• Korean Journal of Weed Science
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• v.31 no.3
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• pp.289-293
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• 2011

Field experiments were conducted to predict rice yield losses caused by Echinochloa crus-galli (L.)P. Beauv., Bidens frondosa L. and Aeschynomeme indica L. at a range of plant densities under machine transplanted rice cultivation in different regions of Korea in 2006, and to determine their economic threshold levels (ET). All data were fitted to Cousens' rectangular hyperbola to estimate parameters for predicting rice yield loss. The rice yield loss models of Bidens frondosa L. was predicted as y=5.43/(1+0.0113x), $R^2$=0.963, A. indica was y=5.47/(1+0.0332x), $R^2$=0.976 and E. crus-galli y=5.43/(1+0.01552x), $R^2$=0.950. The mean competitivities represented by the parameter, whose reciprocal ($1/{\beta}$) is a weed density reducing crop yield by 50%. Those of E. crus-galli, B. frondosa and A. indica were 0.01552, 0.01113 and 0.0332 in normal-season machine transplanting of Korea, respectively. Single year mean economic thresholds (ET) of A. indica were 0.5, 0.6 and 0.7 plant $m^{-2}$ with the application of flucetosulfuron, flucetosulfuron+imazosulfuron GR and flucetosulfuron+imazosulfuron+carfentrazone GR herbicides, respectively. Meanwhile ET values of 1.6, 1.9 and 1.9 plants $m^{-2}$ for B. frondosa, 1.2, 1.4, and 1.4 plants $m^{-2}$ for E. crus-galli.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.304-304
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• 2017

In semi-arid countries such as Namibia, the flooding unexpectedly happens in a rainy season, causing losses in the yield of upland-adapted cereal crop. In flooding conditions, rice roots sequentially form aerenchyma and a barrier to radial oxygen loss (ROL), and oxygen is released into the rhizosphere near the root tips. Iijima et al. (2016) and Awala et al. (2016) reported that close mixed-planting with rice can mitigate the flood stress of co-growing upland-adapted cereal crop by modifying their rhizosphere microenvironments via the oxygen released from the rice roots. Moreover, by using the model system of hydroponic culture, it was confirmed that oxygen from rice roots was transferred to co-growing upland-adapted cereal crop in close mixed planting system (Kawato et al., 2016). However, it is not sure whether the ability of oxygen release varies among rice cultivars, because Kawato et al. (2016) used only one japonica cultivar, Nipponbare (Oryza sativa). The objective of this study was to compare the ability of oxygen release in rhizosphere among rice cultivars. The experiment was conducted in a climate chamber in Kindai University. We used 10 rice cultivars from three different rice species (O. sativa (var. japonica (2), var. indica (3)), Oryza glaberrima Steud. (2) and their interspecific progenies (3)) to compare the ability of oxygen release from the roots. According to the method by Kawato et al. (2016), the dissolved oxygen concentration of phase I (with shoot) and phase II (without shoot) were measured by a fiber optic oxygen-sensing probe. The oxygen released from rice roots was calculated from the difference of the measurements between phase I and phase II. The result in this study indicated that all of the rice cultivars released oxygen from their roots, and the amount of released oxygen was significantly correlated with the above-ground biomass (r = 0.710). The ability of oxygen release (the amount of the oxygen release per fresh root weight) of indica cultivars (O. sativa) tended to be higher as compared with the other cultivars. On the other hand, that of African rice (O. glaberrima) and the interspecific progenies tended to be lower. These results suggested that the ability of oxygen release widely varies among rice cultivars, and some of indica cultivars (O. sativa) may be suitable for close mixed-planting to mitigate flood stress of upland-adapted cereal crop.

• Asian-Australasian Journal of Animal Sciences
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• v.6 no.1
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• pp.41-44
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• 1993

This study was conducted to investigate the chemical components of culm that influencing the resistance to lodging and the in vitro digestibility in indica type rice plants. Indica type rice plants with three levels of lodging resistance were used; resistant type (RT), intermediate type (IT) and susceptible type (ST). For each type there were four varieties. Culm length was shorter in RT and longer in ST (98.1 cm vs. 151.8 cm). Silica content in the culm was highest in RT and lowest in ST (11.0% vs. 7.6%). There was no difference in the level of acid detergent lignin (ADL) between the 3 levels of lodging. For the 12 straw samples, in vitro organic matter digestibility (IVOMD) was negatively correlated with silica content (r = -0.664, p<0.05) but ADL had no significant effect (r = -0.454, p>0.05). Digestibility was more closely correlated with the sum of silica and ADL (r = -0.747, p<0.01) than silica alone. It was concluded that rice plants showed resistance to lodging when the culm was short and its structure was reinforced with larger quantities of silica. However these silicified straws were less digestible.

• Korean Journal of Food Science and Technology
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• v.21 no.6
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• pp.820-825
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• 1989

Yukwa (one of most popular Korean traditional popped rice snacks) was made by four different varieties of rice, Shinsun (Japonica) and Hangang $(Japonica{\times}Indica)$ which are waxy rice and Dongjin (Japonica) and Samgang $(Japonica{\times}Indica)$ which are non waxy rice, for their quality by total expansion volume, hardness and brittleness. It was notified that hydration rate of waxy and non waxy rice for preparation of Yukwa were different by 30% and 42% in moisture content respectively soaked at $12^{\circ}C$ for 12 hours and the gelatinization temperature of their starch was $64.5-67.5^{\circ}C$ with no big difference by varieties. The quality of Yukwa was deeply related with amylose contents ranging from 18.5% of non waxy rice to 2-3% of waxy rice. Superior quality (p<0.05) was got from waxy rice. Lactic acid bacterial fermentation didn't improve the quality, and soybean and rice bran oil can be used for popping in even value.

• The Korea Genome Conference
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• 2004.07a
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• pp.42.1-42.1
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• 2004

• KOREAN JOURNAL OF CROP SCIENCE
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• v.5 no.1
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• pp.37-43
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• 1969

A genetrc study was made on plant height of indica rices with a few segregating F2 populations involving three semi-dwarf varieties such as T(N)I, CP231-SLO17, and B569A12. These populations were grown in breeding nursery at the International Rice Research Institute (IRRI) during several seasons. 20 to 25 day old seedlings grown at upland seedbed were transplanted to the paddy in a single plant hill spacing 30 cm ${\times}$ 25cm. Measurements of plant height were made from the juncture between culm and roots to the tip of the longest panicle of a plant pulled out from the paddy when they are matured. The results are summarized as follows: 1. Tall indica varieties originated from the south-east Asian countries could be classified into two groups depending upon their allelism whether they showed monogenic segregating ratio of 3:1 or not when they were crossed to T(N)1. 2. Most of U.S. varieties, especially semi-dwarf breedirg materials such as CP231 ${\times}$ SIO17 and B569A12, did not show monogenic segregating mode of 3:1 ratio when they were crossed to T(N)1 or to other varieties bearing the same genetic allele of T(N)1 such as Peta and Sigadis.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.50 no.3
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• pp.212-220
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• 2005

One hundred eleven glutinous rice collections from seven countries were evaluated for genetic diversity based on agronomic traits and RAPD analysis. Twelve agronomic traits including yield components amy-lose content, alkali digest value were used to clarify the genetic relationships among glutinous rice collections. Glutinous rice collections were classified into 4 groups and early maturings Korean landraces and high amylose indica belonged to group I with RAPD analysis, 15 primers selected for polymorphic bands generated 117 bands and 81 bands $(69.2\%)$ showed polymorphism. The number of amplified bands per primer ranged from 5 to 11, with the average number of bands of 7.8. With the similarity value of 0.78 in dendrogram derived from the cluster analysis based on RAPDs, glutinous rice collections were classified into 9 groups. Seventy-seven percent of the collections were classified into group I that is the largest one, while the others $(23\%)$ were distributed to group Il-IX. Group I included most indica type rices and early ripening collections, while the small groups of III-IX included most of the Korean collections.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.22 no.2
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• pp.23-26
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• 1977

In order to test cold tolerance of rice plants 16 varieties were treated at day/night temperature of 10/5$^{\circ}C$ at the 2nd, 4th, and 6th leaf stages. Indica$\times$japonica varieties were more sensitive to low temperature than a japonica variety. Among indica$\times$japonica varieties, "Tongil", "Suweon ＃251", and "Suweon ＃277" were less sensitive to low temperature compared to other indica$\times$japonica varieties tested. The 4th leaf stage was more sensitive to low temperature than 2nd and 6th leaf stages. than 2nd and 6th leaf stages.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.2
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• pp.187-192
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• 1994

This study was conducted to investigate varietal difference in viviparous germinability at different days after heading and temperature conditions. Three Japonica rice varieties, Sobaekbyeo, Odaebyeo and Hwaseongbyeo, and Sare type rice variety, Jakwangdo, showed higher viviparous germination rate from 20 days after heading, while a Tongil type rice, ]ungwonbyeo, and a Indica varieyt, IR-20, showed still low viviparous germination at 40 days after heading. Viviparous germination rate of rice varieties observed at 4 and 10 days after incubation was greately increased with increasing temperature from 15$^{\circ}C$ to 3$0^{\circ}C$ , and germination rate less than 5% was observed at 4 days after incubating at 15$^{\circ}C$ in all rice varieties teased. Viviparous germination pattern of rice varieties was divided into two types. Three Japonica and Sare type rice varieties showed higher and faster in viviparous germination than a Tongil type and Indica rice verieties. Viviparous germination was delayed under day /night fluctuation of incubation temperature compared with day /night fluctuation of incubation temperature compared with day /night constant condition at the same average temperature. The optimum incubation temperature and duration to evaluate viviparous germinability of rice varieties were 25/15$^{\circ}C$ and 6 days, respectively.

• Journal of Biosystems Engineering
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• v.15 no.2
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• pp.99-109
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• 1990

Rough rice is subjected to a series of static and dynamic forces during mechanical harvesting, handling and processing operations. The mechanical properties such as bioyield point, compressive strength, and deformations at the bioyield point and rupture point are important engineering data needed to develop processing machines and to determine reasonable operating conditions for these machines. The objectives of this study were to determine the mechanical properties of the rough rice kernel at loading rate of 0.664 mm/min and 1.673 mm/min and at various moisture contents, and to examine the effect of the moisture content and the loading rate on these mechanical properties. The follwing results were obtained from the study. 1. Bioyield point, rupture point, bioyield strength and ultimate strength of the rough rice kernel generally decreased in magnitude with an increase in moisture content. A little larger values of these mechanical properties were obtained at the higher loading rate. The rough rice variety and the loading rate affected significantly these mechanical properties at low moisture content, but not at the higher moisture levels. 2. Bioyield point of the sample grains varied from 20 to 80 N, and rupture point varied from 45 to 130N. Bioyield point for Japonica-type rough rice was a little higher than that for Indica-type rough rice, but there were little differnces in rupture point between two types of rough rice. 3. Bioyield strength and ultimate strength of the Japonica-type rough rice varied from 10 MPa. to 39 MPa., and from 13 MPa. to 45 MPa. respectively. Those of the Indica-type rough rice varied from 12 MPa. to 42 MPa., and from 15 MPa. to 53 MPa. respectively. 4. Deformations at bioyield point and rupture point ranged from 0.18 mm/min to 0.26 mm, and from 0.28 mm to 0.53 mm respectively. These deformations decreased with an increase in moisture content up to moisture content of approximately 17% (w.b.) and increased again thereafter. 5. Regression equations were developed to predict these mechanical properties for the rough rice kernel as a function of moisture content.