• Research in Plant Disease
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• v.26 no.1
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• pp.57-60
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• 2020

Citrus scab symptoms were observed on leaves of trifoliate orange (Poncirus trifoliata) in open field of Citrus Research Institute, National Institute of Horticultural and Herbal Science. Typical scab pustules were formed and they were elevated protuberances form and light brown to grey. The pathogens were isolated from the symptomatic leaves and then were identified to Elsinoë fawcettii by morphological characteristics, pathogenicity and PCR assay. The morphological characteristics of colonies formed very slow-growing, pulvinate, or raised and deeply fissured, gummy to mucoid or tomentose colonies on potato dextrose agar medium. The pathogens were pathogenic to leaves of Satsuma mandarin, lemon, sour orange and grapefruit with typical scab symptoms. In PCR assay, specific amplified of products of 717 bp with Efaw-1 and 384 bp with Efaw-2 were observed from trifoliate isolates and E. fawcettii as reference but not from E. australis. This is first report of trifoliate orange being positive for citrus scab disease.

• Korean Journal Plant Pathology
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• v.14 no.4
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• pp.303-307
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• 1998

Citrus scab caused warty and scabby lesions on the surface of leaves, twigs and fruits of Satsuma mandarin. Warty lesions were mainly developed before July but scabby ones were developed during summer season in Cheju island, Korea. The casual organism of scab was morphologically identified as Sphaceloma fawcettii and was thought to be Tryon's pathotype of Elsinoe fawcettii, because it was pathogenic on rough lemon and Cleopatra mandarin but non-pathogenic on sour orange, grapefruit and sweet orange among the 5 differential hosts of E. fawcettii.

• Korean Journal of Organic Agriculture
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• v.28 no.2
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• pp.223-233
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• 2020

The aim of the present study was to investigate the suppressive effects of the bio-sulfur used by eco-friendly farms on the outbreak of citrus scab. To evaluate the inhibiting effect of bio-sulfur on citrus scab germ tube growth, the citrus scab pathogen Elsinoe fawcettiiwas cultured in PDB and agar media, and germ tube growth was observed after bio-sulfur treatment. At both 40 and 88 h after inoculation, germ tube formation was inhibited by 500-, 1000-, and 2000-fold diluted bio-sulfur, and at dilutions above 4000-fold, germ tube formation was observed, although growth was still inhibited, when compared to untreated cultures. Meanwhile, the occurrence of citrus scab on spring-flush leaves in the field was 40.3% in the untreated control and 5.3, 10.3, 12.3, 15.3, and 24.0% when treated with imibenconazole, 2-4 and 6-6 lime-Bordeaux mixtures, which are also used by eco-friendly farms, 500-fold diluted bio-sulfur, lime sulfur, and 1000-fold diluted bio-sulfur, respectively. The occurrence of citrus scab on citrus fruit was 79.3% in the untreated control and 4.0, 33.8, 42.0, 43.3, 44.8, and 78.0% when treated with imibenconazole, 2-4 lime-Bordeaux mixture, 6-6 lime-Bordeaux mixture, 500-fold diluted bio-sulfur, lime sulfur, and 1000-fold diluted bio-sulfur, respectively. Because citrus scab can infect citrus leaves as early as May, as the spring flush begins, preventative control should be implemented by mid- to late-April, thereby increase disease control and reducing both labor and farming costs.

• The Plant Pathology Journal
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• v.31 no.4
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• pp.421-427
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• 2015

Citrus scab disease is one of the destructive diseases that reduce the value of fruit for the fresh market. We analyzed the process of symptom development after infection with scab pathogen $Elsino{\ddot{e}}$ fawcettii in the susceptible satsuma mandarin leaves to observe the structural modification against pathogen. The cuticle and epidermal cells along with 3-5 layers of mesophyll tissue were degraded 1-2 days post inoculation. Surrounding peripheral cells of degraded tissues grew rapidly and then enveloped the necrotic area along with the growing conidia. Cross sections through the lesion revealed hyphal colonization in epidermis and mesophyll tissues. In response to the pathogen colonization, host cell walls were lignified, inner cells were rapidly compartmentalized and a semi-circular boundary was formed that separated the infected region from the non-infected region, and finally prevented the intercellular pathogen spread.

• The Plant Pathology Journal
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• v.37 no.3
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• pp.268-279
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• 2021

Citrus scab, caused by the fungal pathogen Elsinoë fawcettii, is one of the most important fungal diseases affecting Citrus spp. Citrus scab affects young tissues, including the leaves, twigs, and fruits, and produces severe fruit blemishes that reduce the market value of fresh fruits. To study the molecular responses of satsuma mandarin (C. unshiu) to E. fawcettii, plant hormone-related gene expression was analyzed in response to host-compatible (SM16-1) and host-incompatible (DAR70024) isolates. In the early phase of infection by E. fawcettii, jasmonic acid- and salicylic acid-related gene expression was induced in response to infection with the compatible isolate. However, as symptoms advanced during the late phase of the infection, the jasmonic acid- and salicylic acid-related gene expression was downregulated. The gene expression patterns were compared between compatible and incompatible interactions. As scabs were accompanied by altered tissue growth surrounding the infection site, we conducted gibberellic acid- and abscisic acid-related gene expression analysis and assessed the content of these acids during scab symptom development. Our results showed that gibberellic and abscisic acid-related gene expression and hormonal changes were reduced and induced in response to the infection, respectively. Accordingly, we propose that jasmonic and salicylic acids play a role in the early response to citrus scab, whereas gibberellic and abscisic acids participate in symptom development.

• Korean Journal of Organic Agriculture
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• v.22 no.1
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• pp.115-127
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• 2014

This study was conducted to select environmental friendly organic materials for controlling the main disease of Yuzu (Citrus junos Sieb). Meloanose caused by Phomopsi scitri and Scab caused by Elsinoe fawettii are the most common disease in Yuzu. In this study, of which Meloanose disease severity was severe at late of June corresponded with high humidity due to frequent rainfall at that time. In addition, occurrence of two disease have shown in old tree than young. After processing with environmental friendly organic materials, reduction of disease severity was 51~73% and 41~75% in case of Meloanose and scab, respectively. Based on result, environmental friendly organic materials tested in this study may source for controlling both Meloanose and scab diseases on Yuzu.

• Research in Plant Disease
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• v.21 no.3
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• pp.231-234
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• 2015

Elsinoe fawcettii and E. australis are two currently recognized scab pathogens of citrus. E. fawcettii has at least six pathotypes while E. australis has at least two pathotypes. Colonies of E. fawcettii and E. australis do not sporulate in artificial media including potato dextrose agar (PDA). Whiteside's method has been widely used for preparing conidial inoculum in vitro. This study was carried out to develop efficient method for conidia production from artificial media. We developed a shaking method which included the following steps: 1) Colony grown on PDA was mashed with a steel spatula; 2) Mycelia fragments were cultured in 50 ml sterilized rain water in a rotary shaker-incubator (180 rpm) at $25^{\circ}C$ for 24 h: 3) The conidia suspension was filtered through two layers of cheesecloth. Average conidia production of all isolates tested using this shaking method was approximately 13.1 times higher than that from Whiteside's method in this study.

• Research in Plant Disease
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• v.17 no.3
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• pp.302-310
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• 2011

Elsinoe fawcettii is one of major pathogenic fungi which cause citrus scab diseases, resulting in fruit blemishes that reduce the economic value of fruit. By increasing interest to safe products of crops, the alternative methods of disease control is highly required. We investigated whether the 215 bacterial strains isolated from Jeju Island possess antifungal effect or suppression effect on the symptom development by Elsinoe fawcettii on citrus. Among them, three bacterial strains THJ 609-3, MRL408-3, and TRH423-3 that exhibited antifungal capacity against Elsinoe fawcettii were selected. To illustrate the disease suppression mechanism, pre-inoculation with the selected bacterial strains was carried out whether could suppress the citrus crab on the leaves. The observation with a fluorescence microscope revealed that the selected bacteria could decrease the number of fungal spores. The ratio of germ tube formation was also decreased by the selected bacterial strains at one day after fungus challenge. The strain THJ 609-3 was identified as Pseudomonas putida as a result of analyzing the internal transcript spaces of the rhizobacterial rDNA. The strains MRL 408-3 and TRH 423-3 were identified as Burkholderia gladioli. Our results may be valuable when the selected rhizobacterial strains used as the environment-friendly microbe for biological control on citrus scab caused by Elsinoe fawcettii.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2002.11a
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• pp.94.1-95
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• 2002

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2002.11a
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• pp.94.2-95
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• 2002