• Korean Journal Plant Pathology
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• v.2 no.3
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• pp.193-198
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• 1986

Bottom rot of Chinese cabbage (Brassica pekinensis Rupr) hitherto undescribed in Korea is caused by Rhizoctonia solani Kuhn. Development of bottom rot in fall crops was observed and the efficiencies of fungiciial control in naturally infested field in Southern region were studied. Bottom rot symptom started to develop 20 days after transplanting 20 day old seedlings, which corresponded to the middle growing stage. At the reading stage, the infection rate increased substantially, which progressed upto an average of $52\%$ at harvesting time. The overall infection rate was about $30\%$ in Chinese cabbage field under plastic film house cultivation. However, disease intensity of fall crops was less severe than that of crops in plastic film house. where plants infested earlier, stunted and their growth was extremely poor. Optimum temperature for mycelial growth of bottom rot isolates of R. solani was $20\~25^{\circ}C$ on potato-sucrose agar. This fungus was highly pathogenic on seedlings of Chinese cabbage, radish, sesame and rape resulting in high percentage of damping-off. For other crops, such as lettuce, tomato the cucumber, the germination was delayed for 2-3 days and the percentage damping-off was lower. Anastomosis group of this fungus was idenlfied as AG II-I. Soil drenching of fungicide pencycr WP., three applications at 10 day interval, was effective; indicating the most promising one with control value $80\%$.

• Korean Journal of Medicinal Crop Science
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• v.22 no.5
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• pp.391-397
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• 2014

To control the disease of root rot in ginseng nursery, inorganic sulfur solution of 0.1%, 1.0%, and 2.0% were irrigated by amount of $10{\ell}$ per $3.3m^2$ before sowing. On the last ten days of July, Fusarium solani and F. oxysporum were similarly detected by 44.8% and 43.8%, respectively, while Cylindrocarpon destructans was low detected by 4.4% in the diseased seedling. The more sulfur's concentration was increased, the more soil pH was decreased. Soil pH was decreased from 5.87 to 4.59 by the irrigation of sulfur solution of 1.0%. The more sulfur's concentration was increased, the more electrical conductivity (EC) of soil was increased. EC was increased from 0.27 dS/m to 1.28 dS/m by the irrigation of sulfur solution of 1.0%. Irrigation of sulfur solution was effective on the inhibition of damping-off caused by Rhizoctonia solani in ginseng seedling. Control value for damping-off by the irrigation of sulfur solution of 1.0% and 2.0% were 75.7%, and 78.5%, respectively. Growth of leaf was inhibited by the irrigation of sulfur solution of 2.0%. Root weight per $3.3m^2$ showed the peak in sulfur solution of 1.0%, while survived-root ratio and root weight per plant were decreased in the level of 2.0%. Survived-root ratio of seedling in sulfur solution of 1.0% was distinctly increased by 4.7 times compare to the control, but control value for root rot was relatively low as 49.2%. Mycelium growth of C. destructans, F. solani, and R. solani were distinctly inhibited by the increase of sulfur's concentration in vitro culture using PDA medium.

• Research in Plant Disease
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• v.30 no.3
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• pp.288-293
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• 2024

Fusarium basal rot (FBR), caused by the ascomycete fungus Fusarium oxysporum, is an economically important disease of onion worldwide. The most economical and effective way to manage FBR would be the use of FBR resistant onion cultivars. This study was carried out to develop a rapid screening method for resistant onion cultivars in seedling stage. We used the F. oxysporum 19-385 isolate, which causes damping-off in onion seedlings and basal rot in onion bulbs. We optimized broth incubation and medium composition for the production of inoculum, and determined conidial concentration for the preparation of F. oxysporum infected soil. Ten commercial cultivars of onion were evaluated the seedling survival rates and heights by infected soil inoculation methods. As a result, 'K-force' was the most resistant cultivar with 97.4% of relative seedling survival rate against the pathogen, whereas 'Sunpower' was the most susceptible cultivar with 20.0% of relative seedling survival rate.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 1994.06a
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• pp.27-49
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• 1994

Root colonization of biocontrol agents via seed treatment was investigated and a compatible combination, Gliocladium virens G872B and Pseudomonas putida Pf3, in colonizing cucumber rhizosphere was confirmed through the study. Much higher number of fungal and bacterial propagules were detected when two isolates were inoculated together. The presence of Pf3 in root system was greatly helpful to G872B to colonize at root tip. The mechanism of this phenomenon is partially elucidated through the results of in vitro experiments and the observations of scanning electron and fluorescence microscope. Addition of Pf3 cells resulted earlier germination of G872B conidia and increased mycelial growth. And the more number of germinated conidia on seed coat, the more vigorous hypal streching and sporulation on the root surface were observed in coinoculated treatment. The propagules of G872B on the cucumber root when they were challenged against the pathogenic Fusarium oxysporum, were even higher than that of G872B treated alone, and the magnitude of such a difference was getting grater toward the root ip and the population of F. oxysporum on the root was reduced by seed inoculation of G872B. The rhizosphere competence was obviously reflected to disease suppression and plant growth promotion that induced by the given isolate. Green house experiments revealed that the combined treatment provided long-term disease suppression with greater rate and the larger amount of fruit yield than single treatments. Through this study the low temperature growing Pseudomonas fluorescens M45 and MC07 were evaluated to apply them to the winter crops in field or plastic film house. In vitro tests reveal that M45 and MC07 inhibited the mycelial growth of Pythium ultimum, Rhizoctona solani and Phytophthora capsici and enhanced growth of cucumber cotyledon in MS agar. This effect was more pronounced when the bacteria were incubated at 14$^{\circ}C$ than at 27$^{\circ}C$. And disease suppression and plant growth promotion in green house were also superior at low temperature condition. Seed treatment of M45 or soil treatment of MC07 brought successful control of damping-off and enhanced seedling growth of cucumber. The combined treatment of two isolates was more effective than any single treatment.

• Korean journal of applied entomology
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• v.26 no.4 s.73
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• pp.229-237
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• 1987

In order to study the biological control of soil-borne disease of sesame, antagonistic isolates of Trichoderma , Bacillus sand streptomyces to Fusarium oxysporum and Rhizoctonia solani were isolated from the rhizosphere soils of sesame plants and some other habitats. Out of the isolates of microorganisms collected a strain of Trichoderma viride was selected as a biological control agent for the study and its effect on the control of damping-off and the seedling growth of sesame was investigated. The results obtained are as follows: 26 percents of Bacillus spp. isolated from the rhizosphere soil of sesame plants showed antagonism to two pathogenic fungi. Important species were B. Subtilis and B. polymyxa. Streptomyces species isolated from the rhizosphere soils of sesame lysed the cell wall of hyphae and conidia of F. oxysporum and reduced conspicuously the formation of macroconidia and chlamydospores of the fungus. 84 percents of Trichoderma spp. isolated from the rhizosphere soil of sesame plants were antagonistic to F. oxysporum and 60 percents of the isolates were antagonistic to both F. oxysporum and R. solani. Trichoderma viride TV-192 selected from antagonistic isolates of Trichoderma spp. was highly antagonistic to F. oxysporum and soil treatment with the isolate reduced notably damping-off of sesame. T. viride TV-192 showed better growth in crushed rice straw, barley straw and sawdust media than F. oxysporum. Sawdust was selective for the growth of T. viride. Supplementation of wheat bran and mixtures of wheat bran and sawdust inoculated with T. viride TV-192 in the soil reduced remarkably damping-off of sesame by F. oxysporum but high density of the fungus TV-192 caused the inhibition of seed germination and seedling growth of sesame. Inhibitory effects of Trichoderma species on seed germination and seedling growth of sesame were different according to the isolates of the fungus. Normal sesame seedlings on the bed treated with the fungus showed better growth than not treated seedlings.

• Mycobiology
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• v.42 no.1
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• pp.66-72
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• 2014

Roselle (Hibiscus sabdariffa L.) family Malvaceae is an important crop used in food, cosmetics and pharmaceutics industries. Roselle is cultivated mainly in Upper Egypt (Qena and Aswan governorates) producing 94% of total production. Root rot disease of roselle is one of the most important diseases that attack both seedlings and adult plants causing serious losses in crop productivity and quality. The main objective of the present study is to identify and characterize pathogens associated with root rot and wilt symptoms of roselle in Qena, Upper Egypt and evaluate their pathogenicity under greenhouse and field condition. Fusarium oxysporum, Macrophomina phaseolina, Fusarium solani, Fusarium equiseti and Fusarium semitectum were isolated from the natural root rot diseases in roselle. All isolated fungi were morphologically characterized and varied in their pathogenic potentialities. They could attack roselle plants causing damping-off and root rot/wilt diseases in different pathogenicity tests. The highest pathogenicity was caused by F. oxysporum and M. phaseolina followed by F. solani. The least pathogenic fungi were F. equiseti followed by F. semitectum. It obviously noted that Baladi roselle cultivar was more susceptible to infection with all tested fungi than Sobhia 17 under greenhouse and field conditions. This is the first report of fungal pathogens causing root rot and vascular wilt in roselle in Upper Egypt.

• Journal of Bio-Environment Control
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• v.12 no.4
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• pp.180-183
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• 2003

P. wasabiae was isolated from discolored seeds of wasabi(Wasabia japonical Mtsum.) and inoculated to fresh seeds, then the effect of fungicides on suppression of diseases were determined. Emergence rate of wasabi seeds where suppressed to 52.5% by the inoculation and it reached up to 92.7% by dipping treatment of inoculated seeds ito benomyl solution. The incidence rate of black leg disease and damping off were 32.0 and 22.0%, respectively, in control treatment that sown in the soil inoculated with P. wasabiae. But dipping treatment of inoculated seeds into benomyl solution resulted in 12.0% and 10.7% in incidence rate of those two diseases, respectively.

• The Korean Journal of Pesticide Science
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• v.7 no.3
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• pp.223-227
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• 2003

Survey on plant diseases occurring on cucumber cultivated in plastic film house of experimental farm in Suwon was conducted. Through the survey, occurrence of damping-off, downey mildew, powdery mildew and Fusarium wilt was observed. Especially downey mildew caused by Pseudoperonospora cubensis was the most severe foliar disease of cucumber. To control the disease effectively, effects of installation of ventilation fan and optimal spray timing of a chemical, dimethomorph+copper oxychloride WP, were investigated. Two ventilation fans installed at the front and at the back of plastic film house reduced air relative humidity by about 6.4% and downey mildew incidence by 55.7%. Downey mildew incidence on cucumber from untreated chemicals plot in plastic film house installed with ventilation fan was on a equal level with that from treated chemicals plot with three times application of dimethomorph+copper oxychloride WP in plastic film house without ventilation fan. Meanwhile in order to select optimal chemical application time, dimethomorth+copper oxychloride WP was treated three times at 7 days-interval from three days before the disease occurred, right after the disease occurred, and two days after the disease occurred, respectively. The result showed that dimethomorth+copper oxychloride WP applied to cucumber leaves and stems from three days prior to, right after, two days after occurrence of downey mildew reduced downey mildew incidence by 72.9, 61.8, and 23.7%, respectively. The above results showed that regulation of environmental factors like air relative humidity and preventive application of chemicals should be considered to establish control strategy to downey mildew.

• The Korean Journal of Pesticide Science
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• v.14 no.1
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• pp.65-71
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• 2010

This study was performed to investigate the inhibiting activity of etridiazole and thiophanate-mthyl on mycelial growth of Rhizoctonia solani and Pythium ultimum and the effect of inoculum density of each pathogen on the control efficacy of the mixture of etridiazole and thiophanate-methyl in a seedling assay test. In mycelial growth inhibition test, $EC_{50}$ values of etridiazole and thiophanate-methyl against R. solani were 15.87 and 9.34 ${\mu}g\;mL^{-1}$, while those were 0.2 and more than $500\;{\mu}g\;mL^{-1}$ against P. ultimum, respectively. Controlling activity of the mixture of etridiazole and thiophanate-methyl against damping-off of pepper and cucumber, caused by R. solani and P. ultimum was tested in a greenhouse. With the inoculation of R. solani, disease incidences of seedling in pepper were 73% and 95% at 0.5% and 1.0% of inoculum concentration, while in cucumber those were 55% and 62% at 1.0% and 2.0%. When P. ultimum was inoculated into soil by 2.0% of inoculum concentration, those in pepper and cucumber were 66.7% and 96.8%, respectively. The efficacy of the mixture was somehow affected by the concentration of R. solani. While each control value of the mixture was 94.4% and 90.7% in pepper and cucumber at low inoculum concentration (0.05%), the efficacy of the fungicide decreased in pepper and cucumber by 70.7% and 72.9% at high concentration of R. solani (0.1% in pepper and 0.5% in cucumber). However, the control value of the mixture was 100% in pepper and cucumber, irrespective of the inoculum concentration of P. ultimum, however, the increase of inoculum concentration in soil did not result in the decrease of the fungicide efficacy.

• Research in Plant Disease
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• v.26 no.1
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• pp.29-37
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• 2020

Stem blight symptom of soybean was severely developed in 2016 in Hwaseong and Yeoncheon. During the seedling period, the damping-off of seedlings and the brown or black spots of cotyledons were observed. After August, the leaves began to be yellowed, and partially browned areas on leaves began to develop. After September, microsclerotia began to form even on the surface of the stems that had exhibited water-soaking symptom. After mid-October of the harvest season, the epidermis of the stem was peeled off, resulting in the formation of a large number of microsclerotia in the cortex. The pathogens isolated from these symptoms were the best in mycelial growth at 32-35℃, and the formation of microsclerotia was the most at 20-28℃. The pathogen was identified as Macrophomina phaseolina through the morphological characteristics of the pathogen and the sequencing of the internal transcribed spacer region gene. In addition, when inoculated with a soybean stem using toothpicks cultured with the pathogen, the same symptoms as seen on the soybean field occurred. When the pathogen was re-isolated at the lesion site, the same pathogen was isolated and identified as Macrophomina phaseolina. Based on the results, the disease is reported as soybean charcoal rot.