Takashi Motobayashi

Biomass Production and Lodging Resistance in ‘Leaf Star’, a New Long-Culm Rice Forage Cultivar

Abstract Biomass production and lodging resistance in the new long-culm forage cultivar ‘Leaf Star’, developed using a precise evaluation method for lodging resistance, were evaluated by comparing these properties with those of its parents and recently improved forage rice cultivars. Leaf Star had a higher biomass production of above-ground parts than its parents, and its straw yield was 13 t ha-1. The bending moment of the basal internode at breaking in Leaf Star was three times higher than that in Koshihikari, owing to a large section modulus and a high bending stress. Biomass production of above-ground parts of Leaf Star did not differ significantly from that of other forage cultivars. However, Leaf Star had the highest straw yield of all forage cultivars. Leaf Star accumulated a large amount of starch in straw. Bending moment of the basal internode was the highest among forage cultivars owing to a large section modulus. These results show that the traits related to lodging resistance such as culm thickness and culm stiffness could be introduced into long-culm cultivars by using the precise evaluation method for the traits related to lodging resistance. The results also show that Leaf Star has a large biomass and high quality, which are suitable properties for feed and biofuel production.

Performance of a High-Yielding Modern Rice Cultivar Takanari and Several Old and New Cultivars Grown with and without Chemical Fertilizer in a Submerged Paddy Field

Abstract A high nitrogen-uptake capacity and effective use of absorbed nitrogen for dry matter and grain production are required to improve the production cost and environmental pollution. We characterized grain yield, dry matter production and nitrogen accumulation in six rice cultivars: Sekitori (released in 1848) and Aikoku (1882), referred to as SA cultivars hereafter; Koshihikari (1956); Nipponbare (1963) and Asanohikari (1987), referred to as NA cultivars hereafter; and Takanari (in 1990) as a high-yielding modern cultivar. The plants were grown with and without chemical fertilizer in a submerged paddy field. When plants were supplied with manure and chemical fertilizer, Takanari consistently produced the heaviest grain and dry matter, followed by the NA cultivars, and the SA cultivars the lightest. Dry matter production before heading was greater in Takanari and the NA cultivars due to the longer duration of vegetative growth. Dry matter production after heading was greatest in Takanari, with a larger crop growth rate (CGR), and smallest in the SA cultivars with a shorter ripening time. Greater dry matter production during ripening was accompanied by the greater accumulation of nitrogen by Takanari and NA cultivars. These plants developed a larger amount of roots. The smaller light extinction coefficient of the canopy was also attributed to the higher CGR in Takanari. When plants were grown without chemical fertilizer, Takanari also produced heavier grain and dry matter, followed by the NA cultivars. The heavier grain in these cultivars resulted from the greater dry matter production before heading, which was due to the longer period of vegetative growth. The greater dry matter production and nitrogen accumulation by Takanari and NA cultivars were evident when plants were grown with chemical fertilizer. Koshihikari was characterized by a higher CGR and greater nitrogen accumulation during ripening in the absence of chemical fertilizer which should be noted in efforts to decrease rates of nitrogen application.

Suppression of ammonia volatilization from a paddy soil fertilized with anaerobically digested cattle slurry by wood vinegar application and floodwater management

Abstract Ammonia (NH3) volatilization from animal manure application is detrimental to the environment, crop nutrition and human health and investigations into mitigation strategies are a great challenge among agro-environmental issues. The objective of the present study was to reduce NH3 volatilization in a paddy soil fertilized with anaerobically digested cattle slurry (ADCS). In laboratory experiments, several mitigation methods for NH3 volatilization were tested. Among these methods, acidification of ADCS with wood vinegar (WV) from pH 7.8 to pH 6.0 was the most effective in suppressing NH3 volatilization. Increasing the depth of the floodwater threefold also reduced NH3 volatilization by more than 80%. A lysimeter (1 m square with 0.5 m depth) experiment was conducted in triplicate with the following treatments: (1) chemical fertilizer ([CF] N:P:K = 14:14:14), (2) ADCS, (3) acidifying ADCS with WV to pH 6.0, (4) keeping a deeper floodwater level (DFW) at 10 cm at the ADCS applications (3–4 cm in the other treatments). A total fertilization of 30 g NH+ 4–N m−2 (basal and three times as a top dressing) was done for all treatments either with CF or ADCS and other fertilizations were not conducted. The NH3 volatilization was measured using the dynamic flow chamber method for 1 week after each fertilizer application. The results highlighted that the use of ADCS, instead of CF, enhanced NH3 volatilization approximately eightfold, and the total amount of NH3 volatilization corresponded to 13% of the applied NH+ 4–N in the ADCS treatment. This increased N loss was effectively (63–82%) reduced by adding WV and by keeping the floodwater level deeper. Biomass production was not significantly different between the CF (2880 ± 226 g [dry basis] m−2) treatment and the three ADCS treatments (3320 ± 249, 2720 ± 384 and 3330 ± 359 g [dry basis] m−2 in the ADCS, ADCS + WV and ADCS + DFW treatments, respectively). These results demonstrated that enhanced NH3 volatilization in soil fertilized with ADCS was mitigated by the simultaneous application of an acid residue, such as WV, and by the management of the floodwater level.

Increased lodging resistance in long-culm, low-lignin gh2 rice for improved feed and bioenergy production.

Lignin modification has been a breeding target for the improvements of forage digestibility and energy yields in forage and bioenergy crops, but decreased lignin levels are often accompanied by reduced lodging resistance. The rice mutant gold hull and internode2 (gh2) has been identified to be lignin deficient. GH2 has been mapped to the short arm of chromosome 2 and encodes cinnamyl-alcohol dehydrogenase (CAD). We developed a long-culm variety, ‘Leaf Star’, with superior lodging resistance and a gh phenotype similar to one of its parents, ‘Chugoku 117’. The gh loci in Leaf Star and Chugoku 117 were localized to the same region of chromosome 2 as the gh2 mutant. Leaf Star had culms with low lignin concentrations due to a natural mutation in OsCAD2 that was not present in Chugoku 117. However, this variety had high culm strength due to its strong, thick culms. Additionally, this variety had a thick layer of cortical fiber tissue with well-developed secondary cell walls. Our results suggest that rice can be improved for forage and bioenergy production by combining superior lodging resistance, which can be obtained by introducing thick and stiff culm traits, with low lignin concentrations, which can be obtained using the gh2 variety.

Precise estimation of genomic regions controlling lodging resistance using a set of reciprocal chromosome segment substitution lines in rice

Severe lodging has occurred in many improved rice varieties after the recent strong typhoons in East and Southeast Asian countries. The indica variety Takanari possesses strong culm characteristics due to its large section modulus, which indicates culm thickness, whereas the japonica variety Koshihikari is subject to substantial bending stress due to its thick cortical fibre tissue. To detect quantitative trait loci (QTLs) for lodging resistance and to eliminate the effects of genetic background, we used reciprocal chromosome segment substitution lines (CSSLs) derived from a cross between Koshihikari and Takanari. The oppositional effects of QTLs for section modulus were confirmed in both genetic backgrounds on chromosomes 1, 5 and 6, suggesting that these QTLs are not affected by the genetic background and are controlled independently by a single factor. The candidate region of a QTL for section modulus included SD1. The section modulus of NIL-sd1 was lower than that of Koshihikari, whereas the section modulus of NIL-SD1 was higher than that of Takanari. This result indicated that those regions regulate the culm thickness. The reciprocal effects of the QTLs for cortical fibre tissue thickness were confirmed in both genetic backgrounds on chromosome 9 using CSSLs.

Effects of Soil Moisture Conditions before Heading on Growth of Wheat Plants under Drought Conditions in the Ripening Stage: Insufficient Soil Moisture Conditions before Heading Render Wheat Plants More Resistant to Drought during Ripening

Abstract Plants growing on soil with insufficient moisture need deep and dense roots to avoid water stress. In crop plants, the production of dry matter during ripening of grains is critically important for grain yield. We postulated that shoot growth would be suppressed but root growth would continue under an insufficient soil moisture condition before heading, while shoot growth would be more vigorous than root growth under a sufficient soil moisture condition. We anticipated that the plants growing under an insufficient soil moisture condition before heading would produce more dry matter and grain under an insufficient soil moisture condition during ripening. In order to examine our hypotheses and to determine the fundamental conditions for improving grain yield and efficient use of irrigated water under limited irrigation, we grew wheat plants (Triticum aestivum L., cv. Ayahikari) in pots (30 cm in diameter, 150 cm in height) with insufficient soil moisture (PD-D pots) or sufficient soil moisture (PW-D pots) for six weeks before heading followed by full irrigation, and then insufficient soil moisture condition during ripening. The growth of shoots was suppressed significantly but that of roots was not before heading in PD-D plants, with a higher resultant ratio of root to shoot than in PW-D plants. The former retained a high leaf water potential and, therefore, were able to produce more dry matter and grain during soil moisture depletion during ripening as compared with the latter plants. We also obtained similar results with field-grown plants.

The influence of phosphate fertilizer application levels and cultivars on cadmium uptake by Komatsuna (Brassica rapa L. var. perviridis)

Cadmium (Cd) is a common impurity in phosphate fertilizers and application of phosphate fertilizer may contribute to soil Cd accumulation. Changes in Cd burdens to agricultural soils and the potential for plant Cd accumulation resulting from fertilizer input were investigated in this study. A field experiment was conducted on Haplaquept to investigate the influence of calcium superphosphate on extractable and total soil Cd and on growth and Cd uptake of different Komatsuna (Brassica rapa L. var. perviridis) cultivars. Four cultivars of Komatsuna were grown on the soil and harvested after 60 days. The superphosphate application increased total soil Cd from 2.51 to 2.75 mg kg−1, 0.1 mol L−1 hydrochloric acid (HCl) extractable Cd from 1.48 to 1.55 mg kg−1, 0.01 mol L−1 HCl extractable Cd from 0.043 to 0.046 mg kg−1 and water extractable Cd from 0.0057 to 0.0077 mg kg−1. Cd input reached 5.68 g ha–1 at a rate of 240 kg ha–1 superphosphate fertilizer application. Superphosphate affected dry-matter yield of leaves to different degrees in each cultivar. ‘Nakamachi’ produced the highest yield in 2008 and ‘Hamami No. 2’ in 2009. Compared with the control (no phosphate fertilizer), application of superphosphate at a rate of 240 kg ha–1 increased the Cd concentration in dry leaves by 0.14 mg kg−1 in ‘Maruha’, 1.03 mg kg−1 in ‘Nakamachi’, 0.63 mg kg−1 in ‘SC8-007’ in 2008, and by 0.19 mg kg−1 in Maruha’, 0.17 mg kg−1 in ‘Hamami No. 2’, while it decreased by 0.27 mg kg−1 in ‘Nakamachi’ in 2009. Field experiments in two years demonstrated that applications of different levels of calcium superphosphate did not influence Cd concentration in soil and Komatsuna significantly. However, there was a significant difference in Cd concentration of fresh and dry Komatsuna leaves among four cultivars in 2008 and 2009. The highest Cd concentration was found in the ‘Nakamachi’ cultivar (2.14 mg kg−1 in 2008 and 1.91 mg kg−1 in 2009). The lowest Cd concentration was observed in the ‘Maruha’ cultivar (1.51 mg kg−1 dry weight (DW)) in 2008 and in the ‘Hamami No. 2’ cultivar (1.56 mg kg−1 DW) in 2009. A decreasing trend in Cd concentration was found in ‘Nakamachi’, followed by ‘SC8-007’, ‘Hamami No. 2’ and ‘Maruha’ successively. It is necessary to consider a low-uptake cultivar for growing in a Cd polluted soil. In these two years’ results, ‘Maruha’ cultivar was the lowest Cd uptake cultivar compared to the others.

Effect of biogas slurry application on CH4 and N2O emissions, Cu and Zn uptakes by whole crop rice in a paddy field in Japan

Abstract Effects of 4-year consecutive application of biogas slurry (BS) at rates of 0 (NF), 100 (BS100) and 300 (BS300) kg nitrogen (N) ha−1 on yield of whole crop rice (Oryza sativa L. var. Leaf Star) and environmental impacts were investigated in a field experiment in comparison with a conventional rate of chemical fertilizer CF100 (100 kg N ha−1). Average biomass production was comparable between BS100 (1.9 ± 0.1 kg dry matter m−2) and CF100 (1.8 ± 0.1 kg m−2) and significantly (P < 0.01) highest in BS300 (2.1 ± 0.1 kg m−2). Four years’ average methane (CH4) emissions during the growing periods were significantly (P < 0.05) highest in BS300 (43.7 ± 18.4 g m−2 season−1), followed by BS100 (32.0 ± 3.0 g m−2 season−1) and then NF (23.5 ± 8.2 g m−2 season−1) and CF100 (20.3 ± 3.3 g m−2 season−1), indicating that BS application may cause a potential risk of CH4 emission. There were no significant differences in copper (Cu) and zinc (Zn) uptakes by the rice plant between BS100 and CF100, but significantly higher Zn content was observed in the grain of BS300 in 2011, indicating a potential risk of higher heavy metal uptake in BS300. Compared with CF100, no significant higher accumulations of extractable and total forms of Cu and Zn in soil were observed from four years of consecutive BS application. This study revealed that the application of BS, generated from pig manure, to rice fields at the conventional rate (100 kg N ha−1) may be considered to substitute chemical fertilizer utilization without additional environmental impacts in greenhouse gas emission and heavy metal uptake.

Effects of Planting Pattern on the Interception of Solar Radiation by the Canopy and the Light Extinction Coefficient of the Canopy in Rice Plants Direct-sown in a Submerged Paddy Field

Abstract In order to investigate effects of planting pattern on the interception of solar radiation by the canopy and the light extinction coefficient of the canopy in rice, the rice plants direct-sown in a submerged paddy field were grown in six planting patterns (A through F). In plots A, B and C, the planting density was 20.7 hills m-2 (22 cm × 22 cm spacing) with five, three and one plant per hill, respectively, and in plots D, E and F, the planting density was 82.6 hills m-2 (11 cm × 11 cm spacing), 44.4 hills m-2 (15 cm × 15 cm spacing), and 44.4 hills m-2 (7.5 cm × 30 cm spacing), respectively, with one plant per hill. At the tillering stage, the greater the tiller number and leaf area index, the larger the interception of solar radiation by the canopy. The tiller number was larger in the plots with one plant per hill, higher plant density and square arrangement of hills. At the early ripening stage, the light extinction coefficient of the canopy was smaller in such plots. The larger the average inclination of leaf blades, the smaller the light extinction coefficient of the canopy. The difference in stem inclination in the canopy might be responsible for the difference in the inclination of leaf blades. In the plots with one plant per hill, higher plant density and square arrangement of hills, stems were more erect. Within the range of planting patterns in our study, both the rate of interception of solar radiation by the canopy and the light-intercepting characteristics were significantly more favorable in the plots with one plant per hill, higher density and a square arrangement of hills.

Effect of two whole-crop rice (Oryza sativa L.) cultivars on methane emission and Cu and Zn uptake in a paddy field fertilized with biogas slurry

ABSTRACT A field experiment was carried out to evaluate the effect of two whole-crop rice (Oryza sativa L.) cultivars, TULT and Takanari, on methane (CH4) emission in a paddy field fertilized with biogas slurry (BS) at rates of 0 (NF), 100 (BS100) and 300 (BS300) kg nitrogen (N) ha−1, in comparison with chemical fertilizer CF100 (100 kg N ha−1). Takanari produced significantly higher biomass (P < 0.001) than TULT and showed significantly (P < 0.01) lower CH4 emission than TULT. BS applications caused higher CH4 emission (52 ± 27 and 80 ± 19 g m−2 in BS100 and BS300, respectively) than did CF100 (42 ± 18 g m−2) and NF (28 ± 10 g m−2) in TULT. In contrast, there was no significant difference in CH4 emission in Takanari among the treatments (26 ± 2, 26 ± 2, 32 ± 4, 29 ± 8 g m−2 in NF, CF100, BS100 and BS300, respectively). Methane oxidizing bacteria (MOB) showed significantly (P < 0.05) higher populations in Takanari than in TULT at harvest, which might be due to the higher root biomass (10.3 ± 2.2 g hill−1) in Takanari than in TULT (8.9 ± 1.8 g hill−1). MOB was significantly correlated with tiller number (R2 = 0.176*) and plant biomass (R2 = 0.242*). BS application showed higher copper (Cu) uptake in Takanari while it was not high in TULT. In contrast, it showed no difference in zinc (Zn) uptake in both varieties. Uptake of Cu was not different between the two varieties, while uptake of Zn in the grain was higher in TULT than in Takanari. The present study suggests that CH4 emission deriving from BS application in paddy field can be mitigated by selecting an appropriate cultivar, like Takanari. However, care should be taken for heavy metal uptake in selecting cultivars.