• Mycobiology
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• 제42권4호
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• pp.376-384
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• 2014

Roselle (Hibiscus sabdariffa L.) is one of the most important medicinal crops in many parts of the world. In this study, the effects of microelements, antioxidants, and bioagents on Fusarium oxysporum, F. solani, and Macrophomina phaseolina, the causal pathogens of root rot and wilt diseases in roselle, were examined under field conditions. Preliminary studies were carried out in vitro in order to select the most effective members to be used in field control trials. Our results showed that microelements (copper and manganese), antioxidants (salicylic acid, ascorbic acid, and EDTA), a fungicide (Dithane M45) and biological control agents (Trichoderma harzianum and Bacillus subtilis) were significantly reduced the linear growth of the causal pathogens. Additionally, application of the previous microelements, antioxidants, a fungicide and biological control agents significantly reduced disease incidence of root rot and wilt diseases under field conditions. Copper, salicylic acid, and T. harzianum showed the best results in this respect. In conclusion, microelements, antioxidants, and biocontrol agents could be used as alternative strategies to fungicides for controlling root rot and wilt diseases in roselle.

• 한국균학회지
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• 제49권4호
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• pp.441-454
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• 2021

Fungal diseases including anthracnose, stem rot, blight, wilting, and root rot of crops are caused by phytopathogens such as Colletotrichum species, Sclerotinia sclerotiorum, Phytophthora species, and Fusarium oxysporum and F. solani which threaten the production of chili pepper. In this study, to identify biological control agents (BCAs) of phytopathogenic fungi, potentially useful Bacillus species were isolated from the field soils. We screened out five Bacillus strains with antagonistic capacity that are efficiently inhibiting the growth of phytopathogenic fungi. Bacillus species were characterized by the production of extracellular enzymes, siderophores, and indole-3-acetic acid (IAA). Furthermore, the influence of bacterial strains on the plant growth promoting activity and seedling vigor index were assessed using Brassica juncea as a model plant. Inoculation with Bacillus subtilis SRCM 121379 significantly increased the length of B. juncea shoots and roots by 45.6% and 52.0%, respectively. Among the bacterial isolates, Bacillus subtilis SRCM 121379 showed the superior enzyme activities, antagonistic capacity and plant growth promoting effects. Based on the experimental results, Bacillus subtilis SRCM 121379 (GenBank accession no. NR027552) was finally selected as a BCA candidate.

• The Plant Pathology Journal
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• 제35권2호
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• pp.149-155
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• 2019

The antimicrobial activity of acetone, hexane, dichloromethane, and methanol extracts from leaves, stems, immature green fruits, and red fruits of tomato plants was examined against six phytopathogens. The minimum inhibitory concentration (MIC) of the acetonic extracts from these four plant parts was lower than that of the other solvents. Among the acetonic extracts, tomato leaves had a lower MIC than the other tomato parts. The acetonic extract from tomato leaves was therefore selected as a source of antimicrobial substances. The acetonic extract from tomato leaves inhibited mycelial growth of Fusarium oxysporum f. sp. lycopersici, Glomerella cingulata, and Rhizoctonia solani. Mycelial growth of R. solani treated with acetone extract from leaves showed more susceptibility than the other phytopathogens. Using 0.31 mg/ml of the acetonic extract from leaves, mycelial growth of R. solani on days 1, 2, and 3 decreased by 50.0, 52.1, and 64.0%, respectively, compared with acetone solvent treatment. The antimicrobial compounds effective against R. solani were identified as linolenic acid and caffeic acid by bioautography and GC-MS. These two compounds were used to treat six phytopathogens to confirm their antimicrobial activities. Linolenic acid inhibited mycelial growth of R. solani, while caffeic acid showed only slight antimicrobial activity. Results indicated that we propose extracts from tomato leaves which included antimicrobial compounds may provide a new lead in the pursuit of new biological sources of agrochemical candidates.

• Journal of Microbiology and Biotechnology
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• 제15권5호
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• pp.1001-1010
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• 2005

Bacillus megaterium KL39, an antibiotic-producing plant growth promoting rhizobacterium (PGPR), was selected from soil. The antifungal antibiotic, denoted KL39, was purified from culture filtrate by column chromatography using Dion HP-20, Silica gel, Sephadex LH-20, and prep-HPLC. Thin layer chromatography, employing the solvent system of ethanol:ammonia:water=8:1:1, showed the $R_{f}$. value of 0.32. The antibiotic KL39 showed a negative reaction with ninhydrin solution, positive with iodine vapor, and also positive with Ehrlich reagent. It was soluble in methanol, ethanol, butanol, and acetonitrile, but insoluble in chloroform, toluene, hexane, ethyl ether, or acetone. Its UV spectrum had the maximum absorption at 208 nm. Amino acid composition, FAB-mass, $^{1}H-NMR,\;^{13}C-NMR$, and atomic analyses showed that the antibiotic KL39 (MW=1,071) has a structure very similar to iturin E. The antibiotic KL39 has a broad antifungal spectrum against a variety of plant pathogenic fungi including Rhizoctonia solani, Pyricularia oryzae, Monilinia froeticola, Botrytis cinenea, Altenaria kikuchiana, Fusarium oxysporum, and F. solani. An MIC value of $10\;{\mu}g/ml$ was determined for Phytophthora capsici. Macromolecular incorporation studies with P. capsici using radioactive [$^{3}H-adenine$] as the precursor, indicated that the antibiotic KL39 strongly inhibits the DNA biosynthesis of the fungal cell. Microscopic observation of the antifungal action showed abnormal hyphal swelling of P. capsici. The purified antibiotic KL39 was very effective for the biocontrol of in vivo Phytophthora-blight disease of pepper.

• 한국균학회소식:학술대회논문집
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• 한국균학회 2014년도 추계학술대회 및 정기총회
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• pp.49-49
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• 2014

In order to find indigenous beneficial fungal species from crop field soils of Nigeria, 23 soil samples were collected from various places of Nigeria in June, 2013 and fungi were isolated through serial dilution technique. Isolated fungi were purified and differentiated according to their morphological and microscopic characteristics. In total, 38 different representative isolates were recovered and the genomic DNA of each isolates was extracted using QIAGEN$^{(R)}$ Plasmid Mini Kit (QIAGEN Sciences, USA) and the identification of fungi was carried out by sequence analysis of internal transcribed spacer (ITS) region of the 18S ribosomal DNA (18S rDNA). Recovered isolates belonged to 9 fungal genera comprising Fusarium, Aspergillus, Chaetomium, Coniothyrium, Dipodascaceae, Myrothecium, Neosartorya, Penicillium and Trichoderma. Aspergillus spp., Penicillium spp. and Trichoderma spp. were the most dominant taxa in this study. The antagonistic potentiality of species belonged to Trichoderma against 10 phytopathogenic fungi (F. oxysporum, C. gloesporoides, P. cytrophthora, A. alternata, A. solani, S. rolfsii, F. solani, R. solani, S. sclerotiorum and P. nicotiana) was assessed in vitro using dual culture assay. The dual culture assay results showed varied degree of antagonism against the tested phytopathogens. The potential Trichoderma spp. will be further evaluated for their antagonistic and plant growth promotion potentiality under in vivo conditions.

• The Plant Pathology Journal
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• 제33권5호
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• pp.499-507
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• 2017

In an attempt to develop a biological control agent against mycotoxigenic Fusarium species, we isolated Bacillus amyloliquefaciens strain DA12 from soil and explored its antimicrobial activities. DA12 was active against the growth of mycotoxigenic F. asiaticum, F. graminearum, F. proliferatum, and F. verticillioides both in vitro and in planta (maize). Further screening using dual culture extended the activity range of strain DA12 against other fungal pathogens including Botrytis cinerea, Colletotrichum coccodes, Endothia parasitica, Fusarium oxysporum, Raffaelea quercus-mongolicae, and Rhizoctonia solani. The butanol extract of the culture filtrate of B. amyloliquefaciens DA12 highly inhibited the germination of F. graminearum macroconidia with inhibition rate 83% at a concentration of $31.3{\mu}g/ml$ and 100% at a concentration of $250{\mu}g/ml$. The antifungal metabolite from the butanol extract was identified as iturin A by thin layer chromatography-bioautography. In addition, volatile organic compounds produced by DA12 were able to inhibit mycelial growth of various phytopathogenic fungi. The volatile compounds were identified as 2-heptanone, 5-methyl heptanone and 6-methyl heptanone by gas chromatography-mass spectrometry (GC-MS) analysis. These results indicate that the antagonistic activity of Bacillus amyloliquefaciens DA12 was attributable to iturin A and volatile heptanones, and the strain could be used as a biocontrol agent to reduce the development of Fusarium diseases and mycotoxin contamination of crops.

• 농약과학회지
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• 제4권3호
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• pp.19-26
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• 2000

토양 및 식물체 시료로부터 분리한 총 70개의 Fusarium속 균주를 감자 즙액배지와 쌀 고체배지에 배양한 다음 살균, 살충 및 제초활성 등의 생물활성을 조사하였다. 액체배지 시료들 중 한 가지 이상의 식물병에 대하여 80% 이상의 방제가를 보이는 것은 8개 시료였으며, 이 중 Fusarium sp. FO-80균주는 여섯 가지 병 중 벼.도열병, 밀.붉은녹병 및 보리 흰가루병 등 세 가지 식물병에 대하여 95% 이상의 높은 방제가를 나타내어 가장 항균활성이 높은 것으로 나타났다. 고체배지 시료에서는 21개의 시료가 80% 이상의 방제효과를 보였고, 이 중 가장 강한 항균활성을 보이는 F. equiseti FO-68균주는 벼 도열병, 토마토 역병 및 밀 붉은녹병에 대하여 95% 이상의 높은 방제효과를 보였다. 살충활성 실험결과 한 가지 이상의 곤충 및 응애에 대하여 80% 이상 살충효과를 보이는 것은 액체배지 시료 2개와 고체배지 시료 1개였다. F. oxysporum FO-61균주와 Fusarium sp. FO-80균주의 액체배지 시료는 복숭아혹진딧물과 배추좀나방에 대하여 각각 80% 이상의 살충효과를 나타내었고, Fusarium sp. FO-510균주의 고체배지 시료는 복숭아혹진딧물에 대하여 80%의 살충활성을 보였다. 그러나 액체배지와 고체배지 시료 모두 밭잡초에 대한 뚜렷한 활성은 보이지 않았다. 그리고 좀 개구리밥을 이용한 생물검정 결과 3개의 액체배지 시료가 배양액 1.25% 이하의 농도에서 70%의 제초활성을 보였고, 고체배지 시료 중에는 9개의 시료가 좀개구리밥 생장에 강한 억제 효과를 보였다. 한편, 여러 가지 생물활성에 대하여 상관관계를 조사한 결과 고체배지 시료와 액체배지 시료 모두 좀개구리밥에 대한 제초활성과 항균활성간에는 상관관계가 있는 것으로 나타났다.

• 한국식품과학회지
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• 제44권5호
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• pp.634-637
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• 2012

딸기병해는 생육기 동안 과실의 생산량감소 및 품질저하를 가져오고 있으며, 약제방제의 어려움 등으로 인해 친환경적인 병해 방제법의 개발이 요구된다. 실내에서 자외선(UV-C, 264 nm)조사에 의한 딸기병원균의 균사생장 억제효과를 구명하기 위하여 5종의 딸기병원균을 자외선을 조사하면서 $25^{\circ}C$ 항온실에서 배양한 후 균총의 직경을 측정하였다. 5종의 딸기병원균을 PDA 상에서 배양하면서 자외선을 조사하면, 하루 1시간 조사에 의해서도 생장이 억제되었고 9-12시간을 조사한 균의 생육은 현저하게 억제되었으며 역병균은 생육이 완전하게 억제되었다. 자외선광원과 병원균의 거리에서는 40-50 cm의 거리에서 자외선을 조사한 배양기에서 병원균생장의 억제효과가 크게 나타났다. 배지에 접종한 후 바로 자외선을 처리한 병원균은 모두 2일간 배양한 후 자외선을 접종한 배양기에서보다 생육이 억제되었다. 딸기 탄저병균(C. gloeosprioides)과 시들음병균(F. oxysporum)은 V8A에서 자외선에 의한 균의 생장억제효과가 큰 것으로 나타났다.

• Journal of Ginseng Research
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• 제40권2호
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• pp.97-104
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• 2016

Background: Rhizobacteria play an important role in plant defense and could be promising sources of biocontrol agents. This study aimed to screen antagonistic bacteria and develop a biocontrol system for root rot complex of Panax notoginseng. Methods: Pure-culture methods were used to isolate bacteria from the rhizosphere soil of notoginseng plants. The identification of isolates was based on the analysis of 16S ribosomal RNA (rRNA) sequences. Results: A total of 279 bacteria were obtained from rhizosphere soils of healthy and root-rot notoginseng plants, and uncultivated soil. Among all the isolates, 88 showed antagonistic activity to at least one of three phytopathogenic fungi, Fusarium oxysporum, Fusarium solani, and Phoma herbarum mainly causing root rot disease of P. notoginseng. Based on the 16S rRNA sequencing, the antagonistic bacteria were characterized into four clusters, Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetesi. The genus Bacillus was the most frequently isolated, and Bacillus siamensis (Hs02), Bacillus atrophaeus (Hs09) showed strong antagonistic activity to the three pathogens. The distribution pattern differed in soil types, genera Achromobacter, Acidovorax, Brevibacterium, Brevundimonas, Flavimonas, and Streptomyces were only found in rhizosphere of healthy plants, while Delftia, Leclercia, Brevibacillus, Microbacterium, Pantoea, Rhizobium, and Stenotrophomonas only exist in soil of diseased plant, and Acinetobacter only exist in uncultivated soil. Conclusion: The results suggest that diverse bacteria exist in the P. notoginseng rhizosphere soil, with differences in community in the same field, and antagonistic isolates may be good potential biological control agent for the notoginseng root-rot diseases caused by F. oxysporum, Fusarium solani, and Panax herbarum.

• The Plant Pathology Journal
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• 제17권3호
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• pp.141-148
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• 2001

Postharvest decay of onion bulbs was examined by inspecting the commercial packages in the market or in storage. Bulb rot incidence was unexpectedly high, and onion bulbs with 1st quality grade were rotten most severely by 51%, followed by 32% for 2nd and 21% for 3rd grades. This indicates that larger bulbs had higher incidences of bulb rots. Major pathogens associated with basal and neck rots were Fusarium oxysporum and Aspergillus sp. or Botrytis allii, respectively, of which basal rot was most prevalent and damaging during storage. Among the epiphytic microorgani는 from onion plants, several Bacillus and Paenibacillus spp. and previously selected Pseudomonas putida and Trichoderma harzianum had inhibitory efficacy against bulb rot pathogens. Among these B. amyloliquefaciens BL-3, Paenibacillus polymyxa BL-4, and P. putida Cha 94 were highly inhibitory to conidial germination of F. oxysporum and B. allii. P. putida Cha 94, B. amyloliquefaciens BL-3, P. polymyxa BL-4, and T. harzianum TM were applied in the rhizoplane of onion at transplanting. Initially antagonist populations decreased rapidly during the first one month. However, among these antagonists, rhizoplane population densities of BL-3, Cha 94, and TM were consistently high thereafter, maintaining about 10$^4$-10$^{5}$ cells or spores per gram of onion root up to harvest time. The other bacterial antagonist BL-4 survived only for two months. TM was the most effective biocontrol agent against basal rot, with the number of rotten bulbs recorded at 4%, while that of the control was 16%. Cha 94 was effective for the first 20 days, but basal rot increased thereafter and had about the same control efficacy as that of BL-3 and BL-4. When the antagonists were applied to the topping areas of onion bulbs at harvest, TM was the most effective in protecting the stored onion bulbs from neck rotting. The second effective antagonist was BL-3. TM and BL-3 completely suppressed the neck rot in another test, suggesting that biocontrol of postharvest decay of onion using these microorganisms either at the time of transplanting or at harvesting may be promising.