 3 leaf primordia. These observations explain well, the presence of 3 or 4 leaves on the last upper nodal tillers.

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For genetic improvement of the monogerm sugar beet (Beta vulgaris L.) that has double-ovule fruits, we examined the distribution of double-ovule fruits in the branching system. We also compared the percentage of double-ovule fruits before anthesis and at maturity. The higher the node position of the branch on the main stem, the higher the percentage of double-ovule fruits, and the primary branch had more double-ovule fruits than the secondary branch. The percentage of double-ovule fruits increased as the thousand grain weight increased, and the percentage in each branch decreased as the percentage in the individual decreased. The percentage of double-ovule fruits in the plant was similar to the percentage on the branch at the highest nodal position among those having secondary branches. Many double-ovule fruits were distributed in the middle part of the primary branch having secondary branches. These results suggest that the formation of double-ovule fruit is related with the developmental stage of fruits on the main stem and branches. The percentage of double-ovule fruits before anthesis was higher than that at maturity with a positive correlation. Thus the formation of double-ovule fruit before anthesis is considered to be genetically controlled before anthesis, but finally determined by the environmental conditions during ovule development after pollination.

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Rice seedlings are often injured during transplanting, mainly due to the damage to the roots, but plant growth recovers after newly emerged roots elongate. The morphological changes during the formation and emergence of crown roots from the rice seedlings with roots pruned by transplanting were examined. The roots of rice seedlings at the 3.2 leaf stage were pruned and serial cross-sections of the stems of the seedlings at the 7.2 leaf stage were observed under a light microscope. By root pruning, the stem length tended to be reduced but the diameters of stems and peripheral cylinder increased. The numbers of crown root primordia and emerged crown roots in every stem section were slightly increased by root pruning, but the diameter of the crown root was unaffected. These results indicate that the numbers of crown root primordia and emerged roots were increased by root pruning and that the number of roots increased gradually and continuously to promote seedling establishment after root pruning.

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Adventitious roots are often developed from soybean stem by farmer’s soil-heaping practice especially in East-Asian countries. Here, we examined the possibility of mitigating flooding injury by the development of adventitious roots. The high soil-moisture after soil-heaping greatly stimulated the development of adventitious roots. Soybean yield increased 11 and 26% compared to the control by soil-heaping at the R1 stage and by saturated soil-moisture treatment for 10 days after soil-heaping, respectively. The yield decrease caused by flooding was considerably mitigated by keeping adventitious roots emerged during 10 days of flooding alive by soil-heaping after the flooding. Effect of early development of adventitious roots on the mitigation of flooding injury was also evaluated using four soybean cultivars differing in the ability to develop adventitious roots. Adventitious roots were developed by one-day flooding pretreatment right after soil-heaping at the V2 stage. In all four cultivars examined, the decrease of growth and yield by flooding at the V5 or R2 stage was mitigated by soil-heaping and flooding for one day, which promoted adventitious root development. Furthermore, the higher the number of adventitious roots, the less flooding injury that occurred. Our results indicate that early development of adventitious roots by a brief saturation of soil-moisture or flooding right after soil-heaping not only increases soybean growth and yield but also enhances its flooding tolerance.

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A new method for assessing resistance to Pythium snow rot of barley was developed. The level of resistance was quantitatively expressed as lesion length extended to the basal direction from the inoculation point at the middle of the leaf blade. The varietal difference of barley in the resistance determined by this method was consistent with that determined by the snow mold chamber method. Using this method, we could evaluate the resistance within 10 days after inoculation. Furthermore this method was useful to estimate the resistance to snow rot of wheat, rye, and oat.

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The chemical properties of creek waters derived from Chikugo and Yabe rivers in southern Fukuoka Prefecture were examined from 1992 to 2001. The waters were sampled at 11 places several times during the period from puddling of paddy fields to the ripening of rice plants and during the non-irrigating period. The waters on average showed a higher value than the standard for agricultural water in T-N and COD. The values except DO, SS and T-P were higher in the irrigating period than in the non-irrigating period. In the last ten years, neither major deterioration nor improvement were found judging from the values of chemical properties measured. However, the yearly fluctuation in NH₄-N and NO₃-N contents were large, especially in the non-irrigating period. The ratio of NO₃-N to total nitrogen was high in the tillering stage of rice in both creeks from Chikugo and Yabe rivers. It is estimated that 40% of the nitrogen fertilizer for the second topdressing at the ear formation staged can be reduced, judging from the amount of nitrogen in irrigating waters.

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The development of sulfonylurea-herbicide (SU) resistant biotypes of Monochoria korsakowii Regel et Maack and Scirpus juncoides Roxb. var. ohwianus. T. Koyama as troublesome paddy weeds in Hokkaido region is a recent problem. The geographical distribution and level of infestation of these weeds were surveyed. Interpretation of the geographical survey data and SU resistance status suggest that SU resistant biotypes of these weed species originated in locales where weed infestation and selection pressure were severe. Once resistant biotypes appeared in these locales, they then quickly spread in seasonal succession to neighboring fields. Field experiments were conducted to investigate the use of combination-herbicides including non-sulfonylurea herbicides for controlling these two SU resistant weed biotypes. Combination herbicides were effective on the weeds and cost-effective ones, comprising of even a few actives, were suggested effective for paddy weed control in Hokkaido, including two SU resistant biotypes.

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