• Research in Plant Disease
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• v.28 no.3
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• pp.143-151
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• 2022

In order to investigate the cause of wilting symptoms in red pepper field of Korea, the frequency of occurrence of red peppers showing wilting symptoms was investigated in pepper cultivation fields in Goesan, Chungcheongbuk-do for 5 years from 2010 to 2014. There was a difference in the frequency of wilting symptoms depending on the year of investigation, but the frequency of occurrence increased as the investigation period passed from June and July to August. During this period, Ralstonia solanacearum causing the bacterial wilt was isolated at a rate four times higher than Phytophthora capsica causing the Phytophthora late blight. In wilted peppers collected in Goesan of Chungbuk and Andong of Gyeongbuk in 2013 and 2014, R. solanacearum and P. capsici were isolated from 20.3% and 3.8% of the total fields, respectively. In the year with a high rate of wilting symptoms, the average temperature was high, and the disease occurrence date of the bacterial wilt, estimated with disease forecasting model, was also fast. The inconsistency between the number of days at risk of Phytophthora late blight and the frequency of occurrence of wither symptoms is thought to be due to the generalization of the use of cultivars resistant to the Phytophthora late blight in the pepper field. In our study, the wilting symptoms were caused by the bacterial wilt caused by R. solanacearum rather than the Phytophthora late blight caused by P. capsica, which is possibly caused by increasing cultivation of pepper varieties resistant to the Phytophthora late blight in the field.

• The Korean Journal of Pesticide Science
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• v.19 no.3
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• pp.323-328
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• 2015

Control efficacy was investigated with fungicides as 3 copper compound, 3 antibiotic fungicides and one fungicide containing to quinolone against the growth of Ralstonia solanacearum on NA medium and the disease occurrence on pepper seedlings. Among 7 fungicides, oxytetracycline was shown the highest activity against a growth of the pathogen in the agar diffusion method, but validamycin showed no activity against the pathogen. With $1000{\mu}g\;mL^{-1}$ of each copper fungicide as copper hydroxide, copper oxychloride+ dithianone and copper sulfate, 2.2, 1.3 and 1.5 mm in size of clear zone only could be found, respectively. In pepper seedling test, oxytetracycline showed a perfect activity in all treatments 7 days after inoculation. However, its activity was decreased from $500{\mu}g\;mL^{-1}$ of treatment over the time. Copper fungicides showed the control efficacy lower than antibiotic fungicides except for validamycin. Based on the results, it was suggested that it would be better to use antibiotic fungicides than copper fungicides to control pepper bacterial wilt in the fields.

• Journal of Bio-Environment Control
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• v.23 no.4
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• pp.329-336
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• 2014

As an abiotic stress, chilling stress is one of the major factors limiting plant growth and increasing susceptibility to pathogens. Therefore, enhancing stress tolerance in plants is an important strategy for their survival under unfavorable environmental conditions. The objective of this study was to determine the effects of the exogenous application of salicylic acid (SA) or nitric oxide (NO) on chilling tolerance in pepper seedlings. Pepper (Capsicum annuum L. 'kidaemanbal') seedlings were grown under normal growing conditions ($20/25^{\circ}C$, 15 hours photoperiod, $145{\pm}5{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, fluorescence lamps) for 23 days after transplanting. The solution (3 mL) of 1 mM SA and 0.3 mM NO with surfactant triton 0.1% were sprayed two times a week, respectively. Right after the completion of chemical application, seedlings were subjected to chilling condition at $4^{\circ}C$ for 6 hours under dark condition and then the seedlings were recovered at the normal growing conditions for 2 days. In order to assess plant tolerance against chilling stress, growth characteristics, chlorophyll fluorescence (Fv/Fm), and membrane permeability were determined after chilling stress imposition. Total phenolic concentration and antioxidant capacity were measured during the whole experimental period. Disease incidence for pepper bacterial spot and wilt was also analyzed. Pepper seedlings treated with SA or NO were maintained similar dry mass ratio, while the value in control increased caused by chilling stress suggesting relatively more water loss in control plants. Electrolyte leakage of pepper seedlings treated with SA or NO was lower than that of control 2 days after chilling treatment. Fv/Fm rapidly decreased after chilling stress in control while the value of SA or NO was maintained about 0.8. SA increased higher total phenolic concentration and antioxidant capacity than NO and control during chemical treatment. In addition, increase in total phenolic concentration was observed after chilling stress in control and NO treatment. SA had an effect on the reduction of bacterial wilt in pepper seedlings. The results from this study revealed that pre-treatment with SA or NO using foliar spray was effective in chilling tolerance and the reduction of disease incidence in pepper seedlings.

• Applied Biological Chemistry
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• v.48 no.1
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• pp.48-52
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• 2005

Six stains of plant growth promoting rhizobacteria were selected through germinating seed assay and root colonization assay. Among them, SKU-78 strain induced significant suppression of bacterial wilt disease in tomato and pepper plants. Seed treatment followed by soil drench application with this strain resulted in over 60% reduction of bacterial wilt disease compared with the control. It was suggested that SKU-78 strain activated the host defense systems in plants, based on lack of direct antibiosis against pathogen. According to Bergey's Manual of Systemic Bacteriology and 16S rDNA sequence data, SKU-78 stain was identified as Bacillus sp. SKU-78.

• Research in Plant Disease
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• v.28 no.1
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• pp.54-56
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• 2022

A peanut plant showing wilt and browned symptom was found in the field of Gochang, Korea, in July 2021. The symptomatic peanut plant was collected from the field and isolation of the pathogen caused the wilt symptom was performed using the collected sample on TZC media. The dominated colony on media was isolated colony on media was isolated and subcultured of purification. The pure cultured bacteria was identified as Ralstonia solanacearum by sequencing of 16S rRNA gene. Multiplex polymerase chain reaction using phylotype-specific primer set identified isolate as phylotype I (R. pseudosolanacearum). Phylogenetic tree was constructed based on 16S rRNA sequence and it was closed with R. pseudosolanacearum. Pathogenicity of the isolates was assessed by soil drenching inoculation on 4-week-old peanut plant. The wilt symptom was successfully reproduced by inoculation of the isolates after 14 days. This is first report of bacterial wilt caused by R. pseudosolanacearum on peanut in Korea.

• Korean Journal Plant Pathology
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• v.10 no.2
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• pp.73-77
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• 1994

Experiments were conducted to determine the method of nioculation and inoculum level, and the optimum age of pepper seedlings for evaluation of resistance to bacterial wilt in pepper. Injection of bacterial suspension(107~108 cells/ml) to the leaf axil of the 3rd or 4th leaf of pepper, and drenching the soil planted with pepper seedling after wounding roots with scalpel, resulted in good varietal difference in resistance to bacterial wilt. PI377688, PI358812 and PI369994 of 298 open-pollinated lines and 10 hybrids tested for resistance to bacterial wilt were highly resistant and such local cultivars as Masan, Anjinbaengi, Kimyongcho and Punggakcho moderately resistant.

• Current Research on Agriculture and Life Sciences
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• v.16
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• pp.64-74
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• 1998

Accessions of pepper germplasm were planted in the field and their characteristics were recorded. Lines introduced from Hungary were very susceptible to virus diseases and as a result poor in adaptability in domestic field condition. KC350 and KC351 which were introduced from Brazil were growing errectly and tolerant to both bacterial spot and virus diseases. KC376, an introduction from China, was bearing large fruits with tolerance to virus. Introductions from Thailand were grown and evaluated in Andong University, and major characters of them were recorded.

• Research in Plant Disease
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• v.8 no.1
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• pp.1-10
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• 2002

Climate in the year of 2001 could be summarized as severe drought from March to May, unusually high temperature in whole plant growth periods and clear weather condition especially in harvesting time of September and October without any typoons. In rice, major diseases such as leaf and panicle blast, bacterial blight, sheath blight and bacterial grain rot developed little due to unfavorable weather conditions, however, brown spot occurred severely due partly to the reduced use of N-fertilizer, Rice stripe virus infection was unusually high mainly in the west coast areas with four times more diseaseD area campared to the previous year, In pepper phytophthora blight was extremely severe in Cheonnam and Cheonbuk provinces, where had frequent rainfalls during growing period. Incidence of major diseases of tomato and cucumber in 2001 was relatively mild. In watermelon, penicillium fruit rot, one of the peculiar disease, spread over major production areas, whereas CGMMV, usually severe in every years was much reduced. Watermelon plants growing in open-fields were more severely diseased than those in plastic houses. Major diseases of chinese melon and strawberry occurred slightly and in particular, sudden wilt syndrome of chinese melon which was severe in 2000 showed mild infections in 2001. Incidence of white rot of garlic and onion was much lower unlike other years due mainly to spring drought and high temperature in the growing period. Infected area of potato bacterial wilt tended to increase in 2001 while fusarium wilt of sweetpotato was decreased. Apple diseases were generally mild, but powdery mildew of pear increased sharply. Barley scab was not severe as seen in other years.

• Journal of Sericultural and Entomological Science
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• v.44 no.2
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• pp.64-68
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• 2002

The antibacterial protein gene, nuecin was expressed in Sf9 cells using baculovirus expression vector system (BEVS). The antibactetial activity of mature nuecin against Pectobacterium carotovorum subsp. carotovorum, Ralstonia solanacearum and Pseudomonas tolaasii was significantly high, demonstrating that nuecin had a wider antibacterial spectrum on gram negative and positive bacteria. The result appears to be superior to other antibacterial peptide, attacin. The nuecin was purified by SP-sepharose and Mono Q HR ion-exchange chromatography, and then by Superdex 200 HR 10/30 column. The purified nuecin is quite stable at 80$\^{C}$ and 100$\^{C}$ for several hours of incubation and in a wide pH range (pH 2-12).

• Research in Plant Disease
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• v.13 no.1
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• pp.24-29
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• 2007

A total of 35 strains of Ralstonia solanacearum isolated from wilted pepper and tomato plants in Korea were analyzed for their genetic diversity by bacteriological, pathological and molecular biological approaches. All the strains were identified as R. solanacearum biovar 4 on the basis of physiological and biochemical tests, and species-specific PCR primers. Pathogenicity of the strains was confirmed by inoculating on 4-week-old pepper and tomato seedlings. Using cluster analysis based on repetitive sequence-based polymerase chain reaction (rep-PCR) genomic fingerprints, R. solanacearum strains isolated from pepper and tomato in Korea divided into 6 groups showing a high degree of genetic diversity at 55% similarity level. The genetic diversify of strains was not significantly correlated with their geographic origins and host plants.