• Research in Plant Disease
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• v.8 no.4
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• pp.228-233
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• 2002

This experiment was carried out to investigate the primary inoculum of strawberry anthracnose in nursery field. The pathogen, Colletotrichum gloeosporioides was not detected in soil and weeds of nursery field but symptom of anthracnose was developed in mother plants collected from market after incubation in humid chamber, The symptom of anthracnose was expressed in the strawberry plant that reserved for 17 days in field after inoculation by spore suspension but was not observed there after. When inoculated leaves were observed by SEM, only appressoria were observed 7 days after inoculation. So, it is guessed that dissemination of Colletotrichum sp. into nursery held will be by contamination of mother plants, and diagnosis by naked eyes may be impossible because symptom will be not developed if environment is to be adequate to penetration and in case of imperfect penetration after germination, the pathogen remains appressorium to achieve penetration.

• Korean Journal Plant Pathology
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• v.2 no.1
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• pp.37-42
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• 1986

Papilla and cytoplasmic aggregates clearly formed on the epidermal cells of barley leaves in response to the primary germ-tubes of Erysiphe graminis f. sp. hordei, but their sizes were much smaller than those in response to the appressoria. Some cells of barley leaves exposed to powdery mildew for 36-48h were more deeply stained as compared to the other cells by acid fuchsin. However, the content of malondialdehydein in powdery mildewed leaves, one of the product of lipid peroxidation, did not increase by 96h after inoculation. Positive reactions for callose, protein and phenolics were recognized in the papilla and cytoplasmic aggregates at 6h after inoculation, but cutin, suberin, cellulose and lignin were not noticeable until 72h after inoculation. The total phenol content in methanol extracts increased with increasing time after inoculation. All histochemical reactions were not race-specific in barley­powdery mildew combinations tested.

• Korean Journal Plant Pathology
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• v.13 no.4
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• pp.195-199
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• 1997

Anthracnose symptoms were observed on the commercially cultivating ultivating cyclamen in Chonbuk province in 1995. The symptoms of infected flowers were small, circular and dark brown ring-spots or water-soaked lesions and gradually changed to lack blight. Mycelial colony of the isolates was light or whitish gray to dark gray on potato dextrose agar. Conidia were straight cylindrical and obtuse at the apex and measured 8.3~15.0${\times}$2.5~6.3 ${\mu}m$ in size. Appressoria were brown to dark brown and clavate, but most of them were irregular. Acervuli on lesions were brown, rounded and measured 50~140${\times}$32.5~90 ${\mu}m$ in size. The optimum temperatures for mycelial growth and conidial sporulation were ranged from 25 to 30$^{\circ}C$. Thus, based on mycological characteristics of the fungus, the causal agent of cyclamen anthracnose was identified as Colletotrichum gloeosporioides Penz.

• Research in Plant Disease
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• v.13 no.2
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• pp.119-121
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• 2007

Anthracnose of Salvia plebeia caused by Colletotrichum acutatum was observed in the exhibition field of Hamyang-gun, Gyeongsangnam-do Agricultural Research and Extension Services, in Korea. The disease mainly occurred on the leaves, petioles and stems of whole plant. The typical symptoms were water-soaked lesions on stems and petioles, rotted stems and withering then eventually died. The color of colonies of the pathogenic fungus grown on potato dextrose agar was pinkish gray. Conidia were fusiform in shape and was $8{\sim}17{\times}3{\sim}4\;{\mu}m$ in size. Appressoria were pale to dark brown in color, clavate in shape and the sizes were $8{\sim}11{\times}4{\sim}6\;{\mu}m$. Optimum temperature for mycelial growth was $25^{\circ}C$. On the basis of mycological characteristics and pathogenicity test on host plants, the fungus was identified as Colletotrichum acutatum J. H. Simmonds. This is the first report on the anthracnose of S. plebeia caused by C. acutatum in Korea.

• The Korean Journal of Mycology
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• v.31 no.1
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• pp.50-52
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• 2003

The powdery mildew of Phlox (Phlox paniculata) extensively occurred in the experimental farm of Cheongam-myon, Hadong-gun, Gyeongnam province in 2002. Both sides of the leaves and stems were covered with the white fungal spores and mycelia, and then the leaves became brown to dark brown in color, eventually died. The conidiophores on the lesion were observed. Conidia were cylindric in shape, colorless, $25.3{\sim}49.4{\times}12.3{\sim}17.2{\mu}m$ in size and borne singly on conidiophore. Fibrosin bodies were not observed. Conidiophores were straight with 2-4 cylindric cells, and $65.7{\sim}124.8{\mu}m$ in size. Appressoria were lobed. Cleistothecia were not formed. This is the first report on powdery mildew of Phlox caused by Oidium sp. in Korea.

• Research in Plant Disease
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• v.14 no.1
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• pp.61-63
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• 2008

Anthracnose of blueberry (Vaccinium spp.) caused by Colletotrichum gloeosporioides was observed in the exhibition orchard of Gyeongsangnam-do Agricultural Research and Extension Services in Korea, 2007. The typical symptoms were initially water-soaked lesions and then rotten on fruits, the infected fruits were dropped but some of them were hunged and mummified. The pathogenic fungus grown on potato dextrose agar showed greyish to dark gray color. Conidia were straight, cylindrical apex obtuse in shape and $10{\sim}20{\times}3{\sim}5\;{\mu}m$ in size. Appressoria were brown in color, clavate or ovate in shape and $6{\sim}18{\times}4{\sim}12\;{\mu}m$ in size. Optimum temperature for mycelial growth was $25{\sim}30^{\circ}C$. On the basis of mycological characteristics and pathogenicity test on host plants, the fungus was identified as Colletotrichum gloeosporioides (Penz.) Penz. & Sacc.. This is the first report on the anthracnose of blueberry (Vaccinium spp.) caused by C. gloeosporioides in Korea.

• Research in Plant Disease
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• v.12 no.2
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• pp.119-121
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• 2006

Anthracnose of pomegranate (Punica granatum) caused by Colletotrichum acutatum was observed in the exhibition field at Hamyang-gun, Gyeongsangnam-do Agricultural Research and Extension Services, and in farmer's orchard at Gaheo-myon, Hapcheon-gun, Gyeongnam province, Korea. The pathogen generally attacks on the fruits and induces dark lesion and rotting. The infected fruits were mostly dropped or mummified. The color of colonies of the pathogenic fungus grown on potato dextrose agar was pinkish gray. Conidia were fusiform in shape and was $8{\sim}16{\times}3{\sim}4{\mu}m$ in size. Appressoria were pale to dark brown in color, clavate in shape and was $8{\sim}12{\times}4{\sim}6{\mu}m$ in size. Optimum temperature for mycelial growth was $25^{\circ}C$. Pathogenicity of the causal organism was proved according to Koch's postulate. On the basis of mycological characteristics and pathogenicity test on fruit, the fungus was identified as Colletotrichum acutatum. This is the first report on the anthracnose of pomegranate caused by C. acutatum in Korea.

• The Plant Pathology Journal
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• v.21 no.4
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• pp.322-327
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• 2005

Regression models for determining infection periods of apple white rot were developed based on conidial germination and appressorium formation of Botryosphaeria dothidea. A total of 120 apple fruits were inoculated with the fungal conidial suspension and subjected to 6 temperatures and 10 wetness periods. Conidia germinated and produced appressoria, exhibiting swollen tips of germ tubes on the fruit surface. Conidial germination (G) increased with temperature (T) and wetness period (W), and was described as $G=-89.273+7.649T+7.056W-0.109T^{2}-0.085W^{2}-0.066TW(R^{2}=0.75)$. Less than 2 hr of wetness period were enough for conidia to germinate at 25 to $30^{\circ}C$. Effects of temperature and wetness period on appressorium formation (A) could be explained as $A=-1.540-2.375W+0.045W^{2}+0.213TW(R^{2}=0.77)$. The relationship between conidial germination and appressorium formation ($A_g$) was described as$A_g=0.381-0.227G+0.005G^{2}(R^{2}=0.67)$, suggesting that conidial germination may have to reach approximately $43.7\%$ to initiate appressorium formation. Using the regression equation for conidial germination and the criterion of $43.7\%$ conidial germination, an infection model was developed to determine infection periods based on temperature and wetness period. The infection model with the criterion of $43.7\%$ conidial germination was apparently more conservative than the appressorium formation model in determining possibility of apple infection. The infection model seemed sensitive to variable weather conditions, suggesting possible use of the model for timing fungicide sprays to control white rot of apples in practice.

• Mycobiology
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• v.47 no.3
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• pp.308-318
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• 2019

Bio-sulfur can be produced in the process of desulfurization from a landfill and collected by some microorganism such as Thiobacillus sp. as a sulfur element. In order to investigate practical use of bio-sulfur as an agent for controlling plant disease, in vitro antifungal activity of bio-sulfur was tested against Colletotrichum orbiculare known to cause cucumber anthracnose. Efficacy of bio-sulfur for suppressing anthracnose disease was also evaluated in vivo using cucumber leaves. Mycelial growth of C. orbiculare on medium containing bio-sulfur was inhibited. Disease severity of cucumber leaves pre-treated with bio-sulfur was significantly decreased compared to that of untreated ones. To illustrate how bio-sulfur could suppress anthracnose disease, structures of cucumber leaves infected with C. orbiculare were observed under a fluorescent microscope and a scanning electron microscope (SEM). Cucumber leaves pre-treated with bio-sulfur showed a low rate of appressorium formation whereas untreated ones showed abundant appressoria. Shrunk fungal hyphae were mostly observed on bio-sulfur-pretreated leaves by SEM. Similar results were observed on leaves pre-treated with a commercial fungicide Benomyl(R). These results suggest that inhibition of appressorium formation of C. orbiculare by bio-sulfur may contribute to its suppression of cucumber anthracnose.

• The Plant Pathology Journal
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• v.35 no.4
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• pp.287-300
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• 2019

Spot blotch caused by Bipolaris sorokiniana has spread to more than 9 million ha of wheat in the warm, humid areas of the Eastern Gangetic Plains (EGP) of South Asia and is a disease of major concern in other similar wheat growing regions worldwide. Differential lignin content in resistant and susceptible genotypes and its association with free radicals such as hydrogen peroxide ($H_2O_2$), superoxide ($O_2{^-}$) and hydroxyl radical ($OH^-$) were studied after inoculation under field conditions for two consecutive years. $H_2O_2$ significantly influenced lignin content in flag leaves, whereas there was a negative correlation among lignin and $H_2O_2$ to the Area Under Disease Progress Curve (AUDPC). The production of $H_2O_2$ was higher in the resistant genotypes than susceptible ones. The $O_2{^-}$ and $OH^-$ positively correlated with AUDPC but negatively with lignin content. This study illustrates that $H_2O_2$ has a vital role in prompting lignification and thereby resistance to spot blotch in wheat. We used cluster analysis to separate the resistant and susceptible genotypes by phenotypic and biochemical traits. $H_2O_2$ associated lignin production significantly reduced the number of appressoria and penetration pegs. We visualized the effect of lignin in disease resistance using differential histochemical staining of tissue from resistant and susceptible genotypes, which shows the variable accumulation of hydrogen peroxide and lignin around penetration sites.