Rice Fields In Thailand Research Articles

Distribution and resistance of barnyardgrass to quinclorac in rice fields in Thailand

Background: In Thailand, Echinochloa crus-galli (L.) P. Beauv. (barnyardgrass) is the most problematic weed in rice. Quinclorac was first commercialized in 1997 in Thailand and became the primary herbicide option for barnyardgrass control. The intensive use of quinclorac in rice fields increases the risk of the evolution of resistant barnyardgrass. Objective: This study was conducted to survey the occurrence of quinclorac-resistant barnyardgrass in Thailand, investigate the levels of quinclorac resistance, and evaluate alternative control measures for quinclorac-resistant barnyardgrass. Methods: [...]

Incidence and Characterization of Rice Root Nematodes, Hirschmanniella mucronata, from Rice Fields in Pathum Thani Province, Thailand

The rice root nematodes, Hirschmanniella oryzae and H. mucronata, are serious and widespread threats to global rice production, especially in tropical and subtropical zones. Reliable and efficient identification of these nematodes is vital to nematode control and management. In this current study, 36 soil or rice root samples were collected from rice fields located in Pathum Thani province and used for nematode extraction. The results demonstrated that Hirschmanniella sp. was found in all paddy fields, especially in Muang District, where RD47 rice cultivars were grown at soil pH of 5.9. Molecular identification based on the analysis of 28S rRNA and 18S-ITS1-1.58S genes revealed 98 – 99 % similarity to H. mucronata, and its phylogenetic trees were grouped with H. mucronata from Cambodia and Philippines. Likewise, the morphometric characterization revealed remarkable features of H. mucronata with long body (1,639 - 2,329 µm), long stylet (24 - 27 µm) and an obvious mucron at the end of terminus. Therefore, the main rice root nematode species found in Pathum Thani’s rice fields were H. mucronata.
 HIGHLIGHTS
 
 The rice root nematodes, Hirschmanniella, are presented the predominant plant-parasitic nematodes in rice cultivated areas of Pathum Thani province, Thailand
 Population densities of Hirschmanniella are encountered in rice roots than in soil, especially in RD47 rice cultivars grown in Muang District
 Both of morphological and molecular characterization illustrating the species of rice root nematodes were mucronate
 This is a first description on the molecular characterization of mucronata from rice fields in Thailand
 
 GRAPHICAL ABSTRACT

Paddy Rice Mapping in Thailand Using Time-Series Sentinel-1 Data and Deep Learning Model

The elimination of hunger is the top concern for developing countries and is the key to maintain national stability and security. Paddy rice occupies an essential status in food supply, whose accurate monitoring is of great importance for human sustainable development. As one of the most important paddy rice production countries in the world, Thailand has a favorable hot and humid climate for paddy rice growing, but the growth patterns of paddy rice are too complicated to construct promising growth models for paddy rice discrimination. To solve this problem, this study proposes a large-scale paddy rice mapping scheme, which uses time-series Sentinel-1 data to generate a convincing annual paddy rice map of Thailand. The proposed method extracts temporal statistical features of the time-series SAR images to overcome the intra-class variability due to different management practices and modifies the U-Net model with the fully connected Conditional Random Field (CRF) to maintain the edge of the fields. In this study, 758 Sentinel-1 images that covered the whole country from the end of 2018 to 2019 were acquired to generate the annual paddy rice map. The accuracy, precision, and recall of the resultant paddy rice map reached 91%, 87%, and 95%, respectively. Compared to SVM classifier and the U-Net model based on feature selection strategy (FS-U-Net), the proposed scheme achieved the best overall performance, which demonstrated the capability of overcoming the complex cultivation conditions and accurately identifying the fragmented paddy rice fields in Thailand. This study provides a promising tool for large-scale paddy rice monitoring in tropical production regions and has great potential in the global sustainable development of food and environment management.

Soil Nutrient Depletion Is Associated with the Presence of Burkholderia pseudomallei.

ABSTRACTBurkholderia pseudomallei is a soil-dwelling bacterium and the cause of melioidosis, which kills an estimated 89,000 people per year worldwide. Agricultural workers are at high risk of infection due to repeated exposure to the bacterium. Little is known about the soil physicochemical properties associated with the presence or absence of the organism. Here, we evaluated the soil physicochemical properties and presence of B. pseudomallei in 6,100 soil samples collected from 61 rice fields in Thailand. The presence of B. pseudomallei was negatively associated with the proportion of clay, proportion of moisture, level of salinity, percentage of organic matter, presence of cadmium, and nutrient levels (phosphorus, potassium, calcium, magnesium, and iron). The presence of B. pseudomallei was not associated with the level of soil acidity (P = 0.54). In a multivariable logistic regression model, the presence of B. pseudomallei was negatively associated with the percentage of organic matter (odds ratio [OR], 0.06; 95% confidence interval [CI], 0.01 to 0.47; P = 0.007), level of salinity (OR, 0.06; 95% CI, 0.01 to 0.74; P = 0.03), and percentage of soil moisture (OR, 0.81; 95% CI, 0.66 to 1.00; P = 0.05). Our study suggests that B. pseudomallei thrives in rice fields that are nutrient depleted. Some agricultural practices result in a decline in soil nutrients, which may impact the presence and amount of B. pseudomallei bacteria in affected areas.IMPORTANCE Burkholderia pseudomallei is an environmental Gram-negative bacillus and the cause of melioidosis. Humans acquire the disease following skin inoculation, inhalation, or ingestion of the bacterium in the environment. The presence of B. pseudomallei in soil defines geographic regions where humans and livestock are at risk of melioidosis, yet little is known about the soil properties associated with the presence of the organism. We evaluated the soil properties and presence of B. pseudomallei in 61 rice fields in East, Central, and Northeast Thailand. We demonstrated that the organism was more commonly found in soils with lower levels of organic matter and nutrients, including phosphorus, potassium, calcium, magnesium, and iron. We also demonstrated that crop residue burning after harvest, which can reduce soil nutrients, was not uncommon. Some agricultural practices result in a decline in soil nutrients, which may impact the presence and amount of B. pseudomallei bacteria in affected areas.

The Type III Secretion System (T3SS) is a Determinant for Rice-Endophyte Colonization by Non-Photosynthetic Bradyrhizobium.

Plant associations by bradyrhizobia have been detected not only in leguminous plants, but also in non-leguminous species including rice. Bradyrhizobium sp. SUTN9-2 was isolated from Aeschynomene americana L., which is a leguminous weed found in the rice fields of Thailand. This strain promoted the highest total rice (Oryza sativa L. cultivar Pathum Thani 1) dry weight among the endophytic bradyrhizobial strains tested, and was, thus, employed for the further characterization of rice-Bradyrhizobium interactions. Some known bacterial genes involved in bacteria-plant interactions were selected. The expression of the type III secretion component (rhcJ), type IV secretion component (virD4), and pectinesterase (peces) genes of the bacterium were up-regulated when the rice root exudate was added to the culture. When SUTN9-2 was inoculated into rice seedlings, the peces, rhcJ, virD4, and exopolysaccharide production (fliP) genes were strongly expressed in the bacterium 6–24 h after the inoculation. The gene for glutathione-S-transferase (gst) was slightly expressed 12 h after the inoculation. In order to determine whether type III secretion system (T3SS) is involved in bradyrhizobial infections in rice plants, wild-type SUTN9-2 and T3SS mutant strains were inoculated into the original host plant (A. americana) and a rice plant (cultivar Pathum Thani 1). The ability of T3SS mutants to invade rice tissues was weaker than that of the wild-type strain; however, their phenotypes in A. americana were not changed by T3SS mutations. These results suggest that T3SS is one of the important determinants modulating rice infection; however, type IV secretion system and peces may also be responsible for the early steps of rice infection.

Invasion of weedy rice in rice fields in Thailand: problems and management

Wild rice ( Oryza rufipogon Griff. ), a relative of cultivated rice ( Oriza sativa L. ), is common in natural habitats throughout Thailand (Chitrakorn 1985). Characteristics of wild rice include seed shattering, black seed coat, awns on seeds, red pericarp, and sensitivity to photoperiod (Oka 1988). The oldest farmers say that wild rice has always been a common feature of rice fields in Thailand. They and younger farmers as well recall that, even 20 y ago, it was found mainly in natural habitats on the edges of farm ditches, deep depressions, and swampy places, but rarely in rice fields. Weedy rice with characteristics of O. rufipogon has been recognized as a weed in rice fields, but the level of infestation had been quite low, until recently.

Distribution of the Apple Snail and Damage in Rice Fields of Thailand and Vietnam

Distribution of the Apple Snail and Damage in Rice Fields of Thailand and Vietnam

The nutritional value of lipids in various tropical aquatic animals from rice–fish farming systems in northeast Thailand

Knowledge on the lipid compositions of tropical freshwater aquatic animals is limited despite their importance in the human diet and the health-related benefits of fish lipids. This study examines the lipid content and fatty acid composition from the edible muscle tissue of some common freshwater aquatic animals that inhabit rice fields in Thailand, namely snakehead ( Channa striatus), Gunther's walking catfish ( Clarias macrocephalus), climbing perch ( Anabas testudineus), blackline rasbora ( Rasbora borapetensis), swamp barb ( Puntius brevis), and freshwater prawn ( Macrobrachium nipponense). All specimens were low in muscle fat (≤1.1% of wet weight). There was considerable variation in the fatty acid composition between species. All species were good sources of the essential fatty acids, and particularly of C22:6n-3 (5.2–13.3% total FA) and C20:4n-6 (7.2–14.6% total FA), signifying their high nutritional quality for human nutrition. The findings indicate that strategies for rural development, food security, and alleviation of poverty in rural areas need to pay special attention to the management of aquatic resources to ensure the health and well-being of rural people.

Validation of revised DNDC model for methane emissions from irrigated rice fields in Thailand and sensitivity analysis of key factors

The original Denitrification–Decomposition (DNDC) model and a revised version were tested against data from field observations of methane (CH4) emissions from irrigated rice fields in Thailand. The revised DNDC model, which was modified for use in Japanese rice fields by revising the crop growth and soil biogeochemical submodels, yielded better simulation results than the original model. In most cases, daily CH4 fluxes predicted by the revised DNDC model agreed well with observations. Seasonal CH4 emissions simulated by the revised model showed significantly higher correlation with observations than those obtained with the original model. Errors in the simulation appear to have resulted from uncertainties in both the input parameters and the model descriptions. Sensitivity analysis revealed that the revised DNDC model is highly sensitive to the concentration of reducible soil Fe, the rate of rice straw incorporation, and rice root biomass. Therefore, uncertainties in these factors may strongly affect the prediction of CH4 emissions. These results suggest that for reliable prediction of CH4 emissions from Thai rice fields, further work is needed to improve the estimates of reducible soil Fe, to quantify the rate of straw incorporation, and to parameterize the crop submodel for the dominant rice varieties grown in Thailand.

Methane Emission from Deepwater Rice Fields in Thailand

Field experiments were conducted in the Prachinburi Rice Research Center (Thailand) from 1994 to 1998. The major objective was to study methane (CH4) emission from deepwater rice as affected by different crop management. Irrigated rice was investigated in adjacent plots, mainly for comparison purposes. The 4-yr average in CH4 emission from deepwater rice with straw ash (burned straw) treatment was 46 mg m−2d−1 and total emission was 98 kg ha−1 yr−1. For irrigated rice, the average emission rate and total emission for the straw ash treatment was 79 mg m−2 d−1 and 74 kg ha−1 yr−1, respectively. Low emission rates may partially be related to acid sulfate soil of the experimental site. Without organic amendment, the seasonal pattern of CH4 emission from deepwater rice was correlated with an increase in biomass of rice plants. Emission rates from deepwater rice depend on the production of biomass and the straw management as well. Methane emission was greatest with straw incorporation, followed by straw compost incorporation, zero-tillage with straw mulching, and least with straw ash incorporation. The seasonal pattern of CH4 ebullition in deepwater rice was consistent with seasonal emission, and total ebullition corresponded to 50% of total emission. Dissolved CH4 concentrations in the surface soil (0–5 cm) were similar to those in the subsoil (5–15 cm), and the seasonal fluctuation of dissolved CH4 was also consistent with the seasonal CH4 emission. Increase in plant density and biomass of irrigated rice grown by pregerminated seed broadcasting enhanced CH4 emission as compared with transplanting.

Ammonium excretion by a mutant of the nitrogen-fixing cyanobacterium Anabaena siamensis

Anabaena siamensis isolated from rice fields in Thailand is a fast growing cyanobacterium with a high nitrogen-fixing activity. Mutant strains resistant to the l-glutamate analogue, l-methionine sulfoximine (MSX) were isolated by ethyl methanesulfonate mutagenesis. A stable mutant named A. siamensis SS1, which released ammonium to the medium, was studied further. In batch cultures the rate of ammonium production peaked at the early log phase and gradually decreased until the 4th day of growth when the cultures reached a density of 90 μg chl ml −1. To obtain constant release of ammonium by SS1, continuous culture experiments were performed at a cell density of 5 μg chl ml −1 and the following results were obtained: (1) growth rate as the parent (μ:0·123 h −1) in the presence and absence of 500 μ m MSX; (2) 48% GS transferase activity when compared with the parent; (3) ammonium excretion at a rate of 8 μmol (mg chl) −1 h −1 as measured up to 20 generations (120 h); (4) depressed nitrogenase activity; and (5) 30% higher nitrogenase activity than that of the parent. SS1 immobilized in alginate beads (5 μg chl ml −1) exhibited values of glutamine synthetase and nitrogenase activity similar to those of free cells. However, ammonium excretion at the rate of 11·61 μmol (mg chl) −1 h −1 was obtained only up to 20 h after loading in bioreactors, due to the fast growth of SS1 as also occurred in batch cultures.

Evaluation of factors contributing to diurnal changes in O2 concentrations in floodwater of deepwater rice fields

SUMMARYGlass chambers were used to isolate 0–75 m deep water columns in situ in deepwater rice fields in Thailand to evaluate the contribution by various factors to the pronounced diurnal changes in O2 concentrations in the floodwater Chambers filled with distilled water provided estimates of O2 flow from the air into the water, indicating the importance of eddy currents associated with wind action and evaporative cooling. Darkening the natural water gave estimates for O2 evolution due to photosynthesis, while comparisons between columns with and without rice distinguished between O2 evolution and consumption by the rice and the biomass other than rice respectively. Removal of the above water portions of the rice shoots showed the importance of the emergent portion of the canopy to O2 movement from the air into the aquatic part of the ecosystem. This flow may be associated with O2 flow through the lacunae and via air envelopes around the leaf, and with turbulence caused by swaying of the rice leaves in the wind.The changes in O2 concentration were analysed quantitatively using several simplifying assumptions. One major input was a net O2 flow from the air into the water, about half being due to a net flow across the air–water interface and the other half to flow associated with the rice plants. During the night, these flows were less than the O2 uptake by the biomass, hence O2 concentrations decreased. In the underwater portion of the rice stand, about 60 % of the O2 uptake was due to the rice and about 40% due to the biomass other than rice. During the day, the O2 requirements by respiration were more than compensated for by O2 evolution due to photosynthesis, resulting in increases in O2 concentration of the water.

Algal ecology of deepwater rice-fields in Thailand

Algal ecology of deepwater rice-fields in Thailand