• The Plant Pathology Journal
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• v.38 no.6
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• pp.692-699
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• 2022

Bacterial wilt caused by Ralstonia solanacearum is considered one of the most harmful diseases of pepper plants. Recently, research on plant disease control through the rhizosphere microbiome has been actively conducted. In this study, the relationship with disease occurrence between the neighboring plant confirmed by analyzing the physicochemical properties of the rhizosphere soil and changes in the microbial community. The results confirmed that the microbial community changes significantly depending on the organic matters, P₂O₅, and clay in the soil. Despite significant differences in microbial communities according to soil composition, Actinobacteriota at the phylum level was higher in healthy plant rhizosphere (mean of relative abundance, D: 8.05 ± 1.13; H: 10.06 ± 1.59). These results suggest that Actinobacteriota may be associated with bacterial wilt disease. In this study, we present basic information for constructing of healthy soil in the future by presenting the major microbial groups that can suppress bacterial wilt.

• The Plant Pathology Journal
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• v.25 no.4
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• pp.352-360
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• 2009

The potential of three plants extracts, to protect potato plants against bacterial wilt caused by Ralstonia solanacearum was determined under greenhouse and field conditions. All soil drenching treatments of aqueous plant extracts of Hibsicus sabdariffa, Punica granatum and Eucalyptus globulus significantly reduced the disease severity compared with inoculated control. Although the applications of all three plant extracts resulted in similar reductions of disease severity in field up 63.23 to 68.39%, treatment of E. globulus leaf extract was found greater in restricting the symptom development than other the two plant extracts in the greenhouse. More than 94% reduction in the bacterial wilt symptom was observed in potato plants. All tested plant extracts were effective in inhibiting the growth of bacterial pathogen, not only in vitro, but also in stem of potato plants as compared with the inoculated control Potato plants treated with extract of H. sabdariffa reduced bacterial growth more effectively than treatment with P. granatum and E. globulus. Activity of defence-related enzymes, including peroxidase, polyphenoloxidase and phenylalanine ammonia lyase, were significantly increased in plants treated with the plant extracts compared to the control during the experimental period. In general, the higher enzymes activities were determined in both inoculated and non-inoculated treated potato plants after 8 days from plant extracts treatment. These results suggested that these plant extracts may be play an important role in controlling the potato bacterial wilt disease, through they have antimicrobial activity and induction of systemic resistance in potato plants.

• The Plant Pathology Journal
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• v.36 no.5
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• pp.398-405
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• 2020

Nutrient manipulation is a promising strategy for controlling plant diseases in sustainable agriculture. Although many studies have investigated the relationships between certain elements and plant diseases, few have comprehensively explored how differing mineral nutrition levels might affect plant-fungal pathogen interactions, namely plant susceptibility and resistance. Here, we systematically explored the effects of the seven mineral elements that plants require in the greatest amounts for normal development on the susceptibility of soybean plants (Glycine max) to Fusarium oxysporum infection in controlled greenhouse conditions. Nitrogen (N) negligibly affected plant susceptibility to infection in the range 4 to 24 mM for both tested soybean cultivars. At relatively high concentrations, phosphorus (P) increased plant susceptibility to infection, which led to severely reduced shoot and root dry weights. Potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), and iron (Fe) induced plant resistance to infection as their concentrations were increased. For K and Ca, moderate concentrations had a positive effect on plant resistance to the pathogen, whereas relatively high doses of either element adversely affected plant growth and promoted disease symptoms. Further experiments were conducted, assessing disease suppression by selected combinations of macro-elements and Fe at screened concentrations, i.e., K (9 mM) plus Fe (0.2 mM), and S (4 mM) plus Fe (0.2 mM). The disease index was significantly reduced by the combination of K plus Fe. In conclusion, this systematic investigation of soybean plant responses to F. oxysporum infection provides a solid basis for future environmentally-friendly choices for application in soybean disease control programs.

• The Plant Pathology Journal
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• v.32 no.5
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• pp.431-440
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• 2016

In 2004, bacterial spot-causing xanthomonads (BSX) were reclassified into 4 species-Xanthomonas euvesicatoria, X. vesicatoria, X. perforans, and X. gardneri. Bacterial spot disease on pepper plant in Korea is known to be caused by both X. axonopodis pv. vesicatoria and X. vesicatoria. Here, we reidentified the pathogen causing bacterial spots on pepper plant based on the new classification. Accordingly, 72 pathogenic isolates were obtained from the lesions on pepper plants at 42 different locations. All isolates were negative for pectolytic activity. Five isolates were positive for amylolytic activity. All of the Korean pepper isolates had a 32 kDa-protein unique to X. euvesicatoria and had the same band pattern of the rpoB gene as that of X. euvesicatoria and X. perforans as indicated by PCR-restriction fragment length polymorphism analysis. A phylogenetic tree of 16S rDNA sequences showed that all of the Korean pepper plant isolates fit into the same group as did all the reference strains of X. euvesicatoria and X. perforans. A phylogenetic tree of the nucleotide sequences of 3 housekeeping genes-gapA, gyrB, and lepA showed that all of the Korean pepper plant isolates fit into the same group as did all of the references strains of X. euvesicatoria. Based on the phenotypic and genotypic characteristics, we identified the pathogen as X. euvesicatoria. Neither X. vesicatoria, the known pathogen of pepper bacterial spot, nor X. perforans, the known pathogen of tomato plant, was isolated. Thus, we suggest that the pathogen causing bacterial spot disease of pepper plants in Korea is X. euvesicatoria.

• Journal of Life Science
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• v.22 no.6
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• pp.794-798
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• 2012

Paratuberculosis (Johne's disease), a chronic wasting disease caused by Mycobacterium avium subspecies paratuberculosis (MAP), is a major cause of economic loss in the cattle industry. In Korea, national monitoring of breeding stock for MAP has been implemented. In this study, we report the results of serological testing to determine the prevalence of MAP in breeding stock of Korean native and dairy cattle during 2008 and 2009. A total of 3,927 serum samples were submitted (3,692 Korean native cattle and 235 dairy cattle) to Animal Disease Diagnostic Division, Animal, Plant and Fisheries Quarantine and Inspection Agency. The samples were classified into four different age groups for MAP; group 1 (${\leq}2$ year, n = 1,509), group 2 (>2 years to ${\leq}3$ years, n = 486), group 3 (>3 years to ${\leq}4$ years, n = 441), and group 4 (>4 years, n = 1,491). Overall seroprevalence of MAP in this study was 0.5% (21/3,927), which was much lower than that of conventional cattle (1.2-16.4%) in Korea. Also, the seroprevalence was determined by age groups: three of group 1 (0.2%), two of group 2 (0.4%), three of group 3 (0.7%), and 13 of group 4 (0.9%) were seropositive for MAP, respectively. Although seropositive samples were found in all age groups, the seroprevalence tended to increase with age. Our study showed that the seroprevalence of MAP in pure-bred breeding dairy cattle (0%) was lower than that in pure-bred breeding Korean native cattle (0.6%).

• Proceedings of the Korean Society of Plant Pathology Conference
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• 1997.06a
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• pp.5-21
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• 1997

Unique virus-like particles were associated with five eriophyid mite-borne plant diseases of unknown etiology; fig mosaic, redbud yellow ringspot, rose orsette, thistle mosaic, and high plains disease of corn and wheat. Quasi-spherical, double membrane-bound particles (DMPs), 120 - 200 nm in diameter, were observed in the cytoplasm of all cell types in symptomatic leaves of infected plants. No DMPs were observed in symptomless plants. The DMPs in symptomatic thistles were associated with two types of inclusions, electron-dense amorphous material and tubular aggregates. Similar amorphous inclusions were also found in corn and wheat with high plains disease, while tubular inclusions were observed in figs with mosaic symptoms. The particles and inclusions were similar in some aspects to immature particles associated with viroplasms of animal and insect poxviruses and also to the double-enveloped particles of tomato spotted wilt virus associated with viroplasms during early stages of infection, but were unique and unlike any known plant viruses. The DMPs and associated viroplasm-like inclusions in the high plains disease were specifically immunogold labeled in situ with the disease-specific antiserum. Thread-like structures, similar to tenuivirus particles, present in the partially purified virus preparations were also immunogold labeled with the antiserum. It is suggested that the thread-like structures are derived from the DMP. In many cells of symptomatic corn and wheat samples, DMPs occurred together with flexuous rod-shaped particles and cylindrical inclusions of wheat streak mosaic potyvirus (WSMV), suggesting that the disease is caused by a mixed infection of WSMV and the agent represented by the DMPs. Based on cytopathology, symptomatology and mite and/or graft-transmissibility, the five diseases described in this paper are potentially caused by virus(es) and the DMPs associated with these diseases may represent virus particles. If the DMPs are indeed viral in nature, they would comprise a new group of plant viruses.

• Korean Journal of Veterinary Service
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• v.41 no.3
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• pp.203-210
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• 2018

Pasteurella multocida is an opportunistic organism that plays a significant role in porcine respiratory disease complex (PRDC). In the current study, we provide nationwide information of P. multocida isolates from pneumonic lungs of slaughter pigs by determining their prevalence, subspecies, biovars, capsular types, virulence-associated genes, and minimum inhibitory concentrations. P. multocida was the second most frequently confirmed (19.2%) bacterial pathogen and most of the isolates (88.9%) showed simultaneous infection with other respiratory pathogens, especially Mycoplasma hyopneumoniae (63.3%, P<0.001) and porcine circovirus type 2 (53.3%, P=0.0205). Of 42 isolates investigated, 41 (97.6%) were identified as P. multocida subspecies multocida, and only one isolate was identified as subspecies septica (biovar 5). All the isolates were capsular type A and the most prevalent biovar was biovar 3 (40.5%), followed by biovar 2 (31.0%). Comparing virulence-associated genes and biovars, all biovar 2 isolates exhibited $hgbB^-pfhA^+$ (P<0.001); all biovar 3 (P=0.0002) and biovar 13 (P=0.0063) isolates presented $hgbB^+pfhA^-$. Additionally, all biovar 2 (P=0.0037) isolates and most of biovar 3 (P=0.0265) isolates harbored tadD. P. multocida showed the highest resistance levels to oxytetracycline (73.8%), followed by florfenicol (11.9%). Continuous monitoring is required for surveillance of the antimicrobial resistance and new emerging strains of P. multocida in slaughter lines.

• Korean Journal of Veterinary Service
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• v.46 no.1
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• pp.35-45
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• 2023

Pathogenic Escherichia coli is the cause of a wide range of diseases in pigs, including diarrhea, edema disease, and septicemia. Diarrhea caused E. coli may result in significant economic losses, making pathogenic E. coli an important pathogen for the swine industry. This study investigated the prevalence of virulence factor genes, antimicrobial resistance phenotypes, and resistance genes in E. coli isolated from feces of piglets in Korea between 2017 and 2020. As a result, 119 pathogenic E. coli isolates were obtained from 601 fecal samples. The F4 adhesin gene and the STb enterotoxin gene were commonly present in E. coli isolated from diarrhea samples. The dominant virulotypes of isolates from diarrhea samples were STb, Stx2e, and F4:LT:STb. More than 80% of the screened isolates were resistant to ampicillin, sulfisoxazole, chloramphenicol, or tetracycline. To confirm the resistance mechanisms for β-lactam or quinolone, we investigated the genotypic factors of resistance. Each of the ceftiofur-resistant E. coli produced an extended-spectrum β-lactamase encoded by bla_CTX-M-14, bla_CTX-M-27, and bla_CTX-M-55. And all ciprofloxacin-resistant E. coli harbored mutations in quinoloneresistance-determining-regions. In addition, some of the ciprofloxacin-resistant E. coli contained the plasmid-mediated-quinolone-resistance genes such as qepA, qnrB1, or qnrD. This study has confirmed that the F4 fimbria and the STb enterotoxin are the most predominant in pathogenic E. coli isolated from piglets with diarrhea in Korea and there is a great need for responsible and prudent use of antimicrobials to treat colibacillosis.

• Korean Journal of Veterinary Research
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• v.63 no.4
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• pp.37.1-37.7
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• 2023

Canine respiratory coronavirus (CRCoV) is a significant pathogen that causes respiratory diseases in dogs, collectively known as a canine infectious respiratory disease. The virus is highly contagious and exhibits high seroprevalence worldwide. Currently, bovine coronavirus (BCoV) enzyme-linked immunosorbent assay (ELISA) kits are used to detect CRCoV antibodies. However, BCoV-ELISA kits cannot differentiate between infections caused by BCoV and those caused by CRCoV. In this study, we evaluated the hemagglutination inhibition (HI) test for CRCoV by comparing it with the virus neutralization (VN) test. Subsequently, we evaluated the seroprevalence of CRCoV in 383 dog serum samples collected from South Korea utilizing the HI test. The HI test for CRCoV showed a strong correlation with the VN test (R = 0.83, p < 0.001). The analysis of seroprevalence revealed that 52.2% (95% confidence interval [CI], 47.2%-57.1%) of the Korean dog serum samples were positive. The seroprevalence exhibited varied with age, with a positivity rate of 43.9% in dogs under 1 year of age and 66.7% in dogs aged 3 to 5 years (odds ratio, 2.54; 95% CI, 1.43-4.59). In conclusion, the HI test to monitor CRCoV antibody proved to be closely related to the VN test. Furthermore, over half of the dogs in Korea tested positive for CRCoV antibodies. These findings contribute to a better understanding of the sero-epidemiology of CRCoV.

• Korean Journal of Veterinary Research
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• v.64 no.1
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• pp.3.1-3.8
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• 2024

Canine distemper virus (CDV), canine adenovirus type 2 (CAV-2), canine parvovirus (CPV), and canine parainfluenza virus 5 (CPIV-5) are the major viral pathogens in dogs. Despite the availability of vaccines for dogs against these 4 viral pathogens, investigations of antibodies against these pathogens have rarely been reported in South Korea. In this study, we investigated the recent incidence of viral diseases in dogs and conducted sero-surveillance for CDV, CAV-2, CPV, and CPIV-5 in Korean dogs. The most frequently diagnosed canine viral disease in Korean dog samples from 2000 to 2022 was CPV infection, which accounted for 48.7% (464/953) of the cases. A total of 400 dog serum samples collected between 2019 and 2022 were screened for the presence of virus-neutralizing antibodies against CDV, CAV-2, CPV, and CPIV-5. The overall seropositivity rates for CDV, CAV-2, CPV, and CPIV-5 were 83.8%, 77.8%, 99.3%, and 82.0%, respectively. The protection rate against CPV was the highest (98.3%) and that against CAV-2 was the lowest (44.8%) in dog sera. Male and female dogs showed no significant differences in seropositivity rates. CDV and CPIV-5 seropositivity increased with age in dogs, and the highest incidence and seropositivity rates of CPV indicated that Korean dogs have been continuously exposed to wild CPV, and that CPV is a pathogen that urgently requires attention among canine viral diseases.