• Research in Plant Disease
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• v.11 no.2
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• pp.179-184
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• 2005

A previous study reported that the stem and root rot of paprika (Capsicum annum L. var, grossum) caused by Nectria haematococca became a threat to safe cultivation of the plant in the country. However, no strategies for control the disease have been suggested. In this study, fungicides registered for pepper were screened to evaluate their control effects on the disease. Among fungicides tested, prochloraz manganase complex com pletely suppressed mycelial growth of the pathogen at 10 ppm a.i. tebuconazole, benomyl, and carbendazim $\cdot$kasugamycin also effectively inhibited mycelial growth of the fungus. However, kresoxim-methyl and triflox ystrobin did not suppress mycelial growth but significantly suppressed conidial germination of the fungus. Azoxystrobin, benomyl, prochloraz, tebuconazol, and carbendazim$\cdot$ kasugamycin were also effective to retard conidial germination. In vivo tests, tebuconazole strongly inhibited the plant growth even at 16,000x (15.6 ppm a.i.), while others did not induce chemical injury at 4,000x or 8,000x when drenched into a rockwool cube. In a greenhouse test, prochloraz manganase complex at 125 ppm a.i. (4,000x) showed highest control value by $89.9\%$. Other fungicides thiophanate-methylthiram, axozystrobin, trifloxystrobin, and benomyl presented $60-80\%$ control value in the hydroponic cultivation system. However, application time and interval remained to be investigated for identify maximum residue limit.

• Research in Plant Disease
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• v.13 no.2
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• pp.104-109
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• 2007

Pink root disease of onion, a known worldwide constraint upon onion production, significantly reduces crop levels in the main Korea cultivation area. In order to examine the effect of flooding on incidence of pink root disease caused by Pyrenochaeta terrestris and on onion growth and on populations of soil fungi, field experiments were conducted during two seasons, 2003/04 and 2004/05 at Onion Research Institute. Populations of soil fungi from fields were assayed on selective media. Flooding treatment was effective in reducing populations of P. terrestris, Pythium spp., and Rhizoctonia sp. in soil; fungal populations in soils flooded for 90 days were reduced to 1/2 to 1/3 of those in non-flooded soils. In nursery bed, protective activities of soils flooded for over 60 days were 93.5 to 99.2% and their pink root incidences were less than 5%, which were 1/11 to 1/18 of that in control. Increased yield of onion bulbs was associated with control of soil borne pathogenic fungi by flooding treatments. As flooding period was prolonged, bulb grade showed the tendency to increase. Soil flooding for over 60 days resulted in effective disease control, facilitated accurate planning of plant population in the field, extension of the growing-season and consequently higher yields of better quality.

• Research in Plant Disease
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• v.15 no.2
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• pp.57-62
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• 2009

Genetic diagnosis method of Virion Captured (VC)/RT-PCR for Rice stripe virus (RSV) and Rice black-streaked dwarf virus (RBSDV), Korean major rice viruses transmitted by small brown plant hopper, Laodelphax striatellus, was developed. Virion extraction buffer for rice plant was 0.01M potassium phosphate buffer, pH 7.0, containing 0.5% sodium sulfite. However, the extraction buffer for L. striatellus was 0.01M potassium phosphate buffer, pH 7.0, containing 0.5% sodium sulfite and 2% polyvinylpyrrolidone wt 40,000 (PVP-40). Specific primers for detection of RSV and RBSDV were selected for VC/RT-PCR method. The specific primers were used as a duplex primer to detect viruliferous small brown plant hopper collected from Gimpo, Pyeongtaek and Siheung areas in Gyeonggi province. The genetic diagnosis methods of single and duplex VC/RT-PCR for RSV and RBSDV could be used easily and economically, especially on the diagnosis of L. striatellus. The rate of viruliferous insect (RVI) for RSV was compared with ELISA and VC/RT-PCR for L. striatellus collected from fields. RVI by ELISA was same as 9.2% with RVI by VC/RT-PCR. However, there were some different detection results between the methods. It could be suggested that there is a possibility of serological and/or genomic differences among RSV isolates. The portion of RVI detected simultaneously by ELISA and VC/RT-PCR was 71.0%, and the detection rate from VC/RT-PCR was higher as 3.2% than that from ELISA, which had a reason of simultaneous detection ability both RSV and RBSDV of VC/RT-PCR.

• Korean journal of applied entomology
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• v.13 no.1 s.18
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• pp.19-23
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• 1974

Since Tongil has been cultivated widely in farmers' fields, the variety is known to be highly resistant to existing races of Pyricularia oryzae in Korea. However, Tongil and the sister lines were moderately susceptible to race IA-65, which was isolated from Tongil at the blast nursery of the College of Agriculture, Seoul National University, 1972. In field tests of 1973, pathogenic reactions of IR lines at the isolated nursery, where IA-65 had been inoculated, were significantly higher than those at the farm nursery. When seedlings of 196 IR lines were inoculated with IA­65, about $30\%$ of the IR lines including IR667-98 were moderately susceptible. Among the 30 isolates of P. oryzae obtained mostly from indicas, 12 were also differentiated in 1973 as IA group known to be the most prevalent races at IRRI in the Philippines, where Tongil has been highly susceptible. This IA group was also pathogenic to Tongil in greenhouse experiments. The race group causing moderately susceptible to Tongil should be new in Korea, since no occurrences of the race IA have ever been reported previously from the areas where japonica types of rice are cultivated. Because some races of P. oryzae present in Korea are pathogenic to Tongil and because these races may become prevalent in the fields, the reaction of Tongil must be continuously monitored.

• The Korean Journal of Mycology
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• v.45 no.1
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• pp.74-82
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• 2017

Lisianthus (Eustoma grandiflorum) is a flowering ornamental plant used widely in Korea. In 2015, wilting, damping-off, stunting, and root rot symptoms were observed in lisianthus plants of Yeoju and Gimhae, Korea. Affected seedlings appeared yellow and showed poor development of root systems in the field and in nursery boxes. Furthermore, affected plants were yellow, stunted, and died at approximately 2-3 months after transplanting. Fusarium species were consistently isolated from the basal stems of diseased plants. Nine isolates were identified as Fusarium solani based on morphological characteristics. Macroconidia of isolates were relatively wide, straight-to-slightly curved, and microconidia formed in false heads on long monophialides. Abundant chlamydospores were produced at the middle or tips of hyphae. To confirm this identification, a molecular analysis of the translation elongation factor 1 alpha (TEF) and RNA polymerase II subunit (RPB2) genes was conducted. The sequences of TEF and RPB2 showed 99.2-99.9% and 98.0-98.1% similarity, respectively, to those of reference F. solani strains in NCBI GenBank. Pathogenicity was tested using root dipping inoculation of healthy lisianthus seedlings. Symptoms were observed within 7 days of inoculation only in inoculated plants. This is the first report of F. solani causing Fusarium root rot on lisianthus in Korea.

• Research in Plant Disease
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• v.21 no.2
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• pp.82-88
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• 2015

Acidovorax citrulli, the causal agent of bacterial fruit blotch, has caused an economically destructive damage in cucurbits cultivation fields worldwide. To consider more effective disease management, 33 A. citrulli isolates collected from various cucurbits in Korea were analysed by multi-locus phylogeny using five conserved loci(16S rRNA, adk, gltA, glyA, pilT). Two distinct groups (KCC1 and KCC2) in the population were identified on the base of group-specific genetic variation. Out of them, the predominant group was KCC2 and both groups included isolates from melon, cucumber and watermelon. Sixty-four percent of KCC1 isolates were recovered from non-watermelon hosts and seventy-two percent of KCC2 isolates from watermelon. This study presented that there was genetic differentiation among A. citrulli population in Korea. Also, these results will be applied as a very useful data in effective disease management.

• Research in Plant Disease
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• v.18 no.2
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• pp.86-92
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• 2012

Clubroot caused by Plasmodiophora brassicae Woron. is one of the most important diseases in Brassica crops worldwide. To establish more simple and reliable screening method for resistant cabbage and broccoli to P. brassicae, the development of clubroot on the plants according to inoculum concentration and incubation period after inoculating with the pathogen was investigated using P. brassicae GN1 isolate (race 9). To facilitate and acquire precise result of resistance screening of cabbage and broccoli to clubroot, 14-day-old seedlings were inoculated by drenching roots with the spore suspension of P. brassicae to give inoculum density of $2.5{\times}10^9$ spores/pot. To develop the disease, the inoculated seedlings were incubated in a growth chamber at $20^{\circ}C$ for 3 days, and then cultivated in a greenhouse ($20{\pm}5^{\circ}C$) for five weeks. Under the optimum conditions, 16 cabbage and 17 broccoli cultivars were tested for resistance to four field isolates (GN1, GN2, GS and YC) of P. brassicae collected from four regions in Korea. Among them, some cabbage and broccoli cultivars showed different resistance response to three isolates (GN1, GN2 and GS) determined as race 9 by using the differential varieties of Williams. On the other hand, all the tested cultivars were highly susceptible to YC isolate (race 2). The results suggest that this method is efficient screening method of cabbage and broccoli for resistance to P. brassicae.

• Korean Journal of Organic Agriculture
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• v.22 no.4
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• pp.855-868
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• 2014

Synthetic agro-chemicals have been widely used to control diseases on paprika but these days negative attention has been increasing to use of them because of several adverse effects. This research was conducted to isolate and to characterize the antagonistic microorganism to control major paprika diseases, gray mold rot, fruit and stem rot, phytophthora blight, sclerotium rot, and wilt disease. Analysis of the fatty acid and analysis of the 16S rDNA gene sequence revealed that YKJ1 isolated in this research belongs to a group of Serratia marcescens. Specially, 16S rDNA gene sequence of YKJ1 showed 99% of sequence similarity with S. marcescens. Observation through the optical microscope revealed that YKJ1 suppressed the spore germination and the hyphal growth of pathogens. YKJ1 treatment on pathogens induced marked morphological changes like hyphal swelling and degradation of cell wall. In the case of phytophthora blight, the zoosporangium formation was restrained. S. marcescens found in this study call as S. marcescens-YKJ1 and it may be valuable as one of biological control agents against major diseases of paprika in the future even though it is require to be tested with more study on field test.

• Journal of Mushroom
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• v.21 no.3
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• pp.179-184
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• 2023

The development of automated bottle cultivation systems has facilitated the large-scale production of Pleurotus ostreatus, a commonly cultivated oyster mushroom species in South Korea. However, as the consumption of this product is decreasing and production quantities are exceeding demand, farmers are seeking various other mushroom types and cultivars. In response to this, we have developed a new oyster mushroom cultivar named 'Sena'. This high-yielding cultivar has a white pileus and excellent quality. The white oyster mushroom cultivars 'Goni' and 'Miso' were selected as parental strains from the genetic resources of the National Institute of Horticultural and Herbal Science's Mushroom Division. By crossing their monokaryons, hybrids were developed and subjected to cultivation trials and characteristic evaluations to select the superior cultivar. The optimal temperature for 'Sena' mycelial growth is 25-30℃, with inhibition occurring at temperatures above 30℃, whereas the temperature for mushroom growth is 14-18℃. The mushrooms grow in clusters, with the white pileus having a shallow funnel shape. Optimal mycelial growth occurs in malt extract agar medium. When cultivated in 1,100 cc bottles, the 'Sena' cultivar had 35 available individuals, surpassing the number 16 available from the control cultivar 'Goni'. The yield per bottle also increased by approximately 157 g, a 24% increase over the control cultivar amount. When 300 g samples of harvested mushrooms were packed and stored at 4℃ in a cold storage facility for 28 days, the weight loss rate of 'Sena' was approximately 4.22%, lower than that of 'Goni'. Moreover, the changes in pileus and stipe whiteness (measuring 6.99 and 8.33, respectively) were also lower than those of the control cultivar. Since the appearance of a white cap is crucial for quality assessment, the 'Sena' cultivar is superior to the 'Goni' cultivar in terms of both weight and quality after undergoing low-temperature storage.

• Research in Plant Disease
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• v.29 no.4
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• pp.414-419
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• 2023

In 2023, a number of seeds suspected to be discolored black oat seeds on oat farms in Gangjin were observed and examined for fungal infection. The species Alternaria alternata was predominant, accounting for 84% of all fungal infections. The appearance and quality of seeds harvested in 2022 were compared with seeds harvested in 2023 from the same field. The lightness value was lower in the seeds harvested in 2023, while the electrical conductivity was higher in the seeds harvested in 2023. The content of avenanthramide was found to be 10 times higher in the 2023 seeds than in those harvested in 2022. The accumulated precipitation in Gangjin in May 2023 was 230 times higher than that in May 2022, and the average relative humidity was high. These conditions created an environment suitable for infection of A. alternata, which were thought to have caused discolored black oat seeds.