• Korean Journal of Medicinal Crop Science
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• v.23 no.2
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• pp.144-149
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• 2015

The peel of Citrus sunki exhibits multiple biological activities such as anti-oxidant, anti-inflammation and anti-obesity, but little is known about neurodegeneration-related activities. In this study, we investigated the protective effect of ethanolic extract from both immature and mature Citrus sunki peel on neuronal cell death. Treatment of the neuroblastoma cell line SH-SY5Y with $MPP^+$, an inducer of Parkinson disease model, increased cell death in a dose dependent manner. Increased levels of active caspase-3 and cleaved PARP were detected. Treatment with immature Citrus sunki peel extract significantly reduced $MPP^+$-induced neurotoxicity. Cytoprotection with immature Citrus sunki peel extract was associated with a decrease in caspase-3 activation and PARP cleavage. In contrast, mature Citrus sunki peel extract had no significant effects. These data suggest that immature Citrus sunki peel extract may exert anti-apoptotic effect through the inhibition of caspase-3 signaling pathway on $MPP^+$-induced neuronal cell death.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.538-545
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• 2020

This study measured the economic impact (from 2012 through the end of 2017) of the KOR-USA FTA (Free Trade Agreement) on the Korean citrus industry according to importing orange from the USA after the implementation of the KOR-USA FTA. Citrus fruits were divided into field citrus grown in open fields, house citrus grown in green houses, and late-maturing citrus (including winter season citrus) based on the cultivation methods and the varieties of citrus. We specified the structural and dynamic recursive demand-supply equilibrium models of three citrus fruits to analyze policy simulations. The results showed that for field citrus, due to the impact of some amounts of TRQ, the annual average of the real gross revenue dropped by 2.39 billion KRW between 2012 and 2017. As for house citrus, due to the impact of oranges and cherries, the annual average of the real gross revenue declined by 3.01 billion KRW between 2012 and 2017, and for late-maturing citrus (including winter season citrus), the annual average of the real gross revenue fell by 15.11 billion KRW between 2012 and 2017. This paper also suggests several policy implications.

• 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.

• The Plant Pathology Journal
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• v.38 no.4
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• pp.287-295
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• 2022

Citrus tristeza virus (CTV) is efficiently transmitted in a semi-persistent manner by the brown citrus aphid (Toxoptera citricida (Kirkaldy)). Currently, the most sensitive method for detecting plant viruses in insect vectors is reverse-transcription quantitative polymerase chain reaction (RT-qPCR). In this study, the elongation factor-1 alpha (EF-1α) gene and acidic p0 ribosomal protein (RPAP0) gene were confirmed to be suitable reference genes for RT-qPCR normalization in viruliferous T. citricida aphids using the geNorm, NormFinder, and BestKeeper tools. Then the relative CTV titer in aphids (T. citricida) at different post-acquisition feeding times on healthy plants was quantified by RT-qPCR using EF-1α and RPAP0 as reference genes. The relative CTV titer retained in the aphids gradually decreased with increasing feeding time. During the first 0.5 h of feeding time on healthy plants, the remaining CTV titer in aphids showed about 80% rapid loss for the highly transmissible isolate CT11A and 40% loss for the poorly transmissible isolate CTLJ. The relative CTV titer in aphids during more than 12 h post-acquisition times for CT11A was significantly lower than at the other feeding times, which is similar to the trend found for CTLJ. To our knowledge, this is the first report about the relative titer variation of CTV remaining in T. citricida at different post-acquisition feeding times on healthy plants.

• The Plant Pathology Journal
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• v.39 no.4
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• pp.309-318
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• 2023

Huanglongbing (HLB) is one of the most destructive diseases in citrus, which imperils the sustainability of citriculture worldwide. The presumed causal agent of HLB, 'Candidatus Liberibacter asiaticus' (CLas) is a non-culturable phloem-limited α-proteobacterium transmitted by Asian citrus psyllids (ACP, Diaphorina citri Kuwayama). A widely adopted method for HLB diagnosis is based on quantitative real-time polymerase chain reaction (qPCR). Although HLB diagnostic qPCR provides high sensitivity and good reproducibility, it is limited by time-consuming DNA preparation from plant tissue or ACP and the requirement of proper lab instruments including a thermal cycler to conduct qPCR. In an attempt to develop a quick assay that can be deployed in the field for CLas detection, we developed a real-time loop-mediated isothermal amplification (rt-LAMP) assay by targeting the CLas five copy nrdB gene. The rt-LAMP assay using various plant sample types and psyllids successfully detected the nrdB target as low as ~2.6 Log10 copies. Although the rt-LAMP assay was less sensitive than laboratory-based qPCR (detection limit ~10 copies), the data obtained with citrus leaf and bark and ACP showed that the rt-LAMP assay has >96% CLas detection rate, compared to that of laboratory-based qPCR. However, the CLas detection rate in fibrous roots was significantly decreased compared to qPCR due to low CLas titer in some root DNA sample. We also demonstrated that the rt-LAMP assay can be used with a crude leaf DNA extract which is fully deployable in the field for quick and reliable HLB screening.

• Korean Journal of Medicinal Crop Science
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• v.22 no.6
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• pp.442-448
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• 2014

The major objective of this study was to investigate the usability as cultivar for processing of new Citrus hybrid 'Hamilgam'. We investigated various antioxidant activities, such as DPPH radical, ABTS radical, Hydroxyl radical and Superoxide anion radical effect, along with total polyphenol content and total flavonoid content of Citrus hybrid 'Hamilgam', C. unshiu, C. natsudaidai. The total polyphenol content and total flavonoid content were the highest in the Hamilgam. The major flavonoids of Hamilgam and Natsudaidai were naringin and neohesperidin, and those of Unshu were narirutin and hesperidin, as determined by HPLC. Especially, the neohesperidin content of Hamilgam showed much higher (100 times over) than that of Unshu. However, the aglycone form was not found. DPPH and ABTS radical scavenging activities were the highest in Hamilgam peels. Hydroxyl radical scavenging activity was high in the order of Unshu, Hamilgam and Natsudaidai. Superoxide anion radical scavenging of 3 cultivars peels displayed low activities compared to DPPH and ABTS radical scavenging. Based on these results, Hamilgam peel extracts possess antioxidant activities and may thus serve as potential sources of functional food, cosmetic products, etc.

• Korean journal of food and cookery science
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• v.21 no.2 s.86
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• pp.243-249
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• 2005

Citrus juice, a concentrate manufactured by the Jeju Provincial Corporation, was converted into vinegar orderly by alcohol and acetate fermentation. The juice with a 6-fold dilution by distilled water was used as the sole nutrient source throughout the experiments. The diluted juice contained 12.96Brix of total sugar, $0.632\%$ of total acid and $20.23{\mu}g/ml$ of hesperidin. Naringin was not detected from the juice. Citrus wine having $5.6\~6.3\%$ alcohol was produced from the diluted juice after 3 days of fermentation at $28^{\circ}C$. A kind of citrus-malomelo-yeast CMY-28 was used for the wine fermentation. The wine was successfully fermented for 8 days at $30^{\circ}C$ after inoculation of seed vinegar which contained active cells of acid producing bacteria CV1. The inoculum size of the seed vinegar was controlled to $10\%$(v/v) of the citrus wine. The wine was converted into vinegar by the fermentation process. Citrus vinegar, the final fermentation product, was colored with very thin, radish-yellow and was transparent. It's acidity ranged between $5.8\~6.2\%$ of that of acetic acid. The vinegar attained the best score by sensory test among several natural fruit vinegars. It was clear from the results that high quality citrus vinegar could be produced from concentrated citrus juice. However, the fermentation conditions should be improved to reduce the amount of reducing alcohol.

• Korean journal of applied entomology
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• v.55 no.4
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• pp.483-487
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• 2016

The damage of citrus fruits caused by Scirtothrips dorsalis Hood has being increased in Jeju, Korea. The seasonal abundance of S. dorsalis and its injury symptoms in citrus orchards have been studied since the endemic outbreak in Jeju, but studies for the occurrence pattern of S. dorsalis in citrus orchards influenced by adjacent primary hosts have not been fully conducted yet. We selected kiwi- and mango-citrus adjacent orchards to study the migration pattern of S. dorsalis toward to citrus orchards. Yellow-colored sticky traps were used for monitoring the seasonal abundance of S. dorsalis and their migration pattern in two orchards. In citrus orchards, also, we placed sticky traps at 0, 5, 10, 15 and 20 m apart from the border of kiwi orchard, and 0, 7 and 20 m apart from the border of mango orchard. The seasonal occurrence pattern of S. dorsalis caught on sticky traps were similar between two adjacent orchards. However, the abundances in kiwi or mango orchard was much higher than those of citrus. Also, it was found that densities, distribution and damage of S. dorsalis in citrus orchards depend highly on the distance from the border of kiwi and mango orchards. This result suggested that the primary hosts such as kiwi and mango plants influence the occurrence of S. dorsalis in adjacent citrus orchards. And this information may provide a basic direction for establishing the management strategy of S. dorsalis in citrus orchards.

• Food Science and Preservation
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• v.2 no.2
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• pp.251-257
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• 1995

In order to determine the quality of Citrus unshiu(medium cultivar of satsuma mandarin) produced in Cheju, citrus fruits sampled at sorting places and harvested directly on citrus tree in south and north area of Cheju were analyzed. The fruits were grown in size till early of November, and soluble solids were increased continuously after that. Compared with the quality of citrus fruits as a factor of soluble solids, firmness, total sugar, pH, and color index, the optimum harvest periods were supposed to be reasonable from early of December for C. unshiu Marc. var. yonezawa and C. unshiu Marc. var. hayashi, Fruit weights and peel thickness had a linear correlation with increasing fruit size, but soluble solids and acid contents had not a correlation. The selection of C. unshiu variety was needed to determine by the properties of storage.

• Plant Disease and Agriculture
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• v.5 no.1
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• pp.34-40
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• 1999

The virus infection rates and disease symptoms of three major citrus viruses, citrus tristeza virus (CTV), satsuma dwarf virus (SDV), and citrus tatter leaf virus (CTLV), were investigated at 35 citrus orchards in Cheju Island from 1995. The infection rates of CTV, SDV, and CTLV were 69.8%, 8.6%, and 9.3%, respectively. However, depending on cultivars there were significant differences in the infection rates. The infection rates of CTV were highest in early satsuma mandarin (Citrusunshiu) with 80.9% and lowest in very early satsuma mandarin with 51.9%. In SDV, the highest was in very early stasuma mandarin with 23.1% and the lowest was in early satsuma mandarin with 6.3%. And the highest infection rate in very early satsuma mandarin with 17.9% and the lowest in tangors with 7.3% in CTLV. The symptoms of virus-infected citrus were very diverse; small and abnormal shape of fruits, abnormal leaves such as narrow boat and small spoon shapes of leaves, stem-pitting on the twig, bud-union crease and swelling of the graft part, reduction of the plant vigor and poor yields.