• Research in Plant Disease
• /
• v.18 no.1
• /
• pp.1-9
• /
• 2012

A total of 20 agricultural organic materials including inorganic compounds, plant oils and plant extracts were used in the study for assessing the control efficacy on pepper diseases. Among inorganic compounds, only copper hydroxide showed inhibitory effect on both Phytophthora capsici causing Phytophthora blight and Colletotrichum acutatum causing anthracnose. Phosphorous acid inhibited the growth of P. capsici on PDA, and Sulfur/quicklime had it on that of C. acutatum. Plant essential oil, rosemary oil, and rapeseed oil among plant oils and plant extract of Japanese apricot/ginkgo nut inhibited the mycelial growth of the two pathogens. In the screening using pepper plant seedlings, the control efficacy on Phytophthora blight in 6-leaf stage of seedling was superior to that in 4-leaf stage of seedling. A protective effect on Phytophthora blight was displayed by copper hydroxide, sulfur/quicklime, water soluble calcium, phosphorous acid, plant essential oil, and cloves extract. When C. acutatum was inoculated by the non-wound method, copper hydroxide and rapeseed oil showed excellent protective activities with control values of 91.3% and 82.6%, respectively. However, copper hydroxide did not show any activity, when C. acutatum was inoculated after wounding pepper fruits. All organic materials never showed the curative effect on Phytophthora blight and anthracnose in pepper seedling assay and fruit assay.

• Korean Journal Plant Pathology
• /
• v.2 no.2
• /
• pp.107-113
• /
• 1986

Each of 48 monoconidial isolates of Colletotrichum gloeosporioides Penz. obtained from diseased fruits of pepper was classified into strain G or strain R based upon pathogenicity to green and red fruits, morphology of conidia, and cultural characteristics in potato dextrose agar. The strain G was designated for isolates to cause anthracnose symptoms both on green and red fruits. All isolates of the strain G produced conidia abundantly. but produced no perithecia and setae in PDA. Conidia of all isolates in the strain G were attenuated or round at one end. The optimum temperature for mycelial growth of strain G was $26-28^{\circ}C$. The mycelia of strain G in PDA appeared to be whitish when young, and turned to be dark in old culture. Symptoms on pepper fruits caused by the strain G were somewhat sunken to be circular to elliptical lesions. Yellowish conidial masse were observed at the center of lesions, and the lesions turned to irregular shape and to reddish brown color in the later stage of disease development. No setae were visible on the acervuli. The strain R was designated for isolates to cause anthracnose symptoms only on red fruits of pepper. All isolates of the strain R produce conidia, and perithecia of Glomerella cingulata (Stonem.) Spauld. & v. Sch. in PDA. Some isolates of the strain R produced setae in culture under fluorescent light. Conidia of all isolates in the strain R were round and blunt at the ends. The optimum temperature for mycelial growth of strain R was the same as that of strain G. The mycelial growth of strain R was faster than that of strain G in PDA. The mycelia of strain R in PDA appeared to be gray to dark. Symptoms on pepper fruits caused by the strain R were circular to irregular black ring-spots Short setae or no setae were visible on the acervuli.

• Research in Plant Disease
• /
• v.18 no.2
• /
• pp.93-100
• /
• 2012

Resistance of pepper (Capsicum spp.) to anthracnose (Colletotrichum acutatum) was evaluated during regeneration of Capsicum spp. in National Agrobiodiversity Center. Disease severity of 896 pepper accessions (430 accessions of C. annuum, 219 accessions of C. baccatum, 14 accessions of C. chacoense, 153 accessions of C. chinense, 70 accessions of C. frutescens, 2 accessions of C. pubescens, and unidentified 8 accessions) was investigated at 14 days after inoculation in $28^{\circ}C$ humid chamber. Forty nine accessions of pepper germplasm were resistant to C. acutatum. Among them, nine accessions were highly resistant to C. acutatum without wounding spray inoculation. Four accessions belonged to the species C. baccatum, one accession to C. chacoense, and four accessions to C. frutescens. Forty two resistant candidate accessions were inoculated with pin-prick wounding using a syringe needle. Five accessions were resistant as a less than 3% of disease severity to C. acutatum with wounding inoculation 5 days after inoculation. All resistant accessions were C. baccatum. These five pepper germplasm might be used as breeding resources for the anthracnose resistance breeding program.

• Research in Plant Disease
• /
• v.12 no.1
• /
• pp.32-39
• /
• 2006

This study has been conducted to investigate the responses of various isolates of four Colletotrichum species such as C. gloeosporioides, C acutatum, C. coccodes, and C. dematium isolated from infected tissues of several crops to fungicides such as carbendazim, carbendazim+diethofencarb, four protective fungicides, and three ergosterol biosynthesis-inhibiting (EBI) fungicides. All the isolates of C. acutatum showed $EC_{50}$ values in a range of 0.001-3.040 ${\mu}g/ml$ against carbandazim, a benzimidazole fungicide. As for the response to carbendazim, the isolates of C. gloeosporioides obtained from pepper, apple, and strawberry were clearly divided into two groups, resistant or sensitive isolates. All the resistant isolates showed $EC_{50}$ values above 1000 ${\mu}g/ml$, whereas the sensitive isolates had lower $EC_{50}$ values than 0.550 ${\mu}g/ml$. The isolates of C. gloeosporioides exhibited a negative cross resistance between carbendazim and diethofencarb (a N-phenylcarbamate fungicide), but isolates of C. acutatum did not. Toward carbendazim, C. coccodes and C. dematium isolates showed a similar response to C. acutatum isolates and the sensitive isolates of C. gioeosporioides, respectively. As for response of Protective fungicides, all the isolates of C. acutatum showed a more resistant reaction than all the isolates of C. gloeosporioides. However, there was no difference among 4 species of Colletotrichum against EBI fungicides.

• The Korean Journal of Pesticide Science
• /
• v.17 no.4
• /
• pp.379-387
• /
• 2013

In order to improve practical utility of agro-microorganisms (AMs) which had been cultured and disseminated to promote plant growth and to control crop diseases, 51 isolates of AMs were collected from 18 agricultural extension centers in local government and screened for multi-functions such as antifungal activity, activities of phosphorus solubilization, IAA and siderophore production, nitrogen fixation, and hydrolytic enzyme activity. Finally we selected one isolate showing good antifungal activity and multi-functions related to plant growth and disease control. The selected isolate, Paenibacillus polymyxa CW, showed good inhibitory effect against plant pathogens, Pyricularia gresea, Colletotrichum acutatum, Fusarium oxysporum, Phomopsis sp., Aspergillus niger, Rhizoctonia solani and Phytophthora capsici. Suppressive effect of P. polymyxa CW against the used plant pathogens except for R. solani was much higher than that of P. polymyxa AC-1 storing in National Academy of Agricultural Science. We found P. polymyxa CW isolate showed good activity in siderophore and IAA formation, and nitrogen fixation. With P. polymyxa CW isolate, siderophore formation activity was similar to that of P. polymyxa AC-1, but IAA formation and nitrogen fixation activity was much higher than that of P. polymyxa AC-1. However neither P. polymyxa CW nor P. polymyxa AC-1 showed hydrolytic enzyme (chitinase, pectinase and cellulase) activity. The treatment of P. polymyxa CW with culture suspension of different cell density ($10^8$, $10^7$. $10^6$ cfu/ml) showed that the highest density reduced incidence of red pepper powdery mildew by 68.3% after 10 days of application. As application density of P. polymyxa CW was decreased, its control efficacy was proportionally decreased. In addition, when P. polymyxa CW was treated to control tomato powdery mildew at the same concentrations and their control effects were investigated after 7 days of inoculation, disease incidence was 0.03, 19.5, 45.7%, respectively, compared to 56.3% that of untreated check. Like red pepper powdery mildew, increase of application density of P. polymyxa CW resulted in increase of its control efficacy proportionally. P. polymyxa CW showed a density-dependent control efficacy against red pepper and tomato powdery mildews. Therefore we think that mode of action of the antagonist for suppressing two powdery mildew diseases might be antibiosis and density of more than $10^8cfu/ml$ was needed to control effectively the two diseases. On this basis, we think that P. polymyxa CW can be a promising control agent for suppressing powdery mildews of red pepper and tomato.

• The Korean Journal of Mycology
• /
• v.32 no.2
• /
• pp.138-141
• /
• 2004

The effect of culture parameters on the production of Colletotrichum gloeosporioides growth inhibitory substance from Bacillus subtilis was investigated. The maximal growth inhibition zone was observed in the medium of pH 7.0. Among the tested carbon sources, glucose showed the largest growth inhibition zone above two fold than other carbon sources. Ammonium sulfate and organic nitrogen sources were effective on the production of growth inhibitory substance. Luria Bertani (LB) medium was the best on the production of antifungal substance from B. subtilis.

• Research in Plant Disease
• /
• v.28 no.3
• /
• pp.122-131
• /
• 2022

Colletotrichum acutatum s. lat. 20JDS8 sensitive and 20CDJ6 resistant to pylaclostrobin were used to investigate the cross-resistance with fungicides belonging to the strobilurins and the characteristics of fungicidal controlling activities with different mechanisms against the isolate resistant to the fungicide. The resistant isolate of 20CDJ6 also showed the resistance to azoxystrobin, trifloxystrobin, and kresoxim-methyl, suggesting that there is a cross-resistance relationship. All fungicides with different action mechanisms inhibited mycelial growth of both susceptible and resistant isolates of C. acutatum s. lat., but their disease control effects in fruits were different according to the fungicides. The disease control effect of isopyrazam against 20JDS8 and 20CDJ6 was very low, and fluazinam showed a control effect of 91.9% and 88.1% against 20JDS8 and 20CDJ6 only when it was treated before inoculation by spraying spore suspensions on pepper fruits without wounds. Tebuconazole and prochloraz effectively inhibited not only the mycelial growth of 20JDS8 and 20CDJ6 on potato dextrose agar medium, but also disease incidence in red pepper fruits. As a result of this study, C. acutatum s. lat. 20CDJ6 resistant to pyraclostrobin showed cross-resistance with other strobilurin fungicides. In addition, we think that fluazinam, tebuconazole, and prochloraz can be recommended as alternative fungicides for the control of red-pepper pyranthracnose pathogens resistant pyraclostrobin. However, fluazinam can be effective only if it is treated protectively before the occurrence of the disease.

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

• Korean Journal Plant Pathology
• /
• v.2 no.3
• /
• pp.185-192
• /
• 1986

Upon germination, a conidium was septated in accordance with number of germ tubes. The percentages of ppressorial formation were not different between the resistant cultivars (Kumchang NO. 2 and Hongilpum) and the susceptible cultivars (Haneulcho and Saegochu). Appressorial form was various such as round, elliptic or star-shapped. The maximum number of appressoria was shown at 12 hours after inoculation. By 24 hours fter inoculation, hypersensitive tiny brown lesions were observed on the leaves and fruits of the resistant cultivars. Epidermal cells under cuticle layer of the resistant Kumchang NO. 2 fruit showed severe plasmolysis, while on the susceptible cultivars, the lession was largely extended to following incubation. Subcuticular infection hyphae were profusely colonized in the disintegrated tissues. Acervuli and setae on the stromatic structure ere formed at 96 hours. The infected seed coat was not only severely collapsed, but also infection hyphae were observed on the disintegrated seed coat, resulting severe plasmolysis of nucellus and embryo.

• KSBB Journal
• /
• v.21 no.1 s.96
• /
• pp.42-48
• /
• 2006

Bacillus subtilis KMU-13 was isolated from the Lillehammer forest soils at Norway and shown a strong antifungal activity on cucumber scab, Cladosporium cucumerinum KACC 40576. B. subtilis KMU-13 produced a maximum level of antifungal substance under incubation aerobically at $30^{\circ}C$, 180 rpm for 48 hours in LB broth containing 0.5% maltose and 0.5% bactopeptone and initial pH adjusted to 6.0. Butanol extract of cultured broth was confirmed inhibitory zone by plate assay and Rf 0.64 value substance by thin layer chromatography (TLC) represented high antifungal activity against C. cucumerinum KACC 40576 and also shown fungal growth inhibitory activity against Botytis cinerea KACC 40573, C. gloeosporioides KACC 40804, D. byoniae KACC 40669, F. oxysporum KACC 40037, F. oxysporum KACC 40052, F. oxysporum f. sp. radicis-lycopersici KACC 40537, F. oxysporum KACC 40902, M. cannonballus KACC 40940, P. cambivora KACC 40160, R. soiani AG-1 KACC 40101, R. solani AG-4 KACC 40142, and S. scleotiorum KACC by agar diffusion method.