• Korean Journal of Microbiology
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• v.53 no.4
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• pp.340-341
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• 2017

Acidovorax citrulli is a causal agent for bacterial fruit blotch on watermelon. Here, we report the complete genome sequence of A. citrulli strain KACC17005. The genome contains 5,349,924 bp with G + C contents of 68.54%, including 4,520 protein coding genes in a circular chromosome. It also possesses at least 15 genes encoding putative type III effector proteins, which may contribute to promoting virulence in susceptible hosts or triggering immune responses in resistant hosts.

• Research in Plant Disease
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• v.12 no.3
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• pp.185-188
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• 2006

In September and October 2005, melons(Cucumis melo L.) from the commercial greenhouses in Naju and Gwangju exhibited severe foliar necrosis and fruit rot. Leaf symptoms initially appeared as V-shaped, necrotic lesions and extending to the midrib. Symptoms on the fruit were occurred randomly as necrotic and sunken spots. Two isolates from diseased leaves and fruits were identified as Acidovorax avenae subsp. citrulli on the basis of bacteriological and genetic characteristics. Pathogenicity of the isolates was confirmed by inoculating on 3-week-old melon and cucumber seedlings. This is the first report of bacterial fruit blotch of melon in Korea.

• Research in Plant Disease
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• v.21 no.2
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• pp.74-81
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• 2015

The specific and sensitive nested-PCR method to detect Acidovorax citrulli, a causal agent of bacterial fruit blotch on cucurbitaceae, was developed. PCR primers were designed from the draft genome sequence which was obtained with the Next Generation Sequencing of A. citrulli KACC10651, and the nested-PCR primer set (Ac-ORF 21F/Ac-ORF 21R) were selected by checking of specificity to A. citrulli with PCR assays. The selected nested-PCR primer amplified the 140 bp DNA only from A. citrulli strains, and detection sensitivity of the nested PCR increased 10,000 times of $1^{st}$ PCR detection limit (10 ng genomic DNA/PCR). The nested PCR detected A. citrulli from the all samples of seed surface wash (external seed detection) of the artificially inoculated watermelon seeds with $10^1cfu/ml$ and above population of A. citrulli while the nested PCR could not detected A. citrulli from the mashed seed suspension (internal seed detection) of the all artificially inoculated watermelon seeds. When the naturally infested watermelon seeds (10% seed infested rate with grow-out test) used, the nested PCR detected A. citrulli from 2 seed samples out of 10 replication samples externally and 5 seed samples out of 10 replication samples internally. We believe that the nested-PCR developed in this study will be useful method to detect A. citrulli from the Cucurbitaceae seeds.

• Journal of Microbiology and Biotechnology
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• v.25 no.9
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• pp.1401-1409
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• 2015

The aim of this study was to develop a SYBR Green-based real-time PCR assay for the rapid, specific, and sensitive detection of Acidovorax avenae subsp. citrulli, which causes bacterial fruit blotch (BFB), a serious disease of cucurbit plants. The molecular and serological methods currently available for the detection of this pathogen are insufficiently sensitive and specific. Thus, a novel SYBR Green-based real-time PCR assay targeting the YD-repeat protein gene of A. avenae subsp. citrulli was developed. The specificity of the primer set was evaluated using DNA purified from 6 isolates of A. avenae subsp. citrulli, 7 other Acidovorax species, and 22 of non-targeted strains, including pathogens and non-pathogens. The AC158F/R primer set amplified a single band of the expected size from genomic DNA obtained from the A. avenae subsp. citrulli strains but not from the genomic DNA of other Acidovorax species, including that of other bacterial genera. Using this assay, it was possible to detect at least one genomeequivalents of the cloned amplified target DNA using 5 × 10⁰ fg/µl of purified genomic DNA per reaction or using a calibrated cell suspension, with 6.5 colony-forming units per reaction being employed. In addition, this assay is a highly sensitive and reliable method for identifying and quantifying the target pathogen in infected samples that does not require DNA extraction. Therefore, we suggest that this approach is suitable for the rapid and efficient diagnosis of A. avenae subsp. citrulli contaminations of seed lots and plants.

• Research in Plant Disease
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• v.27 no.1
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• pp.8-16
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• 2021

This study was conducted to check the sterilization efficacy of microwave plasma (MWP) against the watermelon seeds infected with Acidovorax citrulli 11-251. Watermelon seeds were artificially vacuum inoculated to produce A. citrulli 11-251 infected seeds. Aac ImmunoStrip and scanning electron microscope (SEM) results suggests that, seeds (coat and endosperm) were infected under the concentration of 1×107/30 min. MWP sterlization process was carried out at 50 W (3 min, 5 min, and 10 min), 80 W (3 min, 5 min, and 10 min), and 100 W (3 min, 5 min, and 10 min). According to the results, MWP sterilized the artificially inoculated seed coats by 95.96% at 80 W/10 min and seed endosperms by 100% at 100 W/10 min respectively. Although, seeds were sterlized by MWP, germination rate of seeds were low as compared to non treated (negative control) seeds. Moreover, cell membrane of A. citrulli 11-251 was damaged while observed in SEM after sterilized with MWP. Further studies regarding the appropriate sterilization condition by MWP against A. citrulli infected seeds for germination will be conducted in our next study.

• Research in Plant Disease
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• v.21 no.1
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• pp.12-19
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• 2015

Antimicrobial activities of nano-materials were tested against several plant pathogens. Twelve different nano-materials were used to observe the antagonistic activity against three kinds of mold and sixteen different kinds of watermelon fruit rot pathogens (Acidovorax citrulli). According to the results, no antagonism have been found against the pathogen, Cylindrocarpon destructans. However in the case of Pythium ultimum, combination of Brass/Glucose 1,000 ppm confirmed the mycelial growth reduction by 94%. In addition, little effect was found against Rhizoctonia solani by Ag/Glucose 3,000 ppm. The remaining other nano-materials have different antimicrobial effect depending on the strains of A. citrulli. But in the case of lime (Cu/Salt 1,000 ppm) highest antimicrobial activity was observed with 97%. Moreover growth of five different strains of A. citrulli was checked by 99% with the combination of Ag/Glucose 1,000 ppm. 92% reduction of A. citrulli growth was observed with $Brass/CaCO_3$ 3,000 ppm. Tested nano-materials against different plant pathogens in this study showed the antimicrobial activity at the range of 24-70%.

• Research in Plant Disease
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• v.21 no.2
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• pp.82-88
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• 2015

Acidovorax citrulli, the causal agent of bacterial fruit blotch, has caused an economically destructive damage in cucurbits cultivation fields worldwide. To consider more effective disease management, 33 A. citrulli isolates collected from various cucurbits in Korea were analysed by multi-locus phylogeny using five conserved loci(16S rRNA, adk, gltA, glyA, pilT). Two distinct groups (KCC1 and KCC2) in the population were identified on the base of group-specific genetic variation. Out of them, the predominant group was KCC2 and both groups included isolates from melon, cucumber and watermelon. Sixty-four percent of KCC1 isolates were recovered from non-watermelon hosts and seventy-two percent of KCC2 isolates from watermelon. This study presented that there was genetic differentiation among A. citrulli population in Korea. Also, these results will be applied as a very useful data in effective disease management.

• Korean Journal of Organic Agriculture
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• v.23 no.2
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• pp.323-334
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• 2015

This study was conducted to develop environment-friendly agricultural products with anti-microbial activity against Acidovorax avenae subsp. citrulli as a pathogen of bacterial fruit blotch in cucurbit. Schlechtendalia chinensis was extracted by MeOH and solvent fraction. The hexane fraction, which showed highest value of anti-microbial activity, was analyzed by GC-MS. Each mass spectra, corresponding to each peak of chromatogram, was compared to MS database of Wiley library. As a result, myristic acid, palmitic acid and 3-n-pentadecylphenol were identified as maine compounds showing antimicrobial activity against A. avenae subsp. citrulli. Bioassay using commercial myristic acid, palmitic acid and 3-n-pentadecylphenol to test for the anti-microbial activity conformed the anti-microbial activity of potential active compounds, and myristic acid and 3-n-pentadecylphenol showed strong activity. In conclusion, myristic acid and 3-n-pentadecylphenol identified from S. chinensis were anti-microbial chemicals.

• Korean Journal of Organic Agriculture
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• v.23 no.1
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• pp.77-89
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• 2015

133 Species of medicinal plants were used for the development of natural agrichemicals with anti-microbial activity against Acidovorax avenae subsp. citrulli, a pathogen of bacterial fruit blotch in watermelon. The MeOH-extracts of these medicinal plants were examined for anti-microbial activity by bioassay. The MeOH-extract of Citrus unshiu Markovich had the strongest antibacterial activity against Acidovorax avenae subsp. citrulli. To identify anti-microbial compounds from Citrus unshiu Markovich, solvent-fractionation was used. The fraction of hexane, which showing the highest value of anti-microbial activity, was analyzed by GC-MS. Each mass spectra, corresponding to each peak of chromatogram, was compared to mass database of Wiley library. As a result, d-Limonene, ${\gamma}$-terpinene, ${\beta}$-linalool, terpineol, palmitic acid, 9,12-octadecadienoic acid, Linolenic acid, and stigmasterol were identified. Among them, d-Limonene, ${\gamma}$-terpinene, ${\beta}$-linalool, and terpineol confirmed to be shown the anti-microbial activity by bioassay. Especially, d-Limonene and ${\gamma}$-terpinene found to have strong activity. In conclusion, we thought d-limonene and ${\gamma}$-terpinene from Citrus unshiu Markovich. Latin, had anti-microbial activity against Acidovorax avenae subsp. citrulli and could be candidates for the control agents for the control of bacterial fruit blotch in watermelon.

• The Plant Pathology Journal
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• v.37 no.6
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• pp.673-680
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• 2021

Acidovorax citrulli (Ac) is the causative agent of bacterial fruit blotch disease in watermelon. Since resistant cultivars have not yet been developed, the virulence factors/mechanisms of Ac need to be characterized. This study reports the functions of a putative pyridoxal phosphate-dependent aminotransferase (PpdaAc) that transfers amino groups to its substrates and uses pyridoxal phosphate as a coenzyme. It was observed that a ppdaAc knockout mutant had a significantly reduced virulence in watermelon when introduced via germinated-seed inoculation as well as leaf infiltration. Comparative proteomic analysis predicted the cellular mechanisms related to PpdaAc. Apart from causing virulence, the PpdaAc may have significant roles in energy production, cell membrane, motility, chemotaxis, post-translational modifications, and iron-related mechanisms. Therefore, it is postulated that PpdaAc may possess pleiotropic effects. These results provide new insights into the functions of a previously unidentified PpdaAc in Ac.