• Research in Plant Disease
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• v.25 no.1
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• pp.38-42
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• 2019

While rehmannia (Rehmannia glutinosa Libosch) was identified as a host of at least five viruses, including Rehmannia mosaic virus (ReMV), Youcai mosaic virus (YoMV), Broad bean wilt virus 2 (BBWV2), Plantago asiatica mosaic virus (PlAMV), and Rehmannia virus 1 (ReV1), viral incidence surveys have not been performed yet in rehmannia fields in Korea. In this study, we performed field surveys during 2017-2018 to investigate the incidence of 5 major viruses in rehmannia. A total of 145 symptomatic samples were collected from the rehmannia fields in major cultivation areas of Korea. Molecular diagnosis assays showed that all the collected leaf samples were infected with more than two viruses. Particularly, two species of Tobamovirus, ReMV and YoMV, were detected in all the samples. In addition, our analysis showed that the root stocks of 4 rehmannia cultivars were infected with at least two viruses. Since rehmannia is propagated by vegetative propagation, it is highly important to produce virus-free root stocks of rehmannia to control virus diseases in rehmannia.

• Horticultural Science & Technology
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• v.19 no.1
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• pp.43-47
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• 2001

This study was conducted to investigate the integrated control strategy against pear black leaf spot disease. Using indicator plant PS-95 we selected six virus-free trees (cv. Niitaka) from commercial orchards in the major pear production area. Disease symptom by pear black leaf spot in the shoot of pear (Niitaka) has been successfully inhibited by heat treatments for 3 weeks at temperature of $40^{\circ}C$ (day) and $32^{\circ}C$ (night) or 4 weeks at $37^{\circ}C$ and $30^{\circ}C$, respectively. However, survival rate of the shoot tips on stocks was low. Seven cultivars Niitaka, Imamura- aki, Waseaka, Nijisseiki, Wasenijisseiki, Shinsetsu and Whangkeumbae produced visible symptoms in the first year after inoculation with the virus. Other 11 selections remained symptomless. Two resistant cultivars Suwhangbae and Gamcheonbae were selected, which showed high fruit quality. It is recommended that these cultivars could be top-grafted onto the infected Niitaka trees to overcome the damage caused by the disease in the orchard.

• Research in Plant Disease
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• v.18 no.4
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• pp.290-297
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• 2012

In this study, total number of 1941 Capsicum accessions conserved at RDA Genebank was evaluated for their response to Cucumber mosaic virus (CMV). These accessions were composed with 9 species originated from 89 countries, included 839 Capsicum annuum, 277 C. baccatum, 395 C. chinense, 343 C. frutescens, 49 C. pubescens, and other 38 wild pepper species (C. chacoense, C. galapagoense, etc.). Resistant to CMV was screened with the 240H02SP6 SNP marker related to the Cmr1 (Cucumber mosaic resistance 1). Eighty nine accessions of pepper germplasm were resistant to CMV based on the marker. One hundred sixty two accessions showed heterozygosity. One thousand two hundred seventy accessions were susceptible to CMV. Four hundred twenty accessions did not show distinction by 240H02SP6 marker. These 89 resistant pepper germplasm can be used in a pepper breeding program against CMV.

• Research in Plant Disease
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• v.23 no.4
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• pp.379-382
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• 2017

In March 2016, an isolate of Cucumber mosaic virus (named Gyp-CMV) was isolated from the Sambungai (Gynura procumbens) showing the symptoms of mosaic and chlorosis. The isolate Gyp-CMV was characterized by disease reactions in several indicator plants, reverse transcription-polymerase chain reaction (RT-PCR), PCR-restriction fragment length polymorphism, and sequence analysis of movement protein (3a) and coat protein (CP) genes. Tobacco, tomato, pepper, ground cherry, and lambsquarters (Chenopodium quinoa and C. amaranticolor) appeared typical CMV symptoms, but zucchini and cucumber were not infected. Phylogenetic analysis of the 3a and CP gene indicated that Gyp-CMV belongs to the CMV subgroup II. Sequence identities of the Gyp-CMV 3a and CP genes showed 99.3% and 100% to that of Hnt-CMV at amino acid level. To our knowledge, this is the first report of CMV infection in Gynura procumbens.

• Research in Plant Disease
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• v.18 no.3
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• pp.231-235
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• 2012

Indian citrus ring spot virus (ICRSV) is known to cause a serious disease to citrus, especially to Kinnow mandarin, the popular cultivated citrus species in India. In this study, we developed diagnostic systems based on enzyme-linked immunosorbent assay (ELISA). In order to generate antibodies against ICRSV coat protein, we overexpressed the coat protein in Escherichia coli using the pET15b expression vector containing an optimized ICRSV coat protein gene. The recombinant ICRSV coat protein was overexpressed as soluble form at $37^{\circ}C$ upon IPTG induction. The protein was purified to 95% in purity by Ni-NTA column chromatography. The purified protein was immunized to rabbit for the generation of polyclonal antibody (PAb). The PAb showed a specific immunoreaction to recombinant ICRSV coat protein in western blot analysis and ELISA. Diluted rabbit antisera (10,000 fold) could detect less than 10 ng and 5 ng of the target protein in western blot and ELISA analysis, respectively.

• The Plant Pathology Journal
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• v.19 no.2
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• pp.123-127
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• 2003

A severe disease of muskmelon (Cucumis melo cv. Alsnight) grown on rockwool in a plastic house was characterized by leaf and stem necrosis followed by death of the plants. In 2001, an isolate of Melon necrotic spot virus-MN (MNSV-MN) of the genus Camovirus was identified as the causal agent of the disease on the basis of biological reactions and nucleotide sequence analyses of coat protein (CP) gene. MNSV-MN induced necrotic local lesions on mechanically inoculated leaves and systemic necrotic spots on the upper leaves of melon cvs. Alsnight, Rui III, Party, Imperial, and Seolhang. However, the inoculated leaves of watermelon and cucumber showed only necrotic lesions. DsRNAs extracted from the melon infected with MNSV-MN were separated into three components. Molecular sizes of the dsRNAs were estimated at approximately 4.5, 1.8, and 1.6 kbp. The amplified cDNA products of CP gene for MNSV-MN by RT-PCR showed approximately 1.2 kbp. The amplified DNA was digested to three fragments by MspI treatment. The cDNA of the genomic RNA of MNSV-MN was cloned and the region deduced to encode the CP was sequenced. The CP coding region, located near 3' end of the genome, consisted of 1,170 nucleotides and had the potential to encode a 390 amino acid protein. The nucleotide and amino acid sequences of MNSV-MN CP gene were 84.0-94.6% and 90.8-94.9% identical with other MNSV isolates found in the GeneBank database, respectively. This is the first report on the occurrence of MNSV in Korea.

• The Plant Pathology Journal
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• v.31 no.4
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• pp.363-370
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• 2015

Using the Chinese cabbage (Brassica campestris) cultivar 'Chun-goang' as a host and turnip mosaic virus (TuMV) as a pathogen, we studied the effects of ambient temperature ($13^{\circ}C$, $18^{\circ}C$, $23^{\circ}C$, $28^{\circ}C$ and $33^{\circ}C$) on disease intensity and the speed of systemic infection. The optimal temperature for symptom expression of TuMV was $18-28^{\circ}C$. However, symptoms of viral infection were initiated at $23-28^{\circ}C$ and 6 days post infection (dpi). Plants maintained at $33^{\circ}C$ were systemically infected as early as 6 dpi and remained symptomless until 12 or 22 dpi, depending on growth stage at the time of inoculation. It took 45 days for infection of plants grown at $13^{\circ}C$. Quantitative realtime polymerase chain reaction (q-PCR) results showed that the accumulation of virus coat protein was greater in plants grown at $23-28^{\circ}C$. The speed of systemic infection increased linearly with rising ambient temperature, up to $23^{\circ}C$. The zero-infection temperature was $10.1^{\circ}C$. To study the effects of abruptly elevated temperatures on systemic infection, plants inoculated with TuMV were maintained at $10^{\circ}C$ for 20 d; transferred to a growth chamber at temperatures of $13^{\circ}C$, $18^{\circ}C$, $23^{\circ}C$, $28^{\circ}C$, or $33^{\circ}C$ for 1, 2, or 3 d; and then moved back to $10^{\circ}C$. The numbers of plants infected increased as duration of exposure to higher temperatures and dpi increased.

• The Plant Pathology Journal
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• v.28 no.1
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• pp.68-74
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• 2012

Biocontrol microbes have mainly been screened among large collections of microorganisms $via.$ nutrient-rich $in$ $vitro$ assays to identify novel and effective isolates. However, thus far, isolates from only a few genera, mainly spore-forming bacilli, have been commercially developed. In order to isolate field-effective biocontrol microbes, we screened for more than 200 oligotrophic bacterial strains, isolated from rhizospheres of various soil samples in Korea, which induced systemic resistance against the soft-rot disease caused by $Pectobacterium$ $carotovorum$ SCC1; we subsequently conducted in $planta$ bioassay screening. Two oligotrophic bacterial strains were selected for induced systemic disease resistance against the $Tobacco$ $Mosaic$ $Virus$ and the gray mold disease caused by $Botrytis$ $cinerea$. The oligotrophic bacterial strains were identified as $Pseudomonas$ $manteilii$ B001 and $Bacillus$ $cereus$ C003 by biochemical analysis and the phylogenetic analysis of the 16S rRNA sequence. These bacterial strains did not exhibit any antifungal activities against plant pathogenic fungi but evidenced several other beneficial biocontrol traits, including phosphate solubilization and gelatin utilization. Collectively, our results indicate that the isolated oligotrophic bacterial strains possessing induced systemic disease resistance could provide useful tools as effective biopesticides and might be successfully used as cost-effective and preventive biocontrol agents in the field.

• Korean Journal of Poultry Science
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• v.39 no.2
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• pp.97-104
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• 2012

Newcastle disease virus (NDV) infects a variety of birds with a wide range of clinical signs from asymptomatic to severe. During a 10-month period in 2011, a total of 1,024 sera from wild birds including 42 species of birds in 8 orders were collected and the seroprevalence of NDV in wild birds was evaluated by hemagglutination inhibition (HI) test. Evidence of NDV infection was observed in 12.6% (129/1,024) of wild birds with a maximum prevalence reported in Mandarin duck (27.8%, 32/115) followed by Mallard duck (20.8%, 57/274), Spot-billed duck (11.9%, 36/303), Pintail (2.9%, 1/34), Black-tailed gull (2.9%, 1/34), White-fronted goose (1.8%, 1/56) and Common teal (1.4%, 1/69). None of the other 35 species of wild birds were antibody-positive for NDV. Mandarin duck, Mallard duck and Spot-billed duck showed high sero-prevalance of 12.2% to 42% during winter season (November to March). Our results indicate that Mandarin duck, Mallard duck and Spot-billed duck might be natural reservoirs for NDV in Korea and the prevalence of NDV infection in wild birds displayed a seasonal pattern with high prevalence of NDV in winter season (November to March).

• Research in Plant Disease
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• v.22 no.2
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• pp.65-71
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• 2016

Cymbidium mosaic virus (CymMV) is a major virus infecting orchid plants and causing economic loss. In this study, the incidence of viral infection in Calanthe spp. at the Korean Institute of Calanthe was investigated using reverse transcription polymerase chain reaction. The CymMV infection rate was 42%, and the two viruses Odontoglossum ringspot virus and Cucumber mosaic virus had frequencies of 8% and 2%, respectively. Additionally, we characterized an isolate of CymMV, CymMV-GW, using biological tests and examined the nucleotide sequence properties of its complete genome. CymMV-GW induced chlorotic ringspots and chlorotic spot symptoms in inoculated leaves of Chenopodium amaranticolor and Nicotiana benthamiana, respectively. In this study, we have for the first complete genome sequence of CymMV-GW in Korea. The CymMV-GW genome was 6,225 nucleotides in length, excluding the poly-(A) tail, and showed whole-genome nucleotide and amino acid sequence identities of 97.7% and 100%, respectively, with the NJ-1 isolate of CymMV. Here, we report the complete genome sequence of the CymMV-GW isolate and viral infection rates for Calanthe spp. in Korea.