• The Plant Pathology Journal
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• v.21 no.1
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• pp.7-12
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• 2005

Plant growth-promoting rhizobacteria (PGPR) are a wide range of root-colonizing bacteria with the capacity to enhance plant growth and control plant pathogens. Here we review recent progress that indicate some PGPR strains release a blend of volatile organic compounds (VOCs) that promote growth in Arabidopsis seedlings and induce resistance against Erwinia carotovora subsp. carotovora. In particular, the volatile components 2,3-butanediol and acetoin released exclusively from the PGPR strains triggered the greatest level of growth promotion and induced systemic resistance. Pharmacological applications of 2,3-butanediol promoted the plant growth and induced resistance, while bacterial mutants blocked in 2,3-butanediol and acetoin synthesis was devoid of growth-promotion and induced resistance capacities. The results suggested that the bacterial VOCs play a critical role in the plant growth promotion and induced resistance by PGPR. Using transgenic and mutant lines of Arabidopsis, we provide evidences that the signal pathway activated by volatiles from one PGPR strain is dependent on cyto-kinin activation for growth promotion and dependent on an ethylene-signaling pathway for induced pathogen resistance. This discovery provides new insight into the role of bacterial VOCs as initiators of both plant growth promotion and defense responses in plants.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.53-53
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• 2022

Modem agricultural production needs to provide sustainable management practices that are eco-friendly and low cost. Plant extracts are a cost-effective and environmentally friendly alternative to synthetic plant growth regulators. This study was therefore carried out to investigate the effects of various plant extracts produced using different extraction methods on the vegetative growth of rice under laboratory and greenhouse conditions. For this study, seventeen plant extracts were made from plant species such as leaves of M. arvense, C. asiatica, M. oleifera, V. radiata, V. unguiculate, P. guajava, A. vera, and A. tuberosum, aboveground plant parts of C. rotundus, M. sativa, and P. frutescens, roots of R. undulatum, tubers of A. sativum, leaves and stems of G. max (cv. Taegwang) as well as rice straw and hulls (cv. Hopyeong). As a test crop, we applied these extracts to rice plants. For the purpose of making our extracts, some plant materials and species were collected in fields and others were purchased from Chonnam Hanyaknonghyup Cooperation (South Korea). Leaves, roots, and aboveground plant parts of plant species were dried, ground, extracted (water, boiling water and ethanol) and fermented. Rice growth promotion effects were determined using plant extracts at 0, 0.05, 0.1, 0.5, and 1% concentrations under petri dish conditions. Seven selected plant extracts were applied to rice seeds with soil drench application or seedling at 3-4 leaf stages with soil and foliar applications under greenhouse conditions. For comparison with extracts, we used urea at 0.6%. Of the 17 water extracts used in this study, 10 extracts reduced rice growth, but the other 7 extracts (P. guajava, A. vera, A. tuberosum, M. sativa, A. sativum, and G. max) increased growth by 40-60% on compared to the control in Petri dish bioassay. Thus, these 7 extracts were selected for further study. Under greenhouse conditions, rice growth also increased by 20-40% when the same 7 extracts were applied to rice seeds using soil drench application. Furthermore, at the 3-4 leaf stage rice growth also increased 30-80% or 30-60% when the same 7 extracts were applied using soil and foliar applications. Overall, the 7 extracts produced higher rates of growth promotion when soil drench application was used than when foliar application was used. In the case of boiling water and ethanol extracts, rice growth increased only 20% in response to both soil drench and foliar application of the same 7 extracts. Rice growth promotion was greater when extracts were produced using water extraction method than boiling water and ethanol extraction methods. Most notably, the 7 water extracts used in this study produced higher rates of growth promotion than urea at 0.6% which is typically used for crop growth promotion. Overall, the 7 water extracts when applied using soil drenching method can be used as effective growth promotors of rice in organic agriculture.

• Journal of Microbiology and Biotechnology
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• v.16 no.2
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• pp.184-192
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• 2006

Six-hundred bacterial strains from human milk and milk from Sahiwal cows, Holstein Friesian cows, and buffaloes were screened for their ability to suppress phytopathogenic fungi under in vitro conditions. A consortium of 3 strains, viz., Bacillus lentimorbus B-30486 (B-30486), B. subtilis B-30487 (B-30487), and B. lentimorbus B-30488 (B-30488), isolated from Sahiwal cow milk resulted in better biological control and plant-growth promotion than single-strain treatments. For commercial-scale production of a bioinoculant, the solid-state fermentation of sugarcane agro-industrial residues, i.e., molasses, press mud, and spent wash, using the consortium of B-30486, B-30487, and B-30488, resulted in a value-added product, useful for enhancing plant growth. The application of the consortium to sugarcane fields infested with Fusarium moniliforme and Colletotrichum falcatum resulted in a reduction of mortality and significantly higher (P=0.05) plant height, number of tillers, and cane girth when compared with the control. Furthermore, under field conditions, the treatment of sugarcane with the consortium resulted in significantly (P=0.05) greater plant growth compared with nonbacterized plants. Accordingly, this is the first report on the effective use of bacteria isolated from milk for biological control and enhancing plant growth under field conditions. Furthormore, a solid-state fermentation technology was developed that facilitates the economic utilization of agro-industrial residues for environmental conservation and improving plant and soil health.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.101.2-102
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• 2003

The ability of P. chlororaphis O6 to induce resistance to Erwinia carotovora subsp. carotovara SCCI and to promote growth in tobacco was demonstrated in microtiter assays on plants pre-inoculated at the root level with the bacteria before challenge with the leaf pathogen. To identify th bacterial determinants involved in induced systemic resistance and plant growth promotion, cell culture of O6 grown in King's medium B was fractionated with organic solvents and purified using various columns. in vivo and in vitro assays with samples from successive fractionation steps of the O6 supernatant led to the conclusion that antibacterial compounds were observed in aqueous layer, and to the isolation of fractions containing metabolites that retained most of the resistance-inducing activity (70：30, methanol：water) and the plant growth promotion (80：20 and 90：10, methanol：water) after ODS column chromatography. Although these molecules remain to be purified further and structurally characterized, its isolation is an addition to the range of determinants from plant growth-promoting rhizobacteria known to stimulate plant defence.

• Journal of Microbiology and Biotechnology
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• v.17 no.2
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• pp.280-286
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• 2007

We evaluated a commercial biopreparation of plant growth-promoting rhizobacteria (PGPR) strains Bacillus subtilis GB03 and B. amyloliquefaciens IN937a formulated with the carrier chitosan (Bio Yield) for its capacity to elicit growth promotion and induced systemic resistance against infection by Cucumber Mosaic Virus (CMV) and Pseudomonas syringae pv. tomato DC3000 in Arabidopsis thaliana. The biopreparation promoted plant growth of Arabidopsis hormonal mutants, which included auxin, gibberellic acid, ethylene, jasmonate, salicylic acid, and brassinosteroid insensitive lines as well as each wild-type. The biopreparation protected plants against CMV based on disease severity in wild-type plants. However, virus titre was not lower in control plants and those treated with biopreparation, suggesting that the biopreparation induced tolerance rather than resistance against CMV. Interestingly, the biopreparation induced resistance against CMV in NahG plants, as evidenced by both reduced disease severity and virus titer. The biopreparation also elicited induced resistance against P. syringae pv. tomato in the wild-type but not in NahG transgenic plants, which degrade endogenous salicylic acid, indicating the involvement of salicylic acid signaling. Our results indicate that some PGPR strains can elicit plant growth promotion by mechanisms that are different from known hormonal signaling pathways. In addition, the mechanism for elicitation of induced resistance by PGPR may be pathogen-dependent. Collectively, the two-Bacilli strain mixture can be utilized as a biological inoculant for both protection of plant against bacterial and viral pathogens and enhancement of plant growth.

• Journal of Microbiology and Biotechnology
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• v.19 no.10
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• pp.1250-1258
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• 2009

Bacillus spp., as a type of plant growth-promoting rhizobacteria (PGPR), were studied with regards promoting plant growth and inducing plant systemic resistance. The results of greenhouse experiments with tobacco plants demonstrated that treatment with the Bacillus spp. significantly enhanced the plant height and fresh weight, while clearly lowering the disease severity rating of the tobacco mosaic virus (TMV) at 28 days post-inoculation (dpi). The TMV accumulation in the young non-inoculated leaves was remarkably lower for all the plants treated with the Bacillus spp. An RT-PCR analysis of the signaling regulatory genes Coil and NPR1, and defense genes PR-1a and PR-1b, in the tobacco treated with the Bacillus spp. revealed an association with enhancing the systemic resistance of tobacco to TMV. A further analysis of two expansin genes that regulate plant cell growth, NtEXP2 and NtEXP6, also verified a concomitant growth promotion in the roots and leaves of the tobacco responding to the Bacillus spp.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.95.1-95
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• 2003

Plant growth promoting rhizobacteria (PGPR) have been shown to suppress phytopthora blight. This suppression has been related to both microbial antagonism and induced resistance. The PGPR isolates were screened by dual culture plate method and most of the isolates were showed varying levels of antagonism. Among the PGPR isolates pyoverdin, pyochelin and salicylic acid producing strains showed the maximum inhibition of mycelial growth of Phytopkhora capsici and increased plant growth promotion in red pepper. PGPR isolates further analysed for its ability to induce production of defence related enzymes and chemicals. The activities such as Phenyle alanin ammonia Iyase (PAL), Peroxidase (PO), Polyphenol oxidase (PPO) and accumulation of phenolics were observed in PGPR pretreated red pepper plants challenged with Phytopkhora capsici. The present study shows that an addition of direct antagonism and plant growth promotion, induction of defense related enzymes involved to enhance resistance against invasion of P. capsici in red pepper.

• The Korean Journal of Pesticide Science
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• v.13 no.4
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• pp.262-266
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• 2009

Plant growth-promoting rhizobacteria (PGPR) are beneficial native soil bacteria that colonize plant roots and result in increased plant growth. The objective of this study was to determine the plant growth promotion in canola plants by selected PGPR strain 13-1 under low temperature condition. The seed treatment of strain 13-1 was enhanced plant height and root elongation on canola plant at low temperature condition. This result determined that a selected strain of PGPR can enhance plant growth and root propagation under extremely low temperature conditions. Thus, this PGPR strain extends their role on plant growth promotion on canola until low temperature condition for practical applications.

• The Korean Journal of Mycology
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• v.41 no.2
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• pp.118-126
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• 2013

The experiment was carried out to analyze the inhibition effect of plant pathogenic fungi and growth promotion activity induced by the bacterial strains isolated from peatmoss. Among the isolated bacterial strains, B10-2, B10-4, B10-5 and B10-6 which showed more than 30% inhibition rate against Botrytis cinerea and Rhizoctonia solani in vitro, were further analyzed in the greenhouse for the growth promotion activity on lettuce (Lactuca sativa), pak-choi (Brassica compestris L. ssp. chinensis) and Chinese cabbage (Brassica campestris L. ssp. pekinensis). The results showed the treatment of B10-4 on lettuce showed the highest growth promotion activity with the leaf area ($169.17cm^2$), fresh weight (leaf: 40.29 g, root: 8.80 g)and dry weight (leaf: 11.24 g, root: 4.17 g), which was about two folds as compared to control. On pak-choi, the growth promotion rate was the highest with the leaf area of $112.87cm^2$, leaf fresh weight of 60.70 g, root fresh weight of 3.37 g, leaf dry weight of 14.34 g, and root dry weight of 1.90 g. As a result of treatment of B10-13 on chinese cabbage, the growth promotion rate was the highest with the leaf area ($293.56cm^2$), fresh weight (leaf: 113.67 g, root: 2.40 g) and dry weight (leaf: 6.03 g, root: 0.53 g). The production of Indole Acetic Acid (IAA) and Indole-3-Butylic Acid (IBA) were also analyzed in these bacterial isolates. The IAA and IBA analyses were carried out in all bacterial isolates each day within the 5 days of incubation period. The highest production of IAA was observed with $112.57{\mu}g/mg$ protein in B10-4 after 3 days of incubation and IBA production was the highest in B10-2 with $58.71{\mu}g/mg$ protein after 2 days of incubation. Also, phosphate solubilizing activity was expressed significantly in B10-13 in comparison to that of other bacterial isolates. Bacterial identification showed that B10-2 was Bacillaceae bacterium and B10-5 was Bacillus cereus, B10-4 and B10-6 were Bacillus sp. and B-13 was Staphylococcus sp. by ITS sequence.

• Journal of Physiology & Pathology in Korean Medicine
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• v.17 no.3
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• pp.815-818
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• 2003

Various kinds of chinese herbs have been known as to promote growth rate of animals. We investigated the growth promoting effect of the selected plants by using fish and rats as experimental animals. In a preliminary test by using fish, Eleutherococcus senticosus and Artemisia capillasis were found to be effective. Based on this result, we manufactured the mixture of plant extracts and applied this mixture to rice, named as Kiwoomi/sup TM/. When we administered Kiwoomi/sup TM/ to rats, it was found to be effective in growth promotion. Kiwoomi/sup TM/ - administered group showed 49.3% (0.75g/kg B.W.) and 52.3% (1.59/kg.B.W.) growth promotion, respectively. On the other hand, Control group showed 46.2% growth promotion. This growth promotion was supported by increase of GH and IGF-1 level in the Kiwoomi/sup TM/- administered group. From these results, we suggest that this functional rice could be helpful for growing children.