Germination, elongation, emergence and establishment under low temperature conditions in 18 rice varieties including 8 varieties bred at Tohoku Agricultural Research Center (TARC) were evaluated. Most of the varieties were considered to show dormancy since the days to germination (DG) was shortened by dry heat treatment. When dormancy was weak, varietal differences in DG were clear. Under the cold water condition, varietal differences were observed in coleoptile length. The coleoptiles of non- germinated seed elongated earlier in varieties having shorter DG. Even the coleoptiles of germinated seeds elongated earlier in varieties having shorter DG in some cases. Under a submerged condition, varieties having shorter DG showed shorter days for emergence (DE). The varieties having a shorter DE showed a higher rate of establishment especially under the very low temperature condition. These results suggest that the varieties having a shorter DG were superior in establishment. Among the varieties used, “Arroz da Terra”, “Ta Hung Ku” and “Himenomochi” had shorter DG and were superior in establishment. Among the varieties bred in TARC, varieties for cooking, “Moeminori”,“Eminoaki”, and “Chihominori”, and a glutinous variety “Tokimekimochi” had a risk of late establishment due to weak dormancy. Forage rice varieties, “Bekoaoaba”, “Iwaidawara” and “Bekogenki” had a slightly longer DG and were slightly inferior in establishment.
Increase in production of whole crop rice silage is expected to improve the food self-sufficiency rate in Japan. Introduction of forage rice cultivation under late seeding conditions into the rice-wheat cropping systems is considered a means of cultivation management for high land use efficiency, high productivity, and reduction in cost and labor. It is crucial for improvement of forage digestibility to accumulate non-structural carbohydrate (NSC) in stems rather than in panicles. Furthermore, direct seeding could increase lodging risk. Therefore, we examined the differences in NSC accumulation in stems and lodging resistance among eight cultivars under late direct seeding conditions for two years in Western Japan. Cultivars with a small panicle ratio to the whole aboveground biomass, could accumulate a large amount of NSC in the stems due to the reduction of accumulation of assimilates in panicles during the yellow ripening stage. Meanwhile, these cultivars had a longer yellow ripening stage, and their growth overlapped with the beginning of the winter crop (wheat) season. In some cultivars, however, the NSC concentration in stems could be increased by harvesting at the dough ripening stage. Furthermore, the panicle ratio to the whole aboveground biomass was small at the dough ripening stage resulting in a superior lodging resistance.
Factors related to yield and grain quality was analyzed in a total of 108 rice varieties and lines of the performance test by adding the number of spikelets per panicle (SN) and percentage of ripened grain (RP) as new measurement traits in the Tohoku region of Japan. To develop new varieties having yield equal to or larger than the high yielding variety “Fukuhibiki” and grain quality equal to or better than elite varieties “Akitakomachi” and “Hitomebore”, we set the yield of more than 725 gm–2 and grain quality of less than 4.5 as target values. Yield was significantly related with SN and thousand grain weight (TGW) of less than 25.0 g, but was not significantly related with the number of panicles per area (PN) and RP. Varieties or lines having a yield of more than 725 gm–2 had SN of more than 77 and TGW of 22.9 g to 24.3 g, but PN ranged from 334 m–2 to 540 m–2. Grain quality was not significantly related with SN, but was significantly related with TGW. There were some varieties or lines having good grain quality of less than 4.5 even if SN was more than 80 or TGW ranged from 23.0 g to 24.0 g. We inferred that the crossing and selection based on the target traits, such as SN and TGW, make it possible to develop high yield and superior grain quality varieties in the Tohoku region of Japan.
The objective of this study was to obtain basic knowledge about the breeding of deep-sowing-tolerant varieties suitable for direct sowing cultivation by using 50 Japanese rice varieties sown at the depth of 7 cm. A significant difference among varieties was observed in the emergence percentage, ranging from 94% to 0% (average 59%). Average emergence days ranged from 18.8 to 11.4 days (average 15.6 days), and the emergence coefficient ranged from 7.19 to 0.56 (average 4.04). A significant difference among varieties was observed in both the average emergence days and the emergence coefficient. The emergence coefficient showed a significant positive correlation with the emergence percentage, and significant negative correlation with the average emergence days, but the emergence percentage was not significantly correlated with the average emergence days. Significant differences among varieties were also observed in the starting time of emergence and the increasing exponents of emergence percentage obtained from the regression equation between the days after sowing and emergence percentage. Multiple regression analysis was conducted with the starting time of emergence and the increasing exponents of emergence percentage as the explanatory variable, the emergence percentage and the average emergence days as the objective variable. Thus, the results demonstrated that the contribution ratio of the starting time of emergence to the increasing exponents of emergence percentage for the emergence percentage was 25: 75, and that to the average emergence days was 92: 8. The results of the multiple regression analyses with the mesocotyl length (ML), the first internode length (I L) and the second internode length (II L) as the explanatory variables, and the starting time of emergence, the increasing exponents of emergence percentage and the emergence percentage as the objective variables, was that the contribution ratio of ML, I L and II L to the starting time of emergence was 56: 40: 4, that to the increasing exponents of emergence percentage was 18: 32: 50, and that to the emergence percentage was 6: 40: 54. From these results, the most important characteristic in the deep-sowing tolerance breeding of Japanese varieties was considered to be the second internode length followed by the first internode length. The contribution of the mesocotyl length was considered small in this experiment.
Shattering-resistant soybean cultivars, “Fukuyutaka A1 gou” and “Sachiyutaka A1 gou”, were bred by backcross-breeding using leading cultivars “Fukuyutaka” and “Sachiyutaka” as recurrent parents. These new cultivars were cultivated in the farmers’fields in Okayama, Hyogo, Aichi and Chiba prefectures and the experimental field of NARO institute of crop science (NICS). These shattering-resistant cultivars had a higher yield for machine harvesting and less yield-loss caused by pod shattering. The yield was increased more than 40% by delaying the harvest day. Shattering resistance caused by pdh1 mainly decreased shattering loss before harvesting and secondly shattering loss during harvesting. Yield-loss discharged from harvesting machine with crop residue was less than 3% and did not vary significantly with the shattering resistance of the cultivar. In conclusion, use of these shattering-resistant cultivars may increase the practical yield and the stability without increasing the cost and modification of processing.
Cultivation of paddy rice by applying whole fertilizer as basal dressing in the nursery box and sparse planting are low cost and labor saving cultivation techniques. The number of nursery boxes per unit area can be reduced by sparse planting. But, the amount of fertilizer per nursery box must be increased when combined with application of whole fertilizer as basal dressing. However, the amount of fertilizer used for application of whole fertilizer as basal dressing to the nursery box is usually less than 1 kg, and it is necessary to determine the upper limit of the amount of fertilizer that can be used in sparse planting. Therefore, using the pool raising method, we applied “Naebako-makase” (NK301-100) as whole fertilizer as basal dressing, at the ratio of 600 g to 2500 g per nursery box, and examined the growth of seedlings, seedling mat strength, and planting accuracy in the paddy field for 3 years. As a result, seedling growth, seedling mat strength, and planting accuracy were scarcely influenced by the amount of fertilizer within 1300 g per nursery box.
Effects of sowing date on the yield, quality and palatability of rice cultivated by non-tillage direct sowing were investigated using the leading medium ripening varieties in Kagawa prefecture “Koganemasari”, “Oidemai”, and “Hinohikari”. The sowing dates were April 23, May 7, and May 21, in plot I, II and III, respectively. For comparison, “Koganemasari” was transplanted on June 10. Yield was highest in plot I followed by plot II and plot III in this order. On the other hand, the overall eating-quality in the sensory test compared with that in the transplant plot of “Koganemasari” was highest in plot III followed by plot II and plot I in this order. The ratio of whole grain to above-ground biomass was highest in plot II followed by plot III, and lowest in plot I. The effects of sowing date were determined by the average temperature during the period from heading to maturity (ripening temperature) of the respective sowing plots. That is, the ripening temperature in plot III was 21.4～22.4ºC which is near the suitable temperature for high yield (22ºC), but is lower than the suitable temperature for high palatability (25ºC). Thus, in plot III, the yield was high but palatability was low. The ripening temperature in plot I was 24.2～24.5ºC which was suitable for eating quality but higher than the suitable temperature for yield. Thus in plot I palatability was high but yield was low. Furthermore, grain appearance was inferior in plot I because the ripening temperature exceeded 24ºC, which increases the occurrence of immature grain. Therefore, considering yield, quality of grain, appearance and eating quality comprehensively, the optimum sowing time in non-tillage direct sowing culture in Kagawa Prefecture was considered to be around the sowing date of plot II in this experiment which was 20～14 days earlier than the currently practiced sowing time.
This study was conducted on the experimental field of NARO in Tsukuba in 2014 and 2015 using the sesame variety “Maruhime” which has a high lignan content and is early maturing. Although the period from sowing to flowering was shorter in the plants sown in July than in June, the period from flowering to harvest was longer. It was concluded that the variety “Maruhime” should be harvested at 85 to 95 days after sowing, because the seed yield and thousand-seeds weight were the largest. The seeds harvested from the plants sown in July, had a lower oleic acid content and higher linoleic acid content than in those from the plants sown in June. The temperature during ripening of the plants sown in June was 3°C higher and a negative correlation was observed between the contents of oleic acid and linoleic acid. This suggested that the high temperature inhibited the conversion of oleic acid to linoleic acid. Sowing in June seemed to be appropriate for “Maruhime”, because the sesamin content was higher than in the seeds harvested from the plants sown in July. The sesamin and sesamolin contents decreased as the harvesting date was delayed, the sesamin content being decreased up to 78%. The sesamin content was higher in the seeds from the capsules near the shoot tip than the base, as in the general varieties.
This study was conducted to improve the method to assess the thickness distribution of crude brown rice under poor ripening conditions using a quadrat-sampling slot-sieving grader. Under poor ripening conditions, the standard method for assessing the thickness distribution of crude brown rice is to shake about 200 g of crude brown rice for 8 min, then use a sieving grader. Using “Koshihikari” under poor ripening conditions and a 2 × 3 factorial design with three randomized blocks, assessed the relationship between the duration of shaking (2 min, 5 min, 8 min) and the sample weight of crude brown rice (ca. 200 g, ca. 100 g). A significant correlation was observed for the main effect on the weight ratio of the crude brown rice that had a thickness of 2.1 mm and 1.7 mm. However, the difference in weight ratio between the 200 g and 100 g samples was small. On the other hand, the sample weight and the duration of shaking. From these results, it was estimated that shaking about 100 g crude brown rice for 2 min is appropriate for the rice under poor ripening. It was concluded that this method is generally applicable for the investigation on the grain thickness distribution of the poor crude brown rice.
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