• Korean Journal Plant Pathology
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• v.13 no.3
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• pp.191-193
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• 1997

A new disease of arrowhead (Sagittaria trifolia L.)caused by Plectosporium tabacinum was observed at Yusung area in Korea. Infection occurred on the petioles, leaves, and seeds of young and old arrowhead plants. Small and brown spots developed on the infected areas initially, which later coalesced to form large dead areas resulting in the complete blight of the host plant. Inoculation of arrowhead seedlings by conidial suspension induced typical disease symptoms found in naturally infected plants. The new name for the disease 'arrowhead blight' is suggested. The pathogenic fungus was identified as Plectosporium tabacinum and its morphological and cultural characteristics are described.

• Research in Plant Disease
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• v.17 no.3
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• pp.364-368
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• 2011

Gray mold caused by Botrytis cinerea was found on a carrot seedling in a greenhouse and a field at Daegwallryeong, Gangwon Province in 2007-2009. Symptoms included irregular, brown, blight, or chlorotic halo on leaves and petioles of the carrots. Fungal conidia were globose to subglobose or ellipsoid, hyaline or pale brown, nonseptate, one celled, $7.2-18.2{\times}4.5-11\;{\mu}m$ ($12.1{\times}8.3\;{\mu}m$) in size, and were formed on botryose heads. B. cinerea colonies were hyaline on PDA, and then turned gray and later changed dark gray or brown when spores appeared. The fungal growth stopped at $35^{\circ}C$, temperature range for proper growth was $15-25^{\circ}C$ on MEA and PDA. Carrots inoculated with $1{\times}10^5$ ml conidial suspension were incubated in a moist chamber at $25{\pm}1^{\circ}C$ for pathogenicity testing. Symptoms included irregular, brown, water-soaked rot on carrot roots and irregular, pale brown or dark brown, water-soaked rot on leaves. Symptoms were similar to the original symptoms under natural conditions. The pathogen was reisolated from diseased leaves, sliced roots, and whole roots after inoculation. As a result, this is the first report of carrot gray mold caused by B. cinerea in Korea.

• The Korean Journal of Mycology
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• v.19 no.3
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• pp.231-237
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• 1991

This study was conducted in order to find out biological control of sesame wilt and blight caused by Fusarium of oxysporum f. sp. vasinfectum and Phytophthora nicotianae var. parasitica by using Streptomyces spp. Two sesame pathogens, Fusarium oxysporum f. sp. vasinfectum and Phytophthora nicotianae var. parasitica were purely isolated from diseased sesame plants of the field. Streptomyces species were isolated from 72 soil samples collected from red pepper and sesame uplands in Chungbuk and selected as antagonists according to the results of dual culture. The selected Streptomyces isolates such as St-11 and St-20 were confirmed their antagonistic effect through mycelial inhibition zone and inhibitory effects on the mycelial growth of the pathogens by culture filterate of the antagonists. Inhibitory effects on the conidial germination of Fusarium oxysporum vasinfectum and Phytophthora nicotianae parasitica by the antagonists were also tested in addition to mycelial Iysis. The antagonists St-11 and St-20 showed inhibitory effect on growth of sesame seedlings after seeds soaked in the suspension. Effect of soil inoculation with antagonist St-11 showed 40 to 78 percent of control effect for two diseases in comparison with control under greenhouse.

• Korean Journal Plant Pathology
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• v.14 no.4
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• pp.339-344
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• 1998

Since the leaf inoculation procedures are time-consuming and require considerable growth chamber space, a rapid dioassay method for screening of pathogenicity of Didymella bryoniae, a casual agent of gummy stem blight in watermelon, was established in this paper. The method produced reliable results within 8 days ( 5 days for growing seedlings and 3 days for rapid disease response in the seedlings). After contaminants in the root of 4~5 day-old seedlings had been washed using sterilized water, 5 seedlings were dipped into a vial containing 12 ml of conidial suspension (106 cells/ml). After the vials were placed in a growth chamber (22$^{\circ}C$, RH 50%, 14hr light/10hr darkness) for 3 days, susceptibility and resistance of cultivars were determined by the degree of disease response on cotyledon. The result of obtained by the dip-inoculation method was well coincided with the results by the leaf inoculation procedures and the result that had been observed for several years in the field. Screening of collected watermelon cultivars by the dip-inoculation method revealed that all the 21 domestic cultivars collected were susceptible and only 3 foreign cultivars (PI 189225, PI 482322 and IT 188207) were resistant among 18 cultivars A cucumber cultivar (Marketer) and bitter cucumber were proven to be resistant against the D. bryoniae among 8 other different cucurbits tested. The SDS-PAGE patterns of total proteins from a susceptible (Keumcheon) and a resistant (PI 189225) watermelon cultivars were compared 0, 12, 24 and 36 hrs after inoculation. The amounts of two distinct protein bands (24 kDa and 70 kDa) were gradually increased after inoculation in both cultivars.

• The Plant Pathology Journal
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• v.24 no.4
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• pp.392-399
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• 2008

Detached chili pepper fruits were inoculated with the conidial suspension of Colletotrichum acutatum JC-24 simultaneously (simultaneous inoculation, SI) and at delayed time (delayed inoculation, DI) after wounding with (delayed wound inoculation, DWI) or without additional wounding (delayed non-wound inoculation, DNI) at the inoculation time. Disease severity was significantly lowered by DNI, compared to SI. By DNI, the disease reduction rates were proportional with the length of delayed time, and greater at the high temperature range (18, 23 and $28^{\circ}$) than at the low temperature ($13^{\circ}$) tested. DWI was also effective in reducing the disease severity especially at 18oC; however, its effectiveness was lower than for DNI. In light microscopy, parenchyma cells at the wounding sites were modified structurally, initially forming new cell walls crossing cytoplasm, enlarged with multiple periclinal cell divisions, and finally layered like wound periderms. In DWI, the above structural modifications occurred, showing the restriction of the fungal invasion by the cell walls in enlarged modified cells, while no definite cellular modifications were found with proliferation of fungal hyphae in SI. Sclerenchyma-like cells with thickened cell walls were proliferated around the wounding sites, which were partially dissolved by DWI, probably leading to some disease development. All of these results suggest that the decline of the anthracnose disease in pepper fruit by the delayed inoculations may be derived from the structural modifications related to the healing processes of the previous wound inflicted on the tissues.

• Korean Journal of Agricultural Science
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• v.37 no.3
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• pp.341-350
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• 2010

Blue mold is the most important postharvest disease of apples in Korea. Apple fruits with blue mold symptoms were collected from storages in different locations in Korea and were investigated for their association with Penicillium species. A total of sixty five isolates of Penicillium were sampled from the collected apples. Based on DNA sequence analysis of ${\beta}$-tublin gene and ITS and lsu rDNA (ID region) and morphological characteristics, they were identified as P. crustosum, P. expansum, P. italicum, P. solitum and P. sp.. P. sp. which is closely related to P. hirsutum is a new species, not reported before. P. expansum (35%) was predominant species followed by P. crustosum. The phylogenetic tree inferred from combined ${\beta}$-tublin and ID region sequence showed good correlation with species that are defined by morphological characteristics. In pathogenicity test, apples were wound-inoculated with conidial suspension and incubated at $20-22^{\circ}C$. The most severe and destructive species was P. expansum. The species caused a decayed area 42-50mm in diameter after 8-10days. Decayed area caused by P. crustosum and P. sp. was 26-32mm and 20-26mm, respectively. This is the first record of P. crustosum, P. italicum and P. sp. from apple in Korea.

• The Plant Pathology Journal
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• v.30 no.1
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• pp.25-32
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• 2014

Fusarium head blight (FHB; scab) caused mainly by Fusarium graminearum is a devastating disease of wheat and barley around the world. FHB causes yield reductions and contamination of grain with trichothecene mycotoxins such as deoxynivalenol (DON) which are a major health concern for humans and animals. The objective of this research was to develop an easy seed or seedling inoculation assay, and to compare these assays with whole plant resistance of twenty-nine Korean winter wheat cultivars to FHB. The clip-dipping assay consists of cutting off the coleoptiles apex, dipping the coleoptiles apex in conidial suspension, covering in plastic bag for 3 days, and measuring the lengths of lesions 7 days after inoculation. There were significant cultivar differences after inoculation with F. graminearum in seedling relative to the controls. Correlation coefficients between the lesion lengths of clip-dipping inoculation and FHB Type II resistance from adult plants were significant (r=0.45; P<0.05). Results from two other seedling inoculation methods, spraying and pin-point inoculation, were not correlated with adult FHB resistance. Single linear correlation was not significant between seed germination assays (soaking and soak-dry) and FHB resistance (Type I and Type II), respectively. These results showed that clip-dipping inoculation method using F. graminearum may offer a real possibility of simple, rapid, and reliable for the early screening of FHB resistance in wheat.

• Mycobiology
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• v.30 no.1
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• pp.31-36
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• 2002

Soil bacteria were screened for the ability to control cucumber anthracnose caused by Colletotrichum orbiculare through induced systemic resistance(ISR). Sixty-four bacterial strains having in vitro antifungal activity were used for selecting ISR-inducing strains in cucumber. Cucumber seeds(cv. Baeknokdadagi) were sown in potting mixtures incorporated with the soil bacteria, at a rate of ca. $10^8$ cells per gram of the mixture. Two week-old plants were then transplanted into the steam-sterilized soil. Three leaf-stage plants were inoculated with a conidial suspension($5{\times}10^5$ conidia/ml) of C. orbiculare. Diseased leaf area(%) and number of lesions per $cm^2$ leaf were evaluated on third leaves of the plants, $5{\sim}6$ days after inoculation. Among 64 strains tested, nine strains, GC-B19, GC-B35, GK-B18, MM-B22, PK-B14, RC-B41, RC-B64, RC-B65, and RC-B77 significantly(P=0.05) reduced anthracnose disease compared to the untreated control. In contrast, some bacterial strains promoted susceptibility of cucumber to the disease. From the repeated experiments using the nine bacterial strains, GC-B19, MM-B22, PK-B14, and RC-B65 significantly(P=0.05) reduced both diseased leaf area(%) and number of lesions per $cm^2$ leaf in at lease one experiment. These strains with control efficacy of $37{\sim}80%$ were determined to be effective ISR-inducing strains.

• The Korean Journal of Mycology
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• v.39 no.2
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• pp.131-135
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• 2011

One fungal isolate CM2 parasitic to Sclerotinia sclerotiorum and S. minor causing Sclerotinia rot of lettuce was identified as Paraconiothyrium minitans based on its morphological and molecular characteristics. P. minitans CM2 grew best on PDA with pH 6.5 at $22^{\circ}C$ under alternating cycles of 12 hr near ultraviolet light and 12 hr darkness. Scleroria of S. sclerotiorum and S. minor treated with conidial suspension of P. minitans CM2 did not directly germinate and produced no apothecia.

• The Plant Pathology Journal
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• v.26 no.4
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• pp.394-401
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• 2010

Resin flow, symptom development, and lignin biosynthesis in response to wounding and fungal inoculation were investigated in Pinus rigida and Pinus densiflora. The two-year-old seedling stems were subjected to three types of treatments: (i) wounding without inoculation, (ii) wound-inoculation with a conidial suspension of Fusarium circinatum, and (iii) pre-wounding woundinoculation with the fungus 20 days after the initial wounding. Resin flow from wounding sites was more evident in P. rigida than P. densiflora in all treatments. The wound-inoculation with the fungus induced almost two-fold higher levels of resin flow than the other treatments in both species. The pre-wounding woundinoculation appeared to result in a decrease in pitch canker development in the two pine species. Some reductions in disease severity were observed in the prewounding wound-inoculated P. rigida, showing a mean disease severity of less than 85%, compared with approximately 100% in the wound-inoculated stems. Disease severity was approximately 50% in the woundinoculated P. densiflora, whereas 10% in the pre-wounding wound-inoculated stems. Higher amounts of lignin were found from bark (ca. 40%) than from xylem (ca. 30%). The wound-inoculated bark and the pre-wounding wound-inoculated bark exhibited higher amounts of lignin among the other treatments. These results suggest that the wound-inoculation apparently prompt the increase in resin flow and lignin biosynthesis from the two pine species, and the prior wounding may be involved in decreased disease severity against the further invasion of F. circinatum.