• Korean Journal Plant Pathology
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• v.3 no.2
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• pp.131-136
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• 1987

Rates of lesion development over time and disease gradients over distance for blast disease on the two rice varieties, Brazos and M-20 1 were significantly affected by two different cultural conditions, upland and flooded conditions. Flooding rice field plots lowered the rates of lesion increase and flattened the disease gradients for both varieties. Despite absence of statistically significant differences in the rate of lesion increase between four sampled distances from infection focus, rate of lesion development tended to be slightly greater as distance from the infection focus increases. Rate of lesion increase was greater with more susceptible variety M-201 than with Brazos. Disease gradient was steeper for M-201 than for Brazos. As blast disease progressed, disease gradients became flattened regardless of variety due to the infections originated from secondary foci. Between two empirical disease gradient models examined, Kiyosawa & Shiyomi model was fitted better over Gregory model. Rates of blast isopath movement under upland conditions were calculated as approximately 0.2m/day and 0.4 m/day for Brazos and M-201, respectively. The results in this study suggest that differences in varietal resistance to blast could be detected by measuring disease gradient as efficiently as by measuring infection rate.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.34 no.1
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• pp.14-22
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• 1989

Rice varieties showing different degree of resistance were compared with their yield losses due to the damage of sheath blight disease in field condition through 1985 to 1986. Gayabyeo showed the lowest value of disease severity among 5 varieties tested in 1985 and 8 in 1986. and Taebaekbyeo, Kwanakbyeo and Labelle showed higher value of disease severity under the condition of artificial or natural disease inoculation. Grain yield of Gayabyeo, a moderate resistant rice variety, was reduced by 0.3 to 5％ in the rate due to sheath blight disease damage and Taebaekbyeo. a susceptible variety. showed the highest in the rate of yield loss, 6.8 to 25.8 ％. The matured grain rate and 1000-grain weight of the matured tiller were decreased when the developing disease lesion reached to the flag leaf, and then panicle weight was decreased more than 25 ％ compared with panicle of healthy culm. In conclusion, Gayabyeo showed the lower rate of yield loss because of slow development of disease to the upper leaves after initial disease occurence on the lower parts of rice plants.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.32 no.1
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• pp.103-111
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• 1987

Understanding grain filling characteristics represented by grain filling duration and grain filling rate is import-ant in improving higher yielding varieties and developing better cultural methods of rice (Oryza sativa L.). Recently developed 6 Japonica and 6 Japonica/Indica varieties were grown under 3 nitrogen levels at Experimental Farm of Chungbuk National University in 1986. The range of grain filling duration of 12 varieties was 20.9-39.0 days, while grain filling rate ranged from 53.8 to 136.6 mg. panicle$^{-1}$. day$^{-1}$. Although the difference of the average grain filling duration between Japonica varieties and Japonica/Indica was less than 4 days, the average grain filling rate of Japonica/lndica varieties was greater than Japonica more than 30%. Samgangbyeo showed the shortest grain filling duration of 21.0-24.2 days and the greatest grain filling rate of 119.3-143.8 mgㆍpanicle$^{-1}$. day$^{-1}$ under 3 nitrogen levels, while Seomjinbyeo and Milyang 23 showed the quite opposite grain filling characteristics. Nitrogen levels did not show any significant effects on grain filling characteristics. Negative correlation was round between grain filling duration and grain filling rate, and significant positive correlations of grain filling rate with grains/panicle, grain weight and panicle weight indicated that grain filling rate is more important characteristics of grain filling. Pathway analysis revealed that contribution of grain filling rate to panicle weight is rather indirect through grain weight.

• Proceedings of the Korean Society of Crop Science Conference
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• 1986.06a
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• pp.30-31
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• 1986

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.3
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• pp.214-220
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• 2007

The effects of soil percolation rate on $CH_4$ and $N_2O$ emissions were investigated from paddy fields with different drainage systems. Subsurface tile drainage plot of soil percolation rate $11.9mm\;d^{-1}$ and non-subsurface drainage plots of soil percolation rate $7.4mm\;d^{-1}$ and $6.9mm\;d^{-1}$ were designed. The effects of rice straw application were measured at each drainage plots. The subsurface tile drainage plot of soil percolation rate $11.9mm\;d^{-1}$ showed the lower emission amount both of $CH_4$ and $N_2O$ among treatments. In the subsurface tile drainage plot of $11.9mm\;d^{-1}$ percolation rate, 46% of $CH_4$ and 33% of $N_2O$ emission amounts were reduced in comparison of non-subsurface drainage plot of $6.9mm\;d^{-1}$ percolation rate. With rice straw application, the $CH_4$ emission amount was 2.1 times to that from no-applied plot, the $N_2O$ emission amount was not affected by rice straw application.

• Applied Biological Chemistry
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• v.46 no.2
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• pp.117-122
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• 2003

Starches from 4 rice cultivars, including Whachungchalbyeo and Whachungbyeo, together with two correspondiug conversion mutants with giant embryonic phenotype, Whachungchal-giant embryonic rice and Whachung-giant embryonic rice, were isolated to compare its physico-chemical properties. The amylose content and the length of glucose chains in the fractionated amylose was reduced in response to conversion of the rice cultivars for developing giant embryonic phenotype. For the fine structure of amylopectin, conversion to giant embyonic rice cultivars accompanied with slight increase in the length of B chain plus decrease in the amount of A chain, and also a slight increase in average glucose chains length of amylopectin fractions could be observed. X-ray diffractogram revealed 4 cultivars to be the representative A types. We could also obtain the results that the hydrolysis rate by glucoamylase in the waxy rice cultivars decreased in response to conversion to the giant embryonic rice cultivars, while the rate increased in the non-waxy rice cultivas. Termination temperature for gelatinization was observed to decrease in response to conversion into the giant embryonic rice cultivars, however, the enthalpy for gelatinization was found to increase with the same conversion process.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.69-69
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• 2017

Due to the lack in storage facility, considerable amount of rice is stocked in the open air, which causes increased stale flavor and deteriorates palatability and merchantable quality. Lipoxygenase-3(LOX-3) is involved in the production of volatile constituents in stored rice, and the development of stale flavor is delayed in LOX-3 null rice. LOX activity in the rice grain is localized in bran fraction and the tropical Japonica cultivar 'Dawdam' was reported that the absence of LOX-3 is inherited as a simple recessive trait. Also, it was reported that the peroxidation of unsaturated fatty acids occurs at lower levels in the 'Dawdam' bran fraction during storage than in rice varieties with LOX-3. This study was conducted to develop LOX-3 null rice lines using 'Dawdam' and investigate changes of physicochemical properties of the lines stored at different storage temperatures and periods. So we analyzed texture, toyo glossiness value, germination rate and lipoxygenase activity of 15 LOX-3 null rice lines on the condition of which rough rice had been stored at different temperatures (high temperature condition at $35^{\circ}C$ and low temperature condition at $15^{\circ}C$ for 4months. Hardness and stickiness of the lines tendered to be increased when it was stored at high temperature and adhesiveness, springiness, cohesiveness and chewiness was not considerably different according to storage temperatures and periods. The germination rate of HR29062-B-98-2-1-B among LOX-3 null rice lines was higher than another lines, 99.3, 94.0% after 4months stored at low temperature and high temperature, respectively. The lipoxygenase activity was 3,304, 1,601unit/mg protein after 4months stored at low temperature and high temperatures, respectively. So, it is thought that this line will be useful to breed rice varieties with high storability after tested on agricultural traits.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.52 no.4
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• pp.439-446
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• 2007

We carried out this experiment on the purpose to investigate the quality properties of aseptic-packaged cooked rice by cultivars in 2006. Brown rice was milled for white rice to 89.6% weight of it. Based on cluster analysis of acceptance of sensory evaluation, eleven rice cultivars of 29 cultivars had superior palatability. Whiteness(r=0.42, p<5%), lightness(r=0.39, p<5%), Toyo value(r=0.35, p<10%), and moisture content(r=0.33, p<10%) of milled rice were correlated positively with acceptability. Protein content(r=-0.40, p<5%), expansion rate(r=-0.68, p<1%) and water absorption rate(r=-0.42, p<5%) of milled rice, and yellowness(r=-0.45, p<5%) of aseptic-packaged cooked rice were negatively correlated. In sensory evaluation, correlation coefficients of taste and texture with acceptability were higher than those of appearance and flavor. During storage, hardness and cohesiveness of aseptic-packaged cooked rice before reheating were increased and decreased, but those after reheating had no difference based on storage period and cultivar. On the contrary, whiteness of reheated aseptic-packaged cooked rice with no distinct differences before reheating was decreased during storage. There were no significant differences of texture property, color characteristics and moisture contents by cultivar during storage.

• Korean journal of food and cookery science
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• v.14 no.2
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• pp.133-139
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• 1998

The aim of this study was to assess University students' consumption pattern of Korean rice cakes and to analyze the preference of Korean rice cakes by their demographic backgrounds. The results of this study will be useful information for systematic development and wide distribution of Korean rice cake as a traditional Korean food. A self completed survey of 392 University students in Seoul was undertaken and detailed information was collected. The survey questionnaire consisted of three parts including demographic backgrounds, student's consumption pattern and preference of Korean rice cakes by type. Approximately half of the students were male (52.6%) with the average age of 21.1 years old. Most of the respondents (92.3%) were from nuclear families. The consumption frequency rate showed that 38.8% students had Korean rice cake once or twice a month followed by once a week (29.8%), once per six months (21.7%), and once per two months (8.2%). Ingeolmi received the highest preference score (4.15), whereas Duteopteok had the lowest score (0.18). The correlation coefficient for paired samples between students' preference of Korean rice cake and their knowledge of them was 0.827, showing statistically strong positive correlation between them.

• Journal of the Korean Society of Food Culture
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• v.12 no.3
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• pp.323-329
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• 1997

The research was conducted to investigate the children's consumption pattern and preference of Korean rice cake by analyzing the relation among their socio-demographic backgrounds. This study provides basic information for systematic development and wide spread of Korean rice cake as a traditonal Korean food. A self completed questionnaire survey of 639 elementary school students in Seoul was undertaken. A survey questionnaire consisted of two parts including demographic backgrounds, children's consumption pattern and preference of Korean rice cake. A likert scale of one to five was used to determine the childrem's preference of Korean rice cake. Statistical data analysis was done using the SPSS/PC program for descriptive analysis and $x^2$ test. Approximately half of the participants were male (51.5%) and 5-degree year (50.7%) students. 77.2% of respondents were nuclear families. The results of eating frequency rate showed that 57.1% students had Korean rice cake once a month followed by once a week (18.8%), once per two months (12.2%) and once per six months (10.5%). The major reasons for having Korean rice cake were good taste (55.2%), healthy food (22.3), our traditional food (17.3%), and etc (2.2%) in order. Average children's preference score of 14 Korean rice cakes was $2.82{\pm}1.59$ out of 5, with the highest score of 4.30 for Songpyun and the lowest score of 1.06 for Bukumi.