Mutation breeding is a useful method to improve crops. More than 20 years have passed since mutation breeding with ion beams started in Japan, since which time many mutant varieties have been produced with ion beams. However, ion beams have not been sufficiently characterized in terms of mutagens for plant mutation breeding. This review introduces the characteristics of ion beams as mutagens for mutation breeding; investigated with three objectives: to obtain useful mutants with limited plant damage by irradiation treatment, the width of the mutated sector produced by irradiation, and the mutation spectrum, compared to gamma rays using rice and chrysanthemums. In addition, the optimum dose of ion beams and the criteria for an optimum irradiation dose are shown, based on which the irradiation treatment for the success of mutation breeding with ion beams is also described.

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Andosols are widely distributed in upland fields in Japan and are characterized by a high phosphorus (P) retention capacity. Consequently, the efficiency of P fertilizers is low in Andosols, requiring a high rate of P fertilizer application. However, P resources are becoming depleted globally, and excess P accumulated in soil inhibits trace element uptake by plants, pollutes the environment, and triggers outbreaks of soil-borne diseases. Available P in upland fields in Japan is usually estimated using the Truog method, but the results do not correlate with plant P uptake in Andosols. Soil organic P is also not usually evaluated as available, but remains an important P source for plants. The P in microbes (biomass P) is particularly important, because P from dead microbes is released directly into the soil or easily decomposed. We found a significant correlation between biomass P and P uptake by kidney beans. Therefore, biomass P may serve as a reliable indicator of P availability in Andosols.

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It is known that phosphate rock (PR) deposits that account for most world′s PR production are found in African countries. However, the rate of phosphorus (P) fertilizer use in Africa is typically low, despite the high requirement for application of the same there. This applies particularly to sub-Saharan Africa (SSA), where P deficiency has been suggested as one of the key constraints to crop production, despite the many PR deposits. There have been many excellent reviews on PR utilization in SSA, but hardly any have focused on its effectiveness in lowland rice cultivation. Given this lack of information, we reviewed the potential of PRs produced in the SSA region, focusing particularly on the utilization of PRs for rice cultivation in this region. Our review indicates that PR direct application in lowland rice resulted in high performance, regardless of the PR reactivity and the location investigated. A Phosphate Rock Decision Support System can help disseminate information on PR utilization in SSA; however, there is room for further improvement in predicting agronomic efficiencies in lowland rice cultivation, with consideration of the unique changes in soil condition such as the reduced condition that occurs in submerged paddy soils. In conclusion, the local PRs produced in SSA can be effectively utilized for direct application on lowland rice cultivation, hence the need to elucidate the PRs solubilization mechanism and therefore clarify the condition that maximizes the effect of local PRs direct application in SSA.

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Recent global warming has caused the maize orange leafhopper, Cicadulina bipunctata (Melichar), to proliferate in Kyushu, Japan. This leafhopper feeds on several species of poaceous plants.Some host plants such as maize, rice, wheat and oats show abnormal growth, characterized by stunted growth and swelling (upheaving) of leaf veins when attacked by C. bipunctata. This abnormal growth is not caused by a virus or phytoplasma, but by the injection of chemical(s) from the leafhopper into the plants. In central and southern areas of Kyushu, serious damage arising from this abnormal growth is known as maize wallaby ear symptom (MWES) and occurs on forage maize during the second cropping season (from late June to November). The degree of MWES is highly dependent on the level of infestation (period and density) by C. bipunctata, and since C. bipunctata density is quite low until mid-July, the earlier seeding of the second crop and the use of MWES-resistant varieties is an effective way to avoid damage from MWES. This leafhopper shows a unique relationship between plant and herbivores because MWES induction by adult C. bipunctata helps improve the development of their offspring through the accumulation of amino acids on the host plant.

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Seeds of common buckwheat usually mature while leaves are still green, causing problems for harvest machinery and limiting yields. We developed an early leaf-senescence line, Kyushu 1, from spontaneous mutants. To characterize this mutant line physiologically and genetically, we measured the change in leaf chlorophyll content in two regions of Japan with different environments, and performed genetic analyses with self-compatible lines. The chlorophyll content of Kyushu 1 was lower than that of the wild type at seed maturity in both regions. F₁ progeny of the cross between wild-type plants and Kyushu 1 showed a wild-type phenotype. F₂ progeny segregated into wild-type and early leaf-senescence phenotypes in a 3:1 or 13:3 ratio, suggesting that the early leaf senescence of Kyushu 1 is controlled by either a single recessive gene or an epistatic interaction between two loci.

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In order to help maintain soil fertility, a national survey was conducted in Japan, beginning in 1979. Both soil samples and questionnaires given to farmers on agricultural management were collected. By using the dataset, we described the long-term application rates of on-farm organic amendments (which we denote as OA and consists of livestock waste compost (LWC), and “other OA” such as rice straw residue) that are crucial for maintaining soil fertility. Average LWC and “other OA” application rates (fresh weight, FW) decreased from 17.8 ± 0.5 and 3.2 ± 0.2 (1979-1983) to 12.1 ± 0.4 and 2.7 ± 0.4 (1994-1998) Mg Fw ha^-1, respectively. The long-term change in LWC application rate may be partly due to limited time and labor. The application rates were influenced by the type of crop, possession of livestock, and the part-time/full-time status of farmers. The differences in OA application may be partly due to the separation of crop and livestock farming. When data points were categorized by the joint influence of these factors, there was a difference of more than seven times between the largest and smallest LWC application rates. The largest application rate was achieved by the group with “feed and forage crops” (FFC, such as dent corn) along with full-time farmers possessing livestock, while the smallest rate was achieved by the group of full-time or part-time farmers with neither FFC nor vegetable cropping (e.g. potatoes), and with no possession of livestock.

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Most farmers in Niger live below the poverty line and require low-capital intensification to improve agricultural production. The purpose of this study was to evaluate local knowledge on less beneficial weed for future use in managing the soil fertility of the Sahel region. Sida cordifolia was utilized in a scientific procedure to verify how local farmers utilize this species and the nature of the important roles behind this wild plant in terms of soil fertility management. The results of a questionnaire showed that S. cordifolia was less frequently used than other wild plants found in the same area, but that local farmers recognized this plant as one of the indicators of soil fertility in millet fields. The results of soil analysis also revealed a significant coefficient of variance in certain parameters such as total acidity and aluminum saturation of the soil, while multiple regression analysis showed the high influence of total acidity and soil pH on plant height and dry matter weight, respectively. These results indicate that the significant difference in plant growth of S. cordifolia was mainly due to soil acidity rather than soil fertility. The application of organic matter is one effective approach to resolve this problem and it was shown that the poor growth of S. cordifolia is a particularly useful marker to identify patches where organic matter should be applied. Despite its simplicity, this technique is considered particularly beneficial to allocate limited resources efficiently for sustainable, improved production.

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We conducted a 12-year field experiment to study the combined effects of rice straw compost and chemical fertilizer application on a double rice cropping system in the Mekong Delta, Vietnam and established 7 treatments using a randomized block design with 3 replications. We calculated the yields of treatments relative to those of conventionally fertilized plots (i.e. with no added rice straw compost), and analyzed their annual trends. In the plots with rice straw compost, we observed a positive trend over 12 continuous wet cropping seasons. In comparison with conventional fertilization, the application of rice straw compost with reduced chemical fertilizer can maintain rice productivity over a longer period. We analyzed the nutrient status of the rice straw at harvest over 4 cropping seasons and observed that the Si concentration of the rice straw in conventionally fertilized plots was significantly lower than that in the plots where rice straw compost was applied. The N, P and Mg concentrations of the rice straw increased with the fertilizer application rate, while the concentrations of K, Ca, Mn, Fe, Zn, and Cu did not differ significantly among treatments. Our results suggest that continuous removal of rice straw may reduce the Si availability in soil, thereby decreasing rice productivity. In addition, we verified that rice straw compost can be an effective source of silicon for paddy rice.

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Owing to global warming, sea-level rise (SLR) poses a serious threat to low-lying coastal areas. The potential impacts of SLR include inundation, coastal erosion, salinity intrusion, and degradation of coastal habitat. The Mekong River Delta (MRD) in southern Vietnam is a flat, low-lying land area that has experienced significant effects of climate change and SLR. Sea-level data collected from 1979 to 2006 show that the highest mean surface level of the spring tide has risen by 13 cm. This study investigated the impacts of climate change and SLR on sedimentation processes in the Tien River Estuaries of the Mekong River System. Long-term simulation results were obtained for the baseline and two SLR scenarios. In the low-SLR scenario, morphological evolutions of the Tien River Estuaries showed the same trend as the existing processes in the baseline, but intensified erosion and deposition processes. In the high-SLR scenario, the processes of erosion and deposition become too complex to estimate.

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Rice is one of the major staple crops in many developing countries, so commercializing rice-based processed foods should help boost their economy. We have recently reported that the addition of glutathione, a natural ubiquitous tri-peptide, to rice batter allows it to retain the carbon dioxide gas in fermentation, whereupon subsequent baking swells the rice bread without the need for added gluten. Although we have just detected this phenomenon, further mechanical and qualitative investigation should accelerate studies for its practical application. We speculate that the swelling is due to the “barrier theory”. In short, disulfide-linked protein polymers hinder the adsorption of water by the starch granules. Glutathione may cleave or hinder the formation of the disulfide bonds of the polymers, which boosts starch hydration, resulting in increased viscosity and continuity of the rice batter. In this paper, we have obtained evidence that glutathione modifies the sulfhydryl groups of the barrier proteins (glutathionylation) and increases their solubility, thus fraying the barrier. Although further studies are needed to reveal the complete swelling mechanism, these observations support and extend the hypothesized barrier-linked swelling mechanism of glutathione bread. Moreover, from a bread quality perspective, the fine/coarse property of crumbs is found to be controllable, and the sensory assessment demonstrated that the bread smell is unimpaired by glutathione. All these data will accelerate the practical use of the glutathione bread.

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This paper evaluates the spatial linkages between the livestock product markets in Mongolia and the effects of road conditions on market transactions. It is based on the Engle-Granger test, an error correction model, and a model of market integration using the monthly price datasets of livestock products in Mongolia during 2005-2009. Empirical analysis indicates that the most and least integrated markets are the cashmere and milk markets, respectively. Extending paved roads might tighten the integration of the livestock products markets.

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‘Siberia’ Oriental hybrid lily plants were grown under conditions of changing day temperature (DT) and night temperature (NT). Plants were grown under three fluctuating temperature conditions (average 25.8°C, 23.4°C, and 19.9°C) in a temperature gradient growth chamber (TGC), and under three DT/NT levels (28/23°C, 24/19°C, and 20/15°C) in constant temperature growth chambers (CGCs). In the CGC experiment, 35 days after planting (at the visible bud stage), the plants grown under low temperature conditions had high fresh weight (FW) of the stem and stem roots. At the flowering stage in both TGC and CGC experiments, the plants grown under low temperature conditions had a longer stem length and higher FW of the stem, flower buds, stem roots, and bulb compared than those of plants grown under high temperature conditions. The plants grown under low temperature conditions had high dry weight (DW) of the total plant, stem, and bulb, and a high DW/FW ratio of the stem and bulb. In both TGC and CGC experiments, the plants grown under the low temperature conditions showed a high relative growth rate (RGR) and net assimilation rate (NAR) from planting to flowering. These data demonstrate that cooler growing temperatures are advantageous for the accumulation of dry matter in ‘Siberia’ lilies. The low growing temperature enhances the accumulation of dry matter in ‘Siberia’ lily plants via the promotion of photosynthesis by leaves and the absorption of nutrients by well-developed stem roots.

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To elucidate the anthropogenic nutrient load, nitrate + nitrite and phosphate concentrations were measured at an upstream point where there is little tidal change in the Miyara River, Ishigaki Island, Japan. The environmental conditions of lower trophic level production were observed, and factors related to the relatively high coral cover rate were investigated on the reef slope, although there have been heavy loads on the reef flats and inside the reef edge of Miyara Bay. Though the nitrate + nitrite load was always high, the environmental conditions for lower trophic level production were found to be within an appropriate range for coral growth.

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