• The Plant Pathology Journal
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• v.35 no.3
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• pp.219-233
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• 2019

Soybean cultivars susceptible to Phytophthora root and stem rot are vulnerable to seed rot and damping-off of seedlings and young plants following an infection by Phytophthora sojae. In this study, the disease responses of Japanese soybean cultivars including currently grown main cultivars during the early growth stages were investigated following infections by multiple P. sojae isolates from Japanese fields. The extent of the resistance to 17 P. sojae isolates after inoculations at 14, 21, and 28 days after seeding varied significantly among 18 Japanese and two US soybean cultivars. Moreover, the disease responses of each cultivar differed significantly depending on the P. sojae isolate and the plant age at inoculation. Additionally, the treatment of 'Nattosyo-ryu' seeds with three fungicidal agrochemicals provided significant protection from P. sojae when plants were inoculated at 14-28 days after seeding. These results indicate that none of the Japanese soybean cultivars are completely resistant to all tested P. sojae isolates during the first month after sowing. However, the severity of the disease was limited when plants were inoculated during the later growth stages. Furthermore, the protective effects of the tested agrochemicals were maintained for at least 28 days after the seed treatment. Japanese soybean cultivars susceptible to Phytophthora root and stem rot that are grown under environmental conditions favorable for P. sojae infections require the implementation of certain practices, such as seed treatments with appropriate agrochemicals, to ensure they are protected from P. sojae during the early part of the soybean growing season.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.186-186
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• 2022

Phytophthora root and stem rot (PRSR) and wildfire disease (WFD) of soybean are frequently observed in the field of South Korea. The most environmentally friendly way to control PRSR and WFD is to use soybean varieties with resistance to Phytophthora sojae (P. sojae) and Pseudomonas amygdali pv. tabaci. Plant germplasm is an important gene pool for soybean breeding and improvement. In this study, hundreds of soybean accessions were evaluated for the two pathogens, and genome-wide association analyses were conducted using 104,955 SNPs to identify resistance loci for the two pathogens. Of 193 accessions, 46 genotypes showed resistance reaction, while 143 did susceptibility for PRSP. Twenty SNPs were significantly associated with resistance to P. sojae on chromosomes (Chr.) 3 and 4. Significant SNPs on Chr.3 were located within the known Rps gene region. A region on Chr. 4 is considered as a new candidate resistance loci. For evalation of resistance to WFD, 18, 31,74,36 and 34 genotypes were counted by a scale of 1-5, respectively. Five SNP markers on Chrs 9,11,12,17 and 18 were significantly associated with resistance to P. amygdali pv. tabaci. The identified SNPs and genomic regions will provide a useful information for further researches and breeding for resistance to P. sojae and P. amygdali pv. tabaci.

• The Plant Pathology Journal
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• v.35 no.6
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• pp.698-704
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• 2019

Phytophthora root and stem rot (PRSR) caused by Phytophthora sojae is one of the most destructive diseases of soybean. PRSR recently became an issue as soybean cultivation in paddy fields increased in South Korea. The management of PRSR mainly involves R-gene-mediated resistance, however, little is known about the resistance in Korean cultivars. Major Korean soybean cultivars were investigated for the presence or absence of R-gene-mediated resistance to four P. sojae isolates, two of which were new isolates. Isolate-specific reactions were observed following P. sojae inoculation. Of 21 cultivars, 15-20 cultivars (71.4-95.2%) showed susceptible reaction for each isolate. Ten cultivars were susceptible to all the isolates, and six cultivars were identified to have R-gene-mediated resistance to one or two isolates. The results of this study would provide a framework for the discovery of resistant cultivars, development of new cultivars resistant to P. sojae, and investigation of pathogenic diversity of P. sojae population in South Korea.

• The Plant Pathology Journal
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• v.36 no.6
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• pp.591-599
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• 2020

Phytophthora root and stem rot reduce soybean yields worldwide. The use of R-gene type resistance is currently crucial for protecting soybean production. The present study aimed to identify the genomic location of a gene conferring resistance to Phytophthora sojae isolate 2457 in the recombinant inbred line population developed by a cross of Daepung × Daewon. Singlemarker analysis identified 20 single nucleotide polymorphisms associated with resistance to the P. sojae isolate 2457, which explained ~67% of phenotypic variance. Daewon contributed a resistance allele for the locus. This region is a well-known location for Rps1 and Rps7. The present study is the first, however, to identify an Rps gene locus from a major soybean variety cultivated in South Korea. Linkage analysis also identified a 573 kb region on chromosome 3 with high significance (logarithm of odds = 13.7). This genomic region was not further narrowed down due to lack of recombinants within the interval. Based on the latest soybean genome, ten leucine-rich repeat coding genes and four serine/ threonine protein kinase-coding genes are annotated in this region, which all are well-known types of genes for conferring disease resistance in crops. These genes would be candidates for molecular characterization of the resistance in further studies. The identified R-gene locus would be useful in developing P. sojae resistant varieties in the future. The results of the present study provide foundational knowledge for researchers who are interested in soybean-P. sojae interaction.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.68 no.3
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• pp.134-146
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• 2023

Phytophthora root rot (PRR) is a major soybean disease caused by an oomycete, Phytophthora sojae. PRR can be severe in poorly drained fields or wet soils. The disease management primarily relies on resistance genes called Rps (resistance to P. sojae). This study aimed to identify resistance loci associated with resistance to P. sojae isolate 40468 in Daepung × CheonAl recombinant inbred line (RIL) population. CheonAl is resistant to the isolate, while Daepung is generally susceptible. We genotyped the parents and RIL population via high-throughput single nucleotide polymorphism genotyping and constructed a set of genetic maps. The presence or absence of resistance to P. sojae was evaluated via hypocotyl inoculation technique, and phenotypic distribution fit to a ratio of 1:1 (R:S) (χ² = 0.57, p = 0.75), indicating single gene mediated inheritance. Single-marker association and the linkage analysis identified a highly significant genomic region of 55.9~56.4 megabase pairs on chromosome 18 that explained ~98% of phenotypic variance. Many previous studies have reported several Rps genes in this region, and also it contains nine genes that are annotated to code leucine-rich repeat or serine/threonine kinase within the approximate 500 kilobase pairs interval based on the reference genome database. CheonAl is the first domestic soybean genotype characterized for resistance against P. sojae isolate 40468. Therefore, CheonAl could be a valuable genetic source for breeding resistance to P. sojae.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.188-188
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• 2022

Our previous study identified a resistance locus to Phytophthora sojae (isolate 2457) in an interval of 3.8-4.7 Mbp on chromosome 3 via genetic mapping using a 'Daepung'×'Daewon' recombinant inbred population. Since differential gene expression between Daepung (susceptible) and Daewon (resistant) after inoculation of P. sojae is unknown, RNA sequencing was carried out to compare transcriptomic changes between the two genotypes following inoculation with P. sojae isolate 2457. The two varieties were inoculated using hypocotyl inoculation at the VC stage and stem tissue of 1 cm above and below of the inoculated site were sampled at 0, 6, 12 hours after inoculation (hai), respectively. Differentially expressed genes (DEGs) under same cultivar in different time point and Daepung vs. Daewon in same time point were investigated. In comparison of Daepung vs. Daewon at 12 hai, a total of 3,513 DEGs were identified, including two nucleotide-binding site-leucine rich repeat (NBS-LRR) genes (Glyma.03g034800 and Glyma.03g034900) that are located in the previously reported resistance locus on chromosome 3. In addition, 14,966 DEGs were detected between 0 vs. 6 hai, containing one of candidate genes (Glyma.03g035300). This gene was upregulated by up to 4-fold in Daewon and Daepung. Additional results will be further discussed in the presentation. This study will provide valuable information for soybean crop improvement.

• The Plant Pathology Journal
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• v.15 no.4
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• pp.228-235
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• 1999

Genetic diversity of ninety-five Korean isolates of Phytophthora was investigated on the basis of PCR-RFLP of ribosomal DNA. The isolates were previously identified as following fifteen species by mycological and cultural characteristics; P. boehmeriae, P. cactorum, P. cambivora, P. capsici, P. cinnamoni, P. citricola, P. citrophthora, P. cryptogea, P. drechsleri, P. erythroseptica, P. infestans, P. megasperma, P. nicotianae, P. palmivora and P. sojae. The regions of small subunit (SSU) and internal transcribed spacer (ITS) of rDNA were amplified with primer pair, NS1 and ITS4, by polymerase chain reaction (PCR) and digested with nine restriction enzymes. P. boehmeriae, P. cactorum, P. cambivora, P. capsici, P. cinnamomi, P. citricola, P. citrphthora, P. infestans, P. nicotianae and P. palmivora showed specific band patterns for each species. However, P. sojae and P. erythroseptica presented identical band patterns and P. cryptogea, P. drechsleri and P. megasperma were divided into six groups, which were not compatible with delineation of the species. A group originated from cucurbits showed distinct band patterns from other groups, but the other five groups were closely related within 96.0% similarity, forming one complex group. Consequently, Korean isolates of Phytophthora were divided into thirteen genetic groups and each group was readily differentiated by comparing digestion patterns of AvaII, HaeIII, MboI, HhaI and MspI. Therefore, PCR-RFLP of rDNA using the five enzymes can be used to differentiate or identify the Phytophthora species reported in Korea so far.

• The Plant Pathology Journal
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• v.16 no.1
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• pp.9-18
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• 2000

Using differential display techniques, a new acidic pathogenesis-related (PR) protein-1 cDNA (GMPRla) gene was isolated from a cDNA library of soybean (Glycinemax L.Merr, cultivar Jangyup) hypocotyls infected by Phytophthora sojae f. sp. glycines. The 741 bp of fulllength GMPRla clone contains an open reading frame of 525 nucleotides encoding 174 amino acid residues (pI 4.23) with a putative signal peptide of 27 amino acids in the N-terminus. Predicted molecular weight of the protein is 18,767 Da. The deduced amino acid sequence of GMPRla has a high level of identity with PR-1 proteins from Brassica napus, Nicotiana tabacum, and Sambucus nigra. The GMPRla mRNA was more strongly expressed in the incompatible than the compatible interaction. The transcript accumulation was induced in the soybbean hypocotyls by treatment with ethephon or DL-$\beta$-amino-n-butyric acid, but not by wounding. In situ hybridization data showed that GMPRIa mRNAs were usually localized in the vascular bundle of hypocotyl tissues, especially phloem tissue. Differences between compatible and incompatible interactions in the timing of GMPRla mRNA accumulation were remarkable, but the spatial distribution of GMPRla mRNA was similar in both interactions. However, more GMPRla mRNA was accumulated in soybean hypocotyls at 6 and 24 h after inoculation.

• Proceedings of the Korean Society of Crop Science Conference
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• 2018.10a
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• pp.224-224
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• 2018

• Proceedings of the Korean Society of Crop Science Conference
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• 2020.11a
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• pp.142-142
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• 2020