• International Journal of Industrial Entomology and Biomaterials
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• v.31 no.2
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• pp.107-114
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• 2015

Endophytes provide multifarious benefits such as promotion of plant growth and yield, suppression of phyto-pathogens, phosphate solubilising and fixation nitrogen. A study has been carried out to explore growth promotion and antifungal activities of endophytes of mulberry (Morus spp.). Endophytic bacteria were isolated from mulberry plants and studied their cultural, morphological characters, growth promotion as well as their antifungal activity against Rhizoctonia bataticola and Fusarium oxysporum , two mulberry root rot associated pathogens. Except two isolates, all bacteria were colourless and the colony size of eight isolates was small. The margin of five isolates was irregular and the consistency of three isolates was creamy, six isolates was slimy and one was mucoid. Texture of seven isolates was convex and others were flat. Eight isolates were gram positive and the rest Gram negative, five were cocci and others were bacilli (rod shaped). Four isolates were motile and all were catalase positive and only three isolates were oxidase positive. Spore staining was positive only for two isolates. The growth promotion study showed that there was significant difference in root length and seedling length. The antagonistic effect of the bacterial isolates was tested against R. bataticola showed significant (p <0.05) influence of the bacteria, days after inoculation and their interaction on the inhibition of fungal growth. The isolate En-7 completely inhibited the fungus followed by En-5 (66.67%). The bacterial isolates significantly (p <0.05) inhibited growth of F. oxysporum in PDA. The mean inhibition was higher (70.45%) in case of En-7 followed by En-8 (68.65%) and En-10 (66.44%). The study reveals that some endophytic bacteria associated with mulberry have growth promotion and antifungal activity and could be explored for promotion of mulberry growth and managing root rot disease.

• Journal of Microbiology and Biotechnology
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• v.25 no.6
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• pp.903-909
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• 2015

Indole-3-acetic acid (IAA) production is a typical mechanism of plant growth promotion by some rhizobacteria. However, a functional genomic study is necessary to unravel the function and mechanism of IAA signaling during rhizobacteria-plant interactions. In this study, the expression of SlIAA1 and SlIAA9 among the auxin response genes in tomato was examined during the interaction between IAA-producing Acinetobacter guillouiae SW5 and tomato plants. When 3-day grown tomato seedlings were treated for 30 min with 10~100 µM of IAA produced by bacteria from tryptophan, the relative mRNA levels of SlIAA1 and SlIAA9 increased significantly compared with those of the control, demonstrating that IAA produced by this bacterium can induce the expressions of both genes. Inoculation of live A. guillouiae SW5 to tomato seedlings also increased the expressions of SlIAA1 and SlIAA9, with more mRNA produced at higher bacterial density. In contrast, treatment of tomato seedlings with dead A. guillouiae SW5 did not significantly affect the expression of SlIAA1and SlIAA9. When 3-day bacterial culture in tomato root exudates was administered to tomato seedlings, the relative mRNA level of SlIAA1 increased. This result indicated that the plant may take up IAA produced by bacteria in plant root exudates, which may increase the expression of the auxin response genes, with resulting promotion of plant growth.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.47 no.3
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• pp.161-166
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• 2002

The ultrastructural characteristics of epidermis isolated from healthy and rusty ginseng roots(Panax ginseng) were observed by scanning electron microscopy (SEM), and the distribution profiles of inorganic elements were also examined by energy dispersive X-ray analysis (EDX). The epidermis of rusty ginseng was thick and cell walls were also severely disrupted whereas the epidermal image of healthy ginseng showed relatively thin, clear and rectangular structure. A high amount of rod-shaped bacteria was found in rusty ginseng and cells near bacteria were degraded. The bacterial density in epidermis of rusty ginseng was ranged from 2.9$\times$10$^{6}$ to 3.5 $\times$ 10$^{7}$ CFU/g fresh weight, while that of healthy ones was from 4.7$\times$10$^2$ to 1.2$\times$10$^3$CFU/g. Artificial inoculation of bacteria isolated from rusty ginseng induced similar symptom like rusty ginseng. The mineral contents inculding Al, Si and Fe were Higher in the epidermis of rusty ginseng, but K content was lower compared to healthy ones.

• Journal of Crop Science and Biotechnology
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• v.10 no.3
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• pp.147-158
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• 2007

Xanthomonas axonopodis pv. glycines(Xag) is a pathogen that causes bacterial leaf pustule(BLP) disease in soybeans grown in Korea and the southern United States. Typical and early symptoms of the disease are small, yellow to brown lesions with raised pustules that develop into large necrotic lesions leading to a substantial loss in yield due to premature defoliation. After Xag infects PI 96188, only pustules without chlorotic haloes were observed, indicating the different response to Xag. To identify differentially expressed genes prior to and 24 hr after Xag inoculation to PI 96188 and BLP-resistant SS2-2, an oligonucleotide macroarray was constructed with 100 genes related to disease resistance and metabolism from soybean and Arabidopsis. After cDNAs from each genotype were applied on the oligonucleotide macroarrays with three replicates and dye swapping, 36 and 81 genes were expressed as significantly different between 0 hr and 24 hr in PI 96188 and SS2-2, respectively. Six UniGenes, such as the leucine-rich repeat protein precursor or 14-3-3-like protein, were selected because they down-regulated in PI 96188 and up-regulated in SS2-2 after Xag infection, simultaneously. Using tubulin and cDNA of Jangyeobkong(BLP-susceptible) as controls, the oligonucleotide macroarray data concurred with quantitative real-time RT-PCR(QRT RT-PCR) results in most cases, supporting the accuracy of the oligonucleotide macroarray experiments. Also, QRT RT-PCR data suggested six candidate genes that might be involved in a necrotic response to Xag in PI 96188.

• The Plant Pathology Journal
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• v.36 no.2
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• pp.148-156
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• 2020

Pseudomonas syringae pv. tabaci 6605 has two multidrug resistance (MDR) efflux pump transporters, MexAB-OprM and MexEF-OprN. To understand the role of these MDR efflux pumps in virulence, we generated deletion mutants, ΔmexB, ΔmexF, and ΔmexBΔmexF, and investigated their sensitivity to plant-derived antimicrobial compounds, antibiotics, and virulence. Growth inhibition assays with KB soft agar plate showed that growth of the wild-type (WT) was inhibited by 5 μl of 1 M catechol and 1 M coumarin but not by other plant-derived potential antimicrobial compounds tested including phytoalexins. The sensitivity to these compounds tended to increase in ΔmexB and ΔmexBΔmexF mutants. The ΔmexBΔmexF mutant was also sensitive to 2 M acetovanillone. The mexAB-oprM was constitutively expressed, and activated in the ΔmexF and ΔmexBΔmexF mutant strains. The swarming and swimming motilities were impaired in ΔmexF and ΔmexBΔmexF mutants. The flood inoculation test indicated that bacterial populations in all mutant strains were significantly lower than that of WT, although all mutants and WT caused similar disease symptoms. These results indicate that MexAB-OprM extrudes plant-derived catechol, acetovanillone, or coumarin, and contributes to bacterial virulence. Furthermore, MexAB-OprM and MexEF-OprN complemented each other's functions to some extent.

• The Plant Pathology Journal
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• v.29 no.2
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• pp.168-173
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• 2013

Apple ring rot disease, caused by Botryosphaeria dothidea (Moug. ex. Fr) Ces. et de Not., is one of the most important diseases on apple fruits. In this study, strain 9001 isolated from healthy apple fruits from an infested orchard was evaluated for its biocontrol activity against apple ring rot in vitro and in vivo. Strain 9001 showed obvious antagonistic activity to B. dothidea YL-1 when plated on potato dextrose agar. Soaking healthy apples in the bacterial suspensions of strain 9001 prior to artificial inoculation of fungal pathogen resulted in a dramatic decrease in disease incidence when compared to the control. Moreover, either field application in the growth season or postharvest treatment of apples from infected orchards with bacterial suspensions of strain 9001 resulted in significantly reduced disease incidence within the storage period for 4 months at room temperature. Based on the phylogenetic analysis of 16S rRNA and the gyrA gene, strain 9001 was identified as Bacillus amyloliquefaciens. These results indicated that B. amyloliquefaciens 9001 could be a promising agent in biocontrol of apple ring rot on fruit, which might help to minimize the yield loss of apple fruit during the long postharvest period.

• Journal of Microbiology and Biotechnology
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• v.20 no.12
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• pp.1605-1613
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• 2010

Twenty-nine P. polymyxa strains isolated from rhizospheres of various crops were clustered into five genotypic groups on the basis of BOX-PCR analysis. The characteristics of several plant growth-promoting factors among the isolates revealed the distinct attributes in each allocated group. Under gnotobiotic conditions, inoculation of pepper roots with P. polymyxa isolates significantly increased the biomass in 17 of total 29 treated plants with untreated plants. Experiments on induced systemic resistance (ISR) against bacterial spot pathogen Xanthomonas axonopodis pv. vesicatoria in pepper by P. polymyxa strains were conducted and only one isolate (KNUC265) was selected. Further studies into ISR mediation by the KNUC265 strain against the soft-rot pathogen Erwinia carotovora subsp. carotovora in tobacco demonstrated that the tobacco seedlings exposed to either bacterial volatiles or diffusible metabolites exhibited a reduction in disease severity. In conclusion, ISR and plant growth promotion triggered by P. polymyxa isolates were systemically investigated on pepper for the first time. The P. polymyxa KNUC265 strain, which elicited both ISR and plant growth promotion, could be potentially used in improving the yield of pepper and possibly of other crops.

• Journal of Microbiology and Biotechnology
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• v.29 no.7
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• pp.1096-1103
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• 2019

UCB-1 is the commercial rootstock of pistachio. Reproduction of this rootstock by tissue culture is limited by low levels of proliferation rate. Therefore, any compound that improves the proliferation rate and the quality of the shoots can be used in the process of commercial reproduction of this rootstock. Use of plant growth-promoting bacteria is one of the best ideas. Given the beneficial effects of nanoparticles in enhancement of the growth in plant tissue cultures, the aim of the present study was to investigate the effects of nanoencapsulation of plant growth-promoting rhizobacteria (using silica nanoparticles and carbon nanotubes) and their metabolites in improving UCB1 pistachio micropropagation. The experiment was conducted in a completely randomized design with three replications. Before planting, treatments on the DKW medium were added. The results showed that the use of Pseudomonas fluorescens VUPF5 and Bacillus subtilis VRU1 nanocapsules significantly enhanced the root length and proliferation. The nanoformulation of the VUPF5 metabolite led to the highest root length (6.26 cm) and the largest shoot (3.34 cm). Inoculation of explants with the formulation of the metabolites (both bacterial strains) significantly elevated the average shoot length and the fresh weight of plant compared to the control. The explants were dried completely using both bacterial strains directly and with capsule coating after the three days.

• Mycobiology
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• v.47 no.2
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• pp.180-190
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• 2019

In this study, eight-month-old ectomycorrhizae of Tuber borchii with Corylus avellana were synthesized to explore the influence of T. borchii colonization on the soil properties and the microbial communities associated with C. avellana during the early symbiotic stage. The results showed that the bacterial richness and diversity in the ectomycorrhizae were significantly higher than those in the control roots, whereas the fungal diversity was not changed in response to T. borchii colonization. Tuber was the dominant taxon (82.97%) in ectomycorrhizae. Some pathogenic fungi, including Ilyonectria and Podospora, and other competitive mycorrhizal fungi, such as Hymenochaete, had significantly lower abundance in the T. borchii inoculation treatment. It was found that the ectomycorrhizae of C. avellana contained some more abundant bacterial genera (e.g., Rhizobium, Pedomicrobium, Ilumatobacter, Streptomyces, and Geobacillus) and fungal genera (e.g., Trechispora and Humicola) than the control roots. The properties of rhizosphere soils were also changed by T. borchii colonization, like available nitrogen, available phosphorus and exchangeable magnesium, which indicated a feedback effect of mycorrhizal synthesis on soil properties. Overall, this work highlighted the interactions between the symbionts and the microbes present in the host, which shed light on our understanding of the ecological functions of T. borchii and facilitate its commercial cultivation.

• The Plant Pathology Journal
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• v.38 no.6
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• pp.603-615
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• 2022

Soybean (Glycine max (L) Merr.) provides plant-derived proteins, soy vegetable oils, and various beneficial metabolites to humans and livestock. The importance of soybean is highly underlined, especially when carbon-negative sustainable agriculture is noticeable. However, many diseases by pests and pathogens threaten sustainable soybean production. Therefore, understanding molecular interaction between diverse cultivated varieties and pathogens is essential to developing disease-resistant soybean plants. Here, we established a pathosystem of the Korean domestic cultivar Kwangan against Pseudomonas syringae pv. syringae B728a. This bacterial strain caused apparent disease symptoms and grew well in trifoliate leaves of soybean plants. To examine the disease susceptibility of the cultivar, we analyzed transcriptional changes in soybean leaves on day 5 after P. syringae pv. syringae B728a infection. About 8,900 and 7,780 differentially expressed genes (DEGs) were identified in this study, and significant proportions of DEGs were engaged in various primary and secondary metabolisms. On the other hand, soybean orthologs to well-known plant immune-related genes, especially in plant hormone signal transduction, mitogen-activated protein kinase signaling, and plant-pathogen interaction, were mainly reduced in transcript levels at 5 days post inoculation. These findings present the feature of the compatible interaction between cultivar Kwangan and P. syringae pv. syringae B728a, as a hemibiotroph, at the late infection phase. Collectively, we propose that P. syringae pv. syringae B728a successfully inhibits plant immune response in susceptible plants and deregulates host metabolic processes for their colonization and proliferation, whereas host plants employ diverse metabolites to protect themselves against infection with the hemibiotrophic pathogen at the late infection phase.