Major Rice-producing Areas Research Articles

Identification of Novel Alleles of the Rice Blast-Resistance Gene Pi9 through Sequence-Based Allele Mining

BackgroundAs rice (Oryza sativa) is the staple food of more than half the world’s population, rice production contributes greatly to global food security. Rice blast caused by the fungus Magnaporthe oryzae (M. oryzae) is a devastating disease that affects rice yields and grain quality, resulting in substantial economic losses annually. Because the fungus evolves rapidly, the resistance conferred by most the single blast-resistance genes is broken after a few years of intensive agricultural use. Therefore, effective resistance breeding in rice requires continual enrichment of the reservoir of resistance genes, alleles, or QTLs. Seed banks represent a rich source of genetic diversity; however, they have not been extensively used to identify novel genes and alleles.ResultsWe carried out a large-scale screen for novel blast-resistance alleles in 1883 rice varieties from major rice-producing areas across China. Of these, 361 varieties showed at least moderate resistance to natural infection by rice blast at rice blast nurseries in Enshi and Yichang, Hubei Province. We used sequence-based allele mining to amplify and sequence the allelic variants of the major rice blast-resistance genes at the Pi2/Pi9 locus of chromosome 6 from the 361 blast-resistant varieties, and the full-length coding region of this gene could be amplified from 107 varieties. Thirteen novel Pi9 alleles (named Pi9-Type1 to Pi9-Type13) were identified in these 107 varieties based on comparison to the Pi9 referenced sequence. Based on the sequencing results, the Pi2/Pi9 locus of the 107 varieties was divided into 15 genotypes (including three different genotypes of Pi9-Type5). Fifteen varieties, each representing one genotype, were evaluated for resistance to 34 M. oryzae isolates. The alleles from seven varieties with the highest resistance and widest resistance spectra were selected for transformation into the susceptible variety J23B to construct near-isogenic lines (NILs). These NILs showed resistance in a field test in Enshi and Yichang, indicating that the seven novel rice blast-resistance tandem-repeat regions at the Pi2/Pi9 locus of chromosome 6 could potentially serve as a genetic resource for molecular breeding of resistance to rice blast.ConclusionsThe thirteen novel Pi9 alleles identified in this study expand the list of available of blast-resistance alleles. Seven tandem-repeat regions of the Pi2/Pi9 locus from different donors were characterized as broad-spectrum rice blast-resistance fragments; these donors enrich the genetic resources available for rice blast-resistance breeding programs.

Is there a market power in the Philippine Rice Industry?

Rice, as a staple food for the Filipinos, is widely studied from production to consumption. However, observations of the National Food Authority domestic procurement and price stabilization policy, as well as results of the marketing and market-related studies, still reveal some gaps which call forth for an in-depth investigation and analysis. One ofthese is the possible presence ofmarket power, a market inefficiency in rice. Hence, this study aimed to ascertain the presence of market power in the Philippine rice industry. Secondary data published by the Philippine Statistics Authority from 1990 to 2015 were utilized. A structural econometric model using a time series approach was used in estimating the presence of market power. Results revealed the presence of market power in non-major rice-producing regions for well-milled and regular-milled rice in major rice-producing areas. The more the demand curve becomes inelastic the more the market power becomes apparent. The price elasticity of demand in the non-major rice-producing regions is -0.63 for both well-milled and regular-milled rice and -0.83 and -0.59, respectively, in the major rice producing areas. To minimize, if not solve market power, a substitute staple for rice may be introduced, programs/policies that will encourage more palay traders may be implemented, and farmers may be trained to operate like industry clusters.

First report of Bakanae disease caused by Fusarium proliferatum on rice in Turkey

The Bakanae disease caused by Gibberella fujikuroi species complex is one of the major fungal diseases of rice. It is present in the major rice production areas in the world. In 2016, field surveys were conducted from rice germination to maturity. Four isolates of Fusarium proliferatum associated with Bakanae disease were obtained from infected rice plants and identified using morphological and molecular-based methods. Pathogenicity tests were carried on susceptible rice variety. Initially, pale green to yellowing of leaves and thinner plants were observed. Then, these plants turned brownish and died, while control plants showed no symptoms. All isolates were found to be pathogenic. The disease severity values ranged from 27 to 66%. To our knowledge, this is the first report of the presence of F. proliferatum causing Bakanae disease on rice in Turkey.

The silicon availability in paddy soils as predicated by isothermal adsorption curve

Silicon (Si) is important for rice growth and development. Hence, it is urgent and necessary to evaluate the silicon availability of paddy soils. At present, the content of available silicon in soils is measured with 1 M acetic acid–sodium acetate (pH 4.0) buffer solution to estimate the silicon availability of paddy soils, whereas the method may not be used to evaluate silicon availability of paddy soils which are rich in calcium carbonate, or alkaline or applied with the slag. The sorption equation parameters for predicting the silicon availability of paddy soils are discussed. Isothermal adsorption with silicon equilibrium solutions (SiO2 content 0, 10, 20, 40, 60, 80, 100 mg L−1) and a pot experiment with rice plants (CK and Si treatments) were carried out with 18 paddy soils (0–20 cm) collected from major rice-producing areas in Liaoning Province of Northeast China to quantify the relationships between Si sorption parameters and soil silicon supply availability. The results showed that the equation y = bx − a could describe the Si sorption feature of 18 soils, and there were obvious differences in parameters a, b, and a/b of different soils. The y-axis intercept a of the isothermal adsorption curve linear equation indicates the content of exchangeable silicon in soils and can be used as an index representing soil silicon availability. The a value was significantly correlated with soil organic matter (OM), free iron oxide (Fed), activity of Fe oxides(Feo/Fed), and crystal/cement ratio ((Fed − Feo)/Feo), but not with pH. Parameters b and a/b were not significantly correlated with the soil physical and chemical properties. The relative silicon content (SiRE) and the relative yield of rice (YRE) increased with the a value, and the positive linear correlation between SiRE or YRE and a value reached significant p levels of 5% and 1% respectively. Isothermal adsorption equation parameter a can be used to predict the soil silicon availability, and silicon fertilizer could obviously improve the rice yield at a ≤ 126 mg kg−1 (SiO2).

Baseline determination, susceptibility monitoring and risk assessment to triflumezopyrim in Nilaparvata lugens (Stål)

Triflumezopyrim, a novel mesoionic chemical insecticide, is promoted as a powerful tool for control of susceptible and resistant hopper species in rice throughout Asia. For a newly commercialized insecticide it is important to establish susceptibility baseline, conduct susceptibility monitoring, and assess the risk of resistance via artificial selection to provide foundational information on designing resistance management strategy. The susceptibility baseline of triflumezopyrim was established for three rice planthopper species, Nilarpavata lugens (Stål), Sogatella furcifera (Horváth) and Laodelphax striatellus (Fallén). The LD50 of triflumezopyrim was 0.026, 0.032 and 0.094 ng/individual for the adults of the susceptible strains of S. furcifera, L. striatellus and N. lugens, respectively, determined by a topical application method. Using a rice stem (seedling) dipping method, the LC50 was determined as 0.042, 0.024 and 0.150 mg/L for the nymphs (3rd instar) of the three hopper species, respectively. In the meanwhile, the LC50 of Pyraxalt™ (triflumezopyrim 10% SC) was 0.064 mg/L for the N. lugens susceptible strain. Furthermore, the susceptibility of triflumezopyrim and other five neonicotinoid insecticides were monitored for N. lugens field populations collected from major rice production areas in China in 2015–2019. All monitored populations were susceptible to triflumezopyrim (0.5 to 3.9-fold resistance ratio), and showed no cross-resistance to the other five neonicotinoids. These results suggested that triflumezopyrim is a good option to control resistant N. lugens. In addition, a field-collected population of N. lugens was artificially selected with triflumezopyrim for 20 generations and resulted in 3.5-fold increase in LC50 from F0 and 6.0-fold increase from that of the susceptible strain. The realized heritability (h2) of resistance was estimated as 0.0451 by using threshold trait analysis. With this h2 value, the projected triflumezopyrim resistance development (a 10-fold increase in LC50) would be expected after 30.3 or 24.0 generations if 80% or 90% of the population was killed at each generation.

Exploring the Distribution of Blast Resistance Alleles at the Pi2/9 Locus in Major Rice-Producing Areas of China by a Novel Indel Marker.

Rice blast disease caused by the fungus Magnaporthe oryzae damages cereal crops and poses a high risk to rice production around the world. Currently, planting cultivars with resistance (R) genes is still the most environment-friendly approach to control this disease. Effective identification of R genes existing in diverse rice cultivars is important for understanding the distribution of R genes and predicting their contribution to resistance against blast isolates in regional breeding. Here, we developed a new insertion/deletion (InDel) marker, Pigm/2/9InDel, that can differentiate the cloned R genes (Pigm, Pi9, and Pi2/Piz-t) at the Pi2/9 locus. Pigm/2/9InDel combined with the marker Pi2-LRR for Pi2 was applied to determine the distribution of these four R genes among 905 rice varieties, most of which were collected from the major rice-producing regions in China. In brief, nine Pigm-containing varieties from Fujian and Guangdong provinces were identified. All of the 62 Pi2-containing varieties were collected from Guangdong, and 60 varieties containing Piz-t were from seven provinces. However, Pi9 was not found in any of the Chinese varieties. The newly identified varieties carrying the Pi2/9 alleles were further subjected to inoculation tests with regional blast isolates and field trials. Our results indicate that Pigm and Pi2 alleles have been introgressed for blast resistance breeding mainly in the Fujian and Guangdong region, and Pi9 is a valuable blast resistance resource to be introduced into China.

Rice Irrigation Schedule Optimization Based on the AquaCrop Model: Study of the Longtouqiao Irrigation District

As a crop with high water consumption, rice is an important measure of efforts to improve agricultural irrigation efficiency and alleviate the contradiction between the supply and demand of agricultural water resources. This paper takes the Longtouqiao irrigation district, in the hinterland of the Sanjiang Plain, a major rice-producing area in northern China, as an example, and the AquaCrop crop growth model and entropy-cloud model are jointly used to develop a rice irrigation schedule optimization model based on three kinds of typical rainfall years. Different irrigation schemes are established and evaluated by using the model built based on images. The results showed that the yield’s normalized root mean square error (NRMSE) value of the AquaCrop model was 9.949% (< 10%) after calibration, and the our model results showed a good agreement with observed data, which indicated that the calibrated model was suitable for rice growth simulation in the research area. For the same irrigation water amount, rice was irrigated to a great extent at the tillering stage, and a small amount of irrigation water at the regreening stage of rice could improve rice yield. During irrigation, rice production can also be promoted by regulating the irrigation amount according to the rainfall in each growth period, and the optimal irrigation water amount can be controlled between 20 and 60 mm each time. Under the three typical annual scenarios of dry, normal and wet years, the respective optimal quantification results for the field capacity, total irrigation water amount and irrigation times in the rice growth period to attain the optimal irrigation effect were 25%, 425 mm, and 17 times, respectively; 25%, 450 mm, and 14 times; respectively, and 25%, 425 mm, and 17 times, respectively. The research results can provide a decision-making basis for water-saving measures and efficient rice irrigation water management.

Policy Implications on Socio Ecological and Economic Tranformation in Vietnam’s Agriculture: Experiences from Legato Project

Abstract: As one of the leading countries in rice export, Vietnam has always focused on investing and developing clean and green agriculture with the aim of sustainable development. In addition to traditional farming methods, farmers have gradually approached modern technologies and methods of large-scale goods production. The inter-regional nature between production and agriculture and interdisciplinary interactions between agriculture and services has become increasingly common in Vietnam's major rice production areas such as the Red River Delta and the Mekong Delta. This paper focuses on analyzing the socio-economic-ecological transformation in rice production of Vietnam, adopting the experience of ecological technology application under the framework of the LEGATO project - an interdisciplinary project participated by the Institute of Policy and Management for the period 2011-2016. The results of the project affirmed the importance of combining different research approaches in considering the socio-economic-ecological impacts in ecological technology development of agricultural production in Vietnam
 Keywords: Social, ecological and economic transformation, policy, sustainable development, interdisciplinary approach, stakeholders.

Zinc and Iron Nutrition Status in the Philippines Population and Local Soils.

The Philippines is one of the major rice-producing and rice-consuming countries of Asia. A large portion of its population depends on rice for their daily caloric intake and nutritional needs. The lack of dietary diversity among poor communities has led to nutritional consequences, particularly micronutrient deficiencies. Iron-deficiency anemia (IDA) and zinc deficiency (ZnD) are two serious nutritional problems that affect the health and economic sector of the country. Since rice dominates the Filipino diet by default, biofortification of rice will help improve the micronutrient status. The Philippine government has proactively initiated various programs and policies to address micronutrient deficiencies, particularly through fortification of basic food commodities. Biofortification, the fortification of rice with micronutrients through breeding, is considered the most sustainable and cost-effective strategy that can benefit large vulnerable populations. However, developing promising genotypes with micronutrient-enriched grains should be coupled with improving micronutrient bioavailability in the soil in order to optimize biofortification. This review documents the prevailing soil Zn-deficiency problems in the major rice production areas in the Philippines that may influence the Zn nutritional status of the population. The article also reports on the biofortification efforts that have resulted in the development of two biofortified varieties approved for commercial release in the Philippines. As nutritional security is increasingly recognized as a priority area, greater efforts are required to develop biofortified rice varieties that suit both farmers' and consumers' preferences, and that can address these critical needs for human health in a sustainable and cost-effective manner.

The effect of terrain factors on rice production: A case study in Hunan Province

Rice (Oryza sativa L.) is the most important staple crop of China, and its production is related to both natural condition and human activities. It is fundamental to comprehensively assess the influence of terrain conditions on rice production to ensure a steady increase in rice production. Although many studies have focused on the impact of one or several specific factors on crop production, few studies have investigated the direct influence of terrain conditions on rice production. Therefore, we selected Hunan Province, one of the major rice-producing areas in China, which exhibits complex terrain conditions, as our study area. Based on remote sensing data and statistical data, we applied spatial statistical analysis to explore the effects of terrain factors on rice production in terms of the following three aspects: the spatial patterns of paddy fields, the rice production process and the final yield. We found that 1) terrain has a significant impact on the spatial distribution of paddy fields at both the regional scale and the county scale; 2) terrain controls the distribution of temperature, sunlight and soil, and these three environmental factors consequently directly impact rice growth; 3) compared with the patterns of paddy fields and the rice production process, the influences of terrain factors on the rice yield are not as evident, with the exception of elevation; and 4) the spatial distribution of paddy fields mismatched that of production resources due to terrain factors. Our results strongly suggest that managers should scientifically guide farmers to choose suitable varieties and planting systems and allocate rice production resources in the northern plain regions to ensure food security.

Simulating rice and maize yield potential in the humid tropical environment of Indonesia

Little is known about the yield potential of modern rice and, particularly, maize cultivars in the tropical humid environment of Indonesia where farmers can grow 2–3 consecutive crops on the same piece of land per year. This study provides a first step to fill this knowledge gap by using two crop simulation models to estimate yield potential for rice and maize based on experiments conducted across multiple site-years and measured weather and soil data. Data collected from well-managed irrigated experiments, with observed yields ranging from 7.8 to 10 Mg ha−1 (rice) and 12 to 14.4 Mg ha−1 (maize), were used to calibrate phenology and growth coefficients for both a rice (OryzaV3) and maize crop model (Hybrid Maize). The calibration was performed for commercial, high-yielding irrigated rice and maize cultivars. Subsequently, calibrated models were evaluated on their ability to simulate yield potential using an independent database available from variety (irrigated rice) and fertilizer (irrigated and rainfed maize) trials conducted at multiple site-years across major rice and maize producing areas in Indonesia. Calibrated coefficients for rice were robust at reproducing observed leaf area, aboveground biomass, and biomass partitioning to different plant organs. In the case of maize, close agreement between simulated and observed yields suggests that the generic growth model coefficients originally derived for temperate maize performed well at simulating yield potential of modern tropical maize hybrids. The two models reproduced with acceptable performance the maximum observed yields across variety and fertilizer trials, except for rainfed maize grown in a region with very heavy clay soils. Across site-years, yield potential for irrigated rice and maize averaged 9.1 and 11.6 Mg ha−1, respectively, while rainfed maize averaged 11.5 Mg ha−1. Comparison between simulated yields and average national rice and maize yields (5.2 and 5 Mg ha−1, respectively) suggested that room exists to further increase average farmer yields in rice and maize-based crop systems. Our study also highlighted the high yield potential of modern maize hybrids grown in intensive crop sequences in the humid tropics (>10 Mg ha−1). The two models evaluated here can be used to benchmark productivity in rice and maize crop systems in the humid tropical environments of South East Asia and fine tune current management practices and inputs application.

Identification of new regulatory genes involved in the pathogenic functions of the rice-pathogenic bacterium Burkholderia glumae.

Burkholderia glumae is an emerging plant-pathogenic bacterium that causes disease in rice in several of the major rice-producing areas throughout the world. In the southern United States, B. glumae is the major causal agent of bacterial panicle blight of rice and has caused severe yield losses in recent decades. Despite its importance, few management options are available for diseases caused by B. glumae, and knowledge of how this pathogen causes disease is limited. In an effort to identify novel factors that contribute to the pathogenicity of B. glumae, random mutagenesis using the miniTn5gus transposon was performed on two strains of B. glumae. Resultant mutants were screened in the laboratory for altered phenotypes in various known or putative virulence factors, including toxoflavin, lipase and extracellular polysaccharides. Mutants that exhibited altered phenotypes compared to their parent strain were selected and subsequently characterized using a PCR-based method to identify the approximate location of the transposon insertion. Altogether, approximately 20 000 random mutants were screened and 51 different genes were identified as having potential involvement in the production of toxoflavin, lipase and/or extracellular polysaccharide. Especially, two regulatory genes, ntpR and tepR, encoding a LysR-type transcriptional regulator and a σ54-dependent response regulator, respectively, were discovered in this study as new negative regulatory factors for the production of toxoflavin, the major phytotoxin synthesized by B. glumae and involved in bacterial pathogenesis.

A Genome-Wide Association Study of Field Resistance to Magnaporthe Oryzae in Rice.

BackgroundBreeding of rice cultivars with long-lasting resistance to the rice blast fungus Magnaporthe oryzae is difficult, and identification of new resistance genes is essential. Most of the loci associated with blast resistance against M. oryzae in rice have been identified in controlled environments and with single isolates, and such loci may confer resistance to only a small faction of the M. oryzae strains. In the field, however, rice is commonly attacked by multiple strains. Research is therefore needed to identify loci that confer resistance in the field, i.e., “field blast resistance”. To identify loci associated with field blast resistance (LAFBRs), we conducted a genome-wide association study (GWAS) using the rice diversity panel 1 (RDP1) cultivars. These cultivars were evaluated in the field in three major rice production areas of China.ResultsGWAS identified 16 LAFBRs. Among them, 13 are novel and the other three are co-localized with known blast resistance regions. Seventy-four candidate genes are identified in the 16 LAFBR regions, which encode receptor-like protein kinases, transcription factors, and other defense-related proteins. Using the rice transcriptome data, compared with the rice-rice blast compatible interaction, we identified seven candidate genes that are significantly up-regulated and five genes that are significantly down-regulated in the incompatible interaction among the candidate genes.ConclusionsWe identified 16 LAFBRs involved in field resistance to M. oryzae and 20 cultivars that exhibit high levels of resistance in both the field and growth chamber. The resistant cultivars and the SNP markers identified in this study should be useful for marker-assisted selection of new rice cultivars that confer high levels of resistance against M. oryzae field populations.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-016-0116-3) contains supplementary material, which is available to authorized users.

Geographical Variation of Climate Change Impact on Rice Yield in the Rice-Cropping Areas of Northeast China during 1980–2008

Northeast China (NEC) is one of China’s major rice production areas and has experienced obvious climate warming over the past three decades, similar to other mid- to high-latitude regions in the Northern Hemisphere. The present study investigates the temporal and spatial impacts of climate warming on rice yield in mid–high latitude regions. In this study, two time series datasets of rice yield and climate records in the NEC, including 178 county sites and 105 climate stations and covering the period from 1980 to 2008, were compiled. From these data, the responses of rice yield to the rice-growing season temperature (GST), growing degree days (GDD), and precipitation (GSP) were estimated using a regression model. The results indicate that rice yield benefits from climate warming in the NEC. GST positively impacted rice yield in 64.6% of the counties, with an increase of approximately 3.65%; GDD positively impacted yield in 64% of the counties, an increase of approximately 3.2%; and GSP negatively impacted rice yield in 68% of the counties, with a decrease of approximately −2.3%. Spatial variation was observed in the climate-rice yield relationships. The statistical relationships of GST and GDD with rice yield were significantly and positively correlated with latitude, longitude, and altitude, while that of GSP and rice yield was significantly and negatively correlated with latitude and longitude and showed a nonsignificant positive correlation with altitude. In summary, climate warming has significantly increased rice yield over the last three decades in the region north of 42°N, east of 122.4°E, and at an elevation of 134–473 m, which covers the majority of the rice-growing areas in the NEC.

Resistance monitoring and cross-resistance patterns of three rice planthoppers, Nilaparvata lugens, Sogatella furcifera and Laodelphax striatellus to dinotefuran in China

Three rice planthoppers, brown planthopper, Nilaparvata lugens, white-backed planthopper, Sogatella furcifera and small brown planthopper, Laodelphax striatellus, are important pests of cultivated rice in tropical and temperate Asia. They have caused severe economic loss and developed resistance to insecticides from most chemical classes. Dinotefuran is the third neonicotinoid which possesses a broad spectrum and systemic insecticidal activity. We determined the susceptibility of dinotefuran to field populations from major rice production areas in China from 2013 to 2015. All the populations of S. furcifera and L. striatellus were kept susceptible to dinotefuran (0.7 to 1.4-fold of S. furcifera and 1.1-to 3.4-fold of L. striatellus) However, most strains of N. lugens (except FQ15) collected in 2015 had developed moderate resistance to dinotefuran, with resistance ratios (RR) ranging from 23.1 to 100.0 folds. Cross-resistance studies showed that chlorpyrifos-resistant and buprofezin-resistant Sogatella furcifera, chlorpyrifos-resistant and fipronil-resistant L. striatellus, imidacloprid-resistant and buprofezin-resistant Nilaparvata lugens exhibited negligible or no cross-resistance to dinotefuran. Synergism tests showed that piperonyl butoxide (PBO) produced a high synergism of dinotefuran effects in the DY15 and JS15 populations (2.14 and 2.52-fold, respectively). The obvious increase in resistance to dinotefuran in N. lugens indicates that insecticide resistance management strategies are urgently needed to prevent or delay further increase of insecticide resistance in N. lugens.

Heavy Metal Pollution in a Soil-Rice System in the Yangtze River Region of China.

Heavy metals are regarded as toxic trace elements in the environment. Heavy metal pollution in soil or rice grains is of increasing concern. In this study, 101 pairs of soil and rice samples were collected from the major rice-producing areas along the Yangtze River in China. The soil properties and heavy metal (i.e., Cd, Hg, Pb and Cr) concentrations in the soil and rice grains were analyzed to evaluate the heavy metal accumulation characteristics of the soil-rice systems. The results showed that the Cd, Hg, Pb and Cr concentrations in the soil ranged from 0.10 to 4.64, 0.01 to 1.46, 7.64 to 127.56, and 13.52 to 231.02 mg·kg−1, respectively. Approximately 37%, 16%, 60% and 70% of the rice grain samples were polluted by Cd, Hg, Pb, and Cr, respectively. The degree of heavy metal contamination in the soil-rice systems exhibited a regional variation. The interactions among the heavy metal elements may also influence the migration and accumulation of heavy metals in soil or paddy rice. The accumulation of heavy metals in soil and rice grains is related to a certain extent to the pH and soil organic matter (SOM). This study provides useful information regarding heavy metal accumulation in soil to support the safe production of rice in China. The findings from this study also provide a robust scientific basis for risk assessments regarding ecological protection and food safety.

Differences in rice water consumption and yield under four irrigation schedules in central Jilin Province, China

The center of Jilin Province is one of the major rice-producing areas of Northeast China; however, rice production consumes large amounts of water, which is incompatible with the increasingly limited water supply. Rice yield and water consumption are the two most important considerations in the rice production process, and they may vary under different irrigation schedules. In this study, conducted in 2011 and 2012, differences in water consumption and rice yield were observed and analyzed under four different irrigation schedules—flooding irrigation (FI), shallow-wet irrigation (SWI), intermittent irrigation (II), and controlled irrigation (CI)—in a typical rice-growing area of central Jilin. The results showed that, under the four irrigation schedules, water consumption rates were (from highest to lowest) FI (1137.9 mm), SWI (984.0 mm), II (804.3 mm), and CI (678.5 mm), and rice yield rates were (from highest to lowest) SWI (9777.5 kg/ha), FI (9006.1 kg/ha), II (8936.3 kg/ha), and CI (8843.7 kg/ha), respectively. This indicated that, in central Jilin Province, the application of an advanced irrigation schedule not only saved a large amount of water for irrigation, but also that rice yields were not greatly reduced, and even increased in SWI. Therefore, we hope that in this and other similar rice cultivation areas, a universal high-yield and water-saving irrigation schedule can effectively reduce the problem of agricultural water use.

Evaluation of regional climate scenario data for impact assessment of climate change on rice productivity in Korea

Spatial evaluation of the uncertainty associated with climate data would allow reliable interpretation of simulation results for regional crop yield using gridded climate data as input to a crop growth model. The objective of this study was to examine the spatial uncertainty of regional climate model data through determining optimal seeding date with the ORYZA2000 model for assessment of climate change impact on rice productivity in Korea. The optimal seeding date was determined at each grid point using regional climate model outputs under the RCP 8.5 scenarios. In major rice production areas such as inland plain regions, where temperatures of regional climate data were relatively accurate, the optimal seeding date determined using those gridded data were reasonable. However, areas with complex terrains including areas near bodies of water, e.g. coastal areas, riverbasins, lakes, and mountainous areas, had a relatively large uncertainty of the optimal seeding date determined using the regional climate data. These results indicated that the uncertainty of regional climate data at a high spatial resolution of 12.5 km should be taken into account in the regional impact assessment based on crop growth simulations in Korea. In addition, further studies would be merited to assess the impact of climate change on rice yield at an ultra-high spatial resolution of 1 km in Korea. Crop yields were projected to decrease after the 2020s when crop yield simulations from inland plain areas were considered, which suggested that adaptation strategies should be established and implemented in the near future.

Comparison of regional climate scenario data by a spatial resolution for the impact assessment of the uncertainty associated with meteorological inputs data on crop yield simulations in Korea

Uncertainty of crop yield simulation would be affected by weather input data prepared from different sources of climate datasets. Although regional climate data at a high spatial resolution would be useful for the impact assessment of climate change on crop production, little effort has been made to characterize the uncertainty associated with such climate data in terms of crop yield simulations. The objectives of this study were to compare climate scenario data products obtained from a series of downscaling processes and to identify an overall pattern of uncertainty in these climate data in terms of crop yield simulation. Regional climate scenario data from 2011 to 2014 had a spatiotemporal pattern of uncertainty, which differed by meteorological variables and spatial resolution. Overall, the uncertainty of daily minimum temperature was greater than that of maximum temperature. Daily minimum temperature also had relatively greater uncertainty in an early season of crop production, which could result in the cumulative impact on the uncertainty of crop yield simulations. For the uncertainty of climate data at different spatial resolution, climate data at higher spatial resolution, e.g. 1 km, tended to have lower uncertainty than data at resolution of 12.5 km did. Still, the uncertainty of regional climate data was relatively similar between data at resolution of 12.5 km and 1 km in major rice production areas in Korea except in areas near Seosan. This merits further studies to examine actual differences in projected crop yields using regional climate scenario data in the future and to assess the impact of uncertainty associated with regional climate data on crop yield simulation.

Inorganic arsenic contamination of rice from Chinese major rice-producing areas and exposure assessment in Chinese population

This study examined the total arsenic (Ast) and inorganic arsenic (Asi) content in the main rice growing area of China. The results were compared with other countries and then used for dietary exposure assessment. A total of 446 rice samples from 15 main rice-growing provinces and autonomous regions of China were collected and then divided into unpolished and polished rice. Total arsenic and arsenic species were analyzed in a total of 892 subsamples using inductively coupled plasma-mass spectrometry (ICP-MS) and high performance liquid chromatography (HPLC) coupled ICP-MS, respectively. National Ast means were 255 μg/kg of unpolished rice and 143 μg/kg of polished rice. Asi was found to be the predominant species and mean levels were 209 μg/kg of unpolished rice and 108 μg/kg of polished rice, respectively. Exposure assessment to Asi in polished rice has been calculated for the margin of exposure (MOE), which highlights the fact that Asi levels in the Chinese rice should arouse public health concern.