• Korean Journal of Environmental Agriculture
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• v.30 no.2
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• pp.223-228
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• 2011

BACKGROUND: Rhizosphere bacteria may improve plant growth and productivity both by supply nutrients and hormonal stimulation. Although many experiments have shown improvements in plant growth with inoculation of bacterial cultures to the rhizosphere, the main obstacle in the applications of plant growth promoting rhizobacteria in a large scale is the inconsistency of the results. We tested the growth promoting effects of Azospirillum and Methylobacterium strains on red pepper plant. METHODS AND RESULTS: Red pepper seedlings were grown for 25 days in a growth media inoculated with A. brasilense CW903 or M. oryzae CBMB20. The seedlings were transplanted and grown for 45 days in pots with soil in a greenhouse, at half the recommended level of fertilizer. Bacterial culture, $4.0{\times}10^9$ for A. brasilense CW903 and $5.8{\times}10^8$ CFU for M. oryzae CBMB20, was applied in root zone soil periodically every 10 days during the experiment. Inoculation of M. oryzae CBMB20 significantly increased the red pepper plant growth in terms of leaf number, height and mass of shoot, or root mass compared to uninoculated control plants. Although beneficial effects of A. brasilense on plant growth of many crops were observed, the growthpromoting effect of A. brasilense CW903 on red pepper plant was not found in this study. CONCLUSION(s): The factors responsible for the irregularities in plant growth promoting of rhizobacteria are difficult to elucidate. Extensive inoculation experiments in the greenhouse and in the field should enable us to define the factors critical to obtain successful application of plant growth promoting rhizobacteria.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.4
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• pp.514-521
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• 2010

Fertilizers, plant growth promoting microbes and plant growth regulators should be combined together and used in order to achieve a maximal plant growth and yield in modern sustainable and ecological agricultural systems. In this study rhizosphere inoculation of Methylobacterium oryzae CBMB20 and foliar application of methanol were tested for their ability to promote the growth of red pepper plant at different levels of organic fertilizer. Rhizosphere inoculation of M. oryzae CBMB20 and foliar spray of methanol could promote red pepper plant growth and yield, and the growth promoting effect induced by the combined treatment of M. oryzae CBMB20 inoculation and foliar spray of methanol was more distinctive. This result suggests that a synergistic growth promoting effect of methanol spray and M. oryzae CBMB20 inoculation can be obtained in the combined treatment of the two growth promoting factors. The growth promoting effect was more significant in the lower fertilization rate, and the plant growth was not significantly different between 100 and 300% fertilizer treatments where both M. oryzae CBMB20 inoculation and foliar spray of methanol were included. This result indicates that, with the plant growth promoting effect of M. oryzae CBMB20 and methanol, fertilizer application rate can be profoundly reduced without any significant decreases in biomass accumulation and yield of crops.

• Journal of Microbiology and Biotechnology
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• v.31 no.9
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• pp.1218-1230
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• 2021

Cold-adapted plant growth-promoting bacteria (PGPB) with multiple functions are an important resource for microbial fertilizers with low-temperature application. In this study, culturable cold-adapted PGPB strains with nitrogen fixation and phosphorus solubilization abilities were isolated. They were screened from root and rhizosphere of four dominant grass species in nondegraded alpine grasslands of the Qilian Mountains, China. Their other growth-promoting characteristics, including secretion of indole-3-acetic acid (IAA), production of siderophores and ACC deaminase, and antifungal activity, were further studied by qualitative and quantitative methods. In addition, whether the PGPB strains could still exert plant growth-promoting activity at 4℃ was verified. The results showed that 67 isolates could maintain one or more growth-promoting traits at 4℃, and these isolates were defined as cold-adapted PGPB. They were divided into 8 genera by 16S rRNA gene sequencing and phylogenetic analysis, of which Pseudomonas (64.2%) and Serratia (13.4%) were the common dominant genera, and a few specific genera varied among the plant species. A test-tube culture showed that inoculation of Elymus nutans seedlings with cold-adapted PGPB possessing different functional characteristics had a significant growth-promoting effect under controlled low-temperature conditions, including the development of the roots and aboveground parts. Pearson correlation analysis revealed that different growth-promoting characteristics made different contributions to the development of the roots and aboveground parts. These cold-adapted PGPB can be used as excellent strain resources suitable for the near-natural restoration of degraded alpine grasslands or agriculture stock production in cold areas.

• Journal of Microbiology and Biotechnology
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• v.31 no.3
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• pp.398-407
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• 2021

Using salt-tolerant bacteria to protect plants from salt stress is a promising microbiological treatment strategy for saline-alkali soil improvement. Here, we conducted research on the growth-promoting effect of Brevibacterium frigoritolerans on wheat under salt stress, which has rarely been addressed before. The synergistic effect of B. frigoritolerans combined with representative salt-tolerant bacteria Bacillus velezensis and Bacillus thuringiensis to promote the development of wheat under salt stress was also further studied. Our approach involved two steps: investigation of the plant growth-promoting traits of each strain at six salt stress levels (0, 2, 4, 6, 8, and 10%); examination of the effects of the strains (single or in combination) inoculated on wheat in different salt stress conditions (0, 50, 100, 200, 300, and 400 mM). The experiment of plant growth-promoting traits indicated that among three strains, B. frigoritolerans had the most potential for promoting wheat parameters. In single-strain inoculation, B. frigoritolerans showed the best performance of plant growth promotion. Moreover, a pot experiment proved that the plant growth-promoting potential of co-inoculation with three strains on wheat is better than single-strain inoculation under salt stress condition. Up to now, this is the first report suggesting that B. frigoritolerans has the potential to promote wheat growth under salt stress, especially combined with B. velezensis and B. thuringiensis.

• Journal of Microbiology
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• v.41 no.4
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• pp.271-276
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• 2003

The inoculation of some microorganisms into a microcosm containing soil from a barren lakeside area at Lake Paro in Kangwon-do enhanced plant growth significantly. The direct and viable counts of soil bacteria and soil microbial activities measured by electron transport system assay and fluorescein diacetate hydrolysis assay were higher in inoculated soil. The plant growth promoting effect of this inoculation may be caused by phytohormone production and the solubilization of insoluble phosphates by the inoculated bacteria. Three inoculated strains of Pseudomonas fluorescens produced several plant growth promoting phytohormones, including indole-3-acetic acid (auxin), which was confirmed by thin layer chromatography and GC/MS. P. fluorescens strain B16 and M45 produced 502.4 and 206.1 mg/l of soluble phosphate from Ca3(PO4)2 and hydroxyapatite, respectively. Bacillus megaterium showed similar solubilization rates of insoluble phosphates to those of Pseudomonas spp. We believe that this plant growth promoting capability may be used for the rapid revegetation of barren or disturbed land.

• The Korean Journal of Pesticide Science
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• v.6 no.2
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• pp.64-71
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• 2002

Plant growth promoting activity of quinolinone metabolites, 2-(2-hepteny)-3-methyl-4-quinolinone (1), 2-heptyl-3-methyl-4-quinolinone, and 2-nonyl-3-methyl-4-quinolinone, produced by Pseudomonas cepacia and ethyl 2-methyl-3-alkyl-4-quinolinone carboxylates chemically synthesized were tested by using seed-germination assay, growth increments in plant height after foliar applications. Plant height increment, fresh weight, and the number of fruits were measured after seed-soaking and drench treatment. Compound 1 among the natural products showed a consistent growth promoting effect in seed-germination and plant height after a foliar application. After a seed-soaking and drench treatment, compound 1 and synthetic ethyl 2-methyl-4-quinolinone-3-carboxylate (5) showed a significant enhancement in fresh weight and the number of fruits after harvest. Compound 1 and 5 increased the number of fruits per plant by 44% and 84% over the control, respectively.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.6
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• pp.776-782
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• 2016

Salinity has been a threat to agriculture in some parts of the world; and recently, the threat has grown. Plant growth-promoting rhizobacteria (PGPR) may benefit plant growth, either by improving plant nutrition or producing plant growth hormones. The effects of rhizobacterial strains to attenuate the salinity stress on the germination of Chinese cabbage seeds were tested using four different concentrations of NaCl (50, 100, 150, and 200 mM). Also, PGPR strains were tested to enhance the early germination of Chinese cabbage seeds under normal conditions. Azotobacter chroococcum performed best with enhancing the radicle length of 4.0, 1.2, and 1.0 times at treatments of 50, 100, and 150 mM of NaCl, respectively. Additionally, significant differences were found in plumule length, A. chroococcum and Lactobacillus sp. showed remarkable activation either in normal or under stress conditions. Co-inoculation by three rhizobacterial strains (LAPmix) indicated synergistic effect to enhance the early germination of the seeds. The results of this study are promising for application of rhizobacterial strains that possess plant growth promoting traits to enhance the plant tolerance against salinity.

• KSBB Journal
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• v.31 no.1
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• pp.58-65
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• 2016

In this study, Arthrobacter scleromae SYE-3, which was isolated from indigenous plant in a subtropical region, Neigeria, with plant growth promoting activity was evaluated to determine the optimal culture condition. A bacterial strain SYE-3 had the IAA productivity ($89.15{\pm}0.36mg/L$) and ACC deaminase activity ($0.20{\pm}0.06$ at 72 hours). Also, optimal culture conditions such as temperature and pH of strain SYE-3 were $20^{\circ}C$ and 10 in LB medium, respectively. Strain SYE-3 had up to 3% salt tolerance in the LB medium. Plant growth promoting ability of strain SYE-3 using yam (Dioscorea japonica Thunb.) was evaluated. As a result, strain SYE-3 had showed very powerful effect on the increase of the shoot length and root biomass of yam (190.0% and 282.41% increase for 112 days, respectively). These results indicated that Arthrobacter scleromae SYE-3 can serve as a promising microbial resource for the biofertilizers of subtropical crops.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.1
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• pp.59-65
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• 2012

Plant growth-promoting effects of rhizobacterial inoculation obtained in pot experiments cannot always be dependably reproduced in fields. In this study, we investigated the effect of inoculation with Azospirillum brasilense and Methylobacterium oryzae, which have displayed growth promoting effects in several pot experiments, on growth and fruit yield of red pepper under field condition in a plastic-film house. Four rows spaced 90 cm apart were prepared after application of compost ($10Mg\;ha^{-1}$), and red pepper seedlings (Capsicum annum L., Nocgwang) were transplanted in each row with 40-cm space. Experimental treatments were consisted of A. brasilense CW903 inoculation, M. oryzae CBMB20 inoculation, and uninoculated control. Twelve plots, 10 plants per plot, were allotted to the three treatments with four replicates in a completely randomized design. At the time of transplanting, 50 mL of each inoculum ($1{\times}10^8cells\;mL^{-1}$) was introduced into root zone soil of each plant, and re-inoculated at 7 and 14 days after transplant. Plant growth and fruit yield were measured during the experiment. Both A. brasilense CW903 and M. oryzae CBMB20 could not promote growth of red pepper plants. All growth parameters measured were not significantly different among treatments. There were large variations in fruit yield recorded on plot basis, and no statistically significant differences were found among treatments. The failure to demonstrate the expected plant growth promoting effect of the inoculants is possibly due to various environmental factors, including weather and soil characteristics, reducing the possibility to express the potential of the inoculated bacterial strains.

• Journal of Microbiology
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• v.43 no.6
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• pp.510-515
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• 2005

The growth of red pepper plants was enhanced by treatment with the rhizobacterium, Bacillus cereus MJ-1. Red pepper shoots showed a 1.38-fold increase in fresh weight (fw) and roots showed a 1.28-fold fw gain. This plant growth-promoting rhizobacterium (PGPR) has been reported to produce gibberellins (GAs). Other GAs-producing rhizobacteria, Bacillus macroides CJ-29 and Bacillus pumilus CJ-69, also enhanced the fw of the plants. They were less effective than B. cereus MJ-1, though. The endogenous GAs content of pepper shoots inoculated with MJ-1 was also higher than in shoots inoculated with CJ-29 or CJ-69. When inoculated with MJ-1, bacterial colonization rate of the roots was higher than that of roots inoculated with CJ-29 or CJ-69. These results support the idea that the plant growth-promoting effect of the bacteria also positively related with the efficiency of root colonization by the bacteria. In addition, we identified the major endogenous GAs of the red pepper as originating from both the early C-13 hydroxylation and the early non C-13 hydroxylation pathways, with the latter being the predominant pathway of GA biosynthesis in red pepper shoots.