• Korean Journal of Ecology and Environment
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• v.50 no.2
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• pp.266-274
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• 2017

We surveyed the habitat use and food materials of the endangered Swan Goose (Anser cygnoides) during the wintering period at the Seocheon tidal flat. The bird wintered about six months from October 2014 to early April 2015 at the flat. They showed a remarkable change in choosing their feeding habitat and prey. They stayed entirely at sedge grass patches on Songrim tidal flat during the early wintering period (October), while after November they gradually moved to Janggu bay and used rice paddy fields as well as sedge patches on the tidal flats as their feeding site. The dietary analysis showed the sedge grass (Bolboschoenus sp., Cyperaceae) was the main dietary source during the entire wintering period. Interestingly, the proportion of Cyperaceae on feces decreased slightly over wintering time, while the proportion of Fabaceae increased relatively since November. These results suggest that the Swan Geese switched their habitat and food sources in response to the change of food availability. The Seocheon tidal flat area is the important wintering site for Swan Geese and sedge grass patches in the area need to be managed as the main feeding area for the wintering Swan Geese.

• Research in Plant Disease
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• v.9 no.2
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• pp.68-71
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• 2003

Correlation between rice yield loss and infection time of neck blast after panicle emergence was analyzed in paddy fields at Icheon in 1999 and 2000. As the neck blast occurred at early heading stage, the yield loss of a early maturity variety, Jinmibyeo, ranged from 83.9% to 81.6%, while it ranged from 44.3% to 33.1% when the disease developed 30 days after heading. The regression equations of yield loss(y) caused by the neck blast infection time(x) in Jinmibyeo were y =1.2717x + 79.523(R2 = 0.9487) and y = 1.6872x + 74.545(R2 = 0.7993) in 1999 and 2000. In a mid-lately maturity variety, Chucheongbyeo, yield loss ranged from 64.9% to 47.8% when the disease developed at early heading stage. While it ranged from 29.1% to 8.9% when the disease occurred 40 days after heading. The regression equations of yield loss caused by the disease in Chucheongbyeo were y= 1.2717x + 79.523($R^2$ = 0.9487) and y = 1.6872x + 74.545(($R^2$ = 0.7993) in 1999 and 2000. Weights of 1,000 rice grains of Jinmibyeo and Chucheongbyeo were also drastically decreased to 38.3% and 57.3%, respectively, compared to healthy control when the disease occurred at early heading stage. However, weights of the two cultivars were 87.6% and 92.9% compared to control when the disease developed after 40 days of heading. Results indicated that there is a highly negative correlation between rice yield loss and infection time of the neck blast.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.6
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• pp.522-527
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• 2004

Barley growing in paddy fields often suffers from wet-injury due to oxygen deficiency in rhizospere caused by excessive water in the soil. This study was conducted to investigate responsiveness of growth, development and anaerobic glycolysis enzymes to acute hypoxia in barley seedlings. Barley seedlings at the third leaf stage were subjected to hypoxia (1 ppm dissolved oxygen) by sparging the culture solution with nitrogen gas for up to seven days. Length and fresh weights of the shoot and root were affected little by hypoxia for up to 5 days. But root dry weight was slightly decreased by hypoxia for 7 days. In the root, alcohol dehydrogenase and lactate dehydrogenase activities increased drastically under hypoxia, reaching at their maximum levels in 3 to 5 days of hypoxia and decreasing slightly thereafter. However, the activities of both enzymes changed little in the shoot. Increases of their activities in the root were contributed by all the isozymes found in barley. These results suggest that barley seedlings first adapt to hypoxia by rapidly activating fermentative glycolysis to stabilize cellular pH and to increase energy production for the following morphological adaptative changes.

• Journal of Ecology and Environment
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• v.33 no.1
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• pp.23-36
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• 2010

The Cat Ba Islands in Hai Phong City, northern Vietnam, consist of a large limestone island with a maximum height of 322 m above sea level and 366 small limestone islets with a total area of about $180\;km^2$. The islands are relicts of karst limestone mountains that became submerged during the Holocene transgression 7000 - 8000 year ago. The combination of the longtime karst process and recent marine processes in the monsoonal tropical zone has created a very diversity landscape on the Cat Ba Islands that can be divided into 3 habitat types with 16 forms. The first habitat type is the karst mountains and hills, including karst mountains and hills, karst valleys and dolines, karst lakes, karst caves, and old marine terraces. The second habitat type is the limestone island coast, including beaches, mangrove marshes, tidal flats, rocky coasts, marine notch caves, marine karst lakes, and bights. The third habitat type is karst plains submerged by the sea, including karst cones (fengcong) and towers (fengling), bedrock exposed on the seabed, sandy mud seabed, and submerged channels. Like the landscape, the biodiversity is also high in ecosystems composed of scrub cover - bare hills, rainy tropical forests, paddy fields and gardens, swamps, caves, beaches, mangrove forests, tidal flats, rocky coasts, marine krast lakes, coral reefs, hard bottoms, seagrass beds and soft bottoms. The ecosystems on the Cat Ba Islands that support very high species biodiversity include tropical evergreen rainforests, soft bottoms; coral reefs, mangrove forests, and marine karst lakes. A total of 2,380 species have been recorded in the Cat Ba Islands, included 741 species of terrestrial plants; 282 species of terrestrial animals; 30 species of mangrove plants; 287 species of phytoplankton; 79 species of seaweed; 79 species of zooplankton; 196 species of marine fishes; 154 species of corals; and 538 species of zoobenthos. Many of these species are listed in the Red Book of Vietnam as endangered species, included the white-headed or Cat Ba langur (Trachypithecus poliocephalus), a famous endemic species. Human activities have resulted in significantly changes to the landscape end ecosytems of the Cat Ba islands; however, many natural aspects of the islandsd have been preserved. For this reason, the Cat Ba Islands were recognized as a Biological Reserved Area by UNESCO in 2004.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.50 no.4
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• pp.238-246
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• 2005

Rice yield and protein content have been shown to be highly variable across paddy fields. In order to characterize this spatial variability of rice within a field, two-year experiments were conducted in 2002 and 2003 in a large-scale rice field of $6,600m^2$ In year 2004, an experiment was conducted to know if variable rate treatment (VRT) of N fertilizer, that was prescribed for site-specific management at panicle initiation stage, could reduce spatial variation in yield and protein content of rice while increasing yield compared to conventional uniform N topdressing (UN, 33kg N/ha at PIS) method. VRT nitrogen prescription for each grid was calculated based on the nitrogen (N) uptake (from panicle initiation to harvest) required for target rice protein content of $6.8\%$, natural soil N supply, and recovery of top-dressed N fertilizer. The required N uptake for target rice protein content was calculated from the equations to predict rice yield and protein content from plant growth parameters at panicle initiation stage (PIS) and N uptake from PIS to harvest. This model· equations were developed from the data obtained from the previous two-year experiments. The plant growth parameters for the calculation of the required N were predicted non-destructively by canopy reflectance measurement. Soil N supply for each grid was obtained from the experiment of year 2003, and N recovery was assumed to be $60\%$ according to the previous reports. The prescribed VRT N ranged from 0 to 110kg N/ha with an average of 57kg/ha that was higher than 33 kg/ha of UN. The results showed that VRT application successfully worked not only to reduce spatial variability of rice yield and protein content but also to increase rough rice yield by 960kg/ha. The coefficient of variation (CV) for rice yield and protein content was reduced significantly to $8.1\%$ and $7.1\%$ in VRT from $14.6\%$ and $13.0\%$ in UN, respectively. And also the average protein content of milled rice in VRT showed very similar value of target protein content of $6.8\%$. In conclusion the procedure used in this paper was believed to be reliable and promising method for reducing within-field spatial variability of rice yield and protein content. However, inexpensive, reliable, and fast estimation methods of natural N supply and plant growth and nutrition status should be prepared before this method could be practically used for site-specific crop management in large-scale rice field.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.65 no.2
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• pp.104-112
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• 2020

Maize is thought to be an alternative crop to rice in paddy fields for efficient field management and maintenance of rice production at appropriate levels in Korea. Thus efforts to breed waterlogging-tolerant maize cultivars have been ongoing. However, molecular studies related to waterlogging tolerance are limited for developing molecular markers to select waterlogging tolerant maize varieties. In this study, we examined molecular biological changes of B73 in the V3 stage after immersion treatment for 7 days. Overall growth of maize was lower in treated samples compared to non-immersed control samples. The length of leaf and root decreased by 21.3% and 50.6%, respectively and the weight of root reduced by 21.6%. Soil plant analysis development (SPAD) value and chlorophyll content of leaf also decreased by 55.7% and 35.3%, respectively. Reactive oxygen species (ROS) content of root increased by 46.5% at 2 hours in immersion treatment. In addition, immersed roots were 2.5-fold thickened with additional aerenchyma formation in the cortex. In order to identify the causes of these changes, we performed a microarray and found increased expression of genes, such as WIP1, PMIP2, EXPA1, TPS1, and MAS1, in immersed samples. These differentially expressed genes and expression of previously reported genes, including ALDH2, Wusl1032, UP-1, UP-2, and CAT2 were further confirmed with qRT-PCR. Here, we report 7 differentially expressed genes after immersing treatment, which may be utilized as useful resources for breeding waterlogging- tolerant maize.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.65 no.2
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• pp.151-155
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• 2020

This study was conducted to determine the effects of the selection of an appropriate sowing method in on ginseng growth, and the results are as follows. SAS (semi-automatic sower), commonly used by direct seeding farms, provides fast operation speed but results in high labor cost, while (Hooper Seeder Sowing) offers fast operation speed and high germination rate, but leads to increased laborer's fatigue. Daily working area per sower was 6,611 ㎡ for a motor type, and the operation time to sow 3,305 ㎡ was 15 hours for broadcast planting, and 8 hours for SAS. The germination rate of 1-year-old ginseng according to direct seeding was 69.1% for the treatment plot under broadcast planting, followed by 66.4% and 67.3% for manual sower and hoop sower, respectively, and the germination rate of SAS was the lowest at 64.2%. In addition, there were no differences in shoot and root growth of 1-year-old ginseng among the sowing methods. Therefore, the sowing method can be chosen depending on the economic size of ginseng farmers. That broadcast sowing (BS) is appropriate for small scale farmers, while motor-driven seeder sowing (MDS) for direct seeding is more suitable for large scale farmers.

• Journal of Microbiology and Biotechnology
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• v.19 no.10
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• pp.1213-1222
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• 2009

The search for diverse plant growth-promoting (PGP) diazotrophic bacteria is gaining momentum as efforts are made to exploit them as biofertilizers for various economically important crops. In the present study, 17 diazotrophic strains belonging to eight different genera isolated from rice paddy fields were screened for multiple PGP traits and evaluated for their inoculation effects on canola and rice plants. All of the strains tested positive for 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity and production of indole 3-acetic acid (IAA) and ammonia ($NH_3$). Additionally, four of the strains were able to solubilize phosphorus (P), five tested positive for zinc (Zn) solubilization and sulfur (S) oxidation, and eight strains produced siderophores. Based on the presence of multiple PGP traits, 10 strains were selected for inoculation studies. Treatment with Herbaspirillum sp. RFNB26 resulted in maximum root length (54.3%), seedling vigor, and dry biomass in canola, whereas Paenibacillus sp. RFNB4 exhibited the lowest activity under gnotobiotic conditions. However, under pot culture conditions, Paenibacillus sp. RFNB4 significantly increased plant height and dry biomass production by 42.3% and 29.5%, respectively. Canola plants and rhizosphere soils inoculated with Bacillus sp. RFNB6 exhibited significantly higher nitrogenase activity. In greenhouse experiments, Serratia sp. RFNB18 increased rice plant height by 35.1%, Xanthomonas sp. RFNB24 enhanced biomass production by 84.6%, and rice rhizosphere soils inoculated with Herbaspirillum sp. RFNB26 exhibited the highest nitrogenase activity. Our findings indicate that most of the selected strains possess multiple PGP properties that significantly improve the growth parameters of the two plants when tested under controlled conditions.

• Korean Journal of Environmental Agriculture
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• v.12 no.2
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• pp.176-183
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• 1993

Photolysis experiments were conducted to investigate the stability of a new insecticide, [O,O-Diethyl O-(1-phenyl-3-trifluoromethyl-5-pyrazoyl) thiophosphoric acid ester: KH-502] under the various conditions. In the photolysis experiment, KH-502 was, after being added into the acetone or acetonitrile solution, irradiated under the sunlight or UV lamp $(300{\sim}350nm)$, where acetone or acetonitrile solution was varied with water and $O_2$contents and was treated with humic acid, rosebengal or tryptophan. Results for stability and degradation pattern of KH-502 from the above experiment can be summarized as follows: 1. The significant difference in KH-502 decomposition due to photolysis was shown for between KH-502s irradiated at $300{\sim}350$ nm and non-irradiated. KH-502 was photolyzed in the acetone by the sensitizing effect, but was stable in the acetonitrile. 2. The degradation pattern of KH-502 in the photolysis was different as compared to that in the thermal decomposition, and the decomposed products were O,O-Diethyl O-(1-phenyl-3-trifluoromethyl-5-pyrazoyl)phosphoric acid ester (KH-502 oxo form), O,S-Diethyl O-(1-phenyl-3-trifluoromethyl-5-pyrazoyl)phosphorothiolate(S-ethyl KH-502), 1-Phenyl-3-trifluoromethyl-5-hydroxy pyrazole (PTMHP) and several unknown compounds. 3. Treatments of acetone or acetonitrile solution with humic acid, rosebengal or tryptophan revealed no-sensitizing effect on the photolysis of KH-502. Dissolved oxygen in the acetone played as a cosensitizer with acetone competitively to enhance the photolysis of KH-502. 4. Treatments of acetone with humic acid or paddy soil water collected from fields decreased the photolysis of KH-502.

• The Korean Journal of Pesticide Science
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• v.11 no.4
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• pp.269-275
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• 2007

Four sulfonylurea(SU)-resistant Monochoria vaginalis(M. vaginalis) accessions were tested for levels of resistance to four SU herbicides which have been widely using in paddy fields of Korea, based on whole plant response and sensitivity of the target enzyme, acetolactate synthase(ALS). The resistant Naju, Nonsan and Gimje accessions were not affected to the survival by treatment with recommended dose of all SU herbicides tested. The $GR_{50}$ values for the Naju, Nonsan and Gimje accessions were 8- to 33-fold, 8- to 30-fold and 7- to 32-fold higher to recommended doses of all SU herbicides tested than the susceptible Cheongdo accession, respectively. However, the $GR_{50}$ values for Kimhae accession displayed an intermediate response and was only 4-to 13-fold more resistant than the susceptible accession. The ALS $I_{50}$ values for the Naju, Nonsan and Gimje accessions were 25- to 66-fold, 9- to 26-fold and 10- to 24-fold higher to recommended doses of all SU herbicides tested than the susceptible Cheongdo accession, respectively. However, the $I_{50}$ value for Kimhae accession was 4- to 9-fold more resistant than the susceptible accession, as determined by $I_{50}$ values of ALS.