• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.112-112
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• 2017

Rice blast caused by Magnaporthe oryzae is one of the most serious diseases that affect the quantity and quality of rice production. The use of resistant rice varieties would be the most effective way to control the rice blast. However R gene incorporation into the rice variety takes time and pathogen could overcome the R gene effects after for a while. For monitoring the rice blast resistance gene distribution in Korean varieties, the four major blast resistance genes against M. oryzae were screened in a number of Korean rice varieties using molecular markers. Of the 120 rice varieties tested, 40 were found to contain the Pi-5 gene, 25 for the Pi-9 gene, 79 for Pi-b and 40 for the Pi-ta gene. None of these rice varieties includes tested 4 R genes. 3 R genes combination, Pi-5/Pi-9/Pi-b, Pi-5, Pi-9.Pi-ta, or Pi-9/Pi-b/Pi-ta were found in 12 varieties, the rice blast disease severity were showed as resistant in the rice verities containing Pi-9/Pi-b/Pi-ta R genes combination, respectively. Also pathogenic diversity of M. oryzae isolates collected in the rice field from 2004 to 2015 in rice field in Korea were analyzed using rice blast monogenic lines, each harboring a single blast resistance gene. Compatibility of blast isolates against rice blast monogenic lines carrying the resistance genes Pi5, Pi9, Pib, and Piz showed dynamic changes by year. It indicates that pathogen has high evolutionary potential adapted host resistances to increase fitness and would lead to rice blast resistance bred into the cultivar becoming ineffective eventually.

• The Plant Pathology Journal
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• v.31 no.1
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• pp.12-24
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• 2015

Rice Blast is the most devastating disease causing major yield losses in every year worldwide. It had been proved that using resistant rice varieties would be the most effective way to control this disease. Molecular screening and genetic diversities of major rice blast resistance genes were determined in 192 rice germplasm accessions using simple sequence repeat (SSR) markers. The genetic frequencies of the 10 major rice blast resistance genes varied from 19.79% to 54.69%. Seven accessions IC337593, IC346002, IC346004, IC346813, IC356117, IC356422 and IC383441 had maximum eight blast resistance gene, while FR13B, Hourakani, Kala Rata 1-24, Lemont, Brown Gora, IR87756-20-2-2-3, IC282418, IC356419, PKSLGR-1 and PKSLGR-39 had seven blast resistance genes. Twenty accessions possessed six genes, 36 accessions had five genes, 41 accessions had four genes, 38 accessions had three genes, 26 accessions had two genes, 13 accessions had single R gene and only one accession IC438644 does not possess any one blast resistant gene. Out of 192 accessions only 17 accessions harboured 7 to 8 blast resistance genes.

• Korean Journal of Breeding Science
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• v.40 no.3
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• pp.215-222
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• 2008

Fifty-two Korean japonica rice cultivars were analyzed for leaf blast resistance and genotyped with 4 STS and 26 SSR markers flanking the specific chromosome sites linked with blast resistance genes. In our analysis of resistance genes in 52 japonica cultivars using STS markers tightly linked to Pib, Pita, Pi5(t) and Pi9(t), the blast nursery reaction of the cultivars possessing the each four major genes were not identical to that of the differential lines. Eight of the 26 SSR markers were associated with resistant phenotypes against the isolates of blast nursery as well as the specific Korean blast isolates, 90-008 (KI-1113), 03-177 (KJ-105). These markers were linked to Pit, Pish, Pib, Pi5(t), Piz, Pia, Pik, Pi18, Pita and Pi25(t) resistance gene loci. Three of the eight SSR markers, MRG5836, RM224 and RM7102 only showed significantly associated with the phenotypes of blast nursery test for two consecutive years. These three SSR markers also could distinguish between resistant and susceptible japonica cultivars. These results demonstrate the usefulness of marker-assisted selection and genotypic monitoring for blast resistance of rice in blast breeding programs.

• Korean Journal of Plant Resources
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• v.27 no.6
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• pp.687-700
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• 2014

Rice blast (Magnaporthe oryza B.) is one of the most important diseases in rice that causing great yield losses every year around the world. It is important to screen valuable genetic resources for improving blast resistance. This study was conducted to identify the blast resistance in 279 Korean rice landraces using blast nursery tests and isolate inoculum screening. The results showed that 11 landrace accessions found to be resistant to rice blast in blast nursery and inoculation screening tests and the degree of lesions in most accessions showed that they were susceptible to reactions. In order to find the distribution of blast resistant genes, a molecular survey was conducted to identify the presence of major blast resistance (R) gene in 279 Korean landraces. The results revealed that their frequency distribution was Pik-m (36.2%), Piz (25.4%), Pit (13.6%), and Pik (10%). Besides, the frequency distribution of Piz-t, Pii, Pik-m/Pik-p, Pi-39(t), Pib, Pi-d(t)2, Pita/Pita-2 and Pi-ta genes were identified as less than 10%. The results did not consist with the reactions against blast diseases between genotypes and phenotypic part of the nursery tests and isolate inoculation. For concluding these results, we used genome-wide SSR markers that have closely been located with resistance genes. The PCoA analysis showed that the landrace accessions formed largely two distinct groups according to their degree of blast resistance. By comparing genetic diversities using polymorphic information contents (PIC) value among the resistant, total and susceptible landraces, we found that PIC values decreased in four SSR markers and increased in six markers in the resistant accessions, which showed contrary to total and susceptible groups. These regions might be linked to resistance alleles. In this study, we evaluated the degree of blast resistance and the information about the distribution of rice blast resistant genes in Korean rice landraces. This study might be the basis for association analysis of blast resistance in rice.

• Korean Journal of Plant Resources
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• v.29 no.6
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• pp.658-669
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• 2016

Rice blast, caused by a fungus Magnaporthe oryzae, is one of the most devastating diseases of rice worldwide. Analyzing the valuable genetic resources is important in making progress towards blast resistance. Molecular screening of major rice blast resistance (R) genes was determined in 2,509 accessions of rice germplasm from different geographic regions of Asia and Europe using PCR based markers which showed linkage to twelve major blast R genes, Pik-p, Pi39, Pit, Pik-m, Pi-d(t)2, Pii, Pib, Pik, Pita, Pita/Pita-2, Pi5, and Piz-t. Out of 2,509 accessions, only two accessions had maximum nine blast resistance genes followed by eighteen accessions each with eight R genes. The polygenic combination of three genes was possessed by maximum number of accessions (824), while among others 48 accessions possessed seven genes, 119 accessions had six genes, 267 accessions had five genes, 487 accessions had four genes, 646 accessions had two genes, and 98 accessions had single R gene. The Pik-p gene appeared to be omnipresent and was detected in all germplasm. Furthermore, principal component analysis (PCA) indicated that Pita, Pita/Pita-2, Pi-d(t)2, Pib and Pit were the major genes responsible for resistance in the germplasm. The present investigation revealed that a set of 68 elite germplasm accessions would have a competitive edge over the current resistance donors being utilized in the breeding programs. Overall, these results might be useful to identify and incorporate the resistance genes from germplasm into elite cultivars through marker assisted selection in rice breeding.

• The Plant Pathology Journal
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• v.37 no.2
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• pp.200-203
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• 2021

Rice blast caused by the filamentous fungus Magnaporthe oryzae, is arguably the most devastating rice disease worldwide. Development of a high-throughput and reliable field blast resistance evaluation system is essential for resistant germplasm screening, resistance genes identification and resistant varieties breeding. However, the occurrence of rice blast in paddy field is easily affected by various factors, particularly lack of sufficient inoculum, which always leads to the non-uniform occurrence and reduced disease severity. Here, we described a procedure for adequately inducing the occurrence of rice seedling blast in paddy field, which involves pretreatment of diseased straw, initiation of seedling blast for the first batch of spreader population, inducing the occurrence of the second batch of spreader population and test materials. This procedure enables uniform and consistent infection, which facilitates efficient and accurate assessment of seedling blast resistance for diverse rice materials.

• Korean Journal Plant Pathology
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• v.14 no.5
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• pp.496-501
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• 1998

Incidence of rice blast on new rice cultivars and elite lines was observed from 1995 to 1997 in Icheon, Chuncheon, Jecheon and Naju areas. The observation was made in the nurseries and fields. In the nurseries, three cultivars Grubyeo, Sangjuchalbyeo and Suwon 414 showed moderate levels of resistance to leaf blast, with the disease index 0 to 5. From the field observation, it was found that cultivars Heugjinjubyeo and Unbong 18 were highly resistant to leaf blast, but susceptible to neck blast. In general, there was a great variation yearly and regionally in the incidence of neck blast within the same cultivar, ranging from 0 to 100%. However, the range of neck blast infection was relatively narrower in the cultivars Yunghaebyeo (0∼2.4%) and Suwon 414 (0∼2.2%) during observation period. Races of rice blast fungus were variable at different areas. Among them dominant races were KI-409, KJ-201 and KJ-301.

• Korean Journal Plant Pathology
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• v.13 no.2
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• pp.85-89
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• 1997

Etiological components of the rice cultivars possessing durable resistance to rice blast were evaluated. In the greenhouse test by artificial inoculation, number of leaf blast lesion in Dongjinbyeo was not increased by any race of the pathogen, while the lesion number on the resistant cultivar Palgongbyeo and susceptible cultivar Jinmibyeo was increased rapidly. Size of the lesion in Dongjinbyeo was smaller and progressed more slowly than the resistant cultivar Palgongbyeo until 11 days after inoculation. Latent period in Dongjinbyeo was intermediate. However, the period was significantly variable depending upon the races. Least amount of conidia was produced in Dongjinbyeo by race KJ-107 and the number of conidia was decreased rapidly from 11 days after inoculation.

• Journal of Crop Science and Biotechnology
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• v.10 no.1
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• pp.3-7
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• 2007

Classification of blast resistance type of 129 Korean rice cultivars was carried out based on reaction pattern to 10 Japanese blast pathogen isolates(Pyricularia oryzae). The cultivars were divided into 11 groups based on the presumed resistance genes as follows; Pia type(19 cultivars), Pita-2 type(4), Pik type(3), Pib type(5), Piz type(11), Pik-s type(8), Pik and Pii type(4), Pia and Pita type(8), Pia and Pik type(6), Pita, Pik and Pii type(4) and no-grouping type(57). These results would provide important information to rice breeding for durable and broad resistance to rice blast.

• Korean Journal Plant Pathology
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• v.2 no.2
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• pp.69-81
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• 1986

Thirty two rice cultivars which have been cultivated or used as breeding materials in Korea were tested for screening rice cultivars resistant to leaf blast at adult-plant stages in the blast nursery hill plots. When compared on the basis of disease severities in individual leaves at different growth stages of rice plants under natural field infection, the 16 indica-japonica hybrids tested were highly resistant but the 16 japonica cultivars tested showed various degrees of resistance to leaf blast. With aging of rice plants, the quantitative levels of resistance to leaf blast increased in all the cultivars, although the levels of resistance to leaf blast varied according to rice genotypes. The leaf position of rice plants in which changed from susceptible to resistant reactions varied also with rice genotypes. The susceptible reactions of the rice cultivars to Pyricularia oryzae were distinctly changed to a resistant reaction on upper leaves of rice plants. The rice cultivars, in which the quantitative level of resistance to leaf blast was higher, were resistant on the lower leaves of rice plants. The cultivars Akibare, Palkeum, Jinheung, Olchal, Dobong and Ginga which drastically decreased blast infection at late growth stage were evaluated as adult-plant-resistant to leaf blast in the field. The adult-plant-resistant cultivars became resistant to leaf blast, both qualitatively and quantitatively, as rice plants matured.