Two linked genes on rice chromosome 2 for F1 pollen sterility in a hybrid between Oryza sativa and O. glumaepatula

Hybrid incompatibility plays an important role in establishment of post-zygotic reproductive isolation. To unveil genetic basis of hybrid incompatibilities between diverged species of genus Oryza AA genome species, we conducted genetic dissection of hybrid sterility loci, S22(t), which had been identified in backcross progeny derived from Oryza sativa ssp. japonica (recurrent parent) and South American wild rice O. glumaepatula near the end of the short arm of chromosome 2. The S22(t) region was found to be composed of two loci, designated S22A and S22B, that independently induce F₁ pollen sterility. Pollen grains containing either of the sterile alleles (S22A-glum^s or S22B-glum^s) were sterile if produced on a heterozygous plant. No transmission of the S22A-glum^s allele via pollen was observed, whereas a low frequency of transmission of S22B-glum^s was observed. Cytological analysis showed that the sterile pollen grains caused by S22A could reach the bicellular or tricellular stage, and the nearly-sterile pollen grains caused by S22B could reach the tricellular stage. Our genetic analysis showed repulsion linkage effect is possible to induce strong reproductive barrier by high pollen sterility based on recombination value and transmission ratio of hybrid sterility gene to the progeny was influenced by frequency of competitors on fertilization.     

Promotion of first internode elongation in perennial paddy weeds Sagittaria trifolia and Sagittaria pygmaea tubers by oxygen depletion and carbon dioxide

The semiaquatic plants, S agittaria trifolia and S agittaria pygmaea, are perennial and troublesome weeds of rice paddy fields. These species mainly reproduce vegetatively via tubers, which sprout after the rice paddy fields are irrigated. Sprouting finally leads to the emergence of the shoots from the water in the paddy fields. In both species, the first internode elongates around the time of emergence and this lifts the shoot meristems in the soil, aiding in the establishment of the young plants. Therefore, elongation of the internode is a factor that determines the weed damage to rice caused by these species. In this study, the first internode elongation of both species was characterized. During emergence, S . trifolia and S . pygmaea showed distinct growth patterns. In S . trifolia, the internodes elongated before the emergence of the shoots from the water; whereas, in S . pygmaea, the internodes started to elongate only after emergence. We examined environmental prerequisites for internode elongation, and found that the internode elongation of S . trifolia was induced by submergence and was independent of the soil cover, while that of S . pygmaea required both submergence and covering. Next, we determined which gaseous factors were responsible for internode elongation. Treatment with ethylene, which enhances growth of several other aquatic and semiaquatic plants, did not stimulate internode elongation in either species under an anaerobic condition. Our results suggested that the gaseous factor stimulating internode elongation in S . trifolia and S . pygmaea may be oxygen depletion and carbon dioxide, respectively.     

Estimation of fine root biomass using a minirhizotron technique among three vegetation types in a cool-temperate brackish marsh

The minirhizotron technique is a non-destructive method to evaluate fine roots, which converts two-dimensional image data to three- dimensional root biomass data. Recently, conversion factors in soils at 10-cm depth intervals successfully estimated fine root biomass using image data from the minirhizotron method. However, this technique was conducted only at one forest site and did not consider different vegetation types. Therefore, the objective of this study was to verify a method for calibration of minirhizotron data with the core sampling values obtained by direct measurement of root biomass in wetland ecosystems among three vegetation types. Evaluations by minirhizotron technique and soil-core sampling were made at 30-cm soil depth in a cool-temperate brackish marsh in northern Japan. Linear regression was examined between root volume and weight of fine roots in soil core samples, and the fine root biomass on minirhizotron tubes was calculated from their length and diameter. The technique was well adapted for vegetation types dominated by Phragmites australis, Juncus yokoscensis, and Miscanthus sinensis and Cirsium inundatum. Compared with the fine root biomass estimated by the core sampling method, fine root biomass estimated by the minirhizotron method was overestimated in the 0–10-cm layer. Further, we determined conversion factors based on the ratio of the fine root biomass by the core sampling method to that by the minirhizotron tubes. Estimation of the fine root biomass using the conversion factors for each 10-cm soil depth was well adapted in P. australis vegetation and J. yokoscensis vegetation types as a forest ecosystem; meanwhile, M. sinensis and C. inundatum vegetation types were not well adapted. This study suggests that the minirhizotron technique is available to estimate fine root biomass of single-species dominated vegetation in the brackish marsh using conversion factors for each 10-cm depth.     

Potential of prolonged midseason drainage for reducing methane emission from rice paddies in Japan: a long-term simulation using the DNDC-Rice model

Water management practices, such as midseason drainage (MD) and intermittent irrigation, are effective in reducing methane (CH₄) emission from irrigated rice paddies. In a previous study in which two-year field experiments were conducted at nine sites across Japan, prolonged MD was found to reduce the seasonal total CH₄ emission by 30.5?±?6.7 % (mean?±?95 % confidence interval) compared with conventional MD without compromising rice grain yield. However, the degree of CH₄ reduction by water management is dependent on prevailing weather conditions. To estimate the mean effect of prolonged MD on CH₄ emission at the nine sites with rice straw application, we conducted a long-term (20 years) simulation using a process-based biogeochemistry model, the DNDC-Rice. The model adjusted using site-specific parameters was able to reproduce the measured magnitude of the total CH₄ emission and the suppressive effect of prolonged MD. The number of nonrainy days during MD explained the degree of CH₄ reduction for each site and all sites combined. In the simulation, mean reduction percentage was 20.1?±?5.6 % when acceptable prolonged MD (i.e., having less than 15 % yield loss) was applied compared with conventional MD. The discrepancy of the percentage between measurement and simulation was primarily attributable to longer nonrainy days during prolonged MD at several sites in the measurement than the mean of 20-year simulation. We therefore conclude that the long-term simulation better represents the mean reduction percentage of CH₄ emission by prolonged MD relative to conventional MD at the nine sites across Japan.     

Pathological features of hepatic portal venous gas in a cat

An 8-year 8-month-old castrated male Munchkin presented with vomiting, anorexia and hypoactivity. Computed tomography revealed excessive gas accumulation within the intestinal lumen and gas bubbles in the liver, spleen, and portal venous system, indicating hepatic portal venous gas. The cat died without any significant improvement, and mild splenomegaly was found at necropsy. Histologically, multiple gas vacuoles were diffusely observed in the liver and spleen. In the stomach, multiple gas vacuoles and scattered focal ulcers were detected within the mucosa. Multifocal hemorrhage was noted in the small and large intestines, whereas gas vacuoles were not present. Based on these findings, a gastric ulcer under high gas pressure may have provided an entry point for gas into the portal venous system.     

Evaluation of biochar applications combined with alternate wetting and drying (AWD) water management in rice field as a methane mitigation option for farmers’ adoption

ABSTRACT

Biochar application and alternate wetting and drying (AWD) are emerging as promising technologies recommended for reducing CH₄ emissions and water consumption in rice cultivation. In this study, we hypothesized that both technologies could be practiced in combination and this could further reduce CH₄ emissions and water consumption when compared to practicing alone. The effects of biochar application and its co-application with chemical fertilizer or compost under conventional or AWD water management on CH₄ emissions, productivity of rice, water use, and SOC stock, as well as cost and income were investigated. The experiment was carried out in an irrigated paddy field in the central plain of Thailand during both in the wet and dry seasons. Relative to control (CT), biochar application (BI), its co-application with compost (BC) or chemical fertilizer (BF) reduced seasonal CH₄ emissions by 40.6%, 29.5%, and 12.3%, respectively. BI and BC significantly (p < 0.05) reduced grain yield by 19.9% and 10.8%, respectively, while BF significantly increased grain yield by 3.70%. In addition, BI, BC, and BF significantly enhanced soil organic carbon (SOC) stock by 21.2%, 21.4%, and 18.3%, respectively. Compared to the CT, higher production costs were found in BC and BF, but the farmer’s net incomes were also higher in BF because of its higher grain yield. On the other hand, water management in all amendment treatments under AWD was resulted in the reduction of CH₄ emissions by the average of 18.8% as compared to the conventional system. AWD decreased rice yield by an average of 2.29%. It significantly reduced irrigation water use by an average of 11.9%, resulting in reducing production cost for water pumping. The results show that the practice that combined biochar application, AWD and chemical fertilizer are feasible for CH₄ emission mitigation, SOC stock increase and irrigation water saving without significant effects on yield and farmer income.     

Wheat straw management affects CH4 and N2O emissions from rice fields

A 3-year field experiment was conducted in Jiangsu Province, China from 2004 to 2006 to investigate CH₄ and N₂O emissions from paddy fields as affected by various wheat straw management practices prior to rice cultivation. Five methods of returning wheat straw, no straw, evenly incorporating, burying straw, ditch mulching and strip mulching, were adopted in the experiment. Evenly incorporating is the most common management practice in the region. Results showed that compared with no straw, evenly incorporating increased CH₄ emission significantly by a factor of 3.9-10.5, while decreasing N₂O emission by 1-78%. Methane emission from burying straw was comparable with that from evenly incorporating, while N₂O emission from burying straw was 94-314% of that from evenly incorporating. Compared with evenly incorporating, CH₄ emission was decreased by 23-32% in ditch mulching and by 32% in strip mulching, while N₂O emission was increased by a factor of 1.4-3.7 in ditch mulching and by a factor of 5.1 in strip mulching. During the rice-growing season, the emitted N₂O was negligible compared to that of emitted CH₄. No significant difference in grain yield was observed between ditch mulching, burying straw, evenly incorporating and no straw. Compared with no straw, the grain yield was increased by 27% in strip mulching. Based on these results, the best management practice for returning wheat straw to the soil is strip mulching wheat straw partially or completely onto the field surface, as the method reduced CH₄ emission from rice fields with no decrease in rice yield.     

Mitigation options for N2O emission from a corn field in Kalimantan, Indonesia

Field experiments were designed to quantify N₂O emissions from corn fields after the application of different types of nitrogen fertilizers. Plots were established in South Kalimantan, Indonesia, and given either urea (200 kg ha⁻¹), urea (170 kg ha⁻¹) + dicyandiamide ([DCD] 20 kg ha⁻¹) or controlled-release fertilizer LP-30 (214 kg ha⁻¹) prior to the plantation of corn seeds (variety BISI 2). Each fertilizer treatment was equivalent to 90 kg N ha⁻¹. Plots without chemical N fertilizer were also prepared as a control. The field was designed to have three replicates for each treatment with a randomized block design. Nitrous oxide fluxes were measured at 4, 8, 12, 21, 31, 41, 51, 72 and 92 days after fertilizer application (DAFA). Total N₂O emission was the highest from the urea plots, followed by the LP-30 plots. The emissions from the urea + DCD plots did not differ from those from the control plots. The N₂O emission from the urea + DCD plots was approximately one thirtieth of that from the urea treatment. However, fertilizer type had no effect on grain yield. Thus, the use of urea + DCD is considered to be the best mitigation option among the tested fertilizer applications for N₂O emission from corn fields in Kalimantan, Indonesia.     

A clinical case of a subepiglottic cyst in a Japanese Black calf

A 36-day-old Japanese Black calf exhibited wheezing associated with dyspnea from birth. Arterial blood gas analysis revealed a low oxygen partial pressure of 51 mmHg, low oxygen saturation of 83%, and high carbon dioxide partial pressure of 58.8 mmHg. Computed tomography, endoscopy, and ultrasonography showed cyst formation under the epiglottis. When the cyst was aspirated under ultrasonic guidance to secure the airway, 30 ml of viscous white turbid content was aspirated. The cyst shrank immediately after aspiration, but the wheezing and respiratory symptoms resumed 7 days after aspiration. Therefore, the cyst was surgically removed from the ventral side of the neck. No cyst remodeling was observed 30 days after surgical removal.     

Comparison of the alkalizing abilities between 1.35% sodium bicarbonate solutions with and without dextrose in healthy calves

The present study aimed to clarify the alkalizing ability of 1.35% isotonic sodium bicarbonate solution (ISBS), which did not contain dextrose, compared with that of 1.35% isotonic bicarbonate sodium solution containing 4.03% dextrose (ISBD) in healthy calves. The calves were intravenously administered with 20.7 mL/kg of the solutions for 30 min as the volume required to correct base deficit of 10 mM. ISBS increased the blood pH, HCO₃⁻, and base excess from 7.44 ± 0.02, 29.6 ± 1.9 mM, and 5.3 ± 2.1 mM to 7.49 ± 0.02, 36.9 ± 2.3 mM, and 13.5 ± 2.6 mM respectively (P<0.05). These factors for the ISBD group increased from 7.41 ± 0.02, 29.0 ± 1.1 mM, and 4.5 ± 1.3 mM to 7.43 ± 0.02, 33.5 ± 1.9 mM, and 9.5 ± 1.7 mM (P<0.05), respectively. Furthermore, in the ISBD group, the relative plasma volume and blood glucose level increased while the K⁺ level decreased, which did not occur in the ISBS group. Therefore, the results revealed that ISBS had better alkalizing ability in calves than ISBD.