• Journal of Microbiology and Biotechnology
• /
• v.23 no.7
• /
• pp.897-904
• /
• 2013

Seven bacterial isolates (viz., AB05, AB10, AB11, AB12, AB14, AB15, and AB17) were derived from the rhizosphere and evaluated in terms of plant growth-promoting activities and the inhibition of Phytophthora infestans affecting tomatoes in Korea. According to 16S rDNA sequencing, a majority of the isolates are members of Bacillus, and a single isolate belongs to Paenibacillus. All seven isolates inhibited P. infestans by more than 60% in vitro. However, AB15 was the most effective, inhibiting mycelial growth of the pathogen by more than 80% in vitro and suppressing disease by 74% compared with control plants under greenhouse conditions. In a PGPR assay, all of the bacterial isolates were capable of enhancing different growth parameters (shoot/root length, fresh biomass, dry matter, and chlorophyll content) in comparison with non-inoculated control plants. AB17-treated plants in particular showed the highest enhancement in fresh biomass with 18% and 26% increments in the root and shoot biomass, respectively. However, isolate AB10 showed the highest shoot and root growth with 18% and 26% increments, respectively. Moreover, the total chlorophyll content was 14%~19% higher in treated plants.

• Journal of Microbiology and Biotechnology
• /
• v.19 no.6
• /
• pp.560-565
• /
• 2009

We isolated nine endophytic fungi from the roots of salt-stressed soybean cultivar Daewonkong and screened them for growth-promoting secondary metabolites. Of all fungal isolates, P-4-3 induced maximum growth promotion of waito-c rice and soybean. Analysis of the culture filtrate of P-4-3 showed the presence of physiologically active gibberellins $GA_1$, $GA_3$, $GA_4$, and $GA_7$, along with physiologically inactive $GA_{15}$ and $GA_{24}$. The plant growth promotion and gibberellin-producing capacity of P-4-3 was much higher than wild-type Gibberella fujikuroi, which was taken as the control during the present study. The fungal isolate P-4-3 was identified as a new strain of Scolecobasidium tshawytschae through the morphological characteristics and phylogenetic analysis of 18S rDNA sequence. Gibberellins production and plant growth promoting ability of genus Scolecobasidium was reported for the first time in the present study.

• Horticultural Science & Technology
• /
• v.18 no.6
• /
• pp.827-833
• /
• 2000

This study was carried out to investigate the effect of plant growth retardants (daminozide, chlormequat, uniconazole, paclobutrazole) and fungicides of triazole chemical (hexaconazole, microbutanil, difenoconazole, terbuconazole, bitertanol) on the growh of 'New Guinea' impatiens. Plant height and canopy were decreased by all kinds of plant growth retardants tested in both 'Anguilla' and 'Papete'. Especially, uniconazole and paclobutrazole were most effective in inhibition of top growth. However, the content of chlorophyll increased at all treatments of plant growth retardants and stem diameter tended to be increased at the highest concentration of all kinds of plant growth retardants tested. The results in all cultivars tested, with the experiment of triazole fungicides, were similar to the results of experiment with plant growth retardants. These results suggest that fungicides of triazole chemical such as hexaconazole, microbutanil, difenoconazole, terbuconazole and bitertanol can be used for the promotion of quality in potted 'New Guinea' impatiens.

• Research in Plant Disease
• /
• v.25 no.2
• /
• pp.84-88
• /
• 2019

A variety of microorganisms in rhizosphere affect plant health by plant growth promotion, mitigation of abiotic stresses as well as protection from pathogen attacks. In our previous study, we selected a bacterium, Bacillus mesonae H20-5, for alleviation of salinity stress in tomato plants. In this study, we verified the effect of a liquid formulation of B. mesonae H20-5 (TP-H20-5) on fruit production and phytochemical accumulation including lycopene and polyphenol in cherry tomato and strawberry fruits in on-farm tests of protected cultivation under salinity stress. When vegetables including tomato, cherry tomato, strawberry, and cucumber were treated with TP-H20-5 by irrigated systems, final marketable yields were increased by 21.4% (cherry tomato), 9.3% (ripen tomato), 120.6% (strawberry), and 14.5% (cucumber) compared to untreated control. Moreover, treatment of TP-H20-5 was showed increase of phytochemicals such as lycopene and total polyphenol compared to untreated control in cherry tomato and strawberry. Therefore, these results indicated that a formulant of B. mesonae H20-5 can be used as a potential biofertilizer for increasing fruit production and quality.

• Journal of Microbiology and Biotechnology
• /
• v.31 no.9
• /
• pp.1231-1240
• /
• 2021

Members of the genus Bacillus are known to play an important role in promoting plant growth and protecting plants against phytopathogenic microorganisms. In this study, 21 isolates of Bacillus spp. were obtained from the root micro-ecosystem of Suaeda glauca. Analysis of the 16S rRNA genes indicated that the isolates belong to the species Bacillus amyloliquefaciens, Bacillus velezensis, Bacillus subtilis, Bacillus pumilus, Bacillus aryabhattai and Brevibacterium frigoritolerans. One of the interesting findings of this study is that the four strains B1, B5, B16 and B21 are dominant in rhizosphere soil. Based on gyrA, gyrB, and rpoB gene analyses, B1, B5, and B21 were identified as B. amyloliquefaciens and B16 was identified as B. velezensis. Estimation of antifungal activity showed that the isolate B1 had a significant inhibitory effect on Fusarium verticillioides, B5 and B16 on Colletotrichum capsici (syd.) Butl, and B21 on Rhizoctonia cerealis van der Hoeven. The four strains grew well in medium with 1-10% NaCl, a pH value of 5-8, and promoted the growth of Arabidopsis thaliana. Our results indicate that these strains may be promising agents for the biocontrol and promotion of plant growth and further study of the relevant bacteria will provide a useful reference for the development of microbial resources.

• The Korean Journal of Pesticide Science
• /
• v.17 no.4
• /
• pp.394-401
• /
• 2013

Trichoderma harzianum is one of rhizosphere fungus usually lives near the plant root regions in the soil. T. harzianum plays an important role in plant growth promotion and increases disease resistance against various plant pathogens on crops. In this study, the strain T. harzianum MPA167 was isolated from the barley rhizosphere soil in Suwon, Korea. Among 183 isolates, the strain T. harzianum MPA167 was selected as promising strain in which based on hyperparasitical activity against Phytophthora capsici and estimated disease control activity against P. capsici in the greenhouse conditions. The strain T. harzianum MPA167 was identified using 23s rDNA internal transcribed spacer(ITS) region sequences. MPA167 treatment ($1{\times}10^6$ spores/ml) showed greater disease suppression against Phytophthora blight of red-pepper caused by P. capsici in greenhouse compared with the water-treated control. Volatiles derived from T. harzianum MPA167 elicit growth promotion of tobacco and Arabidopsis seedlings in I-plate assay. In addition, T. harzianum MPA167 strain was also found to be effective for the growth promotion and induction of systemic resistance on red-papper plant. These results suggest that MPA167 might be used as one of the potential biocontrol agents.

• Korean Journal of Soil Science and Fertilizer
• /
• v.47 no.3
• /
• pp.141-146
• /
• 2014

The necessity to develop economical and eco-friendly technologies is steadily increasing. Plant growth promoting rhizomicrobial strains PGPR are a group of microorganisms that actively colonize plant roots and increase plant growth and yield. Pot experiments were used to investigate the potential of some rhizobacterial strains to enhance the Brassica rapa growth. Microbial strains were successfully isolated from the rhizosphere of Panax ginseng and characterized based on its morphological and plant growth promotion characters. Surface disinfected seeds of Wisconsin Fast B. rapa were inoculated with the selected PGPR microorganisms. The different pots treatments were inoculated by its corresponding PGPR ($10^7cfu\;mL^{-1}$) and incubated in the growth chamber at $25^{\circ}C$ and 65% RH, the light period was adjusted to 24 hours (day). NPK chemical fertilizer and trade product (EMRO, USA) of effective microorganisms as well as un-inoculated control were used for comparison. Plants harvested in 40 days were found to have significant increase in leaf chlorophyll units and plant height and also in dry weight of root and shoot in the inoculated seedlings. Root and shoot length and also leaf surface area significantly were increased by bacterial inoculation in sterile soil. The study suggests that Rhodobacter capsulatus and Azotobacter chroococcum are beneficial for B. rapa growth as they enhance growth and induced IAA production and phosphorus solubilization. This study presents some rhizomicrobial strains that significantly promoted growth of Wisconsin Fast Plant B. rapa in pot experiment under different soil conditions.

• Korean Journal of Microbiology
• /
• v.50 no.1
• /
• pp.40-45
• /
• 2014

In order to increase the persistence of plant growth promoting rhizobacteria (PGPR) in rhizpsphere soil, the growth of tomato was examined after the application of Arthrobacter woluwensis ED immobilized in alginate bead, which was known as PGPR. When tomato seedlings were treated with A. woluwensis ED of $1{\times}10^6$ cells g $soil^{-1}$ and incubated for 30 days in a plant growth chamber, the shoot length, root length, fresh weight and dry weight of the grown tomato plants treated with the suspended inoculants significantly increased by 36.2, 59, 51.1, and 37.5%, respectively compared to those of the uninoculated control. The treatment of the immobilized bacteria increased those by 42, 67.4, 62.5, and 60.4%, respectively compared to those of the uninoculated control. Therefore, the enhancement of tomato growth by the treatment of the immobilized bacteria was higher than those by the suspended inoculants. The effects of the inoculation on indigenous bacterial community and the fate of the inoculated bacteria were monitored by denaturing gradient gel electrophoresis analysis. The DNA band intensity of A. woluwensis ED in the tomato rhizosphere treated with the suspended inoculants continuously decreased after the inoculation, but the band intensity in the tomato rhizosphere soils treated with the immobilized inoculants showed the maximum at 1 week after inoculation and the decreasing rate was less than that of the suspended inoculants, which indicated the longer maintenance of the immobilized bacteria at rhizosphere soils. Therefore, encapsulation of PGPR in alginate beads may be more effective than liquid inoculant for the plant growth promotion and survival of PGPR at plant rhizosphere.

• Journal of Plant Biotechnology
• /
• v.49 no.4
• /
• pp.356-361
• /
• 2022

Bacillus sp. is a useful strain for agriculture because it promotes plant growth and controls plant pathogens through a variety of mechanisms. In this study, we obtained a microbial preparation with a high number of viable cells by culturing newly isolated soil bacteria on an optimized medium. Subsequently, we applied this preparation to lettuce to enhance its growth and yield. First, B. amyloliquefaciens ISP-5 was isolated from soil. Next, optimization of culture medium was carried out using 5 L scale fermenters. When culturing B. amyloliquefaciens ISP-5 on this optimized medium, the number of viable cells was approximately 1000 times higher than that obtained from culturing on the commercial medium. Afterwards, the plant growth promotion properties of the ISP-5 strain were evaluated using lettuce as a test plant. Foliar spray treatment of lettuce was carried out by inoculating half the standard concentration suspension (0.5 × 10⁷ cfu/ml). As a result, leaf width increased by 8.6% and leaf length increased by 12.9% compared to the control group. Live weight also increased by 24.2% and dry weight by 23.9%. Considering the results from field test, B. amyloliquefaciens ISP-5 showed potential as a plant growth-promoting bacteria.

• The Plant Pathology Journal
• /
• v.35 no.2
• /
• pp.178-187
• /
• 2019

Plants are exposed to biotic stresses caused by pathogen attack and complex abiotic stresses including heat and drought by dynamic climate changes. To alleviate these stresses, we investigated two bacterial stains, H26-2 and H30-3 in two cultivars ('Ryeokkwang' and 'Buram-3-ho') of Chinese cabbage in plastic pots in a greenhouse. We evaluated effects of bacterial strains on plant growth-promotion and mitigation of heat and drought stresses; the role of exopolysaccharides as one of bacterial determinants on alleviating stresses; biocontrol activity against soft rot caused by Pectobacterium carotovorum subsp. carotovorum PCC21. Strains H26-2 and H30-3 significantly increased fresh weights compared to a $MgSO_4$ solution; reduced leaf wilting and promoted recovery after re-watering under heat and drought stresses. Chinese cabbages treated with H26-2 and H30-3 increased leaf abscisic acid (ABA) content and reduced stomatal opening after stresses treatments, in addition, these strains stably colonized and maintained their populations in rhizosphere during heat and drought stresses. As well as tested bacterial cells, exopolysaccharides (EPS) of H30-3 could be one of bacterial determinants for alleviation of tested stresses in Chinese cabbages, however, the effects were different to cultivars of Chinese cabbages. In addition to bacterial activity to abiotic stresses, H30-3 could suppress incidence (%) of soft rot in 'Buram-3-ho'. The tested strains were identified as Bacillus aryabhattai H26-2 and B. siamensis H30-3 based on 16S rRNA gene sequence analysis. Taken together, H26-2 and H30-3 could be candidates for both plant growth promotion and mitigation of heat and drought stresses in Chinese cabbage.