• Microbiology and Biotechnology Letters
• /
• v.47 no.3
• /
• pp.390-400
• /
• 2019

In this study, strains isolated from soil samples collected from Busan, Changwon, and Jeju Island were examined to verify their abilities of phosphate solubilization and nitrogen fixation, production of indole-3-acetic acid (IAA), siderophore, and 1-aminocylopropane-1-carboxylyic acid (ACC) deaminase in order to select strains that promote plant growth and play a role in biocontrol of pests or pathogens. According to the results of this study, most of the isolated strains were found to have ability of phosphate solubilization, nitrogen fixation, IAA production, siderophore production, and production of ACC deaminase. These isolated strains might help plant growth by directly improving absorption of nutrients essential for phosphate solubilization and nitrogen fixation. In addition, they can promote plant growth and control resistance to plant diseases through extracellular enzyme activity and antifungal activity. In addition, most of the selected strains were found to survive in various environmental conditions such as temperature, salinity, and pH. Therefore, Pseudomonas plecoglossicida ANG14, Pseudarthrobacter equi ANG28, Beijerinckia fluminensis ANG34, and Acinetobacter calcoaceticus ANG35 were finally selected through a comparative advantage analysis to suggest their potential as novel biological agents. Further studies are necessary in order to prove their efficacy as novel biological agents through formulation and optimization of effective microorganisms, their preservation period, and crop cultivation tests.

• Research in Plant Disease
• /
• v.28 no.3
• /
• pp.122-131
• /
• 2022

Colletotrichum acutatum s. lat. 20JDS8 sensitive and 20CDJ6 resistant to pylaclostrobin were used to investigate the cross-resistance with fungicides belonging to the strobilurins and the characteristics of fungicidal controlling activities with different mechanisms against the isolate resistant to the fungicide. The resistant isolate of 20CDJ6 also showed the resistance to azoxystrobin, trifloxystrobin, and kresoxim-methyl, suggesting that there is a cross-resistance relationship. All fungicides with different action mechanisms inhibited mycelial growth of both susceptible and resistant isolates of C. acutatum s. lat., but their disease control effects in fruits were different according to the fungicides. The disease control effect of isopyrazam against 20JDS8 and 20CDJ6 was very low, and fluazinam showed a control effect of 91.9% and 88.1% against 20JDS8 and 20CDJ6 only when it was treated before inoculation by spraying spore suspensions on pepper fruits without wounds. Tebuconazole and prochloraz effectively inhibited not only the mycelial growth of 20JDS8 and 20CDJ6 on potato dextrose agar medium, but also disease incidence in red pepper fruits. As a result of this study, C. acutatum s. lat. 20CDJ6 resistant to pyraclostrobin showed cross-resistance with other strobilurin fungicides. In addition, we think that fluazinam, tebuconazole, and prochloraz can be recommended as alternative fungicides for the control of red-pepper pyranthracnose pathogens resistant pyraclostrobin. However, fluazinam can be effective only if it is treated protectively before the occurrence of the disease.

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

• Research in Plant Disease
• /
• v.14 no.1
• /
• pp.21-25
• /
• 2008

This study was conducted to decide disease incidence level of rice leaf blast required for reasonable fungicide application in paddy field. We induced the disease development by inoculating rice blast pathogens on rice seedlings (Jinmibyeo) in the greenhouse and transplanting the infected seedlings in the field two weeks after rice plants were transplanted. We scored the disease incidence, grouped and marked according to degree of percentage of diseased leaf area at maximum stage of disease development. The percent diseased leaf area (PDLA) had negative correlations with panicle number per hill, ripened grain (%), and total yield; their correlation coefficients (r), $-0.97^{**}$, $-1.00^{**}$ and $-0.96^{**}$, respectively. However, it had positive correlations with spikelets per panicle and thousand grain weight; their correlation coefficients (r), $0.98^{**}$ and $0.98^{**}$, respectively. Gain threshold (GT) calculated based on control cost and market price was estimated to be 8.35. Economic injury level (EIL) obtained based on GT and coefficient of damage of regression equation between disease incidence and the different yield components; panicle number per hill, spikelets per panical, ripened grain(%), thousand grain weight and yield were 41.8, 9.7, 19.1, 291.1 and 3.4%, respectively. Economic threshold (ET) for yield was 2.7% ($3.4%(EIL){\times}0.8$) on PDLA. These results suggest that application of fungicide is necessary when two under leaves are almost covered with lesions or contained more than twenty large lesions under leaves at maximum tillering stage.

• Journal of Life Science
• /
• v.27 no.6
• /
• pp.652-660
• /
• 2017

Fermented medical herbs using Lactobacilli have attracted significant attention due to their enhanced biological activities. A traditional medicinal plant, Artemisia annua L., was fermented using a probiotic strain, L. plantarum SK3494. The strain was isolated from Artemisia princeps var. orientalis and molecularly identified through sequence similarities and phylogenetic tree analysis. The antioxidant activity of L. plantarum-fermented A. annua L. (LFA) was determined using the DPPH free radical scavenging assay. Cellular antioxidant activity of LFA was examined using the superoxide radical reduction assay in MAT-C cells. Total polyphenol contents (TPC) and flavonoid contents (TFC) of LFA were determined. The antibacterial activity of LFA against fish pathogens was also determined in this study. The viable cell number (9.38 log10 CFU/ml) and pH (4.1) results showed good adaptive ability of the selected strain during fermentation. LFA was found to have enhanced antioxidant activity compared to non-fermented A. annua L. (NFA) based on the DPPH assay. Cellular antioxidant activity was present in both LFA and NFA. After 24 hr and 48 hr of fermentation, the LFA also showed antibacterial activities against fish pathogens Photobacterium damselae subsp. damselae and Vibrio ichthyoenteri. These results suggest that L. plantarum-fermented A. annua L. may have potential as a feed additive in aquaculture.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.17 no.4
• /
• pp.112-121
• /
• 2009

To obtain basic design criteria for underground anaerobic digestion and enhance biogas production from swine slurry, a $20m^3$ underground anaerobic digester (UGAD) was constructed and operated at mesophilic ($31{\sim}37^{\circ}C$) temperature with an organic loading rate (OLR) at $23.6kgVS/m^3/day$. The average biogas and $CH_4$ production rate were observed at 8.62 and $5.78m^3/day$, respectively. The mean percentile of $CH_4$ and $CO_2$ were also observed at 67.5% and 19.6%. The relative biogas yield was explored at $733L/kg\;VS_{added}$ and $CH_4$ yield was at $495L/kg\;VS_{added}$ respectively. The removal rate of biochemical constituents and pathogens were noticed considerably at 68%, 74%, 79%, 86%, 89%, 81%, 55%, 79%, 98% and 100% on TS, VS, TSS, $BOD_5$, $TCOD_{cr}$, $SCOD_{cr}$, $NH_3-N$, available P, fecal coliforms and Salmonella, respectively. This study suggested that, the modified UGAD system is a greatly desirable for anaerobic digestion for swine slurry with regards to high methane yield and biodegradability.

• Microbiology and Biotechnology Letters
• /
• v.33 no.2
• /
• pp.123-129
• /
• 2005

Isolation and identification of pathogens from slaughter and meat processing plant were investigated. Antimicrobial activity of Amaranthus lividus against isolated pathogens such as Aeromonas sobria, Escherichia coli, Escherichia coli O157, Listeria monocytogenes, Salmonella spp., and Staphylococcus aureus was investigated. Among the chloroform, ethyl acetate and buthanol fraction of amaranthus lividus showed inhibitory effect against Aeromonas sobria CLFM1 and Escherichia coli CLFM2. Antimicrobial substance in chloroform fraction was isolated by silica gel adsorption column chromatography, sephadex LH-20 column chromatography and silica gel partition column chromatography. The antimicrobial compound of amaranthus lividus was identified as diethyl phtalate by HPLC, GC-MS, H-NMR and C-NMR.

• 한국균학회소식:학술대회논문집
• /
• 2014.10a
• /
• pp.11-11
• /
• 2014

Fungal pathogens have huge impact on health and economic wellbeing of human by causing life-threatening mycoses in immune-compromised patients or by destroying crop plants. A key determinant of fungal pathogenesis is their ability to undergo developmental change in response to host or environmental factors. Genetic pathways that regulate such morphological transitions and adaptation are therefore extensively studied during the last few decades. Given that epigenetic as well as genetic components play pivotal roles in development of plants and mammals, contribution of microbial epigenetic counterparts to this morphogenetic process is intriguing yet nearly unappreciated question to date. To bridge this gap in our knowledge, we set out to investigate histone modifications among epigenetic mechanisms that possibly regulate fungal adaptation and processes involved in pathogenesis of a model plant pathogenic fungus, Magnaporthe oryzae. M. oryzae is a causal agent of rice blast disease, which destroys 10 to 30% of the rice crop annually. Since the rice is the staple food for more than half of human population, the disease is a major threat to global food security. In addition to the socioeconomic impact of the disease it causes, the fungus is genetically tractable and can undergo well-defined morphological transitions including asexual spore production and appressorium (a specialized infection structure) formation in vitro, making it a model to study fungal development and pathogenicity. For functional and comparative analysis of histone modifications, a web-based database (dbHiMo) was constructed to archive and analyze histone modifying enzymes from eukaryotic species whose genome sequences are available. Histone modifying enzymes were identified applying a search pipeline built upon profile hidden Markov model (HMM) to proteomes. The database incorporates 22,169 histone-modifying enzymes identified from 342 species including 214 fungal, 33 plants, and 77 metazoan species. The dbHiMo provides users with web-based personalized data browsing and analysis tools, supporting comparative and evolutionary genomics. Based on the database entries, functional analysis of genes encoding histone acetyltransferases and histone demethylases is under way. Here I provide examples of such analyses that show how histone acetylation and methylation is implicated in regulating important aspects of fungal pathogenesis. Current analysis of histone modifying enzymes will be followed by ChIP-Seq and RNA-seq experiments to pinpoint the genes that are controlled by particular histone modifications. We anticipate that our work will provide not only the significant advances in our understanding of epigenetic mechanisms operating in microbial eukaryotes but also basis to expand our perspective on regulation of development in fungal pathogens.

• The Korean Journal of Mycology
• /
• v.46 no.4
• /
• pp.393-403
• /
• 2018

Bio-aerosols transported by the air have been considered as the major source of dispersal agents that contaminate agricultural products. Unseen fungal spores are known sources of bio-aerosols that harm mushroom and human health during mushroom cultivation. This study was conducted to obtain basic data on the concentration and species distribution of fungi present in the indoor air of oak mushroom cultivation houses in Korea. In 2015 and 2016, we sampled and analyzed indoor airborne fungal spores 21 times from 13 oak mushroom cultivation farms located in six different provinces. The concentration of airborne fungi ranged from $1.30{\times}10^2$ to $1.59{\times}10^4cfu/m^3$. Surprisingly, in 20 sampling cases, the fungal concentration exceeded $500cfu/m^3$, which is recommended as the indoor air quality standard by the Ministry of Environment, Korea. A total of 450 fungi were isolated and identified to belong to 33 genera and 46 species. Among the identified fungi, human pathogens (4 genera and 4 species) and plant pathogens (10 genera and 13 species) were present. In addition, Trichoderma harzianum, Trichoderma atroviride, and Trichoderma longibrachiatum, which are detrimental species that affect mushroom health, were found 17 out of 21 sampling times. Our results provide evidence that indoor air quality should be improved for better management of mushroom cultivation houses.

• Research in Plant Disease
• /
• v.11 no.1
• /
• pp.28-34
• /
• 2005

This study was conducted to investigate the control possibility of garlic white rot causing severe yield losses of Allium species and cultivars using cultural practices such as optimal sowing date and burial depth, and lime application. Inoculum density in infested field soil was investigated at different soil depth, and that on the diseased plant debris was done. Inoculum density and recovery ratio of white rot pathogen of garlic was highly different between two species of Sclerotium cepivorum forming comparatively small sclerotia and Sclerotium sp. forming comparatively large ones. It was confirmed that S. cepivorum formed more sclerotia on bulbs of garlic than S. sp., and sclerotial recovery of S. cepivorum was higher than that of S. sp. Inoculum density of white rot pathogen in the infested field at garlic seeding period ranged from one to thirteen sclerotia per 30 g soil. Inoculum density of white rot pathogen decreased remarkably with increasing soil depth and above 95% of sclerotia were distributed within 5 cm of soil depth. Disease severity of white rot was higher on slightly planted garlics than deeply-planted ones. Garlic seed bulbs infected by white rot pathogens were confirmed to be one of main inoculum sources of white rot in the field and the disease incidences caused by garlic seed transmission showed big differences among garlic varieties. When nine garlic varieties harvested from infested plots were sown in the field, highly susceptible varieties, ‘Wando’, ‘Daeseo’, ‘Namdo’ and ‘Kodang’ showed high disease incidences, whereas other five varieties were not infected at all. It was confirmed that white rot occurred higher on early-sown garlics, before middle October, than on late-sown ones, after late October. Meanwhile, increasing application rate of lime ranged from 100 to 300 g reduced disease severity of white rot.