Red Pepper Anthracnose Research Articles

Evaluation of Trichoderma atroviride and Trichoderma longibrachiatum as biocontrol agents in controlling red pepper anthracnose in Korea.

Anthracnose disease is a serious threat to red pepper crops in Korea and many other countries, resulting in considerable yield losses. There are now no effective control techniques available except for fungicide sprays, which may directly impact consumers. This study aims to investigate the biological activity of Trichoderma isolates in controlling red pepper anthracnose caused by Colletotrichum acutatum in vitro and in the field. Out of 11 Trichoderma isolates screened for biocontrol agents against three fungal pathogens, including C. acutatum; two effective Trichoderma isolates, T. atroviride ATR697 (ATR697) and T. longibrachiatum LON701 (LON701) were selected for further investigation. Using the overlapping plates experiment, it was discovered that the volatile organic compounds (VOCs) produced by ATR697 strongly inhibited C. acutatum mycelial growth to a larger extent than the isolate LON701. A cellophane membrane experiment has shown that mycelial growth of C. acutatum was inhibited by 36% and 27% when treated with ATR697 and LON701, respectively. Culture filtrates (CFs) of two Trichoderma isolates inhibited the mycelial growth of C. acutatum in vitro. When red peppers were treated with spore suspensions of LON701 and ATR697, the disease severity (%) was 44.1% and 55.8%, respectively, in a curative method; while the disease severity (%) was 5% and 11.6%, in LON701- and ATR697-treated red peppers, respectively, in a preventive method. These results showed the suppression of disease severity (%) was relatively higher in the preventive method than in the curative method. Furthermore, Trichoderma isolates ATR697 and LON701 were resistant to commercial chemical fungicides in vitro, indicating these strains may also be used synergistically with a chemical fungicide (pyraclostrobin) against the growth of C. acutatum. There was no difference in the inhibition rate (%) of the pathogen between the treatment with LON701 alone and LON701+pyraclostrobin. Based on in vitro findings, ATR697 and LON701 played a role in effectively controlling red pepper anthracnose in field conditions, with LON701 treatment resulting in a disease rate of 14% when compared to ATR697, chemical, and non-treated controls. Overall, our study showed the ability of Trichoderma isolates to control red pepper anthracnose and their potential to develop as novel biocontrol agents to replace chemical fungicides for eco-friendly, sustainable agriculture.

Identification and characterization of Brevibacillus halotolerans B-4359: a potential antagonistic bacterium against red pepper anthracnose in Korea.

Our study aimed to identify potential biocontrol agents (BCAs) against major phytopathogens under in vitro conditions by screening the Freshwater Bioresources Culture Collection (FBCC), Korea. Of the identified 856 strains, only 65 exhibited antagonistic activity, among which only one representative isolation, Brevibacillus halotolerans B-4359 was selected based on its in vitro antagonistic activity and enzyme production. Cell-free culture filtrate (CF) and volatile organic compounds (VOCs) of B-4359 were shown to be effective against the mycelial growth of Colletotrichum acutatum. Notably, B-4359 was found to promote spore germination in C. acutatum instead of exhibiting a suppressive effect when the bacterial suspension was mixed with the spore suspension of C. acutatum. However, B-4359 showed an excellent biological control effect on the anthracnose of red pepper fruits. Compared to other treatments and untreated control, B-4359 played a more effective role in controlling anthracnose disease under field conditions. The strain was identified as B. halotolerans using BIOLOG and 16S rDNA sequencing analyses. The genetic mechanism underlying the biocontrol traits of B-4359 was characterized using the whole-genome sequence of B-4359, which was closely compared with related strains. The whole-genome sequence of B-4359 consisted of 5,761,776 bp with a GC content of 41.0%, including 5,118 coding sequences, 117 tRNA, and 36 rRNA genes. The genomic analysis identified 23 putative secondary metabolite biosynthetic gene clusters. Our results provide a deep understanding of B-4359 as an effective biocontrol agent against red pepper anthracnose for sustainable agriculture.

Preparation and potential of nanoparticles containing curcuminoids to control fungal diseases in tropical fruits

Colletotrichum species cause anthracnose in various tropical crops in both cultivation and postharvest periods. The current synthetic fungicides to treat anthracnose sometime show toxic effects for farmers, residues on foods, and environmental impacts. In this work, turmeric extract containing curcuminoids was used as an active ingredient and formulated into a nanoemulsion to control anthracnose in red pepper and tomato fruits. The nanoparticles containing turmeric extract (25 %) were successfully prepared by encapsulation using Tween-80 and PEG 400 as emulsifiers. Out of the three main curcuminoids in the turmeric extract, BDMC was determined as the most abundant constituent via HPLC analysis. Turmeric nanoparticles showed an average particle size of 203 nm, polydispersity index (PI) of 0.322, and zeta potential of -92.7 mV. In the in vitro antifungal bioassay, this nanoformulation significantly inhibited the mycelial growth of Colletotrichum gloeosporioides and Colletotrichum orbiculare in a dose-dependent manner. Red pepper anthracnose was also consistently suppressed by turmeric nanoparticles but the tomato anthracnose was resistant to this formulation at 10 mg/mL in vivo. The study results proved the effectiveness of turmeric nanoparticles to control red pepper anthracnose in postharvest preservation and suggested developing the innovative nanoformulation as a green fungicide.

Detection of Colletotrichum spp. Resistant to Benomyl by Using Molecular Techniques.

Colletotrichum species is known as the major causal pathogen of red pepper anthracnose in Korea and various groups of fungicides are registered for the management of the disease. However, the consistent use of fungicides has resulted in the development of resistance in many red pepper-growing areas of Korea. Effective management of the occurrence of fungicide resistance depends on constant monitoring and early detection. Thus, in this study, various methods such as agar dilution method (ADM), gene sequencing, allele-specific polymerase chain reaction (PCR), and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) were applied for the detection of benzimidazole resistance among 24 isolates of Colletotrichum acutatum s. lat. and Colletotrichum gloeosporioides s. lat. The result of the ADM showed that C. gloeosporioides s. lat. was classified into sensitive and resistant isolates to benomyl while C. acutatum s. lat. was insensitive at ≥1 µg/ml of benomyl. The sequence analysis of the β-tubulin gene showed the presence of a single nucleotide mutation at the 198th amino acid position of five isolates (16CACY14, 16CAYY19, 15HN5, 15KJ1, and 16CAYY7) of C. gloeosporioides s. lat. Allele-specific PCR and PCR-RFLP were used to detect point mutation at 198th amino acid position and this was done within a day unlike ADM which usually takes more than one week and thus saving time and resources that are essential in the fungicide resistance management in the field. Therefore, the molecular techniques established in this study can warrant early detection of benzimidazole fungicide resistance for the adoption of management strategies that can prevent yield losses among farmers.

Identification and Characterization of Bacillus tequilensis GYUN-300: An Antagonistic Bacterium Against Red Pepper Anthracnose Caused by Colletotrichum acutatum in Korea.

Anthracnose is a fungal disease caused by Colletotrichum species and has detrimental effects on many crops, including red pepper. This study used Bacillus tequilensis GYUN-300 (GYUN-300), which exhibit antagonistic activity against the fungal pathogen, Colletotrichum acutatum. This pathogen causes anthracnose that manifests primarily as a fruit rot in red pepper. There have been little efforts to identify antagonistic bacteria from mushrooms; this strain of bacteria was identified as B. tequilensis using BIOLOG and 16S rDNA sequencing analysis. The genetic mechanism underpinning the biocontrol traits of GYUN-300 was characterized using the complete genome sequence of GYUN-300, which was closely compared to related strains. GYUN-300 inhibited mycelial growth and spore germination of C. acutatum under in vitro conditions. Important antagonistic traits, such as siderophore production, solubilization of insoluble phosphate, and production of lytic enzymes (cellulase, protease, and amylase), were observed in GYUN-300, These trains promoted growth in terms of seed germination and vigorous seedling growth compared to the non-treated control. When red pepper fruits were treated with GYUN-300, the preventive and curative effects were 66.6 and 38.3% effective, respectively, in wounded red pepper fruits; there was no difference between the preventive and curative effects in non-wounded red pepper fruits. Furthermore, GYUN-300 was resistant to several commercial fungicides, indicating that GYUN-300 bacterial cells may also be used synergistically with chemical fungicides to increase biocontrol efficiency. Based on in vitro results, GYUN-300 played a role to control anthracnose disease effectively in field conditions when compared to other treatments and non-treated controls. The results from this study provide a better understanding of the GYUN-300 strain as an effective biocontrol agent against red pepper anthracnose; this form of biocontrol provides an environment-friendly alternative to chemical fungicides.

IoT 및 클라우드 기반 유해 야생동물과 고추 탄저병 탐지 시스템

본 논문에서는 유해 야생동물과 고추 탄저병을 효율적으로 조기에 탐지하여 농작물 피해를 최소화할 수 있는 IoT 및 클라우드 시스템을 제안한다. 이 시스템은 실시간 처리가 가능하고 인식성능이 우수한 객체인식 알고리즘인 You Only Look Once (YOLO)와 농지를 이동하는 탐색로봇을 이용하여 신속하게 유해동물과 고추 탄저병을 탐지하고 탐지된 객체에 따라 적절한 조치를 취한다. 또한 제안한 시스템은 수집한 센서 데이터 및 기상 정보를 활용하여 고추 탄저병 발생 위험도를 예측하고 사전에 방제할 수 있는 기능을 제공한다. 이 시스템은 사용자 편의를 위해 음성인식 기능을 제공하여 사용자가 스마트폰 상의 음성명령으로 이 시스템을 동작시킬 수 있다. 제안한 시스템의 성능 검증을 위해 이 시스템을 실제 구현하여 유해동물과 고추 탄저병 인식률, 음성명령 인식률, 고추 탄저병 발생위험도 예측 등에 대한 평가실험을 수행한다. 그리고 그 실험결과로부터 제안한 시스템의 우수성을 보인다.

Selection of Antifungal Bacteria <i>Burkholderia lata</i> CAB13001 for Control on Red Pepper Anthracnose and Its Control Efficacy in Field

Selection of Antifungal Bacteria <i>Burkholderia lata</i> CAB13001 for Control on Red Pepper Anthracnose and Its Control Efficacy in Field

Diffusible and Volatile Antifungal Compounds Produced by an Antagonistic Bacillus velezensis G341 against Various Phytopathogenic Fungi.

The aim of this study was to identify volatile and agar-diffusible antifungal metabolites produced by Bacillus sp. G341 with strong antifungal activity against various phytopathogenic fungi. Strain G341 isolated from four-year-old roots of Korean ginseng with rot symptoms was identified as Bacillus velezensis based on 16S rDNA and gyrA sequences. Strain G341 inhibited mycelial growth of all phytopathogenic fungi tested. In vivo experiment results revealed that n-butanol extract of fermentation broth effectively controlled the development of rice sheath blight, tomato gray mold, tomato late blight, wheat leaf rust, barley powdery mildew, and red pepper anthracnose. Two antifungal compounds were isolated from strain G341 and identified as bacillomycin L and fengycin A by MS/MS analysis. Moreover, volatile compounds emitted from strain G341 were found to be able to inhibit mycelial growth of various phytopathogenic fungi. Based on volatile compound profiles of strain G341 obtained through headspace collection and analysis on GC-MS, dimethylsulfoxide, 1-butanol, and 3-hydroxy-2-butanone (acetoin) were identified. Taken together, these results suggest that B. valezensis G341 can be used as a biocontrol agent for various plant diseases caused by phytopathogenic fungi.

올리고키토산에 의한 토마토 역병과 감자 역병의 방제

키토산은 D-glucosamine과 N-acetyl-D-glucosamine이 <TEX>${\beta}$</TEX>-(1-4)로 연결된 직선상의 다당류이다. 분자량이 3,000 amu 이상인 키토산에 대한 in vivo 항균활성 및 저항성 유도 활성에 대한 보고는 많지만, 분자량이 3,000 이하인 올리고키토산에 대한 in vivo 항균활성에 대한 논문은 거의 전무한 상태이다. 본 연구에서 올리고키토산은 P. infestans에 의해 발생하는 토마토 역병에 대하여 500 <TEX>${\mu}g$</TEX>/ml과 1,000 <TEX>${\mu}g$</TEX>/ml 수준에서 94% 이상의 매우 높은 접종 1일전 예방효과를 보였으며, 고추 탄저병과 밀 붉은녹병에 대해서는 500 <TEX>${\mu}g$</TEX>/ml과 1,000 <TEX>${\mu}g$</TEX>/ml 수준에서 67% 내지 89%의 중간 정도의 에방효과를 항온항습실 조건에서 보였다. 다른 한편으로 올리고키토산은 고추 탄저병에 대하여 접종 16시간 후 치료효과를 보였지만, 토마토 역병에 대해서는 치료효과를 전혀 보이지 않았다. 포장에서 올리고키토산 액제는 감자 역병과 토마토 역병에 대하여 각각 72%와 48%의 방제효과를 보였다. 이상의 결과는 올리고키토산이 감자 및 토마토 역병 방제를 위한 친환경 유기농자재로서 사용이 가능하다는 것을 강력하게 나타낸다. Chitosan is a linear polysaccharide composed of randomly distributed <TEX>${\ss}$</TEX>-(1-4)-linked D-glucosamine and Nacetyl-D-glucosamine. There have been many reports on the induced systemic resistance and in vivo antifungal activities of higher molecular weight chitosans with molecular weights over 3,000 amu (atomatic mass unit), but there are few papers on in vivo antifungal activities of low molecular weight chitosans (oligochitosans) with molecular weights less than 3,000 amu. In our study, an oligochitosan sample (320.3,000 amu) showed a potent 1-day protective activity with control values more than 94% at concentrations of 500 and 1,000 <TEX>${\mu}g$</TEX>/ml especially against tomato late blight caused by Phytophthora infestans under growth chamber conditions. It also displayed a moderate 1-day protective activity with control values of 67.89% at concentrations of 500 and 1,000 <TEX>${\mu}g$</TEX>/ml against wheat leaf rust and red pepper anthracnose. On the other hand, it showed a 16-hr curative activity against red pepper anthracnose, but not against tomato late blight and wheat leaf rust. In field experiments, oligochitosan effectively suppressed the development of late blight on potato and tomato plants with control values of 72% and 48%, respectively. The results strongly indicate that oligochitosan can be used as an eco-friendly organic material for the control of late blight on tomato and potato plants.

당귀로부터 분리한 decursinol angelate의 밀 붉은녹병에 대한 항균활성

녹병은 다양한 작물의 품질과 수확량에 큰 영향을 끼친다. 따라서 이들을 방제하기 위하여 효과적이고 환경친화적인 살균제의 개발이 절실하다. 본 연구에서는 한약재로부터 항균 물질을 탐색하는 과정에서, 당귀 메탄올 추출물이 Puccinia recondita에 의해 발생하는 밀 붉은녹병에 대하여 우수한 방제효과를 나타내는 것을 확인하였다. 밀 붉은녹병에 대하여 활성을 보이는 한 개의 항균물질을 silica gel chromatography, alumina column chromatography와 <TEX>$C_{18}$</TEX> preparative HPLC를 통해 분리, 정제하였다. 분리한 항균물질은 EI-MS와 <TEX>$^1H$</TEX>-NMR의 기기 분석 결과 decursinol angelate로 동정되었다. 이 물질은 시험한 6개의 식물병 중에서 밀 붉은녹병과 고추 탄저병에 대하여 우수한 항균활성을 보였다. 또한, 당귀의 에틸아세테이트 추출물의 수화제도 밀 붉은녹병에 대해 우수한 항균활성이 보였다. 따라서 decursinol angelate와 이를 포함한 당귀 추출물을 이용할 경우 밀 붉은녹병을 방제할 수 있는 새로운 살균제의 개발이 가능하리라 생각된다. 본 논문에서 decursinol angelate에 의한 밀 붉은녹병 방제 효과를 처음 보고하는 바이다. Rust causes significant losses in the yield and quality of various crops. The development of new effective and environmentally benign agents against the pathogen is of great interest. In the course of searching a natural antifungal compound from medicinal plants, we found that the methanol extract of Angelica gigas roots had a potent control efficacy against wheat leaf rust (WLR) caused by Puccinia recondita. The antifungal substance was isolated from the methanol extract by silica gel column chromatography, alumina column chromatography and <TEX>$C_{18}$</TEX> preparative HPLC. It was identified as decursinol angelate by EI-MS and <TEX>$^1H$</TEX>-NMR data. In in vivo test, decursinol angelate effectively suppressed the development of WLR and red pepper anthracnose (RPA) among the 6 plant diseases tested. In addition, the wettable powder-type formulation of ethyl acetate extract of A. gigas roots significantly suppressed the development of WLR. The crude extract containing decursinol angelate and the chemical appear to be a potential candidate for control of WLR. In addition, this is the first report on the in vivo antifungal activity of decursinol angelate against WLR as well as RPA.

Antifungal activity of polyacetylenes isolated from Cirsium japonicum roots against various phytopathogenic fungi

Antifungal substances from a methanol extract of Cirsium japonicum roots were purified and characterized, and their antifungal activities against various plant pathogens were evaluated. Three polyacetylene substances were isolated from roots of C. japonicum using repeated column chromatography; these were identified as ciryneol A, ciryneol C and 1-heptadecene-11,13-diyne-8,9,10-triol by mass and nuclear magnetic resonance spectral analyses. In vitro antifungal activity of the three substances varied according to compound and target species. Magnaporthe oryzae, Colletotrichum coccodes, Colletotrichum acutatum, Pythium ultimum and Botrytis cinerea were relatively sensitive to the three polyacetylenes, with IC 50 values below 50 μg mL −1. In vivo, they all showed similar and broad antifungal spectra against the seven plant diseases tested. At 500 μg mL −1, all three compounds effectively suppressed the development of rice blast, rice sheath blight, tomato late blight, wheat leaf rust and red pepper anthracnose, with control values over 90%. They were highly active especially against wheat leaf rust; they controlled the development of this disease more than 88% even at a concentration of 125 μg mL −1. In addition, ciryneol C effectively suppressed barley powdery mildew. This is the first report on the antifungal activities of the three polyacetylenes from roots of C. japonicum against plant pathogenic fungi. Polyacetylenes from roots of C. japonicum may contribute to the development of environmentally safer alternatives to protect crops from various phytopathogenic fungi.

Effect of polyacetylenic acids from Prunella vulgaris on various plant pathogens

This study is aiming at characterizing antifungal substances from the methanol extract of Prunella vulgaris and at investigating those substances' antifungal and antioomycete activities against various plant pathogens. Two polyacetylenic acids were isolated from P. vulgaris as active principles and identified as octadeca-9,11,13-triynoic acid and trans-octadec-13-ene-9,11-diynoic acid. These two compounds inhibited the growth of Magnaporthe oryzae, Rhizoctonia solani, Phytophthora infestans, Sclerotinia sclerotiorum, Fusarium oxysporum f. sp. raphani, and Phytophthora capsici. In addition, these two compounds and the wettable powder-type formulation of an n-hexane fraction of P. vulgaris significantly suppressed the development of rice blast, tomato late blight, wheat leaf rust, and red pepper anthracnose. These data show that the extract of P. vulgaris and two polyacetylenic acids possess antifungal and antioomycete activities against a broad spectrum of tested plant pathogens. This is the first report on the occurrence of octadeca-9,11,13-triynoic acid and trans-octadec-13-ene-9,11-diynoic acid in P. vulgaris and their efficacy against plant diseases. The crude extract containing the two polyacetylenic acids can be used as a natural fungicide for the control of various plant diseases.

Control Efficacy of Phloretin Isolated from Apple Fruits Against Several Plant Diseases

In the course of a searching natural antifungal compounds from plant sources, we found that the methanol extract (<TEX>$3,000\;{\mu}g/ml$</TEX>) of Malus domestica fruits had potential of control against rice blast (Magnaporthe grisea) and tomato late blight (Phytophthora infestans). Under bioassay-guided purification, we isolated phloretin, a phenolic compound, with in vivo antifungal activity against M. grisea. By 1-day protective application of phloretin (<TEX>$500\;{\mu}g/ml$</TEX>), the compound strongly inhibited the disease development of M. grisea and P. infestans on rice and tomato seedlings, respectively. And red pepper anthracnose caused by Colletotrichum coccodes also was moderately suppressed. However, rice sheath blight (Rhizoctonia solani AG1), and barley powdery mildew (Blumeria graminis f. sp. hordei) were hardly controlled. In addition, the compound showed in vitro antifungal activity against some plant pathogenic fungi including Phytophthora capsici, Alternaria panax, Sclerotinia sclerotiorum, R. solani AG4, and M. grisea. This is the first report on the antifungal activity of phloretin against plant pathogenic fungi.

Pseudomonas sp. RRj 228이 분비하는 항균물질의 동정과 고추탄저균 C. acutatum에 대한 항균활성

식물 근권미생물은 식물의 뿌리 표면과 내부에 정착하면서 식물생장 촉진물질을 분비하여 식물생육에 직접적인 영향을 주거나, 항균물질을 분비하여 병원균으로부터 식물 근권환경을 보호하여 식물의 생육을 촉진하게 된다. 이러한 활성을 갖고 있는 미생물을 분리하여 동정하며, 항균물질을 분리, 동정하여 지속농업의 발전과 농업환경의 보전을 위하여 연구를 실시하였다. 논토양으로부터 식물생육촉진활성과 항균활성을 갖는 RRj 228균주를 분리하여, 생리 생화학적방법과 유전학적 방법으로 동정한 결과, Pseudomonas sp.로 동정되었다. RRj 228균주는 B. cinerea, P. ultimum, P. capsici와 R. solani에도 높은 항균활성을 보였으며, 특히 고추탄저병원균인 C. acutatum에 강력한 항균활성을 나타냈다. RRj 228균의 배양여액을 C. acutatum, R. solani 및 P. ultimum에 대한 <TEX>$ED_{50}$</TEX>값을 측정한 결과 0.14, 0.16, 0.29 mg/ml로 나타났다. 항균활성물질은 RRj 228 배양여액으로부터 각종 크로마토그라피법으로 순수분리하고, NMR과 GC/MS 등의 기기분석을 실시하여 구조를 Phenazine-1-carboxylic acid (분자량 224)로 동정하였다. Microorganisms near the plant rhizosphere usually inhabit the surface or the inside of the plant roots and have a direct effect on plant growth by secreting plant growth promoters or antagonistic materials which protect the root zone system from various pathogens. This study was carried out to identify and isolate the antagonistic materials after isolation of microorganisms showing high antagonistic activities, in hopes of contributing to the development of sustainable agriculture and the preservation of agricultural environments. A number of antagonistic bacteria were isolated from paddy soil. Among isolates, RRj 228 showed plant growth promotion and antagonistic activity. RRj 228 was identified as Pseudomonas sp. according to the results of physiological properties and genetic methods. On the basis of the results of anti-fungal spectrum against several pathogens by RRj 228, the antagonistic effect of the isolate against Botrytis cinerea, Pythium ultimum, Phytopthola capsici, and Rhizoctonia solani, especially against red-pepper anthracnose caused by Colletotrichum acutatum, was remarkable. The experiment evaluating the biological control effect by RRj 228 revealed that the <TEX>$ED_{50}$</TEX> value by the RRj 228 culture against C. acutatum, R. solani and P. ultimum were 0.14 mg/ml, 0.16 mg/ml and 0.29 mg/ml, respectively. An antagonistic substance was isolated and purified by several chromatographies from the RRj 228 culture. The <TEX>$^1H$</TEX> and <TEX>$^{13}C$</TEX> assignment of the antagonistic substance was achieved from two-dimensional <TEX>$^1H-^1H$</TEX> COSY, HMQC, and HMBC. Finally, the antagonistic substance was identified as Phenazine-1-carboxylic acid (<TEX>$C_{13}H_8N_2O_2$</TEX>, M.W.=224).

Rhamnolipid B에 의한 토마토 잿빛곰팡이병과 역병의 억제효과

기계유가 심하게 오염된 토양으로부터 생물계면활성제를 생산하고 항균활성과 살충활성을 보이는 Pseudomonas sp. SG3 균주를 분리하였다. 이 길항세균은 시험한 8개의 식물병원곰팡이 모두에 대하여 균사생육저해활성을 보였다. 또한 in vivo assay에서는 SG3 액체 배양액 처리시 벼도열병, 토마토 잿빛곰팡이병, 토마토 역병, 밀 붉은녹병, 보리 흰가루병 및 고추 탄저병에 강한 항균 효과를 보였다. 액체배양액으로부터 ethyl acetate 추출, silica gel column chromatography 및 preparative HPLC 등을 통하여 한 개의 항균물질을 분리하였다. 질량분석과 핵자기공명분석을 통해 분리한 물질의 구조를 동정한 결과 rhamnolipid B로 동정되었다. Rhamnolipid B는 토마토 잿빛곰팡이병과 토마토 역병에 높은 방제활성을 보였다. 그리고 토마토 잿빛곰팡이병균인 B. cinerea의 균사 생장과 토마토 역병균인 P. infestans의 유주자 발아 및 균사 생장을 효과적으로 억제하였다. Rhamnolipid B를 생산하는 Pseudomonas sp. SG3는 토마토에서 발생하는 식물병을 방제하는 새로운 생물방제제로서 이용이 가능할 것으로 기대된다. A Pseudomonas strain SG3 producing biosurfactant and showing antifungal and insecticidal activities was isolated from agricultural soil severely contaminated with machine oils. The antagonistic bacterium inhibited mycelial growth of all of the tested fungal pathogens. The fermentation broth of SG3 also effectively suppressed the development of various plant diseases including rice blast, tomato gray mold, tomato late blight, wheat leaf rust, barley powdery mildew and red pepper anthracnose. An antifungal substance was isolated from the fermentation broth of SG3 by ethyl acetate partitioning, silica gel column chromatography and preparative HPLC under the guide of bioassay. The chemical structure of the antifungal substance was determined to be rhamnolipid B by mass and NMR spectral analyses. The antifungal biosurfactant showed a potent in vivo antifungal activity against gray mold and late blight on tomato plants. In addition, rhamnolipid B inhibited mycelial growth of B. cinerea causing tomato gray mold and zoospore germination and mycelial growth of P. infestans causing tomato late blight. Pseudomonas sp. SG3 producing rhamnolipid B could be used as a new biocontrol agent for the control of plant diseases occurring on tomato plants.

Effects of neolignans from the stem bark ofMagnolia obovataon plant pathogenic fungi

To characterize antifungal principles from the methanol extract of Magnolia obovata and to evaluate their antifungal activities against various plant pathogenic fungi. Four neolignans were isolated from stem bark of M. obovata as antifungal principles and identified as magnolol, honokiol, 4-methoxyhonokiol and obovatol. In mycelial growth inhibition assay, both magnolol and honokiol displayed more potent antifungal activity than 4-methoxyhonokiol and obovatol. Both magnolol and honokiol showed similar in vivo antifungal spectrum against seven plant diseases tested; both compounds effectively suppressed the development of rice blast, tomato late blight, wheat leaf rust and red pepper anthracnose. 4-Methoxyhonokiol and obovatol were highly active to only rice blast and wheat leaf rust respectively. The extract of M. obovata and four neolignans had potent in vivo antifungal activities against plant pathogenic fungi. Neolignans from Magnolia spp. can be used and suggested as a novel antifungal lead compound for the development of new fungicide and directly as a natural fungicide for the control of plant diseases such as rice blast and wheat leaf rust.

Antifungal Activity of the Methanol Extract of Myristica malabarica Fruit Rinds and the Active Ingredients Malabaricones Against Phytopathogenic Fungi

In a search for plant extracts with in vivo antifungal activity for plant diseases, we found that the methanol extract of Myristica malabarica fruit rinds effectively suppressed the development of several plant diseases. The methanol extract exhibited potent 1-day protective activity against rice blast, tomato late blight, wheat leaf rust and red pepper anthracnose. It also showed 7-day and 4-day protective activities against the plant diseases. Three antifungal resorcinols were isolated from the methanol extract of M. malabarica fruit rinds and identified as malabaricones A(MA), B(MB), and C(MC). Inhibitory activity of the three resorcinols against mycelial growth of plant pathogenic fungi varied according to compound and target species. All three compounds effectively reduced the development of rice blast, wheat leaf rust and red pepper anthracnose. In addition, MC was highly active for reducing the development of tomato late blight. This is the first report on the antifungal activities of malabaricones against filamentous fungi.

고추탄저병균 Colletotrichum gloeosporioides의 방제를 위한 길항 미생물의 분리 및 항진균 활성

노르웨이의 Oslo시 지역의 토양시료로부터 분리된 Bacillus sp. KMU-991를 이용하여 고추탄저병균인 Colletotruchum gloeosporioides KACC 40804에 대한 항진균 활성을 위한 배양 조건을 조사하였다. 항진균 물질의 생산은 기본배지로 TSB를 사용하였으며 탄소원으로 1.0% mannitol과 질소원으로 1.0% ammonium chloride를 첨가하였을 매 가장 높은 항진균 활성을 나타내었다. 배양조건으로는 <TEX>$30^{\circ}C$</TEX>, 180 rpm, 48시간 배양하였을 때 가장 높은 항진균 활성을 나타내었다. <TEX>$30{\sim}60%$</TEX> ammonium sulfate 침전물을 첨가하였을 때 가장 양호한 항진균 활성을 나타내었으며 butanol을 이용하여 배양액 중에 존재하는 항진균 물질을 회수하여 다양한 작물병원성 곰팡이에 대한 spectrum을 조사한 결과 B. cinerea KACC 40573, C. orbiculare KACC 40808, F. oxysporum f. sp. radicus-lycopersici KACC 40537, P. cambivora KACC 40160, 그리고 R. solani AG-4 KACC 40142등에 대하여도 높은 항진균 활성을 나타내었다. Bacillus sp. KMU-991 was isolated from Oslo city soils at Norway and shown a strong antifungal activity on red-pepper anthracnose, Colletotrichum gloeosporioides. Bacillus sp. KMU-991 produced a maximum level of antifungal substrate under aerobic incubation at <TEX>$30^{\circ}C$</TEX>, 180 rpm for 48 hours in TSB medium(initial pH 7.0) containing 1.0% mannitol and 1.0% ammonium chloride. Precipitate of culture broth by <TEX>$30{\sim}60%$</TEX> ammonium sulfate precipitation exhibited strong antifungal activity against C. gloeosporioides KACC 40804. Butanol extract of cultured broth also shown fungal growth inhibitory activity against Fusarium oxysporum f. sp. radicus-lycopersici KACC 40537, Rhizoctonia solani AG-4 KACC 40142, Botrytis cinerea KACC 40573, Colletotrichum orbiculare KACC 40808, and Phytophthora cambivora KACC 40160 by agar diffusion method.

Dehydro‐α‐lapachone isolated from Catalpa ovata stems: activity against plant pathogenic fungi

The methanol extract of stems of Catalpa ovata G Don exhibits potent in vivo antifungal activity against Magnaporthe grisea (Hebert) Barr (rice blast) on rice plants, Botrytis cinerea Pers ex Fr (tomato grey mould) and Phytophthora infestans (Mont) de Bary (tomato late blight) on tomato plants, Puccinia recondita Rob ex Desm (wheat leaf rust) on wheat plants and Blumeria graminis (DC) Speer f. sp. hordei Marchal (barley powdery mildew) on barley plants. An antifungal substance was isolated and identified as dehydro-alpha-lapachone from mass and nuclear magnetic resonance spectral data. It completely inhibited the mycelial growth of B. cinerea, Colletotrichum acutatum Simmonds, Colletotrichum gloeosporioides Simmonds, M. grisea and Pythium ultimum Trow over a range of 0.4-33.3 mg litre(-1). It also controlled the development of rice blast, tomato late blight, wheat leaf rust, barley powdery mildew and red pepper anthracnose (Colletotrichum coccodes (Wallr) S Hughes). The chemical was particularly effective in suppressing red pepper anthracnose by 95% at a concentration of 125 mg litre(-1).

보호용 살균제와 ergosterol 생합성 저해 살균제에 대한 고추 탄저병균의 약제 반응

전국의 고추 재배지에서 1999년과 2002년에 채집한 병든 고추로부터 각각 130개와 258개의 고추 탄저병균을 분리한 후, 4종의 보호용 살균제와 3종의 ergosterol생합성 저해 살균제에 대한 균사 생장 저해 정도를 측정함으로서 살균제들에 대한 저항성 모니터링을 실시하였다. 1999년에 분리한 균주는 세 가지 보호용 살균제, 즉 dithianon, chlorothalonil 및 propineb에 대해서는 2002년의 균주보다 더 저항성을 보였다. 이에 반하여 다른 보호용 살균제인 iminoctadine에 대해서는 오히려 2002년의 균주가 더 저항성인 것으로 나타났다. 세 개의 ergosterol 생합성 저해(EBI) 살균제, 즉 tebuconazole, hexaconazole 및 prochloraz에 대해서는 2002년의 균주가 1999년의 균주보다 더 저항성이 컸으며, 2002년도의 균주들의 <TEX>$EC_{50}$</TEX> 값은 1999년 균주들보다 1.2배 내지 4.4배가 높았다 위의 살균제들에 대한 탄저병균의 반응을 보면, 채집한 지역 간에 저항성을 차이가 크게 나타나고 있었다. 단기간내에 충북에서 분리한 균주들은 채집한 시기가 늦어질수록, 고추의 생육 초기에 주로 많이 사용되는 보호용 살균제들에 대한 <TEX>$EC_{50}$</TEX>값은 감소하였다. 그러나 ergosterol 생합성 저해 살균제에 대한 균주들의 반응은 정해진 생육 기간 중에는 변화가 거의 없었다. In 1999 and 2002, 130 and 258 isolates of Colletotrichum spp. causing red pepper anthracnose were obtained from infected red pepper fruits, respectively. Their responses to 4 protective and 3 ergosterol biosynthesis-inhibiting(EBI) fungicides were investigated by observing their mycelial growth on PDA incorporated with different concentrations of each fungicide. The Colletotrichum isolates obtained in 1999 showed higher <TEX>$EC_{50}$</TEX> values than those isolated in 2002 against three protective fungicides such as dithianon, chlorothalonil, and propineb, whereas the response was reversed toward other protective fungicide, iminoctadine. On the other hand, the isolates of year 1999 were more resistant against three EBI fungicides such as tebuconazole, hexaconazole, and prochloraz than those of year 2002; the <TEX>$EC_{50}$</TEX> values of the former were 1.2-4.4 times higher than those of the latter, The responses of the Colletotrichum isolates toward protective and EBI fungicides were fluctuated according to regions, where the infected fruits were collected. On the other hand, the resis tance of Colletotrichum isolates to protective fungicides increased during monitoring from July to September, However, their responses towards EBI fungicides were not changed.