• Journal of Microbiology and Biotechnology
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• v.33 no.5
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• pp.607-620
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• 2023

The biocontrol approach using beneficial microorganisms to control crop diseases is becoming an essential alternative to chemical fungicides. Therefore, new and efficient biocontrol agents (BCA) are needed. In this study, a rhizospheric actinomycete isolate showed unique and promising antagonistic activity against three of the most common phytopathogenic fungi, Fusarium oxysporum MH105, Rhizoctonia solani To18, and Alternaria brassicicola CBS107. Identification of the antagonistic strain, which was performed according to spore morphology and cell wall chemotype, suggested that it belongs to the Nocardiopsaceae. Furthermore, cultural, physiological, and biochemical characteristics, together with phylogenetic analysis of the 16S rRNA gene (OP869859.1), indicated the identity of this strain to Nocardiopsis alba. The cell-free filtrate (CFF) of the strain was evaluated for its antifungal potency, and the resultant inhibition zone diameters ranged from 17.0 ± 0.92 to 19.5 ± 0.28 mm for the tested fungal species. Additionally, the CFF was evaluated in vitro to control Fusarium wilt disease in Vicia faba using the spraying method under greenhouse conditions, and the results showed marked differences in virulence between the control and treatment plants, indicating the biocontrol efficacy of this actinomycete. A promising plant-growth promoting (PGP) ability in seed germination and seedling growth of V. faba was also recorded in vitro for the CFF, which displayed PGP traits of phosphate solubilization (48 mg/100 ml) as well as production of indole acetic acid (34 ㎍/ml) and ammonia (20 ㎍/ml). This study provided scientific validation that the new rhizobacterium Nocardiopsis alba strain BH35 could be further utilized in bioformulation and possesses biocontrol and plant growth-promoting capabilities.

• Research in Plant Disease
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• v.22 no.2
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• pp.72-80
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• 2016

Gummy stem blight, caused by the fungus Didymella bryoniae, is major disease of watermelons worldwide. The objective of the present study was to establish an efficient screening system to identify watermelon resistant to D. bryoniae. An GSB3 isolate was prepared from a watermelon plant showing typical symptoms of gummy stem blight in Haman-gun and identified as D. bryoniae based on molecular analysis of internal transcribed spacer sequence. A simple mass-production technique of inoculum was developed based on spore production of D. bryoniae GSB3 under several incubation conditions and their virulence on watermelon plants. Resistance degrees of 22 commercial watermelon cultivars to the GSB3 isolate were evaluated. Among them, four watermelon cultivars showing different degree of resistance response were selected for further study. Development of disease on the cultivars according to various conditions including inoculum concentrations, incubation periods in dew chamber, and incubation temperatures was investigated. From the results, we suggest an efficient screening method for resistant watermelon cultivars to gummy stem blight. Seeds of watermelon cultivar are sown and grown in a greenhouse until plant stage of 2-fully expanded leaves. Seedlings are inoculated with D. bryoniae by spraying spore suspension of the fungus at a concentration of $5.0{\times}10^5spores/ml$. The infected plants are incubated in humidity chamber at $25^{\circ}C$ for 48 hours and then transferred to a growth chamber at $25^{\circ}C$ and 80% relative humidity with 12-hour light a day. Three to four days after inoculation, disease severity of the plant are measured using percentage of infected leaf area.

• Journal of Sericultural and Entomological Science
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• v.47 no.1
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• pp.5-11
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• 2005

When inoculating with B. bassiana 101A for the mass production of B. corpus, the infection ratio was high with regardless of the treating time with highly-humidity if the concentration of spore was 1.0${\times}$$10^8$ spores/m/, but that was low if the concentration was 1.0${\times}$$10^7$ spores/m/. In the study of the activities according to the coserving temperature or days of the B. bassiana spawn, the infection ratio of 90% was maintained for 12 days in the temperature of $4^{\circ}C$. However, the infection ratio was rapidly dropped to the below of 5% after conserved for 48 hours in the temperature of $25^{\circ}C$. Besides, the activities of the original isolate had no difference after conserved for 12 months in the temperature of $4^{\circ}C$, so that the infection ratio 90% could be mintatined. In the measure of liver-protecting activities of B. bassiana 101A, the recovering effect was 43.5% and 65.7% respectively in the poisonous treatment induced with galactosamine, compared with liver-protecting activities of Silymarin and DDB in the $H_2O$ fraction. In the poisonous treatment induced with $CCl_4$ the recovering effect was 100% and 69.3% respectively, compared with liver-protecting activities of Silymarin and DDB in the EtOAc fraction.

• Asian-Australasian Journal of Animal Sciences
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• v.23 no.12
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• pp.1657-1667
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• 2010

Direct-fed microbials (DFM) are dietary supplements that inhibit gastrointestinal infection and provide optimally regulated microbial environments in the digestive tract. As the use of antibiotics in ruminant feeds has been banned, DFM have been emphasized as antimicrobial replacements. Microorganisms that are used in DFM for ruminants may be classified as lactic acid producing bacteria (LAB), lactic acid utilizing bacteria (LUB), or other microorganisms including species of Lactobacillus, Bifidobacterium, Enterococcus, Streptococcus, Bacillus and Propionibacterium, strains of Megasphaera elsdenii and Prevotella bryantii and yeast products containing Saccharomyces and Aspergillus. LAB may have beneficial effects in the intestinal tract and rumen. Both LAB and LUB potentially moderate rumen conditions and improve feed efficiency. Yeast DFM may reduce harmful oxygen, prevent excess lactate production, increase feed digestibility, and improve fermentation in the rumen. DFM may also compete with and inhibit the growth of pathogens, stimulate immune function, and modulate microbial balance in the gastrointestinal tract. LAB may regulate the incidence of diarrhea, and improve weight gain and feed efficiency. LUB improved weight gain in calves. DFM has been reported to improve dry matter intake, milk yield, fat corrected milk yield and milk fat content in mature animals. However, contradictory reports about the effects of DFM, dosages, feeding times and frequencies, strains of DFM, and effects on different animal conditions are available. Cultivation and preparation of ready-to-use strict anaerobes as DFM may be cost-prohibitive, and dosing methods, such as drenching, that are required for anaerobic DFM are unlikely to be acceptable as general on-farm practice. Aero-tolerant rumen microorganisms are limited to only few species, although the potential isolation and utilization of aero-tolerant ruminal strains as DFM has been reported. Spore forming bacteria are characterized by convenience of preparation and effectiveness of DFM delivery to target organs and therefore have been proposed as DFM strains. Recent studies have supported the positive effects of DFM on ruminant performance.

• Journal of Mushroom
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• v.16 no.3
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• pp.175-179
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• 2018

The button mushroom 'A. bisporus' is the most commonly grown mushroom worldwide. The color of 'Agaricus bisporus' is white and brown. Recently, the consumption of brown button mushrooms has been increasing steadily. 'Danseok-1ho' was bred using the multi-spore random mating method and named after Danseok Mountain in Gyeongju, the region where 'A. bisporus' was first grown in Korea. The optimum temperature for mycelial growth was between $20^{\circ}C$ and $30^{\circ}C$, and the mushroom production temperature was between $15^{\circ}C$ and $20^{\circ}C$. The color and shape of 'Danseok-1ho' are medium brown and spherical, respectively. The width and thickness of the pileus are 45.1 mm and 23.5 mm, respectively. The hardness and L of chromaticity of 'Danseok-1ho' are $8,937g/{\Phi}5mm$ and 50.4, respectively. The incubation period is around 20 days and mushroom production takes about 18 days after casing. A typical characteristic of 'Danseok-1ho' is that the individual occurrence rate is high, so mushroom losses are low during harvest.

• Journal of Life Science
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• v.23 no.8
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• pp.1010-1018
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• 2013

The greenhouse whitefly, Bemisia tabaci, is considered one of the most destructive pests of crops. In this study, we aimed to determine the optimal liquid culture conditions in shake flasks for maximal sporulation of Beauveria bassiana M130 using rice bran. The optimal initial pH for the spore production of B. bassiana using extracted rice bran medium was 5.2 and $28^{\circ}C$. The screening in shake flasks of carbon and nitrogen sources resulted in the identification of an optimal medium based on 0.5% $(NH_4)_2SO_4$, with extracted rice bran 8:1. Using this medium, a production level of $2.15{\times}10^9$ spores per ml was obtained after six days from culture inoculation at $28^{\circ}C$ in a rotary shaking incubator at 130 rpm. In addition, the specific activities of extracellular enzymes of chitinase and protease were $4,296{\mu}mol$ and $375{\mu}mol$, respectively. These results suggest that Beauveria bassiana M130 could be a bio-controller for the greenhouse whitefly.

• Mycobiology
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• v.39 no.4
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• pp.317-320
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• 2011

Honey production from approximately 1.6 million colonies owned by about 199,000 Korean beekeepers was almost 23,000 metric tons in 2009. Nosema causes significant losses in honey production and the virus decreases population size. We initiated a survey of honey bee colonies on the blooming period of Acacia to determine the prevalence of Nosema and virus in 2011. Most Korean beekeepers have moved from the south to north of Korea to get Acacia nectar for 2 mon. This provided a valuable opportunity to sample bees originating from diverse areas in one location. Twenty hives owned by 18 beekeepers were sampled in this year. Nosema spore counts ranged from zero to 1,710,000 spores per bee. The average number of nosema spores per bee was 580,000. Approximately 95% of the colonies were infected with Nosema, based on the presence of spores in the flowering period of Acacia. This indicates that Nosema is the predominant species affecting honeybee colonies. Also, the seven most important honeybee viruses were investigated by reverse transcription-PCR. Among them, four different viruses were detected in samples. Black queen cell virus was present in all samples. Chronic bee paralysis virus was detected in 10% of samples. Deformed wing virus was present in only 5% of the samples. Prevalence of Sacbrood virus was 15%. However, Cloudy wing virus, Israel acute paralysis virus and kashmir bee virus were not detected in any of samples.

• Applied Biological Chemistry
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• v.11
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• pp.137-141
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• 1969

In order to obtain amino acids and nucleic acid derivatives from adenine auxotrophic mutants of Bacillus subtilis and Escherichia coli, vitamin, nucleic acid analogue, streptomycin as well as ultraviolet light were adopted for the production of adenine auxotrophic mutants and the results showed efficient production of desired mutants. 1. Ultraviolet ray $(2530\;{\AA}\;2080\;erg/mm^2)$ irradiation to Bacillus subtilis and E. coli at a distance of 30 cm for 80-90 sec. and for 15-20 sec. respetively induced four and eight strains of auxotrophic mutants. 2. Treatment of aminopterine$(200\;{\mu}g/ml)$ inhibited the growth of Bacillus sultilis significantly but a subsequent irradiation of ultraviolet light at the above mentioned conditions induced six times as much mutants as compared to the irradiation alone. In case of E. coli a similar tendency was observed with treatment of streptomycin$(200\;{\mu}g/ml)$ with doubled induction rate of adenine auxotrophic mutants as compared to the irradiation alone.

• Research in Plant Disease
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• v.18 no.3
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• pp.201-209
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• 2012

The multi-function of 18 Bacillus subtilis isolates collected from agricultural extension centers of local government and National Academy of Agricultural Science was investigated by measuring their antifungal activities against five plant pathogens, such as Rhizoctonia solani, Colletotrichum acutatum, Fusarium oxysporum, Magnaporthe oryzae and Phytophthora capsici, phosphorus solubilization ability, production of indole acetic acid (IAA) and siderophore, and nitrogen fixation. The B. subtilis isolates showed antifungal activity against several plant pathogens and nitrogen fixation activity, and produced siderophore and IAA. They could control pepper powdery mildew (Leveillula taurica), but there was no difference in control efficacy among the B. subtilis isolates. In fields, the control efficacy of B. subtilis R2-1 ($10^8$ cells/ml) was compared with two microbial fungicides, Q-pect and Topsid. In 2009, the control efficacy of B. subtilis R2-1 (37.7%) was lower than that of Topsid (47.6%), but higher than that of Q-pect (25.7%). In 2010, the control efficacy of B. subtilis R2-1 (83.3%) was higher than that of Topsid (67.9%). In order to elucidate mode of action of B. subtilis R2-1 for controlling pepper powdery mildew, spore germination rates of pepper powdery mildew pathogen collected on treated leaves was investigated when suspensions of B. subtilis R2-1 and two microbial fungicides (Q-pect and Topsid) were foliar-sprayed. They highly suppressed spore germination of the pathogen with inhibition values of 84.2% for B. subtilis R2-1, 97.9% for Q-pect and 94.7% for Topsid. Further study on the mass-culturing method and formulation is needed for development of a microbial fungicide.

• Journal of the Korean Geographical Society
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• v.40 no.4 s.109
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• pp.428-440
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• 2005

There is currently no agreement among archaeologists, environmental historians, and paleoecologists as to the relative significance of pre- and post-Conquest human impact on the environments of Highland Mexico. This paper presents the results of pollen, microscopic charcoal, dung fungal spore, isotope, and magnetic susceptibility analyses on ca. 4m sediment core. The coring site is Hoya Rincon de Parangueo, one of the seven maar lakes in the Valle do Santiago. Amaranthaceae pollen, one of important disturbance indicators and Zea mays pollen obviously indicate two periods of agricultural activities. The first period begins ca. 400 B.C. and ends ca. A.D. 850. The second begins around A.D. 1550 and continues to the present. During the first period, the degree of agricultural activities was related to periodical sunspot cycles and the most intense activities were present between ca. A.D. 150-ca. A.D. 400. The abrupt increase of $\delta^{18}O$ around 280cm may reflect that an important transition to a dry phase took place around A.D. 450. People probably stopped cultivating crops due to dry conditions prevailing since ca. A.D. 450. The second period, the post-Conquest, exhibits a dramatic increase of sporormiella, dung fungal spores resulted fron the introduction of cattle. Low Poaceae frequency and charcoal production and high $\delta^{13}C$ values, magnetic susceptibility, and organic contents all indicate the arrival of the Spanish. Most importantly, it seems that mesquite (Prosopis juliflora) could have benefits from declined fire frequencies caused by cattle grazing. The study area is now entirely dominated by woody plants like mesquite, which clearly demonstrates that serious vegetation change occurred in the study area.