• Korean journal of applied entomology
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• v.58 no.3
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• pp.175-182
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• 2019

The citrus leafminer, Phyllocnistis citrella (Lepidoptera: Gracillaridae), is an important pest that decreases the productivity of citrus trees by attacking citrus leaves, and especially it causes a severe damage during the young growth stage. In this study, we investigated the distribution of eggs on the leaves of shoots according to the position and the survival rate of this pest in the field condition. The occurrence patterns of P. citrella eggs in citrus orchards were largely affected by the occurrence of shoots. Even if the adults were still being attracted in the pheromone traps, the eggs were not observed on leaves when the growth of shoots was stopped. The density of P. citrella eggs in the citrus shoots peaked at the fifth or sixth leaf from the terminal leaf, and over 90% of the eggs were found in the first to eighth leaves as a whole. In 2015 and 2016, the average survival rate of larvae surviving to pupa was 1.4%, and the rate of survival to adults was 0.2%, indicating that most of them died. Furthermore, we have discussed the management strategy of P. citrella considering the distribution of eggs and the larval survival rate in the citrus shoots.

• The Korean Journal of Mycology
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• v.25 no.1 s.80
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• pp.30-34
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• 1997

Glomerella cingulata (conidial state: Colletotrichum gloeosporioides) was identified as the causal organism of anthracnose of citrus on the basis of morphological characteristics of the conidial state of the fungus isolated from infected leaves of Satsuma mandarin and its ascigerous state isolated from diseased twigs. The pathogen infected the leaves of Satsuma mandarin, citron and Natsu daidai only by wound inoculation. The optimum temperature range for mycelial growth and sporulation of conidia of the strain was $25{\sim}30^{\circ}C$, respectively. The characteristics of anthracnose strain of Satsuma mandarin such as growth rate and color of colony, shape and size of conidia, and appressoria were similar to those of FGG strain. However, the strain isolated from infected leaves and twigs of Satsuma mandarin was different from FGG strain to cause postharvest anthracnose of citrus, because some of morphological and pathological characteristics of the strain isolated did not correspond to those of FGG strain.

• Journal of Applied Biological Chemistry
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• v.59 no.3
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• pp.207-213
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• 2016

Little information about the biological activities of Citrus limon (lemon) leaves has been reported, whereas the fruit of Citrus limon (lemon) has been well-documented to contain various pro-health bio-functional compounds. In the present study, the antiproliferative activities of the lemon leaves were evaluated using several cancer cell lines. From the n-hexane, chloroform, ethyl acetate, n-butanol, and water fractions of methanolic extract of the leaves, the chloroform fraction of lemon leaves (CFLL) showed the most potent antiproliferative activity in the AGS human gastric cancer cells. The current study demonstrates that CFLL induces apoptosis in AGS cells, as evidenced by an increase in apoptotic bodies, cell population in the sub-G1 phase, Bax/Bcl-2 ratio, and cleavage of poly (ADP-ribose) polymerase (PARP), caspase-3 and caspase-9. Compositional analysis of the CFLL using gas chromatography mass spectrometry (GC-MS) resulted in the identification of 27 compounds including trans, trans-farnesol (3.19 %), farnesol (3.26 %), vanillic acid (1.45 %), (-)-loliolide (5.24 %) and palmitic acid (6.96 %). Understanding the modes of action of these compounds individually and/or synergistically would provide useful information about their applications in cancer prevention and therapy.

• 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 Pharmacognosy
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• v.10 no.1
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• pp.13-16
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• 1979

The essential oil composition by means of gas liquid chromatography, and the occurrence and distribution of flavonoid glycosides in leaves, peels and barks of citrus plants native to Je Ju island were investigated. Results indicate that the occurrence of p-cymene, d,l-limonene, linalool, geraniol and linalyl acetate in the essential oils, and of hesperidin in leaves, peels and barks are fairly common to these species.

• Korean journal of applied entomology
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• v.53 no.1
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• pp.1-6
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• 2014

The pink citrus rust mite, Aculops pelekassi (Keifer) (Acari: Eriophyoidea), is an important pest in the citrus orchards of Jeju, Korea. This study was performed to investigate the seasonal population abundance of A. pelekassi, and the effects of humidity and citrus leaf age on the multiplication of this pest. Relative humidity (RH) significantly affected the longevity and fecundity of A. pelekassi. Longevity was 7.5, 14.5 and 14.6 d and fecundity was 5.4, 21.5, and 27.1 eggs at 33, 75 and 84% RH, respectively. The leaf age of citrus significantly affected the multiplication of A. pelekassi. The population abundance on 40 day-old leaves was much higher more than 3 times that on 10-day old leaves at 4 weeks after introduction. Overwintered A. pelekassi adults between the bud scales of the citrus trees became active in late April; they were found on newly emerged leaves, followed by their settlement on young fruits in mid-June. The population levels of A. pelekassi peaked on the leaves in late June to July, and on the fruits in early August. The results obtained in this study should be useful for the control of A. pelekassi in citrus orchards in Jeju.

• Korean journal of applied entomology
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• v.50 no.3
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• pp.203-208
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• 2011

This study was conducted to evaluate Geometridae (Lepidoptera) species as pests and the damage they cause in citrus orchards in Jeju, Korea. Seven geometridae species occurred in citrus orchards: Ascotis selenaria, Ectropis excellens, Menophra senilis, Biston panterinaria, Ourapteryx nivea, Odontopera arida and Hypomecis punctinalis. Among them, A. selenaria was most abundant, followed by E. excellens and M. senilis. Most Geometridae larvae fed on citrus leaves, but A. selenaria larvae ate fruits and leaves. Fruit damage of Citrus unshiu appeared as gnawed scars caused by young larvae feeding on fruit surface. Fruit damage on Shiranui fruits appeared as a wide hole or deep scars caused by feeding by mature larvae (6th instar). Citrus leaves damage due to Geometridae larvae was high during May to June. Fruit damage started in late June as the spring-shoots of citrus hardened and increased sharply in late July. In the field experiment, fruit damage in the late season reached 4.2% in both 2008 and 2009 and reached 5.2% in 2010. In citrus orchards, A. selenaria larvae started to appear in mid-May and their populations peaked in mid June, late July, and early to mid-September. Adult males of A. selenaria had a maximum peak in mid-May, and two other peaks in early to late July and late August to early September. A. selenaria male adults were collected in a pheromone traps constantly throughout Jeju Island.

• 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.

• Food Science and Biotechnology
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• v.17 no.5
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• pp.1086-1091
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• 2008

The antioxidant activities of the extracts of dangyuja (Citrus grandis Osbeck) leaves were evaluated. The highest phenolic content was obtained from the ethyl acetate fraction (EF) (202.1$\pm$0.8 mg GAE/g dried extract) and it exhibited the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity. The cytoprotective effects of EF on oxidative damage induced by tert-butyl hydroperoxide (t-BHP) in a human hepatoma cell line, HepG2 cells, were investigated to understand the intracellular antioxidant mechanisms. Treatment of HepG2 cells with EF prior to oxidative stress was found to inhibit reactive oxygen species (ROS) generation, lipid peroxidation, and DNA damage in a dose-dependent manner. Gas chromatography-mass spectrometry (GC-MS) studies on EF resulted in tentative identification of 19 compounds representing 94.3% of the total content. Taken together, these results demonstrated that EF has excellent antioxidant activities and thus dangyuja leaves have great potential as a source for natural antioxidant which can be applied in food products.

• 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.