• Research in Plant Disease
• /
• v.12 no.2
• /
• pp.81-84
• /
• 2006

Trichoderma harzianum 23 WP and Bacillus subtilis 122 WP were formulated as antagonists of Sclerotium cepivorum and Sclerotium sp. of garlic white rot. In the field test, applications of Trichoderma harzianum WP and Bacillus subtilis WP reduced garlic white rot by Sclerotium cepivrum from 10.9% in the control to 4.1% and 6.2%, respectively at Taean. Also at Seosan, applications of Trichoderma harzianum 23 WP and Bacillus subtilis 122 WP reduced garlic white rot by Sclerotium sp. from 17.8% in the control to 1.2% and 2.6%, respectively. Treatment of Trichoderma harzianum 23 WP and Bacillus subtilis 122 WP increased garlic yield in two area. Therefore, Trichoderma harzianum 23 WP and Bacillus subtilis 122 WP have shown potential as biofungicides of garlic white rot in the two different pathogens.

• Research in Plant Disease
• /
• v.12 no.2
• /
• pp.69-74
• /
• 2006

Basal rot of freesia caused by a Sclerotium sp. occurred at Incheon areas. Incidence of the disease reached up to 45% and averaged 17.0% in the fields. Typical symptoms consisted of sheath dry and leaf blight due to rots on basal leaves. The causal fungus was identified as Sclerotium sp. based on following mycological characteristics. The fungus formed sclerotia on cultural media and plant tissues, but did not produce asexual spores. On cultural medium, aerial mycelia of the fungus changed color from white to clay with cultural age and smelled musty odor. Numerous irregular and elliptical black microsclerotia of the fungus were formed on potato dextrose agar (PDA) after 5 days of incubation at $25^{\circ}C$ and sized $115{\sim}200{\times}95{\sim}150 (av. 145{\sim}126.5){\mu}m$. The fungus grew at $10{\sim}32^{\circ}C$ and $pH 4.0{\sim}8.5$. However, the optimal temperature and pH for mycelial growth of the fungus were $24^{\circ}C$ and 5.5 respectively. The isolate showed present pathogenicity to not only freesia but gladiolus in the pathogenicity test, and the symptoms were similar to those observed in the fields. Basal rot of freesia caused by Sclerotium sp. is firstly reported in Korea.

• Proceedings of the Korean Society of Plant Pathology Conference
• /
• 2003.10a
• /
• pp.131.2-132
• /
• 2003

White rot on garlic caused by Sclerotium cepivorum firstly occurred at Goheoung, Jeonnam in 1998. Thereafter, the disease rapidly spread throughout the country except Gangwon and became a major limiting factor for the cultivation of various Allium species such as garlic, onion, and welsh onion. The disease that has not been reported on a wild garlic(Allium monanthum) previously occurred severely at Seosan, Choongnam in 2003. Among cultivation areas in the region, 10.7％ were infected by the disease and the ratio of diseased plant reached up to 55.0％ in some heavily infected fields. Two species of Sclerotium were consistently isolated from infected samples and identified as S. cepivorum or another Sclerotium sp. Averaged size of sclerotium of the former was 455.0x562.2 urn, while the later was 374.4${\times}$347.2$\mu\textrm{m}$. Patogenicity to Allium species and mycological characteristics such as sclerotium size, growth temperature, and microconidia of the fungi were similar to those reported on other Allium species previously. Consequently, the wild garlic is a newly reported host of the two pathogenic fungi in Korea.

• Research in Plant Disease
• /
• v.10 no.2
• /
• pp.105-111
• /
• 2004

Mycelial growth and days required for sclerotial formation(DRSF) in vitro, and disease incidence of infected plants in the field were investigated to evaluate disease resistance of nine garlic cultivars against two species of Sclerotium causing garlic white rot. There were differences among mycelial growth and sclerotial formation of two white rot pathogens on different garlic cultivars in vitro. Mycelial growth showed the highest level on the clove of 'Daeseo'. Sclerotia of two white rot pathogen were formed the earliest on the clove of 'Kodang' and the latest on the clove of 'Namdo'. In field trial all of nine garlic cultivars were highly susceptible to Sclerotium cepivorum and cold-type garlics were less susceptible than warm-type garlics. Meanwhile garlic cultivars used showed differences among resistant responses to Sclerotium sp., forming large sclerotia. All of warm-type garlics showed highly susceptible response, but three cold-type garlics, 'Seosan', 'Danyang' and 'Yechon' showed moderate resistant response and 'Euisung' showed resistant response. To evaluate cultivar resistance of garlics quantitatively disease progress curve was transformed as linear regression equation. Among the intercept (early disease incidence) and the slope (disease infection rate) obtained from the transformed equation, final disease incidence, and area under disease progress curve(AUDPC), AUDPC was the most effective to evaluate disease resistance of garlics to both of white rot pathogens. There was little correlation between mycelial growth and sclerotial formation on garlic cloves in vitro, and epidemiological parameters (early disease incidence, final disease incidence, disease infection rate, AUDPC) obtained from the field trial. Mycelial growth of S. cepivorum was positively correlated with final disease incidence and disease infection rate obtained from the field trial, meanwhile DRSF was negatively correlated with the epidemiological parameters.

• Research in Plant Disease
• /
• v.11 no.2
• /
• pp.128-134
• /
• 2005

This study was conducted to elucidate effect of environmental factors on the development of white rot. In order to identify the causal agents causing white rot of Allium crops, we compared DNA profiles of a representative isolate, Sclerotium cepivorum, introduced from foreign country with Korean isolates using UP-PCR. As a result, Sclerotium isolates forming round-shaped sclerotia were identified as Sclerotium cepivorum pertaining in UP-PCR b group and Sclerotium isolates farming anamorphic-shaped sclerotia presumed to be a novel species of Sclerotium based on DNA profiles of UP-PCR. There was a big difference in DNA band pattern between two species of Sclerotium isolated in Korea. Electron micrographs of scanning electron microscope and transmission electron microscope showed morphological differences in sclerotial surface structure and rind layers between two species of Sclerotium. There were more wrinkles and pore spaces on sclerotial surface of Sclerotium sp. forming anamorphic-shaped sclerotia than that of Sclerotium cepivorum forming round-shaped sclerotia. Both of two white rot pathogens grew well at the temperature range of $10-25^{\circ}C$ with optimal temperature of $20^{\circ}C$. Sclerotia of the two pathogens were well formed at $20^{\circ}C$ and well germinated at the temperature range of $20-24^{\circ}C$, Effect of pre-incubation of sclerotia on destruction of sclerotial dormancy of two pathogens was evaluated through storing sclerotia under different temperature condition. The sclerotia of the two pathogens showed an increased capacity to germinate on potato dextroise agar when the sclerotia were incubated for 7 days at $10^{\circ}C$ after pre-treatment at $35^{\circ}C$ for 7 days. At that time, germination rate of Sclerotium sp. and 5. cepivorum was $100\%\;and\;70\%$, respectively. Flooding period and treatment temperature had an effect on sclerotial survival rate of the two pathogens. As flooding period and treatment temperature increased, sclerotial germination rate of the two pathogens decreased. It was confirmed that soil humidity played an important role on development of white rot. It was the highest disease incidence of garlic white rot when garlic were sown at potted soils infested with the two pathogens and adjusted soil humidity to $15\%$ (field moisture capacity, about -300 mb). As soil humidity increase or decrease based on $15\%$ of soil humidity, disease incidence decreased move and more.

• Journal of Life Science
• /
• v.18 no.6
• /
• pp.858-864
• /
• 2008

In the greenhouse fields for fruits and vegetables during the winter in Korea, there are serious damages by the sclerotium diseases due to the low temperature and humidity. This study was carried out to select an antagonic agent for the biological control of the sclerotium diseases. The 55 antagonic agents were selected from the rhizosphere in soil where the fruits and vegetables were cultivated in the green house fields, and strain AB02 among the tested isolates was estimated to be the strongest antagonist against the sclerotium disease. Using strain AB02, the antifungal spectrum was tested against 5 different plant pathogens. According to the results of the test, strain AB02 . showed the high antagonistic effect against Botrytis cinerea and Sclerotinia sclerotiorum. For the experiment of biological control against the sclerotium disease, it was estimated the suppression effect and the control effect by the strain in the pot experiment using the green perilla. According to the result of the pot experiments, the suppression effect was 40% and the control effect was 62%, respectively. For the stimulation effect of the tested plant growth by strain AB02 compared to the control, it was improved as 120% for the total length, 141% for the liveweight, 121% for the total number of leaves, 185% for the leaf area, and 327% for the liveweight of the root, respectively. Strain AB02 showing the antagonistic effect against the sclerotium disease and the stimulation effect for the plant growth was identified as Bacillus sp.

• Proceedings of the Korean Society of Plant Pathology Conference
• /
• 2002.11a
• /
• pp.102.1-102
• /
• 2002

• Food Science and Preservation
• /
• v.10 no.2
• /
• pp.224-229
• /
• 2003

This study was carried out to isolate of antagonistic bacterium to Allium cepa L. pathogens. A total of 250 strains were isolated from A. cepa L. roots. The isolates were screened for antagonism to A. cepa L. pathogens and the isolated strain No. YJ-4 was selected among these bacteria. It was identified as Bacillus ehimensis based on morphological and physiological characteristics according to the Bergey's mannual of systematic bacteriology, Sherlock system of Microbial ID Int and 165 rDNA sequences methods. Bacillus ehimensis YJ-4 showed broad spectrum of antibacterial and antifungal activities against plant pathogens as Alternaria porri, Botrytis cinerea, Erwinia carotovora subsp. carotovora Fusarium of oxysporium, penicillium sp., Pseudomonas sp., Rhizoctonia solani, Sclerotium cepivotum, Septoria sp., Stemphylium botryosum. Speially B. ehimensis YJ-4 showed high antifungal activity on growth against F. oxysporium, the causal agent of onion Fusarium wilt.

• Research in Plant Disease
• /
• v.11 no.1
• /
• pp.28-34
• /
• 2005

This study was conducted to investigate the control possibility of garlic white rot causing severe yield losses of Allium species and cultivars using cultural practices such as optimal sowing date and burial depth, and lime application. Inoculum density in infested field soil was investigated at different soil depth, and that on the diseased plant debris was done. Inoculum density and recovery ratio of white rot pathogen of garlic was highly different between two species of Sclerotium cepivorum forming comparatively small sclerotia and Sclerotium sp. forming comparatively large ones. It was confirmed that S. cepivorum formed more sclerotia on bulbs of garlic than S. sp., and sclerotial recovery of S. cepivorum was higher than that of S. sp. Inoculum density of white rot pathogen in the infested field at garlic seeding period ranged from one to thirteen sclerotia per 30 g soil. Inoculum density of white rot pathogen decreased remarkably with increasing soil depth and above 95% of sclerotia were distributed within 5 cm of soil depth. Disease severity of white rot was higher on slightly planted garlics than deeply-planted ones. Garlic seed bulbs infected by white rot pathogens were confirmed to be one of main inoculum sources of white rot in the field and the disease incidences caused by garlic seed transmission showed big differences among garlic varieties. When nine garlic varieties harvested from infested plots were sown in the field, highly susceptible varieties, ‘Wando’, ‘Daeseo’, ‘Namdo’ and ‘Kodang’ showed high disease incidences, whereas other five varieties were not infected at all. It was confirmed that white rot occurred higher on early-sown garlics, before middle October, than on late-sown ones, after late October. Meanwhile, increasing application rate of lime ranged from 100 to 300 g reduced disease severity of white rot.

• The Korean Journal of Mycology
• /
• v.6 no.2
• /
• pp.19-24
• /
• 1978

Four species of Pythium and two species of Sclerotium previously not recorded in Korea during 1976 and Leptosphaeria salvinii which previosly reported but reidentified. Pythium aristosporm Vantery, Pythium sp. and Pythium myriotylum Drechsler were isolated from diseased rice seedlings and from green withered rice plants and Pythium irreglare Buisman was isolated from paddy soil. Three species of Pythium except P. irregulare grew well at $40^{\circ}C$ on Potato dextrose agar and were confirmed as highly pathogenic but P. irregulare showed low pathogenicity on Yushin variety of rice. Sclerotium hydrophilum and Sclerotium oryzae-sativae appeared to be weakly pathogenic, but Leptosphaeria salvinii was confirmed as a highly pathogenic. Ordinally the two species of Sclerotium grew and produced many sclerotia on dead sheath and stems of rice. There are still some problems to clarify and reconsider in regard to the pathogenicity of the sclerotial fungi because their populations were so very high in paddy fields, but their role might be wound parasite.