• The Plant Pathology Journal
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• v.30 no.4
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• pp.407-415
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• 2014

Viral diseases have been a major limiting factor threating sustainable potato (Solanum tuberosum L.) production in Pakistan. Surveys were conducted to serologically quantify the incidence of RNA viruses infecting potato; Potato virus X (PVX), Potato virus Y (PVY), Potato virus S (PVS), Potato virus A (PVA), Potato virus M (PVM) and Potato leaf roll virus (PLRV) in two major potato cultivars (Desiree and Cardinal). The results suggest the prevalence of multiple viruses in all surveyed areas with PVY, PVS and PVX dominantly widespread with infection levels of up to 50% in some regions. Co-infections were detected with the highest incidence (15.5%) for PVX and PVS. Additionally the data showed a positive correlation between co-infecting viruses with significant increase in absorbance value (virus titre) for at least one of the virus in an infected plant and suggested a synergistic interaction. To test this hypothesis, glasshouse grown potato plants were challenged with multiple viruses and analyzed for systemic infections and symptomology studies. The results obtained conclude that multiple viral infections dramatically increase disease epidemics as compared to single infection and an effective resistance strategy in targeting multiple RNA viruses is required to save potato crop.

• Korean Journal Plant Pathology
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• v.3 no.2
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• pp.120-123
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• 1987

Four types of spore trap (Kim's original, improved Kim's original, Yoshino's original and mixed type of Kim's and Yoshino's original) were evaluated for their efficacy to "estimate the amount of spores released from leaf blast lesions under the natural conditions. It was found that all four types had one or two defects in allowance for adequate sporulation/release, spore catch or spore counting. Thus, an improved type of spore trap was devised considering that it could cover the defects mentioned above. As a result, newly developed spore trap was quite satisfactory in above mentioned aspects and it could be used for pursuit of spore release phase under the natural conditions.

• The Plant Pathology Journal
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• v.36 no.1
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• pp.29-42
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• 2020

Acidovorax citrulli causes bacterial fruit blotch in Cucurbitaceae, including watermelon. Although A. citrulli is a seed-borne pathogen, it can cause diverse symptoms in other plant organs like leaves, stems and fruits. To determine the infection routes of A. citrulli, we examined the virulence of six isolates (Ac0, Ac1, Ac2, Ac4, Ac8, and Ac11) on watermelon using several inoculation methods. Among six isolates, DNA polymorphism reveals that three isolates Ac0, Ac1, and Ac4 belong to Clonal Complex (CC) group II and the others do CC group I. Ac0, Ac4, and Ac8 isolates efficiently infected seeds during germination in soil, and Ac0 and Ac4 also infected the roots of watermelon seedlings wounded prior to inoculation. Infection through leaves was successful only by three isolates belonging to CC group II, and two of these also infected the mature watermelon fruits. Ac2 did not cause the disease in all assays. Interestingly, three putative type III effectors (Aave_2166, Aave_2708, and Aave_3062) with intact forms were only found in CC group II. Overall, our results indicate that A. citrulli can infect watermelons through diverse routes, and the CC grouping of A. citrulli was only correlated with virulence in leaf infection assays.

• The Plant Pathology Journal
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• v.39 no.1
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• pp.149-157
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• 2023

Phytoplasmas were discovered in diseased Elaeocarpus sylvestris trees growing on Jeju Island that showed symptoms of yellowing and darkening in the leaves. Leaf samples from 14 symptomatic plants in Jeju-si and Seogwipo-si were collected and phytoplasma 16S rRNA was successfully amplified by nested polymerase chain reaction using universal primers. The sequence analysis detected two phytoplasmas, which showed 99.5% identity to 'Candidatus Phytoplasma asteris' and 'Ca. P. malaysianum' affiliated to 16SrI and 16SrXXXII groups, respectively. Through polymerase chain reaction-restriction fragment length polymorphism (RFLP) analyses using the AfaI (RsaI) restriction enzyme, the presence of two phytoplasmas strains as well as cases of mixed infection of these strains was detected. In a virtual RFLP analysis with 17 restriction enzymes, the 16S rRNA sequence of the 'Ca. P. asteris' strain was found to match the pattern of the 16SrI-B subgroup. In addition, the phytoplasmas in the mixed-infection cases could be distinguished using specific primer sets. In conclusion, this study confirmed mixed infection of two phytoplasmas in one E. sylvestris plant, and also the presence of two phytoplasmas (of the 16SrI and 16SrXXXII groups) in Jeju Island (Republic of Korea).

• Research in Plant Disease
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• v.29 no.4
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• pp.425-432
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• 2023

Kiwifruit industry has been threatened by the emergence of kiwifruit vine decline syndrome causing plant death within one or two years from symptom appearance. The main symptoms of this syndrome are root cortex breakdown, leaf necrosis, phylloptosis, fruit skin wrinkling, and twig wilting. Kiwifruit vine decline syndrome occurred on both Actinidia chinensis var. chinensis and A. chinensis var. deliciosa in mid-summer after rainy season. Kiwifruit vine decline syndrome was turned out to be severely occurred in wettable clay soils affected by waterlogging or poor aeration. No pathogens were directly correlated with the syndrome. Kiwifruit vine decline syndrome could be expected to be efficiently prevented controlled using Bounty 71 rootstock tolerant to water stress such as waterlogging.

• Research in Plant Disease
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• v.22 no.1
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• pp.50-54
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• 2016

In early June 2014, leaf spot symptoms were observed on black chokeberry (Aronia melanocarpa) in Yesan-gun and Geumsan-gun, Chungcheongnam-do in Korea. The initial symptoms on leave surfaces were brown small-circular spots with a yellow halo lesion, and gradually the small spots were fused, all of infected leaves dropped eventually. A fungus were isolated from the initial lesion, and cultured on potato dextrose agar. Colony color on upper surface of plate varied from olive gray to charcoal gray. Size of conidia mostly extend to $19-50{\times}5-9{\mu}m$ in nature and $20-59{\times}8-13{\mu}m$ in culture, with 3-8 transverse septa and usually no longitudinal septum or only 1 longitudinal septum in 1-3 of the transverse compartments, and also have a short or long beak. Pathogenicity was investigated using wounded or unwounded black chokeberry and apple leaves. After 7 days of inoculation, leaf spots were similar to the symptoms naturally occurred in the field. On the basis of mycological characteristics, pathogenicity, and ITS rDNA sequence analysis, this fungus was identified as Alternaria mali. This is the first report of Alternaria leaf spot on black chokeberry caused by A. mali in Korea.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.10a
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• pp.73-73
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• 2018

Bacterial leaf blight(BLB), caused by X. oryzae pv. oryzae(Xoo), is one of the most destructive diseases of rice due to its high epidemic potential. Understanding BLB resistance at a genetic level is important to further improve the rice breeding that provides one of the best approaches to control BLB disease. In the present investigation, a collection of 192 accessions was used in the genome-wide association study (GWAS) for BLB resistance loci against four Korean races of Xoo that were represented by the prevailing BLB isolates under Xoo differential system. A total of 192 accessions of rice germplasm were selected on the basis of the bioassay using four isolated races of Xoo such as K1, K2, K3 and K3a. The selected accessions was used to prepare 384-plex genotyping by sequencing (GBS) libraries and Illumina HiSeq 2000 paired- end read was used for GBS sequencing. GWAS was conducted using T ASSEL 5.0. The T ASSEL program uses a mixed linear model (MLM). T he results of the bioassay using a selected set of 192 accessions showed that a large number of accessions (93.75%) were resistant to K1 race, while the least number of accessions (34.37%) resisted K3a race. For races K2 and K3, the resistant germplasm proportion remained between 66.67 to 70.83%. T he genotypic data produced SNP matrix for a total of 293,379 SNPs. After imputation the missing data was removed, which exhibited 34,724 SNPs for association analysis. GWAS results showed strong signals of association at a threshold of [-log10(P-value)] more than5 (K1 and K2) and more than4 (K3 and K3a) for nine of the 39 SNPs, which are plausible candidate loci of resistance genes. T hese SNP loci were positioned on rice chromosome 2, 9, and 11 for K1 and K2 races, whereas on chromosome 4, 6, 11, and 12 for K3 and K3a races. The significant loci detected have also been illustrated, NBS-LRR type disease resistance protein, SNARE domain containing protein, Histone deacetylase 19, NADP-dependent oxidoreductase, and other expressed and unknown proteins. Our results provide a better understanding of the distribution of genetic variation of BLB resistance to Korean pathogen races and breeding of resistant rice.

• Research in Plant Disease
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• v.23 no.1
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• pp.69-74
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• 2017

In 2015, a nationwide survey was carried out to investigate about occurrence pattern of virus infecting foxtail millet. A total 100 foxtail millet leaf samples showing virus-like and abnormal symptoms were collected in the seven main cultivated regions of Korea. Four viruses were identified using reverse transcription polymerase chain reaction and RNA sequencing. Of the collected 100 foxtail millet samples, 10 were Barley virus G (BVG), 4 were Rice stripe virus (RSV), 1 was Northern cereal mosaic virus (NCMV), and 1 was Sugarcane yellow leaf virus (ScYLV) infection. To our best knowledge, this is the first report of BVG and NCMV infecting foxtail millet in Korea and ScYLV is expected as new Polerovirus species. This research will be useful in breeding for improved disease-resistant foxtail millet cultivars.

• Research in Plant Disease
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• v.11 no.2
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• pp.115-121
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• 2005

This studies were carried out to elucidate the control effect of copper fungicides against some citrus diseases, assess copper spray injury on leaf and fruit of citrus by spraying of copper fungicides according to growth stages and spray seasons and by tank mixing with paraffin oil in field experiments for 3 years (2003-2005 season). As results, the control value was approximately $75\%$ against scab disease in all tested copper fungicides, $85-88\%$ to canker and $75-86\%$ to melanose. In case of leaf, the copper injury was the severest in early stage of shooting, and the injury was gradually weakened according to growth of leaf. In fruit, the copper injury was more severe in midsummer (late of July and August) than early of summer and spring season (June and ealy of July). Among copper fungicides, the bordeaux mixture which made by level of farm induced more injury compared to other copper fungicides commercialized. Less copper spray injury was observed on treatments in which copper fungicide was sprayed as tank mixtures with paraffin oil when compared to treatment which sprayed with only copper fungicide.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2019.04a
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• pp.62-62
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• 2019

Bacterial leaf blight(BLB), caused by X. oryzae pv. oryzae(Xoo), is one of the most destructive diseases of rice due to its high epidemic potential. Understanding BLB resistance at a genetic level is important to further improve the rice breeding that provides one of the best approaches to control BLB disease. In the present investigation, a collection of 192 accessions was used in the genome-wide association study (GWAS) for BLB resistance loci against four Korean races of Xoo that were represented by the prevailing BLB isolates under Xoo differential system. A total of 192 accessions of rice germplasm were selected on the basis of the bioassay using four isolated races of Xoo such as K1 and K2. The selected accessions was used to prepare 384-plex genotyping by sequencing (GBS) libraries and Illumina HiSeq 2000 pairedend read was used for GBS sequencing. GWAS was conducted using TASSEL 5.0. The TASSEL program uses a mixed linear model (MLM). The results of the bioassay using a selected set of 192 accessions showed that a large number of accessions (93.75%) were resistant to K1 race and K2 resistant germplasm proportion remained between 66.67. The genotypic data produced SNP matrix for a total of 293,379 SNPs. After imputation the missing data was removed, which exhibited 34,724 SNPs for association analysis. GWAS results showed strong signals of association at a threshold of [-log10(P-value)] more than 5 (K1 and K2) for nine of the 39 SNPs, which are plausible candidate loci of resistance genes. These SNP loci were positioned on rice chromosome 2, 9, and 11 for K1 and K2 races. The significant loci detected have also been illustrated and make the CPAS markers for NBS-LRR type disease resistance protein, SNARE domain containing protein, Histone deacetylase 19, NADP-dependent oxidoreductase, and other expressed and unknown proteins. Our results provide a better understanding of the distribution of genetic variation of BLB resistance to Korean pathogen races and breeding of resistant rice.