• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.27-27
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• 2017

The rapid growth of world population, reduction of cultivated areas for crop production, and detrimental effects of pests, diseases, and climate changes have required to breed new rice cultivars with high yield, accepted quality, but strong resistance to abiotic and biotic stresses. However, traditional breeding needs much time to breed a new cultivar, whereas the successful use of molecular breeding is still questionable. We have developed a novel mutation which allow to cross many rice cultivars together with low segregation, that allow to breed a new cultivar in only several cropping. The mechanism has been unknown, but we suggest that gene linkage may play a crucial role, of which the semi dwarf gene might be the center gene for gene linkage occurrence. The phenomenon of this possible gene linkage is contrary to Mendel rules, but it is promising to breed new rice cultivars, of which, the most elite genes in rice might be able to gather in a targeted rice variety.

• The Plant Pathology Journal
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• v.28 no.2
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• pp.164-171
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• 2012

Rice blast disease caused by Magnaporthe grisea (Hebert) Barr [teleomorph] is one of the most devastating diseases in rice plantation areas. Silicon is considered as a useful element for a large variety of plants. Rice variety MR219 was grown in the glasshouse to investigate the function of silicon in conferring resistance against blast. Silica gel was applied to soil while sodium silicate was used as foliar spray at the rates of 0, 60, 120, 180 g/5 kg soil and 0, 1, 2, 3 ml/l respectively. The treatments were arranged in a completely randomized design. Disease severity and silicon content of leaves were compared between the non-amended controls and rice plants receiving the different rates and sources of silicon. Silicon at all rates of application significantly (${\alpha}$ = 0.05) reduced the severity of disease with highest reduction (75%) recorded in treatments receiving 120 g of silica gel. SEM/EDX observations demonstrated a significant difference in weight concentration of silicon in silica cells on the leaf epidermis between silicon treated (25.79%) and non treated plants (7.87%) indicating that Si-fertilization resulted in higher deposition of Si in silica cells in comparison with non-treated plants. Application of silicon also led to a significant increase in Si contents of leaves. Contrast procedures indicated higher efficiency of silica gel in comparison to sodium silicate in almost all parameters assessed. The results suggest that mitigated levels of disease were associated with silicification and fortification of leaf epidermal cells through silicon fertilization.

• Magazine of the Korean Society of Agricultural Engineers
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• v.28 no.2
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• pp.31-41
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• 1986

Knowledge of the degree of yield reduction due to water stress at different crop growth stages in rice production is important for rational scheduling of irrigation during periods of insufficient water supply. Previous studies to determine the degree of yield reduction duo to water stress suffered from interruptions by rain during experiment. Also the findings did rot relate the degree of water stress to the soil water potential and water deficit status of rice plants. In this study, two years experiments were conducted using the high yielding rice varieties, an Indica x Japonica (Nampoong) and a Japonica variety(Choochung). These were grown in 1/200$^{\circ}$ plastic pots placed under a rainfall autosensing, sliding clear plastic roof facility to control rainfall interruptions. The results obtained were as follows. 1.The two varieties differed in the growth stage most sensitive to water stress as well as the degree of yield reductions. When rice plants were stressed to the leaf rolling score 4 and soil water potential of about - 20 bar at major crop growth stages which included heading, booting, non-effective tillering, panicle initiation and early tillering stages, the yield reductions in the Indica x Japonica variety were 58%, 34%, 27%, 22%, and 21%, respectively, whereas in the Japonica vairety they were 23%, 36%, 1%, 13% and 22%, respectively. This result show that the recommended drainage during non-effective tillering is valid only for the Japonica variety. Sufficient irrigation at booting, heading and early tillering stages are necessary for both varieties. 2.The two varieties showed visible wilting symptoms when the soil water potential dropped to about - 3.0 bar. The Japonica variety showed more leaf rolling than the Indica X Japonica. However, it had a higher retention of leaf water content and greater stomatal diffusive resistance. When the soil water potential dropped, the Japonica variety showed leaf rolling score (LRS) 1 at 0 soil-5. 0 bar and LRS 2 at 0 soil -6.0 bar while the Indica X Japonica showed LRS 1 at 0 soil - 5.5 bar and LRS 2at 0 Soil - 9.0 bar. The stomatal diffusive resistance was maximum at the second top leaf blade in both varieties at intermediate water stress of 0 soil - 4.5 bar. 3.The number of days that was required for the soil water potential to drop to-3. 0 bar and to - 20.0 bar after drainage of irrigation water from the 20cm deep silty clay loam soil in the pots were 6 and 13 days, respectively for booting stage, and 7 and 11 days, respectively for heading stage, 9 and 12 days, respectively for panicle initiation stage, and 12 and 19 days, respectively for early tillering stage. 4.Water stress during the early tillering stage recorded the longest delay in beading time, the largest reduction in panicle numbers and a substantial yield decrease of 20%. This calls for better water management to ensure the availability of water at this stage, particularly during drought periods. In addition, a reexamination of the conventional inter-drainage practice during the non-effective tillering stage is necessary for the high yielding Indica X Japonica varieties.

• Korean Journal of Breeding Science
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• v.40 no.4
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• pp.443-446
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• 2008

'Gangbaek' is a japonica rice variety developed and registered by the rice breeding team of Department of Rice and Winter Cereal Crop, NICS, RDA in 2006. 'Gangbaek' was derived from a cross between 'Suweon345' with good grain quality and 'DV85' resistant to bacterial blight, $K_{3a}$. $F_1$ plants were grown in the greenhouse in winter of 1992/1993 and backcrossed with 'Suweon345' as the recurrent parent. Plants resistant to $K_{3a}$ race of bacterial blight (BB) were selected from $BC_1F_1$ to $BC_4F_1$ and used as parents in the backcrossing processes. This variety has about 120 days growth duration from transplanting to harvesting in west-southern coast and Honam plain of Korea. It is about 69 cm in culm length and tolerance to lodging. In reaction to biotic and abiotic stresses, it shows moderately resistance to blast, and resistance to bacterial blight pathogen, $K_1$, $K_2$, $K_3$ and $K_{3a}$, but susceptible to other major diseases and insect pests. The milled rice of 'Gangbaek' exhibits translucent, relatively clear non-glutinous endosperm and midium short grain. It has lower amylose content of 18.6% and protein content of 6.4% compared with 'Nampyeongbyeo'. The milled rice yield performance of this variety is about 5.28 MT/ha in local adaptability test for three years. This cultivar would be adaptable to the bacterial blight-prone area in the south-western coastal and Honam plain of Korea.

• Korean Journal of Breeding Science
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• v.50 no.4
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• pp.529-533
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• 2018

Hyowon6, a mid-late maturing, good eating quality rice variety with multi-resistance, was developed by the rice breeding team of Pusan National University in 2013. This variety was derived from a cross between Hwayeong (as a multi-resistant parent) and Koshihikari (as a good eating quality parent). Selection by the pedigree breeding method was carried out until the $F_8$ generation. A promising line, JS14-12-36-8-5-3-1-1-1, was developed and designated as HY103 in 2013. This variety headed on August 22, which was 11 days later than that of Hwayeong. The culm length and panicle length of Hyowon6 was 85.7 cm and 21.1 cm, respectively. The number of panicles per hill was 14.5 and the number of grains per panicle was 101.7. The ratio of ripened grain was approximately 92% and the 1,000-grain weight was approximately 21.36 g for brown rice, which were similar to those of Hwayeong. Hyowon6 was moderately resistant to lodging and also to neck blast, leaf blight, and stripe virus. The glossiness value of Hyowon6 was 83, which was considerably higher than that of Hwayeong.

• 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.

• Research in Plant Disease
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• v.24 no.4
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• pp.313-320
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• 2018

Fusarium infection rate of the paddy rice grain after harvest seemed to be influenced by the average temperature from late July (before heading) to the end of September (during ripening). In case of 2010 and 2013 in which average temperature of the same period was similar, Fusarium infection was related to cumulative precipitation, cumulative precipitation days, and precipitation durations over two days. The distribution ratio of Fusarium species complex isolated from paddy rice grains after harvest was 57% in 2010 and 45% in 2013 for Fusarium graminearum species complex (FGSC), 35% and 50% for Fusarium incarnatum-equiseti species complex, and 8% and 5% for Fusarium fujikuroi species complex (FFSC). The distribution ratios of FGSC and FFSC were higher in 2010 than 2013. Among the total 26 promoted rice varieties, the 'Mihyang' showed resistant response against the natural infection with Fusarium species belonging to FGSC and the varieties of 'Nampyeong', 'Hi-ami'and 'Younghojinmi' showed resistant response against the natural infection with overall Fusarium pathogens. Majority of the promoted rice varieties could not be classified for resistance or susceptibility. These results are valuable as basic data to determine the resistance and susceptibility of rice variety against Fusarium spp. infection in the field.

• Korean Journal of Breeding Science
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• v.40 no.4
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• pp.408-413
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• 2008

Rice blast resistance is considered one of the most important traits in rice breeding and the disease, caused by Magnaporthe grisea Barr, has brought significant crop losses annually. Moreover, breakdown of resistance normally occurs in two to five years after cultivar release, thus a more durable resistance is needed for better control of this disease. We developed a new variety, Keumo3, which showed strong resistance to leaf blast. It was tested in 2003 to 2007 at fourteen blast nursery sites covering entire rice-growing regions of South Korea. It showed resistance reactions in 12 regions and moderate in 2 regions without showing susceptible reactions. Durability test by sequential planting method indicated that this variety had better resistance. Results showed that Keumo3 was incompatible against 19 blast isolates with the exception of KI101 by artificial inoculation. To understand the genetic control of blast resistance in rice cultivar Keumo3 and facilitate its utilization, recombinant inbred lines (RIL) consisting of 290 F5 lines derived from Akidagomachi/Keumo3 were analyzed and genotyped with Pizt InDel marker zt56591. The recombination value between the marker allele of zt56591 and bioassay data of blast nursery test was 1.1%. These results indicated that MAS can be applied in selecting breeding populations for blast resistance using zt56591 as DNA marker.

• Korean journal of applied entomology
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• v.41 no.2
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• pp.113-121
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• 2002

This study investigated the changes in the fitness of brown planthopper, NilapaHata lugens, to several rice varieties with different resistance background, after multi-generational selection on a resistant rice variety. A susceptible strain of brown planthopper (Dongjin-5) had been reared on the Chungchungbyeo with Bph1 resistance gene for three generations (Chungchung-G3) and six generations (Chungchung-G6), then the fitness change was evaluated by measuring their longevity, fecundity, preferences, and survivorships on the varieties with various background of resistance. After being selected three to six generations on Chungchungbyeo, feeding preference, adult longevity, and fecundity increased, where as nymphal period reduced when they were reared on various varieties with Bph1 gene. The egg Periods were not much different among the varieties fed on, except for the Chungchung-G6 on the rice varieties of Milyang63 (bph2 gene) and Gayabyeo (Bph1+bph2 gene). These results suggest that the susecptible Donajin-5 (Biotype-1) can be easily converted to a resistant biotype-2 capable of overcoming the resistant varieties with Bph 1 gene.

• Korean Journal of Microbiology
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• v.6 no.1
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• pp.1-5
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• 1968

This experiment was undertaken the purpose of investigating the difference of the content of free amino acids in the diseased and healthy leaves of the resistance and susceptible rice varieties, to blast by means of paper chromatography. The results obtained are summarized as follows. (1) In the healthy and diseased leaves, the former was founded nine to tell sorts of free amino acids and later was observed eleven. In the both of leaves, alanine and valine were contained in larger amount, and aspartic acid, glycine and arginine were found relatively less in general. (2) In the diseased leaves, the amino acids were increased in quantity, especially glutamine and aspartic acid were remarkable, and cystine were found only in the diseased ones. (3) It seems to that the health leaves in all varieties were observed the amino acid contents, in notably increase and decrease, but in the diseased ones were not changed in amount. Tatacho, susceptible variety was more contained the amount of glutamine and aspartic acid than Zenith, resistance one.