• 한국버섯학회지
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• 제19권3호
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• pp.134-139
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• 2021

A diverse group of plant-growth promoting bacteria were isolated in button mushroom (Agaricus bisporus) media to investigate the plant-growth promoting traits of compounds including indole acetic acid (IAA), ammonia, 1-aminocyclopropane-1-carboxylic acid deaminase, siderophore, and hydrogen cyanide. Twenty-one bacterial strains showing positive effects for all the test traits were selected and classified to confirm bacterial diversity in the media habitat. Plant-growth promoting traits of the isolates were also assessed. All strains produced IAA ranging from 20 ㎍/mL to 250 ㎍/mL. Most of the isolates produced more than 80% siderophore. Four strains (Pantoea sp., PSB-08, Bacillus sp., PSB-13, Pseudomonas sp., PSB-17, and Enterobacter sp., PSB-21) showed outstanding performances for all the tested traits. In a bioassay of these four strains using mung bean plant, the best growth performances (23.16 cm, 22.98 cm, 2.27 g/plant, and 1.83 g/plant for shoot length, root length, shoot dry weight, and root dry weight, respectively) were obtained from the plants co-inoculated with Bacillus sp., PSB-13. The resultant data indicate that button mushroom media have got a diverse group of bacteria with plant growth promoting abilities. Thus, the media could be a good recycling resource for using to an effective bio-fertilizer.

• The Plant Pathology Journal
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• 제38권5호
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• pp.490-502
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• 2022

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial leaf blight (BLB) disease in rice (Oryza sativa L.) and it is among the most destructive pathogen responsible for severe yield losses. Potential bacterial biocontrol agents (BCAs) with plant growth promotion (PGP) abilities can be applied to better manage the BLB disease and increase crop yield, compared to current conventional practices. Thus, this study aimed to isolate, screen, and identify potential BCAs with PGP abilities. Isolation of the BCAs was performed from internal plant tissues and rhizosphere soil of healthy and Xoo-infected rice. A total of 18 bacterial strains were successfully screened for in vitro antagonistic ability against Xoo, siderophore production and PGP potentials. Among the bacterial strains, 3 endophytes, Bacillus sp. strain USML8, Bacillus sp. strain USML9, and Bacillus sp. strain USMR1 which were isolated from diseased plants harbored the BCA traits and significantly reduced leaf blight severity of rice. Simultaneously, the endophytic BCAs also possessed plant growth promoting traits and were able to enhance rice growth. Application of the selected endophytes (BCAs-PGP) at the early growth stage of rice exhibited potential in suppressing BLB disease and promoting rice growth.

• Journal of Microbiology and Biotechnology
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• 제29권1호
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• pp.66-78
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• 2019

In this study, strain KNU17Pc1 was tested for its antifungal activity against Rhizoctonia solani AG-1(IA), which causes banded leaf and sheath blight (BLSB) of maize. KNU17Pc1 was tested further for its broad-spectrum antifungal activity and in vitro plant growth promoting (PGP) traits. In addition, the in vivo effects of KNU17Pc1 on reduction of BLSB severity and seedling growth promotion of two maize cultivars under greenhouse conditions were investigated. On the basis of multilocus sequence analysis (MLSA), KNU17Pc1 was confirmed as P. chlororaphis subsp. aurantiaca. The study revealed that KNU17Pc1 had strong in vitro antifungal activity and was effective toward all in vitro PGP traits except phosphate solubilization. In this study, for the first time, a strain of P. chlororaphis against Colletotrichum dematium, Colletotrichum gloeosporioides, Fusarium oxysporum f.sp. melonis, Fusarium subglutinans and Stemphylium lycopersici has been reported. Further biochemical studies showed that KNU17Pc1 was able to produce both types of phenazine derivatives, PCA and 2-OH-PCA. In addition, solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) analysis identified 13 volatile organic compounds (VOCs) in the TSB culture of KNU17Pc1, 1-undecene being the most abundant volatile. Moreover, for the first time, Octamethylcyclotetrasiloxan (D4), dimethyl disulfide, 2-methyl-1,3-butadiene and 1-undecene were detected in P. chlororaphis. Furthermore, this study reported for the first time the effectiveness of P. chlororaphis to control BLSB of maize. Hence, further studies are necessary to test the effectiveness of KNU17Pc1 under different environmental conditions so that it can be exploited further for biocontrol and plant growth promotion.

• Journal of Microbiology and Biotechnology
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• 제31권3호
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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.

• 한국토양비료학회지
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• 제45권1호
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• pp.66-73
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• 2012

Plant growth promoting traits like production of indoleacetic acid (IAA), ammonia, hydrogen cyanide (HCN), siderophore, and like the enzyme activities of catalase, ACC deaminase, cellulase, chitinase and protease were assayed in vitro for twenty one phosphorus solubilizing bacteria isolated from soil isolates. Except SPP-5 and SPP-15 strains, all the other isolated strains produced IAA in various amounts of 10 to $23{\mu}g\;ml^{-1}$. All strains showed positive response for ammonia production and ACC deaminase activity implying that they are capable of growing in a N-free basal medium. Catalase activity was found to be superior in SPP-2, SPP-7, SPP-12 and SPP-17 compared to the other strains tested. HCN production was detected by 15 strains and among them SPP-9, SPP-15, SAph-11, and SAph-24 were found to be strong HCN producers. Except the isolates SPP-10, SPP-12, SPP-13 and SPP-14, all the other isolates produced more than 80% siderophore units. None of the strains showed cellulose and chitinase activity. SAph-8, SAPh-11, SAPh-24 and SPP-15 strains showed 35.84, 50.33, 56.64 and 34.78 U/ml protease activities, respectively. SPP-1, SPP-2, SPP-3, SPP-11, SPP-17, SPP-18, SAph-11 and SAph-24 strains showed positive response for all the tested plant growth promotion traits except cell wall degrading enzyme activities. According to the results, all the tested phosphorus solubilizing isolates could exhibit more than three or four plant growth promoting traits, which may promote plant growth directly or indirectly or synergistically. Therefore, these phosphorus solubilizing strains could be employed as bio-inoculants for agriculture soils.

• 한국식물병리학회:학술대회논문집
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• 한국식물병리학회 2003년도 정기총회 및 추계학술발표회
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• pp.94.2-95
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• 2003

E. intermedium 60-2G possessing a strong ability to solubilize insoluble phosphate, has plant growth-promoting activity, induced systemic resistance activity against scab pathogen in cucumber, and antifungal activity against various phytopathogenic fungi. The phosphate solubilizing activity of 60-2G may be mainly accomplished by production of gluconic acid through a direct extracellular oxidation of glucose by glucose dehydrogenase that required a PQQ cofactor for its activation. A pqq gene cluster conferred Phosphate-solubilizing activity in E. coli DH5${\alpha}$ was cloned and sequenced. The 6,783 bP pqq sequence had six open reading frames (from A to F) and showed 50-95％ homology to pqq genes from other bacteria. The E. coli strain expressing the pqq genes solubilized phosphate from hydroxyapatite after a pH drop to 4.0, which paralleled in time the secretion of gluconic acid. To study the role of PQQ in biocontrol traits of E. intermedium, PQQ mutants of 60-2G were constructed by marker exchangee mutagenesis. The PQQ mutants of E. intermedium were lost activities of solubilizing phosphate, growth inhibition of phytopathogenic fungi, and plant growth promotion. These findings suggest that PQQ plays an important role, possibly activation of certain enzymes, in several beneficial bacterial traits of E. intermedium by as yet an unknown mechanism.

• Journal of Microbiology and Biotechnology
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• 제25권8호
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• pp.1349-1360
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• 2015

The rhizospheric zone abutting plant roots usually clutches a wealth of microbes. In the recent past, enormous genetic resources have been excavated with potential applications in host plant interaction and ancillary aspects. Two Pseudomonas strains were isolated and identified through 16S rRNA and rpoD sequence analyses as P. fluorescens QAU67 and P. putida QAU90. Initial biochemical characterization and their root-colonizing traits indicated their potential role in plant growth promotion. Such aerobic systems, involved in gluconic acid production and phosphate solubilization, essentially require the pyrroloquinoline quinine (PQQ)-dependent glucose dehydrogenase (GDH) in the genome. The PCR screening and amplification of GDH and PQQ and subsequent induction of mutagenesis characterized their possible role as antioxidants as well as in growth promotion, as probed in vitro in lettuce and in vivo in rice, bean, and tomato plants. The results showed significant differences (p ≤ 0.05) in parameters of plant height, fresh weight, and dry weight, etc., deciphering a clear and in fact complementary role of GDH and PQQ in plant growth promotion. Our study not only provides direct evidence of the in vivo role of GDH and PQQ in host plants but also reveals their functional inadequacy in the event of mutation at either of these loci.

• 농업과학연구
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• 제50권4호
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• pp.759-771
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• 2023

Plant growth-promoting rhizobacteria (PGPR) are naturally occurring bacteria that intensively colonize plant roots and are crucial in promoting the crop growth. These beneficial microorganisms have garnered considerable attention as potential bio-inoculants for sustainable agriculture. PGPR directly interacts with plants by providing essential nutrients through nitrogen fixation and phosphate solubilization and accelerating the accessibility of other trace elements such as Cu, Zn, and Fe. Additionally, they produce plant growth-promoting phytohormones, such as indole acetic acids (IAA), indole butyric acids (IBA), gibberellins, and cytokinins.PGPR interacts with plants indirectly by protecting them from diseases and infections by producing antibiotics, siderophores, hydrogen cyanide, and fungal cell wall-degrading enzymes such as glucanases, chitinases, and proteases. Furthermore, PGPR protects plants against abiotic stresses such as drought and salinity by producing 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase and modulating plant stress markers. Bacteria belonging to genera such as Bacillus, Pseudomonas, Burkholderia, Pantoa, and Enterobacter exhibit multiple plant growth-promoting traits, that can enhance plant growth directly, indirectly, or through synergetic effects. This comprehensive review emphasizes how PGPR influences plant growth promotion and presents promising prospects for its application in sustainable agriculture.

• 한국토양비료학회지
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• 제49권6호
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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.

• Journal of Microbiology and Biotechnology
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• 제20권12호
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• pp.1724-1734
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• 2010

A phosphate-solubilizing bacterial strain isolated from Hippophae rhamnoides rhizosphere was identified as Rahnella sp. based on its phenotypic features and 16S rRNA gene sequence. The bacterial strain showed the growth characteristics of a cold-adapted psychrotroph, with the multiple plant growth-promoting traits of inorganic and organic phosphate solubilization, 1-aminocyclopropane-1-carboxylate-deaminase activity, ammonia generation, and siderophore production. The strain also produced indole-3-acetic acid, indole-3-acetaldehyde, indole-3-acetamide, indole-3-acetonitrile, indole-3-lactic acid, and indole-3-pyruvic acid in tryptophan-supplemented nutrient broth. Gluconic, citric and isocitric acids were the major organic acids detected during tricalcium phosphate solubilization. A rifampicin-resistant mutant of the strain exhibited high rhizosphere competence without disturbance to the resident microbial populations in pea rhizosphere. Seed bacterization with a charcoal-based inoculum significantly increased growth in barley, chickpea, pea, and maize under the controlled environment. Microplot testing of the inoculum at two different locations in pea also showed significant increase in growth and yield. The attributes of cold-tolerance, high rhizosphere competence, and broad-spectrum plant growth-promoting activity exhibited the potential of Rahnella sp. BIHB 783 for increasing agriculture productivity.