• Korean Journal of Veterinary Service
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• v.27 no.2
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• pp.159-164
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• 2004

A dairy farm that has been suffered continuously(more than 2 years) from brucellosis in Korea in spite of repeated legal test-and-slaughter was investigated the main source of infection in the farm. All cattle(22 milking cows, 44 heifers, 60 calves, 8 bull), dogs(3 mixed breed), feces from wild birds(3 samples), drinking water(3 sites), and soil in the paddocks(14 sites) inside the farm were examined with serological and/or bacteriological methods including specific DNA detection with PCR method. Brucella spp in the milk and blood were detected in 12/22 and 5/22 milking cows, respectively, although all of them were negative with conventional tube agglutination test. The number of serologically positive heifer was 15(15/44), but the isolation of Brucella spp was succeeded in the only 11(11/15) of them. Brucella were detected in vagina 1(1/11) and nasal(3/12) excretion in serologically positive heifers. All the three dogs were serologically positive, and Brucella spp were isolated from their blood. However, Brucella spp were not detected in the drinking water, soil in the paddocks, nor the feces of wild birds. The results suggest that milking cow secrete Brucella spp through milk, genital tract and nasal cavity, which are the major source of infection in this farm, The main infection route of Brucella spp is contact to contact with Brucella spp excreting animals rather than environmental contamination. The animals, living together with infected cow such as dogs, are the readily susceptible and are required to be examined for Brucella spp.

• Korean journal of applied entomology
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• v.3
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• pp.21-25
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• 1964

1. Purpose of this experiment is to investigate the influence of wheat scab fungus(Gibberella zeae) remaining in soil or residues of infected plants to the growth of the seedlings of 14 different crops. 2. Susceptibility of these crops to the infection by G. zeae was investigated by planting these crops both to the artificially inoculated soils and naturally infected soils where both serious and light wheat scab epidemic have occurred previously. 3. In artifical inoculation tests, bailey, wheat, rye, soybean, rice, buckwheat, corn, cotton and greenbean has shown susceptible reaction, while indianbean, sesame, sorghum, chinese cabbage and radish has shown resistant reaction. 4. In artificial inoculation tests, there was significant difference in the germination ratio of the susceptible crops between the plants planted in inoculated soils and uninoculated soils with the exception of rice, com and cotton. Preemergence seedling blight was confined only to barley and corn, whereas postemergence seedling blight was confined to rye, wheat, rice buckwheat, barley and corn. la most of the susceptible crops secondary roots were almost rotted and the primary roots were either partially rotted or discolorated in inoculated soil. There was significant difference in the stem length of the plants grown in inoculated soils and uninoculated soils in susceptible crops. 5. No infection by G. zeae was observed when wheat, barley and rye plants were sown to the soils where both serious and light wheat scab epidemic occurred naturally.

• The Plant Pathology Journal
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• v.27 no.2
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• pp.138-147
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• 2011

Xylogone ganodermophthora, an ascomycetous fungus, is known to cause yellow rot in the cultivated mushroom Ganoderma lucidum. In this study, we investigated the dissemination of this fungal pathogen in G. lucidum grown in cultivation houses. To determine the role of ascospores produced by X. ganodermophthora in disease development, we constructed a green fluorescent protein-labeled transgenic strain. This X. ganodermophthora strain produced a number of ascomata in the tissues of oak logs on which G. lucidum had been grown and on the mushroom fruit bodies. However, the ascospores released from the ascomata were not able to germinate on water agar or potato dextrose agar. Moreover, less than 0.1% of the ascospores showed green fluorescence, indicating that most ascospores of X. ganodermophthora were not viable. To determine the manner in which X. ganodermophthora disseminates, diseased oak logs were either buried in isolated soil beds as soil-borne inocula or placed around soil beds as air-borne inocula. In addition, culture bottles in which G. lucidum mycelia had been grown were placed on each floor of a five-floor shelf near X. ganodermophthora inocula. One year after cultivation, yellow rot occurred in almost all of the oak logs in the soil beds, including those in beds without soil-borne inocula. In contrast, none of the G. lucidum in the culture bottles was infected, suggesting that dissemination of X. ganodermophthora can occur via the cultivation soil.

• The Plant Pathology Journal
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• v.23 no.1
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• pp.3-6
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• 2007

Chickpea wilt caused by Fusarium oxysporum f. sp. ciceris(FOC) is the most destructive disease in India. It is seed-borne as well as soil-borne pathogen. The role of seed-borne FOC in introducing and establishing wilt in FOC free soils is unknown. Using seeds of FOC infected chickpea cultivar K 850, we provided an evidence of establishing wilt disease in the FOC free soils within three crop cycles or seasons. In the first cycle, typical wilt symptoms were observed in 24 pots in 41 days after sowing. These 24 pots were used for second and third cycles without changing the soil. These 24 pots were sown with seeds collected from healthy plants of a susceptible cultivar JG 62, one seed per pot and development of wilt symptom was recorded. Wilt symptoms appeared in all the pots 26 days after sowing in second cycle and in 16 days after sowing in third cycle. On selective medium, all of the wilted plants yielded FOC in all the three cycles indicating that the mortality was due to wilt. FOC propagules on selective medium were 172, 1197, and 2280 $g^{-1}$ soil at the end of the first, second, and third cycles, respectively. These studies indicated that Fusarium wilt of chickpea is seed-borne and seeds harvested from wilted plants when mixed with healthy seeds can carry the wilt fungus to new areas and can establish the disease in the soil to economic threshold levels within three seasons.

• Research in Plant Disease
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• v.6 no.1
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• pp.27-33
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• 2000

Population density of Plasmodiophora brassicae in soil of severely infested fields of Chinese cabbage decreased as soil depth increases. More than 97% of total population was found in surface soil (0-5cm depth), and a few resting spores of the pathogen were also detected in 40 cm-deep soil. the clubroot pathogen was evenly distributed over the surface soil without clustering around a Chinese cabbage plant. Density of P. brassicae in soil at 23 Chinese cabbage fields in Pyongchang, Kangwon province ranged widely from less than 10$^4$resting spores/g soil to above 10$\^$6/ resting spores/g soil. Few or none of P. brassicae was found in virgin soil without any cropping history, intermediate with 0.36-2.75$\times$10$^4$resting spores/g soil in fields of other crops but more than 10 times higher population was found in severely infected Chinese cabbage fields. Density of P. brassicae was highest in the fields of monocropping of crucifers with some exceptions, but was low in rotated fields with corn, rye, medicinal crops or other non-host vegetables. Pathoen density in soil was decreased rapidly when rye or medicinal crops were cultivated after Chinese cabbage, suggesting that survival of clubroot pathogen appears to be influenced greatly by cropping system. The improved method for detecting resting spores of P. brassicae in soil used in this study seemed to be adequate for estimating population density of P. brassicae in soil in aspects of clearer dyeing, increased detecting sensitivity, and simplicity in preparation.

• The Plant Pathology Journal
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• v.31 no.2
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• pp.140-151
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• 2015

Bacillus subtilis B006 strain effectively suppresses the cucumber fusarium wilt caused by Fusarium oxysporum f. sp. cucumerinum (Foc). The population dynamics of Foc, strain B006 and its surfactin over-producing mutant B841 and surfactin-deficient mutant B1020, in the rhizosphere were determined under greenhouse conditions to elucidate the importance of the lipopeptides excreted by these strains in suppressing Foc. Results showed that B. subtilis strain B006 effectively suppressed the disease in natural soil by 42.9%, five weeks after transplanting, whereas B841 and B1020 suppressed the disease by only 22.6% and 7.1%, respectively. Quantitative PCR assays showed that effective colonization of strain B006 in the rhizosphere suppressed Foc propagation by more than 10 times both in nursery substrate and in field-infected soil. Reduction of Foc population at the cucumber stems in a range of $0.96log_{10}ng/g$ to $2.39log_{10}ng/g$ was attained at the third and the fifth weeks of B006 treatment in nursery substrate. In field-infected soil, all three treatments with B. subtilis suppressed Foc infection, indicated by the reduction of Foc population at a range of $2.91log_{10}ng/g$ to $3.36log_{10}ng/g$ at the stem base, one week after transplanting. This study reveals that the suppression of fusarium wilt disease is affected by the effective colonization of the surfactin-producing B. subtilis strain in the rhizosphere. These results improved our understanding of the biocontrol mechanism of the B. subtilis strain B006 in the natural soil and facilitate its application as biocontrol agent in the field.

• The Plant Pathology Journal
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• v.25 no.1
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• pp.6-12
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• 2009

Snow molds are the most important winter diseases of turfgrass in the United States and Canada. Eight isolates of three snow mold fungal species (three isolates of Typhula ishikariensis, three of T. incarnata, and two of Microdochium nivale) were collected from infected turfgrasses on golf courses. The isolates were evaluated for their relative aggressiveness on three cultivars (L-93, Penncross, and Providence) of creeping bentgrass (Agrostis palustris) under the same controlled conditions. Four plant ages (15, 19, 23 and 27 week-old plants from germination to inoculation) were evaluated for their susceptibility to the three pathogens and for the recovery of the plants. Regardless of age or cultivar of the host plant, M. nivale was found to be more aggressive and faster to infect and colonize than Typhula species. After three weeks recovery, M. nivale-inoculated plants showed higher disease severity than plants inoculated with the two Typhula species. Plants infected by Typhula species displayed no significant difference in disease severity. As creeping bentgrass plants get older, the severity of disease caused by three snow molds gradually decreases. This effect was observed in all cultivars tested, suggesting expression of age-related resistance as the bentgrass plants matured.

• Research in Plant Disease
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• v.16 no.3
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• pp.323-325
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• 2010

The stem rot of sunflower (Helianthus annuus) occurred sporadically in the experimental field of Gyeongsangnam-do Agricultural Research and Extension Services, on September, 2009. The infected plants were wilted and water-soaked brown spots were formed on the stem, than infected stems were mostly died. White mycelial mats were spread over lesions, and then sclerotia were formed on stem and near soil line. The sclerotia were globoid in shape, 1~3 mm in size and white to brown in color. The optimum temperature for mycelial growth and sclerotia formation on PDA was $30^{\circ}C$ and the hyphal width was $4{\sim}8\;{\mu}m$. The typical clamp connections were observed in the hyphae of the pathogenic fungus. On the basis of mycological characteristics and pathogenicity to host plants, this fungus was identified as Sclerotium rolfsii. This is the first report on the stem rot of sunflower by S. rolfsii in Korea.

• The Plant Pathology Journal
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• v.19 no.3
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• pp.184-187
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• 2003

Verticillium wilt was first observed in 2001 on potatoes (Solanum tuberosum) cv. Superior at Daegwallyong area, one of the major seed potato producing areas in Korea. The wilted potato plants showed typical symptoms including gradual yellowing and interveinal necrosis. There was discoloration in the vascular tissues of the infected stems which turned light brown. Fungal isolates from discolored vascular tissues were whitish to creamy with folding on potato dextrose agar medium, where they used to produce resting dark mycelia but no micro-sclerotia. Conidiophores were septate with side branches, swelled at the base, and arranged in a whorl. Conidia were 2.5-11.2$\times$2.0-4.5 $\mu\textrm{m}$ um in size and were borne in small clusters at the tips of phialides. Optimal temperature range for mycelial growth was $25-30^{\circ}C$. Based on these cultural and morphological characteristics, the fungus was identified as Verticillium albo-atrum Reink & Berth. Pathogenicity tests by root dipping method revealed that the fungus caused the same symptoms as observed in naturally infected potato plants. This is the first report of Verticillium wilt on potato caused by Verticillium albo-atrum in Korea.

• Mycobiology
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• v.30 no.2
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• pp.102-104
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• 2002

In July 2001, a destructive stem rot of tatarian aster(Aster taturicus) was occurred sporadically in exhibition farm of Gyeongsangnam-do Agricultural Research and Extension Services, in Hamyang, Korea. The fungus also caused collar and crown rot and systemic wilt or blight of whole plant. White mycelium spread over stems and petioles of infected plants and sclerotia formed on the old lesions and near the soil surface. The fungus showed maximum mycelial growth was obtained around $30^{\circ}C$ but did not grow below $5^{\circ}C$ or above $45^{\circ}C$. The mycelial width ranges $4.2{\sim}10.4{\mu}m$. and the color is white, usually many narrow mycelial stand grow in the aerial mycelium and formed clamp connection. Numerous sclerotia were formed in artificial media like PDA at $30^{\circ}C$. The shape of sclerotia were sphere and $1.0{\sim}3.2{\mu}m$ in diameter. The fungus was isolated repeatedly from the infected, tissues and confirmed its pathogenecity to aster and identified as Sclerotium rolfsii. This is the first report that Sclerotium rolfsii causes stem rot of tatarian aster in Korea.