• The Korean Journal of Pesticide Science
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• v.5 no.1
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• pp.1-11
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• 2001

Climate in the year of 2000 was characterized as a long severe drought in tile spring, unusually high and low temperature in summer, two times of typoons, and floods by heavy rains in fall. Rice leaf and panicle blast and bacterial grain rot occurred severely comparing with 1999 and Bipolaris leaf spot spread over tile country. Phytophthora blight and anthracnose in red-pepper became epidemic especially in the late season causing severe yield losses. Tomato fusaruim wilt, CGMMV, powdery mildew, and sudden wilt syndrom of cucurbits and strawberry powdery mildew were also severe in 2000. In garlic, sclerotium rot occurred severely mainly due to the frequent rainfalls in planting time and much snowfalls in 1999's winter. Spring potato had severe infection of viruses due to a long spring drought, and fall potato had high incidence of bacterial soft rot and bacterial wilt due to fall floods by heavy rains. In sweet potato fusarium wilt was the most severe as in other year. Disease incidence of apple and pear trees was rotatively mild compared with previous years. In wheat and barley, Gibberella petch rarely occurred because of spring drought.

• The Plant Pathology Journal
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• v.30 no.2
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• pp.125-135
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• 2014

A population model of bacterial spot caused by Xanthomonas campestris pv. vesicatoria on hot pepper was developed to predict the primary disease infection date. The model estimated the pathogen population on the surface and within the leaf of the host based on the wetness period and temperature. For successful infection, at least 5,000 cells/ml of the bacterial population were required. Also, wind and rain were necessary according to regression analyses of the monitored data. Bacterial spot on the model is initiated when the pathogen population exceeds $10^{15}cells/g$ within the leaf. The developed model was validated using 94 assessed samples from 2000 to 2007 obtained from monitored fields. Based on the validation study, the predicted initial infection dates varied based on the year rather than the location. Differences in initial infection dates between the model predictions and the monitored data in the field were minimal. For example, predicted infection dates for 7 locations were within the same month as the actual infection dates, 11 locations were within 1 month of the actual infection, and only 3 locations were more than 2 months apart from the actual infection. The predicted infection dates were mapped from 2009 to 2012; 2011 was the most severe year. Although the model was not sensitive enough to predict disease severity of less than 0.1% in the field, our model predicted bacterial spot severity of 1% or more. Therefore, this model can be applied in the field to determine when bacterial spot control is required.

• Journal of Ginseng Research
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• v.40 no.1
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• pp.90-96
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• 2016

Background: Knowledge on microclimate conditions under artificial shades in a ginseng field would facilitate climate-aware management of ginseng production. Methods: Weather data were measured under the shade and outside the shade at two fields located in Gochang-gun and Jeongeup-si, Korea, in 2011 and 2012 seasons to assess temperature and humidity conditions under the shade. An empirical approach was developed and validated for the estimation of leaf wetness duration (LWD) using weather measurements outside the shade as inputs to the model. Results: Air temperature and relative humidity were similar between under the shade and outside the shade. For example, temperature conditions favorable for ginseng growth, e.g., between $8^{\circ}C$ and $27^{\circ}C$, occurred slightly less frequently in hours during night times under the shade (91%) than outside (92%). Humidity conditions favorable for development of a foliar disease, e.g., relative humidity > 70%, occurred slightly more frequently under the shade (84%) than outside (82%). Effectiveness of correction schemes to an empirical LWD model differed by rainfall conditions for the estimation of LWD under the shade using weather measurements outside the shade as inputs to the model. During dew eligible days, a correction scheme to an empirical LWD model was slightly effective (10%) in reducing estimation errors under the shade. However, another correction approach during rainfall eligible days reduced errors of LWD estimation by 17%. Conclusion: Weather measurements outside the shade and LWD estimates derived from these measurements would be useful as inputs for decision support systems to predict ginseng growth and disease development.

• The Plant Pathology Journal
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• v.38 no.2
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• pp.115-130
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• 2022

Though information exists regarding the pathogenesis of the shot-hole disease (SH) in flowering cherry (FC), there has been a lack of research focusing on SH management. Therefore, here, we investigated the inhibitory activities of antagonistic bacteria against SH pathogens both in vitro and in vivo as well as their biochemical characteristics and bioactive compounds. Two biosurfactant-producing bacterial antagonists, identified as Bacillus velezensis strains JCK-1618 and JCK-1696, exhibited the best effects against the growth of both bacterial and fungal SH pathogens in vitro through their cell-free culture filtrates (CFCFs). These two strains also strongly inhibited the growth of the pathogens via the action of their antimicrobial diffusible compounds and antimicrobial volatile organic compounds (VOCs). Crude enzymes, solvent extracts, and biosurfactants of the two strains exhibited antimicrobial activities. Liquid chromatography/electrospray ionization time-of-flight mass spectrometric analysis of the partially purified active fractions revealed that the two antagonists produced three cyclic lipopeptides, including iturin A, fengycin A, and surfactin, and a polyketide, oxydifficidin. In a detached leaf assay, pre-treatment and co-treatment of FC leaves with the CFCFs led to a large reduction in the severity of the leaf spots caused by Epicoccum tobaicum and Bukholderia contaminans, respectively. In addition, the two antagonists produced indole-3-acetic acid, siderophore, and a series of hydrolytic enzymes, along with the formation of a substantial biofilm. To our knowledge, this is the first report of the antimicrobial activities of the diffusible compounds and VOCs of B. velezensis against the SH pathogens and their efficiency in the biocontrol of SH.

• Research in Plant Disease
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• v.16 no.2
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• pp.125-128
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• 2010

Bacterial black spot disease of prune fruit (Prunus salicina cv. formosa) has outbroke around major prune production area, Gimcheon, Euiseong and Gunwi in Gyungbuk province and has caused severe economic loss. Integrons PCR primer was designed along with sample pre-incubation and nested PCR method to enhance detection sensitivity for early detection of bacteria in fields. Designed integrons PCR primer successfully detected Xanthomonas arboricola pv. pruni from field collected samples, fruit, leaf, branch and even in raindrop collected from prune orchard. Pre-incubation along with nested PCR enhanced sensitivity to detect X. arboricola pv. pruni from seemingly healthy looking, symptomless branches. Designed integrons PCR can be used in prune nursery fields and in plant quarantine practice for the detection of X. arboricola pv. pruni.

• The Plant Pathology Journal
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• v.26 no.4
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• pp.306-312
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• 2010

The pathotypes of Cercospora beticola, causal agent of sugar beet leaf spot disease, were identified by application of pathogenicity test using 100 isolates obtained from the provinces with intensive sugar beet cultivation. For the identification of pathotypes, five sugar beet cultivars were used each with different resistance factors. Cultivar reactions were determined by inoculation of cultivars with the isolates under controlled conditions and measuring disease severity on the $15^{th}$ day according to the 1-9 KWS Scale. Based on the reactions of the five cultivars, a total of 15 pathotypes were detected. All employed sugar beet cultivars were resistant to Pathotype no:1 comprising most of the isolates. Genetic diversity of the causal agent was characterized by AFLP reaction. The products acquired at the end of AFLP reaction were detected by means of Beckman CEQ 8800 DNA Capillary Series Analysis and the results obtained were evaluated according to the similarity index UPGMA. For the genetic analysis of C. beticola isolates, 9874 polymorphic fragments of sizes between 100 and 500 bp were analysed which were generated by nine primers. The dendrogram derived from AFLP analysis depicted the existence of five different subgroups. The polymorphism rate among isolates was 91.13% and the dendrogram distribution of the pathotypes obtained by pathogenicity indicated that pathotypes were not discriminated and did not compose any groups.

• Research in Plant Disease
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• v.12 no.2
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• pp.134-138
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• 2006

A new bacterial disease of broccoli (Brassica oleracea var. italica) was observed on field-grown plants in Pyungchang during 2003 and 2004. Seedling infections first appeared as a blackening along the margins of the cotyledon. Cotyledon shriveled and dropped off. Infected seedlings were stunted and yellowed and eventually died. The disease was easily recognized by the presence of yellow, V-shaped, or U-shaped areas extending inward from margin of the leaf. As the disease progressed, the yellow lesions turned brown and the tissues died. Isolations made from diseased leaves on yeast extract dextrose calcium carbonate agar yielded nearly pure cultures of a yellow-pigmented bacterium typical of a xanthomonad. Two bacterial strains were purified and used for further tests. Pathogenicity of strains was confirmed on 3-week-old crucifer (cabbage, Chinese cabbage, kale, radish and broccoli) plants cut by scissors with bacterial suspensions containing $10^8 cfu/ml$ of phosphate buffered saline. The Biolog and fatty acid analyses and 16S rDNA sequencing of two strains (SL4797 and SL4800) from broccoli black rot showed that they could be identified as X. campestris pv. campestris because of their high similarity to the tester strain (X. campestris pv. campestris NCPPB528) with a match probability of 100%. This is the first report of black rot of broccoli in Korea.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.7 no.1
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• pp.31-63
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• 1969

A series of experiment was carried out to study on the production of disease-free seed potatoes at the Alpine Experiment Station from 1960 to 1968, which initiated a study of comparison on degeneration of plain warm region and high altitude products and the effect of latent potato virus X (PVX) and potato leaf roll virus(PLRV) on degeneration. Particular observations were made on some aspect of the nature of potato virus disease and its control such as concentrations of PVX, range of host plants, physical properties such as concentrations of PYX, range of host plants, physical properties and carrying effect of insects, by investigating 9 different areas of the main potato producing regions (Kimhae, Taegu, Choongju, Taejoen, Suwon, Kwangju, Chonju, Cheju and Chinju). Highly purified anti-serum was separated and tested for control of the virus disease and also various method of prevention and control of PLRV were observed, using cultivation of sprouted seed tubers, early harvesting method, and systemic chemicals. The results obtained are summarized as follows; 1. Potato yield in the plain region decreased by 32.8~66.3% in the first year cultivation of seed potatoes from colder region, and the rate of virus infection was 92.9 to 95.4%. 2. Plants of three families including, 20 species were susceptible to the PVX, and among the plants Salvia officinalis of a habits only was the carrier while the symptom of Digitalis purpurea of Screphulariaceae was masked. Necrosis and ring spot was occurred in most pJants of the Solanaceae and ring spot symptom also was observed in Nicotiana tabacum L. var. White Burley and in N. glutinosa. 3. The 8$C_2$ strain of virus had the following physical properties; thermal inactivation point, 68-$72^{\circ}C$ : dilution inactivation point, above 1, 000, 000 dilution: ageing in vitro, 240-360 days: and ageing in dry plant tissue, 30 days. 4. Myzus persicae and Oxya spp. did not transmit the 8$C_2$ strain of potato virus. 5. Virus was purified through the ammonium sulphate isolating method, and higher titer value, 1/2048 was obtained through anti-serum test. 6. Inhibition Chenopodiacae on the virus infection of potato was remarkable, and inhibition of local lesion host also was observed. 7, By earlier planting of sprouted seed tubers, growth period could be prolonged by 10 to 12 days. 8. Earlier harvest decreased much the rate of virus infection of seed potatoes. 9. According to the results of aphid control trial using systemic soil insecticides at Kangnung and Taekwanlyung, PSP 204, Disyston and Thimet was effective to aphid control. In particular, control effect of twice treatments of PSP 204 was great. 10. Treatmental effect of those chemicals lasted about 60-70 days. However, single foliar application of emulsified chemicals was not effective to potato virus control. 11. The effect of PSP 204, Disyston, and Thimet on the control of potato leaf roll virus was great, particularly in the case of two treatments of PSP 204, at Kangnung as well as at Taekwanlyung. Higher negative correlationship between the control effect of potato leaf roll virus and potato yield was observed showing the value r=-0.85 at Kangnung, and r=-0.87 at Taekwanlyung. 12. Differences in the control effects among PSP 204, Disyston, and Thimet was not noticed.

• The Plant Pathology Journal
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• v.30 no.4
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• pp.355-366
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• 2014

In this study, resistance responses were investigated during the interaction of Botrytis fabae with two faba bean cultivars expressing different levels of resistance against this pathogen, Nubaria (resistant) and Giza 40 (susceptible). Disease severity was assessed on leaves using a rating scale from 1 to 9. Accumulation levels of reactive oxygen species (ROS), lipid peroxidation and antioxidant enzymes (superoxide dismutase, catalase and ascorbate peroxidase) were measured in leaf tissues at different times of infection. The expression profiles of two pathogenesis-related proteins (PRPs) encoded by the genes PR-1 and ${\beta}$-1,3-glucanase were also investigated using reverse transcription RT-PCR analysis. The accumulation of these defense responses was induced significantly in both cultivars upon infection with B. fabae compared with un-inoculated controls. The resistant cultivar showed weaker necrotic symptom expression, less ROS accumulation, a lower rate of lipid peroxidation and higher activity of the enzymatic ROS scavenging system compared with susceptible cultivar. Interestingly, ROS accumulated rapidly in the resistant leaf tissues and peaked during the early stages of infection, whereas accumulation was stronger and more intense in the susceptible tissues in later stages. Moreover, the response of the resistant cultivar to infection was earlier and stronger, exhibiting high transcript accumulation of the PR genes. These results indicated that the induction of oxidant/antioxidant responses and the accumulation of PRPs are part of the faba bean defense mechanism against the necrotrophic fungus B. fabae with a different intensity and timing of induction, depending on the resistance levels.

• Korean Journal of Environmental Agriculture
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• v.41 no.4
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• pp.245-251
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• 2022

BACKGROUND: Selection an suitable light source is essential in the year-round production of horticultural crops in closed production systems such as plant factory with controlled environments. This study was investigated to confirm the effects of artificial light sources on growth of cherry tomato'CF Jelly'(Lycopersicon esculentum var.) under high-pressure sodium lamps (HPS), metal-halide lamps (MH), and LEDs. METHODS AND RESULTS: Light intensity of the light sources was controlled at 220±30 µmol/m²/s with 12 hrs of photoperiod for a day. Flower development was significantly faster in HPS and MH treatments compared to the LEDs. There was no significant difference between the leaf number and leaf shape under the HPS and MH treatments. Reproductive growth of cherry tomato was significantly promoted by the LEDs treatment of blue plus red lights. Fruit yield per plant also increased under the LEDs compared to the others. CONCLUSION(S): Growth, flowering, and fruit setting of the cherry tomato were accomplished by the artificial lights under plant factory conditions. The HPS treatment showed negative effect on fruit quality in terms of blossom-end rot incidence compared to the LEDs or MH treatment. Effect of the LEDs on promotion of fruit weight and yield was also proved. Additional research should be carried out for improving sugar metabolism or decreasing disease in the fruits under plant factory system using only artificial lights.