• The Plant Pathology Journal
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• v.17 no.6
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• pp.382.4-382
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• 2001

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2000.10a
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• pp.39.1-39
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• 2000

• Mycobiology
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• v.28 no.3
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• pp.158-162
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• 2000

Twenty-three isolates of Fusarium spp. were obtained from decayed citrus fruits in the fields and storages in 1998-1999. Of them, six and five isolates belonged to F. proliferatum and F. moniliforme, respectively, which were the most common. F. solani and F. sambucinum had each two isolates, F. equiseti had one isolate and seven isolates were unidentified. They produced symptoms of two types in pathogenicity test: those with leathery, beige to light or dark brown, and sunken lesions without surface mycelium (type-1) and those with lesions covered with white, beige or pink surface mycelium (type-2). Four of six isolates identified to F. proliferatum and two unidentified isolates produced type-1 lesions, and all isolates identified to F. moniliforme, F. solani, F. sambucinum, F. equiseti and five unidentified isolates produced type-2 lesions.

• The Plant Pathology Journal
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• v.17 no.3
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• pp.184-188
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• 2001

Phytophthora-induced diseases on citrus in Jeju island have been considered of minor importance because of the use as root stock of trifoliate orange, which is immune to Phytophthora. However, brown rot on fruit, which severely occurred in 1998 and 1999, has become a great threat to citrus production in the island. About one-half of the surveyed orchards were infected in 1998 and 4 out of 19 infected fields showed over 20% fruit infection rate. The disease was less severe in 1999, with an estimated infected area and total fruit reduction of 3,155 ha and 15,300 tons, respectively. Typical gummosis was also occasionally observed on cv. Shiranugi, which is mostly cultivated under plastic film houses. Two types of Phytophthora were consistently isolated from various plant parts, identified as P. citrophthora and P. nicotianae. The former was isolated from the aerial parts of the fruit, young leaf, and shoot in the fields. Meanwhile, the latter was only isolated from the basal stem showing gummosis in plastic film houses.

• Biomolecules & Therapeutics
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• v.21 no.2
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• pp.138-145
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• 2013

Citrus fruit contain various flavonoids that have multiple biological activities. However, the content of these flavonoids are changed during maturation and immature Citrus is known to contain larger amounts than mature. Chemokines are significant mediators for cell migration, while thymus and activation-regulated chemokine (TARC/CCL17) and macrophage-derived chemokine (MDC/CCL22) are well known as the typical inflammatory chemokines in atopic dermatitis (AD), a pruritic and chronic inflammatory skin disease. We reported recently that the EtOH extract of immature Citrus unshiu inhibits TARC and MDC production. Therefore, we investigated the activity of flavonoids contained in immature Citrus on TARC and MDC levels. As a result, among the various flavonoids, quercetagetin has stronger inhibitory effects on the protein and mRNA expression of TARC and MDC than other flavonoids. Quercetagetin particularly has better activity on TARC and MDC level than quercetin. In HPLC analysis, the standard peak of quercetagetin matches the peaks of extract of immature C. unshiu. This suggests that quercetagetin is an anti-inflammatory component in immature C. unshiu.

• Journal of Radiation Industry
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• v.4 no.3
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• pp.215-219
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• 2010

We have subjected to gamma-irradiation to citrus buds and then grafted onto mature citrus tree. Mutant citrus branch lines have been induced. As a result of first selection, we found the several mutant lines showing interesting phenotypes such as higher sugar content. We have selected several branches showing good qualities such as higher sweetness and/or lower acidity. Some branch lines showed over $13^{\circ}Brix$ sugar content and below 0.9% acidity. Other mutant branch lines showed the changes of shape, size, peel thickness, and fiber contents or distribution of fruits. The results suggest that gamma-irradiation is an effective tool for induction of citrus mutant lines.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.392-402
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• 2018

Citrus fruits can be classified as field citrus, greenhouse citrus, citrus produced by rain proof cultivation and late-harvested citrus such as Hallabong, Chunhaehyang, and Jinjihyang according to cultivation method or variety in Jeju province of Korea. The consumption of late-harvested citrus has been increasing steadily since 1990 because the sugar content of the fruits is ordinary higher than field citrus. The cultivation land of citrus produced by rain proof cultivation has been also enlarged continuously aided by Korean government support program and quality increasing effect of this cultivation method. However, the cultivation land of field citrus has been decreasing since 2010. In spite of such a decrease of cultivation land, recently the price of field citrus rather declined according to increasing of yield per 10a. For the estimation and forecast of the long-term supply-demand model in the field citrus, we constructed a partial balance model for the individual field citrus and estimated individual equation in each item's model by using the econometric method. As a result of the production storage scenario analysis, the cultivation area is expected to store 5%(14.49ha), 10%(14.97ha). 15%(15.50ha) of citrus production in 2027. This study reviews the structure of storage, and storability in Jeju field citrus and suggest several policy implications.

• The Plant Pathology Journal
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• v.39 no.4
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• pp.351-360
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• 2023

Citrus melanose, caused by Diaporthe citri, has been one of the serious diseases, and chemical fungicides were used for protection in many citrus orchards of Jeju Island. Establishing a disinfectant resistance management system and reducing pesticide usage would be important for contributing to safe agricultural production. In this study, monitoring of chemical resistance was performed with 40 representative D. citri isolates from many citrus orchards in Jeju Island. Four different fungicides, kresoxim-methyl, benomyl, fluazinam, and prochloraz manganese, with seven different concentrations were tested in vitro by growing the mycelium of the fungal isolates on the artificial medium potato dextrose agar. Among the 40 fungal isolates, 12 isolates were investigated as resistant to kresoxim-methyl which could not inhibit the mycelium growth to more than 50%. Especially isolate NEL21-2 was also resistant against benomyl, whose hyphae grew well even on the highest chemical concentration. However, any chemical resistance of fungal isolates was found against neither fluazinam nor prochloraz manganese. On the other hand, in vivo bio-testing of some resistant isolates was performed against both kresoxim-methyl and benomyl on young citrus leaves. Typical melanose symptoms developed on the citrus leaves pre-treated with both agrochemicals after inoculation with the resistant isolates. However, no or less symptoms were observed when the susceptible isolates were inoculated. Based on these results, it was suggested that some resistant isolates of D. citri occurred against both systemic fungicides, which may be valuable to build a strategy for protecting citrus disease.

• Applied Biological Chemistry
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• v.23 no.3
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• pp.178-183
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• 1980

Citrus fruits harvested in 1979 were collected from markets scattered in Jeju and Seogwipo area on Jeju island and also from citrus orchards with five, ten, fifteen, twenty, and thirty years of cultivation history. Organophorous insecticides and organochloro acaricides in the pulp of fruits were analysed by gas liquid chromatograph. It was found that EPN and Kelthane were most significant residues found in the citrus fruits in terms of both level and frequency of occurrence. Among citrus fruits collected from various markets, EPN was detected in 28% of the fruits samples in the range of 0.009 to 0.025 ppm, while Kelthane, at lower level, was found in all citrus fruits in the range of trace to 0.007 ppm. Residue levels of citrus fruits from orchards of various cultivated periods, in general, confirmed those of the fruits collected from commercial markets. However, residues of Kelthane in the citrus fruits tended to increase with orchards having longer cultivation history.

• Research in Plant Disease
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• v.20 no.2
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• pp.101-106
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• 2014

Citrus canker caused by Xanthomonas citri subsp. citri (Xcc) is one of the most important diseases on citrus. Although Satsuma mandarin cultivating mostly in Korea is moderately resistance to canker, occurrence of the disease were more frequently reported since last decade. Like other diseases in citrus, citrus canker was mainly protected by chemical fungicide in the field. Due to the side effect of the chemicals, alternative method of disease control is recently required. In this study four rhizobacterial strains TRH423-3, MRL408-3, THJ609-3 and TRH415-2 are selected by testing its antifungal activity against Xcc. Pre-inoculation with the selected rhizobacterial strains caused disease suppression on the citrus leaves after inoculation with the citrus canker pathogen. Similarly, in the field test symptoms of citrus canker were less developed in the citrus trees applied several times with the selected rhizobacterial strains compared with those of untreated trees. Therefore, it is suggested that the selected rhizobacterial strains may be valuable as an alternative method in the environment-friendly citrus farm.