• Korean Journal of Poultry Science
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• v.48 no.4
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• pp.327-335
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• 2021

Riemerella anatipestifer (RA) can cause septicemia, polyserositis, and ataxia in ducks. It can also colonize the upper respiratory tract of healthy ducks. These differences in pathogenicity are probably the result of diverse mechanisms of virulence in different strains. Since serum resistance is a feature frequently found in systemic pathogens, 130 RA strains having different clinical origins were tested. A variety of serum susceptibility levels were detected. Pharynx strains from healthy ducks were mainly susceptible to the bactericidal effect of the serum, while systemic strains were serum resistant. Heat-treatment of the sera abolished the bactericidal activity, indicating that complement is a key factor in this effect. In an attempt to associate serum-resistance to surface determinant genes of the bacteria, we screened for six genes involved in lipopolysaccharide synthesis and membrane proteins in RA. Of these, three genes (AS87_09335, AS87_00480, and AS87_05195) encoding outer membrane proteins might be implicated in serum resistance statistically. The results indicate that serum resistance is a virulence mechanism in RA.

• The Plant Pathology Journal
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• v.38 no.1
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• pp.12-24
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• 2022

In this study, we conducted whole-genome sequencing with six species of Pectobacterium composed of seven strains, JR1.1, BP201601.1, JK2.1, HNP201719, MYP201603, PZ1, and HC, for the analysis of pathogenic factors associated with the genome of Pectobacterium. The genome sizes ranged from 4,724,337 bp to 5,208,618 bp, with the GC content ranging from 50.4% to 52.3%. The average nucleotide identity was 98% among the two Pectobacterium species and ranged from 88% to 96% among the remaining six species. A similar distribution was observed in the carbohydrate-active enzymes (CAZymes) class and extracellular plant cell wall degrading enzymes (PCWDEs). HC showed the highest number of enzymes in CAZymes and the lowest number in the extracellular PCWDEs. Six strains showed four subsets, and HC demonstrated three subsets, except hasDEF, in type I secretion system, while the type II secretion system of the seven strains was conserved. Components of human pathogens, such as Salmonella pathogenicity island 1 type type III secretion system (T3SS) and effectors, were identified in PZ1; T3SSa was not identified in HC. Two putative effectors, including hrpK, were identified in seven strains along with dspEF. We also identified 13 structural genes, six regulator genes, and five accessory genes in the type VI secretion system (T6SS) gene cluster of six Pectobacterium species, along with the loss of T6SS in PZ1. HC had two subsets, and JK2.1 had three subsets of T6SS. With the GxSxG motif, the phospholipase A gene did locate among tssID and duf4123 genes in the T6SSa cluster of all strains. Important domains were identified in the vgrG/paar islands, including duf4123, duf2235, vrr-nuc, and duf3396.

• Journal of fish pathology
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• v.35 no.1
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• pp.27-40
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• 2022

Yellow head virus (YHV), Infectious hypodermal and hematopoietic necrosis (IHHNV), Taura syndrome virus (TSV), and Infectious myositis virus (IMNV) cause serious mortality to Penaeidae shrimp in the aquaculture. In this study, YHV, IHHNV, TSV, and IMNV were surveyed from imported frozen shrimps between 2019 and 2020 via molecular diagnostic assay. Among 10 shrimp groups, YHV (n=1) and IHHNV (n=4) were detected by RT-PCR and PCR, respectively. From the phylogenetic analysis based on the partial ORF 1b region of YHV, YHV was classified into YHV genotype 3 (YHV3). And IHHNVs (n=2) detected from Litopenaeus vannamei belong to infectious IHHNV type 2. Although IHHNVs (n=2) identified from Penaeus monodon showed PCR positive results (MG 831F/R primer set), the sequences of ORF 2 and 3 were not amplified, suggesting that those samples might possess type A IHHNV related sequence of P. monodon. Furthermore, in the challenge test, even though PCR-detected isolates (YHV3/type A IHHNV related sequence or infectious IHHNV type 2) were not induced mortality to L. vannamei, viral genes were amplified suggesting that the viruses in the frozen shrimp could be non-pathogenic particles which are not enough to induce mortality.

• Research in Plant Disease
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• v.29 no.3
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• pp.234-242
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• 2023

In early spring, water-soaked lesions appeared on the petals and leaves of gaenari (Forsythia koreana), and the tissues were necrotic and dry. Cankers appeared on the infected branches around late spring and the above part of a branch withered and died. However, it was very rare that the base of the cankered-branch died. The identical fungi were isolated from the lesions on various tissues, and they grew with white colonies on potato dextrose agar medium. The fungus grew most actively at 23℃ and produced many sclerotia of various sizes. In a pathogenicity assay in which mycelial and sclerotial suspensions were inoculated on each organ of forsythia, it was found that the pathogen infects the flower only, but not the leaves or branches. Symptoms on the flowers spread to the next leaves and branches over time and the infected branches were eventually withered. To identify the isolates, DNA sequences of four phylogenetic markers including ITS, LSU, Tub2, and CAL were analyzed and all isolates were identified as a species in the genus Septotinia. This is not only the first report of gaenari (forsythia) shoot blight caused by the fungus Septotinia sp., but also the first report on the genus Septotinia as a plant pathogen in Korea.

• Research in Plant Disease
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• v.29 no.3
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• pp.258-267
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• 2023

Fusarium wilt, caused by Fusarium oxysporum f. sp. niveum (Fon) is a serious disease in watermelon cultivation. Most of commercialized watermelon cultivars to Fusarium wilt are susceptible in Korea. Fon isolates were divided into four races (races 0, 1, 2, and 3), based on pathogenicity in four watermelon differentials including 'Sugar baby', 'Charleston gray', 'Calhoun gray' and 'PI-296341-FR'. We obtained 7 isolates of Fon and tested to determine race of the fungal strains. Fon KACC 40902 and Fon HA were race 0 and Fon NW1, Fon NW2, Fon CW and Fon KACC 40901 were race 1. And Fon KACC 40905 was race 2, but race 3 isolate of Fon was not founded. We also tested virulence of seven Fon isolates on three-susceptible cultivars of watermelon. The isolates showed different virulence on the cultivars. In addition, to study the resistance characteristics of watermelon to Fon, we selected three moderately or highly resistant cultivars of watermelon and occurrence of Fusarium wilt in seedlings of the cultivars by seven Fon isolates was investigated. Among them, 'Calhoun gray' is highly resistant to six Fon isolates except Fon KACC 40905. On the other two cultivars, disease severity of Fusarium wilt caused by each isolate was positively correlated with the virulence of the Fon isolates. The results suggest that resistance of the watermelon cultivars to Fon isolates is likely affected by the virulence of the pathogen.

• Research in Plant Disease
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• v.29 no.1
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• pp.52-59
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• 2023

Cucurbit chlorotic yellows virus (CCYV) is a plant virus that causes damage to cucurbit crops such as watermelon and cucumber, and is transmitted by an insect vector known as the whitefly. Since CCYV was first detected on cucumber in Chungbuk in 2018, it has been reported in other areas including Gyeongsang in Korea. In 2020, we performed field surveys of yellowing diseases in the greenhouses growing melon and watermelon in Chungbuk (Jincheon and Eumseong). Reverse transcription-polymerase chain reaction analysis of 79 collected samples including melon, watermelon, and weeds resulted in detection of CCYV in 4 samples: Three samples were singly infected with CCYV and one samples was mixed infected with CCYV, Cucurbit aphid borne yellows virus, and Watermelon mosaic virus. The complete genome sequences of the four collected CCYV melon isolates (ES 1-ES 4) were determined and genetically compared with those of previously reported CCYV isolates retrieved from GenBank. Phylogenetic analyses of RNA 1 and 2 sequences revealed that four ES isolates were clustered in one group and closely related to the CCYV isolates from China. The analysis also revealed very low genetic diversity among the CCYV ES isolates. In general, CCYV isolates showed little genetic diversity, regardless of host or geographic origins. CCYV has the potential to pose a serious threat to melon, watermelon, and cucumber production in Korea. Further studies are needed to examine the pathogenicity and transmissibility of CCYV in weeds and other cucurbits including watermelon.

• Research in Plant Disease
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• v.29 no.1
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• pp.79-81
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• 2023

During the nationwide survey of fire blight, the typical shoot blight symptoms were found on Korean mountain ash (Sorbus alnifolia) which was located near an orchard that produced fire blight on pear trees in Eumseong, Korea, May 2021. To identify the causal agent, we progressed isolation from the symptomatic leaves and shoots. Two white and mucoid colonies were isolated into the pure culture. Two isolates were identified as Erwinia amylovora according to the colony-polymerase chain reaction (PCR) with amsB primers and the phylogenetic tree using 16S rRNA sequences. To test of pathogenicity of two isolates, we inoculated immature pear fruits and understock of apple. We observed necrosis and oozes on immature pear fruits and shoot blight resulting in necrosis on apple shoots six days after inoculation. Colonies were recovered from the inoculated pears and apples, and identity was confirmed through colony PCR for amsB genes. To our knowledge, E. amylovora was first reported on Korean mountain ash native to South Korea.

• Journal of Microbiology and Biotechnology
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• v.33 no.1
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• pp.51-60
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• 2023

The foodborne illness is the important public health concerns, and the livestock feces are known to be one of the major reservoirs of foodborne pathogens. Also, it was reported that 45.5% of foodborne illness outbreaks have been associated with the animal products contaminated with the livestock feces. In addition, it has been known that the persistence of a pathogens depends on many potential virulent factors including the various virulent genes. Therefore, the first step to understanding the public health risk of livestock feces is to identify and describe microbial communities and potential virulent genes that contribute to bacterial pathogenicity. We used the whole metagenome shotgun sequencing to evaluate the prevalence of foodborne pathogens and to characterize the virulence associated genes in pig and chicken feces. Our data showed that the relative abundance of potential foodborne pathogens, such as Bacillus cereus was higher in chickens than pigs at the species level while the relative abundance of foodborne pathogens including Campylobacter coli was only detected in pigs. Also, the microbial functional characteristics of livestock feces revealed that the gene families related to "Biofilm formation and quorum sensing" were highly enriched in pigs than chicken. Moreover, the variety of gene families associated with "Resistance to antibiotics and toxic compounds" were detected in both animals. These results will help us to prepare the scientific action plans to improve awareness and understanding of the public health risks of livestock feces.

• Research in Plant Disease
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• v.29 no.2
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• pp.118-129
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• 2023

Fusarium sambucinum species complex (FSAMSC) is an important taxonomic group, causing severe plant diseases. Many studies were carried out on FSAMSC plant diseases in Korea, but only 2 species (F. graminearum, F. sambucinum) from 14 host plants were registered in the List of Plant Disease in Korea. To clarify FSAMSC diversity and their pathogenecity, we examined FSAMSC isolates preserved in the Korean Agricultural Culture Collection. Fifty-seven strains were reidentifed as 7 species (F. asiaticum, F. graminearum, F. vorosii, F. meridionale, F. boothii, F. kyushuense, F. armeniacum) based on multi-locus sequence typing analysis. According to previous reports and result of this study, 5 species (F. asiaticum, F. graminearum, F. vorosii, F. armeniacum, F. sambucinum) were pathogenic on 24 host plants in FSAMSC, while the pathogenicity of 3 species (F. meridionale, F. boothii, F. kyushuense) were not clear.

• The Plant Pathology Journal
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• v.39 no.4
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• pp.361-373
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• 2023

In plant-pathogen interactions, Magnaporthe oryzae causes blast disease on more than 50 species of 14 monocot plants, including important crops such as rice, millet, and most 15 recently wheat. M. oryzae is a model fungus for studying plant-microbe interaction, and the main source for fungal pathogenesis in the field. Here we report that MoJMJD6 is required for conidium germination and appressorium formation in M. oryzae. We obtained MoJMJD6 mutants (ΔMojmjd6) using a target gene replacement strategy. The MoJMD6 deletion mutants were delayed for conidium germination, glycogen, and lipid droplets utilization and consequently had decreased virulence. In the ΔMojmjd6 null mutants, global histone methyltransferase modifications (H3K4me3, H3K9me3, H3K27me3, and H3K36me2/3) of the genome were unaffected. Taken together, our results indicated that MoJMJD6 function as a nuclear protein which plays an important role in conidium germination and appressorium formation in the M. oryzae. Our work provides insights into MoJMJD6-mediated regulation in the early stage of pathogenesis in plant fungi.