• The Plant Pathology Journal
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• v.39 no.1
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• pp.108-122
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• 2023

Fusarium oxysporum f. sp. lycopersici (Fol) and Fusarium oxysporum f. sp. cubense (Foc), are the causal agent of Fusarium wilt disease of tomato and banana, respectively, and cause significant yield losses worldwide. A cost-effective measure, such as biological control agents, was used as an alternative method to control these pathogens. Therefore, in this study, six isolates of the Streptomyces-like colony were isolated from soils and their antagonistic activity against phytopathogenic fungi and plant growth-promoting (PGP) activity were assessed. The results showed that these isolates could inhibit the mycelial growth of Fol and Foc. Among them, isolate STRM304 showed the highest percentage of mycelial growth reduction and broad-spectrum antagonistic activity against all tested fungi. In the pot experiment study, the culture filtrate of isolates STRM103 and STRM104 significantly decreased disease severity and symptoms in Fol inoculated plants. Similarly, the culture filtrate of the STRM304 isolate significantly reduced the severity of the disease and symptoms of the disease in Foc inoculated plants. The PGP activity test presents PGP activities, such as indole acetic acid production, phosphate solubilization, starch hydrolysis, lignin hydrolysis, and cellulase activity. Interestingly, the application of the culture filtrate from all isolates increased the percentage of tomato seed germination and stimulated the growth of tomato plants and banana seedlings, increasing the elongation of the shoot and the root and shoot and root weight compared to the control treatment. Therefore, the isolate STRM103 and STRM104, and STRM304 could be used as biocontrol and PGP agents for tomato and banana, respectively, in sustainable agriculture.

• The Plant Pathology Journal
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• v.40 no.3
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• pp.251-260
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• 2024

Flavobacterium is a genus within the phylum Bacteroidota that remains relatively unexplored. Recent analyses of plant microbiota have identified the phylum Bacteroidota as a major bacterial group in the plant rhizosphere. While Flavobacterium species within the phylum Bacteroidota have been recognized as pathogens in the aquatic habitats, microbiome analysis and the characterization of novel Flavobacterium species have indicated the great diversity and potential of their presence in various environments. Many Flavobacterium species have positively contribute to plant health and development, including growth promotion, disease control, and tolerance to abiotic stress. Despite the well-described beneficial interactions of the Flavobacterium species with plants, the molecular mechanisms and bacterial determinants underlying these interactions remain unclear. To broaden our understanding of the genus Flavobacterium's role in plant health, we review the recent studies focusing on their ecological niche, functional roles, and determinants in plant-beneficial interactions. Additionally, this review discusses putative mechanisms explaining the interactions between plants and Flavobacterium. We have also introduced the importance of future research on Flavobacterium spp. and its potential applications in agriculture.

• The Korean Journal of Pesticide Science
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• v.13 no.4
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• pp.275-282
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• 2009

The effect of two plant growth-promoting rhizobacteria (PGPR) on plant growth and systemic protection against soft rot disease and stem rot disease of canola (Brassica napus), caused by Erwinia carotovora and Sclerotinia sclerotiorum was investigated in a laboratory and a greenhouse. Selected PGPR strains C4 and D8 were treated to canola seeds by soaking. Strains C4 and D8 significantly not only increased plant height and root length about 74% and 40.3% and also reduced disease severity of soft rot disease by 80% by C4 and D8 respectively, compared to the control. Especially strain C4 showed antifungal activity against 6 fungal pathogens, S. sclerotiorum, Rhizoctonia solani, Botrytis cinerea, Fusarium oxysporum, Phytophthora capsici and Colletotrichum acutatum. In greenhouse experiment, the seed treatment of both of them increased plant height, leaf width and leaf length of canola plant to 19.5% and 24.9%, 11.3% and 15.3%, and 14.1% and 20.7% by C4 and D8, respectively, and reduced disease severity of S. sclerotiorium. These results indicate that these two PGPR strains can decrease disease severity and increased plant growth under greenhouse condition. Therefore, these two bacteria have a potential in controlling Sclerotinia stem rot of canola. These strains have to investigate under field condition to determine their role of antibiosis, induced systemic resistance and plant growth promotion on canola.

• Journal of Life Science
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• v.15 no.1 s.68
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• pp.112-117
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• 2005

Plants living riverside show diverse resistance responses to submergence. The promoted petiole elongation of semi-aquaitc plants, e.g., such as Ranunculus sceleratus and Rumex palustris, is one of the adaptive responses mediated by the plant hormone ethylene. The gaseous hormone is trapped in submerged plant tissues and enhances the petiole growth by increasing sensitivity of the tissues to some plant hormones including auxin. Due to the stimulated growth of petioles, the leaves finally reach the water surface and can respirate again. At the water surface, the accumulated ethylene diffuses out from the tissues to the air. As a result, the increased hormone sensitivity decreases again, and thus the growth rate reduces to the basal level as before. The increased auxin sensitivities by ethylene observed in Ranunculus sceleratus, revealed by the changes in the auxin dose-response curves, indicate the increase of affinities of the receptors to auxin. However, the molecular mechanism of the affinity regulation remains still largely unknown, because the identity of the auxin receptor is still unclear.

• Journal of Microbiology and Biotechnology
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• v.20 no.11
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• pp.1491-1499
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• 2010

Rhizosphere microorganisms possessing phytase activity are considered important for rendering phytate-phosphorus (P) available to plants. In the present study, the Citrobacter braakii phytase gene (appA) was overexpressed in rhizobacteria possessing plant growth promoting (PGP) traits, for increasing their potential as bioinoculants. AppA was cloned under the lac promoter in the broadhost-range expression vector pBBR1MCS-2. Transformation of the recombinant construct pCBappA resulted in high constitutive phytase activity in all of the eight rhizobacterial strains belonging to genera Pantoea, Citrobacter, Enterobacter, Pseudomonas (two strains), Rhizobium (two strains), and Ensifer that were studied. Transgenic rhizobacterial strains were found to display varying levels of phytase activity, ranging from 10-folds to 538-folds higher than the corresponding control strains. The transgenic derivative of Pseudomonas fluorescens CHA0, a well-characterized plant growth promoting rhizobacterium, showed the highest expression of phytase (~8 U/mg) activity in crude extracts. Although all transformants showed high phytase activity, rhizobacteria having the ability to secrete organic acid showed significantly higher release of P from Ca-phytate in buffered minimal media. AppA overexpressing rhizobacteria showed increased P content, and dry weight (shoot) or shoot/ root ratio of mung bean (Vigna radiata) plants, to different extents, when grown in semisolid agar (SSA) medium containing Na-phytate or Ca-phytate as the P sources. This is the first report of the overexpression of phytase in rhizobacterial strains and its exploitation for plant growth enhancement.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.4
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• pp.625-636
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• 2011

Cold-adapted bacteria survive in extremely cold temperature conditions and exhibit various mechanisms of adaptation to sustain their regular metabolic functions. These adaptations include several physiological and metabolic changes that assist growth in a myriad of ways. Successfully sensing of the drop in temperature in these bacteria is followed by responses which include changes in the outer cell membrane to changes in the central nucleoid of the cell. Their survival is facilitated through many ways such as synthesis of cryoprotectants, cold acclimation proteins, cold shock proteins, RNA degradosomes, Antifreeze proteins and ice nucleators. Agricultural productivity in cereals and legumes under low temperature is influenced by several cold adopted bacteria including Pseudomonas, Acinetobacter, Burkholderia, Exiguobacterium, Pantoea, Rahnella, Rhodococcus and Serratia. They use plant growth promotion mechanisms including production of IAA, HCN, and ACC deaminase, phosphate solublization and biocontrol against plant pathogens such as Alternaria, Fusarium, Sclerotium, Rhizoctonia and Pythium.

• Korean Journal of Microbiology
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• v.53 no.4
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• pp.351-353
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• 2017

Chryseobacterium sp. strain T16E-39, isolated from roots of a tomato plant, promotes plant growth and suppresses phytophthora blight and bacterial wilt diseases. The complete genome of strain T16E-39 consists of a circular chromosome with 4,872,888 base pairs with a G + C content of 35.22%. The genome includes 4,289 coding sequences, 15 rRNAs, and 71 tRNAs. We detected genes involved in phosphate solubilization, phytohormone regulation, antioxidant activity, chitin degradation, and the type IX secretion system (T9SS) that may be related to growth promotion and disease suppression in plants.

• The Plant Pathology Journal
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• v.31 no.3
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• pp.259-268
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• 2015

This study investigated the chemical characteristics and microbial population during incubation of four kinds of aerated compost teas based on oriental medicinal herbs compost, vermicompost, rice straw compost, and mixtures of three composts (MOVR). It aimed to determine the effects of the aerated compost tea (ACT) based on MOVR on the growth promotion of red leaf lettuce, soybean and sweet corn. Findings showed that the pH level and EC of the compost tea slightly increased based on the incubation time except for rice straw compost tea. All compost teas except for oriental medicinal herbs and rice straw compost tea contained more ${NO^-}_3-N$ than ${NH^+}_4-N$. Plate counts of bacteria and fungi were significantly higher than the initial compost in ACT. Microbial communities of all ACT were predominantly bacteria. The dominant bacterial genera were analyzed as Bacillus (63.0%), Ochrobactrum (13.0%), Spingomonas (6.0%) and uncultured bacterium (4.0%) by 16S rDNA analysis. The effect of four concentrations, 0.1%, 0.2%, 0.4% and 0.8% MOVR on the growth of red leaf lettuce, soybean and sweet corn was also studied in the greenhouse. The red leaf lettuce with 0.4% MOVR had the most effective concentration on growth parameters in foliage part. However, 0.8% MOVR significantly promoted the growth of root and shoot of both soybean and sweet corn. The soybean treated with higher MOVR concentration was more effective in increasing the root nodule formation by 7.25 times than in the lower MOVR concentrations Results indicated that ACT could be used as liquid nutrient fertilizer with active microorganisms for culture of variable crops under organic farming condition.

• Journal of Life Science
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• v.18 no.10
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• pp.1355-1359
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• 2008

Endophytic fungi predominantly inhabit grasses, and produce a variety of beneficial metabolites for plant growth, as well as help their hosts against pathogens and herbivores. Current study was focused on plant growth promoting activity of endophytic fungi inhabited in the roots of sand dune grasses. We collected 49 fungal isolates from the roots of four most common sand dune grasses and screened them for their growth promoting capacity. Results showed that 37 fungal isolates (75.5%) promoted plant height and shoot length of waito-c rice, 11 fungal isolates (22.5%) suppressed it, while 1 fungus (2%) showed no effect on the growth attributes. The fungal strain Gibberella fujikuroi, along with distilled water and Czapek broth medium, were taken as control for this experiment. It was concluded that a major proportion of endophytic fungi inhabited in the sand dune plants produce metabolites, and thus help in growth and development of the host plant.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.4
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• pp.506-513
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• 2010

Plant growth promoting ability of Methylobacterium oryzae CBMB20 was evaluated under different levels of organic fertilizer application on red pepper plants in a pot experiment. Oil cake as an organic N fertilizer was applied at the rates of 70, 85, 100 and 120% of the conventional recommended level. Each treatment was further treated with or without M. oryzae CBMB20 inoculation. The recommended amount of compost for red pepper was added in all the treatments. Results revealed that plant height, dry biomass and fruit yield were enhanced in increasing order as the rate of fertilization increased. Overall plant growth was improved due to the inoculation of M. oryzae CBMB20 and red pepper fruit yield was also increased by 10-35% in the plants inoculated with M. oryzae CBMB20 at different rates of organic fert1izer application. Total methylotrophic bacterial population in rhizosphere soil measured at the time of harvest was significantly higher in M. oryzae CBMB20 inoculated treatments. The growth promoting effect of M. oryzae CBMB20 found in red pepper could be due to the effective colonization of the bacteria in the rhizosphere and its ability of enhancing nutrient availability and producing plant growth hormones. With the plant growth promoting effect of M. oryzae CBMB20, the rate of organic fertilizer application can be reduced without any significant decreases in biomass production and yield of red pepper.