Jeju Island Research Articles

Genomic Analysis of the Carrot Bacterial Blight Pathogen Xanthomonas hortorum pv. carotae in Korea.

Bacterial leaf blight of carrots caused by Xanthomonas hortorum pv. carotae (Xhc) is an important worldwide seed-borne disease. In 2012 and 2013, symptoms similar to bacterial leaf blight were found in carrot farms in Jeju Island, Korea. The phenotypic characteristics of the Korean isolation strains were similar to the type strain of Xhc. Pathogenicity showed symptoms on the 14th day after inoculation on carrot plants. Identification by genetic method was multi-position sequencing of the isolated strain JJ2001 was performed using four genes (danK, gyrB, fyuA, and rpoD). The isolated strain was confirmed to be most similar to Xhc M081. Furthermore, in order to analyze the genetic characteristics of the isolated strain, whole genome analysis was performed through the next-generation sequencing method. The draft genome size of JJ2001 is 5,443,372 bp, which contains 63.57% of G + C and has 4,547 open reading frames. Specifically, the classification of pathovar can be confirmed to be similar to that of the host lineage. Plant pathogenic factors and determinants of the majority of the secretion system are conserved in strain JJ2001. This genetic information enables detailed comparative analysis in the pathovar stage of pathogenic bacteria. Furthermore, these findings provide basic data for the distribution and diagnosis of Xanthomonas hortorum pv. carotae, a major plant pathogen that infects carrots in Korea.

Chemical Resistance of Diaporthe citri against Systemic Fungicides on Citrus.

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.

The Operation Strategy of the MIDC Systems for Optimizing Renewable Energy Integration of Jeju Power System

The power system on Jeju Island currently faces challenges due to an imbalance between power supply and demand owing to increasing renewable energy (RE) generation. Consequently, the multi-infeed high-voltage direct-current (MIDC) systems are expected to play an important role in reducing RE curtailment and increasing RE penetration. However, despite the balance between power supply and demand, transmission line (TL) overloads on Jeju Island, which has a low permissible rating, may lead to RE curtailment. We propose an operational strategy for the MIDC systems to mitigate TL overloading and RE curtailment. This strategy was aimed at managing the possible congestion of TLs, maintaining a power supply–demand balance, and increasing the penetration level of RE. In this paper, we present a scheme for calculating the operating points of the MIDC systems and allocating RE curtailment using optimization with security constraints to mitigate TL overloading. The proposed optimization model simplifies solving the mathematical equations involved by employing a sensitivity factor called the power transfer distribution factor (PTDF), using which linear programming (LP) optimization can be performed. To verify the feasibility of the operational strategy, case studies are conducted using an actual Jeju Island power system with a power system analysis tool—Power System Simulator for Engineering (PSS/E). The optimization problem was solved using MATLAB.

Alternating patterns of cross-shelf suspended sediment transport in the northern East China Sea in winter

Suspended sediment transport across the continental shelf is a key process for the materials exchange between coastal seas and the deep ocean. The cross-shelf transport through the Yangtze Shoal in the northern East China Sea (ECS) exhibits a unique pattern, which is characterized by alternations between high and low values in suspended sediment concentration (SSC). This study is conducted to reveal the underlying mechanisms and their effects on sediment fluxes. Surface SSC retrieved from GOCI data are combined with in situ observations of concentration and particle sizes of suspended sediment to study the temporal and spatial variations of the SSC in the Yangtze Shoal. Additionally, a numerical model for examining ocean circulation based on the FVCOM is established to display the hydrodynamic feature in the study area. The alternating SSC pattern is closely related to the topography of three ridges and two troughs. High SSC with fine particle size can be found over the ridge, while low SSC is detected at the surface layer of water in the trough. Even during the flood and ebb tides, this alternating pattern of high and low SSCs does not change, except for the expansion and contraction of coverage areas of high SSC. The high SSC near the tidal ridge should have resulted from the combined effect of resuspension and upwelling since the stronger bottom shear stress and a surface divergence that may induce an upwelling can be found in this area. Combined with the simulated current, the sediment transport flux between ridges and troughs is estimated. The sediment flux in the ridge is substantially increased than that in the trough, especially during the flood maximum and ebb maximum time. The contribution of suspended sediments from the Yangtze Shoal to the Southwestern Cheju Island Mud (SCIM) is relatively small during the normal weather in winter. However, cross-shelf transport can be remarkably strengthened by strong northerly winds in winter. This work puts forward a detailed cross-shelf transportation process induced by topography.

The Utilization of Serum Folate and Homocysteine Tests and the Prevalence of Folate Deficiency in Reproductive-Age Korean Women during the COVID-19 Pandemic.

We investigated the prevalence of folate deficiency and associated factors in a large population of Korean women of reproductive age during the COVID-19 pandemic. We utilized different cut-offs and evaluated age, year of testing, geographical region, and the utilization of serum homocysteine levels. Out of the 27,758 women evaluated, the overall prevalence of folate deficiency was 12.5% (<4 ng/mL, metabolic indicator) and 5.4% (<3 ng/mL, hematologic indicator). Homocysteine testing was observed in 8.4% of women, with 2.7% having elevated homocysteine levels (>15.4 µmol/L). According to our multiple logistic regression analysis, younger women, particularly those aged 20 to 24 years, tested in 2020, and from Jeolla province, Gyeongsang province, and Jeju Island, were identified as being more prone to folate deficiency. Receiver operating characteristic curve analysis demonstrated that a cut-off of >8.4 µmol/L provided the most accurate definition of folate deficiency with serum folate levels <4 ng/mL, while a cut-off of >8.8 µmol/L best defined folate deficiency with serum folate levels <3 ng/mL, with both cut-offs being lower than 15.4 µmol/L. Our study emphasizes the prevalence of folate deficiency, associated factors, and the role of homocysteine in planning nutritional support programs in Korea.

Genomic surveillance of genes encoding the SARS-CoV-2 spike protein to monitor for emerging variants on Jeju Island, Republic of Korea.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has been fueled by new variants emerging from circulating strains. Here, we report results from a genomic surveillance study of SARS-CoV-2 on Jeju Island, Republic of Korea, from February 2021 to September 2022. A total of 3,585 SARS-CoV-2 positive samples were analyzed by Sanger sequencing of the gene encoding the spike protein before performing phylogenetic analyses. We found that the Alpha variant (B.1.1.7) was dominant in May 2021 before being replaced by the Delta variant (B.1.617.2) in July 2021, which was dominant until December 2021 before being replaced by the Omicron variant. Mutations in the spike protein, including N440K and G446S, have been proposed to contribute to immune evasion, accelerating the spread of Omicron variants. Our results from Juju Island, Republic of Korea, are consistent with and contribute to global surveillance efforts crucial for identifying new variants of concern of SARS-CoV-2 and for monitoring the transmission dynamics and characteristics of known strains.

Relationship between Submerged Marine Debris and Macrobenthic Fauna in Jeju Island, South Korea

Pollution associated with marine debris is of global ecological concern, as it threatens wildlife and local economies. Submerged marine debris alters local benthic species composition and community characteristics. The study site of Jaguri, Jeju Island, where a variety of submerged marine debris was found, was used to investigate the impact of submerged marine debris on the macrobenthic fauna of sandy and rocky substrates. The dominant macrobenthos taxon differed by sediment type; the polychaete Armandia lanceolata was dominant in sandy bottom environments and the mollusk Leiosolenus lischkei was dominant in rocky bottom environments. The presence of marine debris was associated with differences in biomass in both the soft and rocky areas. The site without debris had higher biomass in the soft area, and the site with nets had a higher density of benthic animals within the site with debris. In the rocky area. the site with debris had a higher biomass. Macrobenthos were affected by the type of deposited marine debris and the type of sediment substrate. This study provides a basis for future studies on the impact of debris on marine ecosystems and identified the benthos species affected by marine debris.

Strontium-90 levels in seawater southeast of Jeju Island during 2021–2023

This study introduces an efficient method for determining 90Sr activity levels in seawater, reducing the processing time to <3 h for 50 L of seawater. The key feature of the proposed method is the chemical separation of 90Y when it is in equilibrium with 90Sr, which is achieved by utilizing custom-made sample-loading equipment and an automated radionuclide separation instrument. As a result, the procedure consistently yields a recovery rate > 90 % for 90Y. Investigations of 90Sr levels were conducted in the ocean southeast of Jeju Island from November 2021 to January 2023. Owing to the regional ocean circulation, this region was among the first within the Korean Peninsula to experience the impact of the Fukushima-accident-derived radionuclides. Throughout the investigation period, the observed 90Sr activity concentration ranged from 0.57 to 1.0 Bq m−3. No distinct temporal variation of 90Sr was observed in the selected area during the investigation.

Testing heavy rainfall change in Jeju Island, Korea and its linkage to typhoon activity over East Asia during the Holocene

Understanding the spatiotemporal variability of extreme hydrologic events, especially those driven by typhoons over Asia, and their controlling factors is essential to testing and predicting their future changes under global warming. Here, we present a series of direct heavy-rainfall records over the past ca. 10,000 years based on lake sediments from a volcanic cone (Sara Oreum) on Jeju Island, Korea, where orographic amplification of precipitation is dominant and sensitive to present typhoon activity. The reconstructed heavy rainfall index based on the high-resolution elemental ratios (e.g., Ti/Al and Sr/Si) shows clear variability at centennial timescales and is similar to records of coastal flooding events along the southern coast of Korea, typhoon-driven overwash events along the south-western coast of Japan, indicating strong typhoon influence on the heavy rainfall events in Jeju Island during the Holocene. Furthermore, this heavy rainfall-typhoon linkage has been influenced by past El Niño–Southern Oscillation (ENSO) activity and sea surface temperature (SST) in the western Tropical Pacific, showing time-varying influences. This study suggests that on decadal to multi-centennial timescales, stronger ENSO activity is responsible for eastward shift in the location of typhoon genesis, resulting in more frequent recurving tracks of typhoon and increased landfalls in Korea and Japan, whereas SST affects the intensification rate of typhoon. The heavy rainfall index reconstructed from the volcanic cones of Jeju Island may be used as an indicator of past frequency and track changes of typhoon over highly populated East Asia.

Neo-octaploids of Asplenium prolongatum Hook. (Aspleniaceae) occurred in Korea

Asplenium L. is a sub-cosmopolitan genus of ferns comprising approximately 700 species. It includes various ploidy-leveled taxa, and, in particular, polyploid species occupy a higher proportion than diploid species within the genus. In addition, it is regarded as an essential process to confirm the cytotype of taxa because the ploidy level is sometimes used to identify a particular taxon in Asplenium. In the case of A. prolongatum, two cytotypes, tetraploid and hexaploid, have been reported in Japanese and Chinese populations. However, to date, there have been no attempts to confirm the ploidy of the Korean species. In the present study, we investigated the cytotype of Korean A. prolongatum using chromosome counting and genome size measurements, and we found that two cytotypes, hexaploid (2n = 6x = 216) and octaploid (2n = 8x = 288), were distributed in Jeju Island, Korea. To the best of our knowledge, this is the first report of a neo-cytotype of A. prolongatum. The hexaploids mostly had empty, shrunken sporangia, which is one of the traits observed in sterile hybrid ferns. From these results, it was concluded that A. prolongatum has three cytotypes: tetraploid, hexaploid, and octaploid.

심방의 어원과 그 신화적 맥락

Simbang in Jeju, which refers to a shaman, is a term that is not used in other regions. This word is related to the shaman, which is shared by various ethnic groups of Tungus, including Hosemi, a noun that calls the shaman in Hamgyeong Province.&#x0D; The root of the shaman is sam. Based on this root, Hosemi is analyzed as “ho+sam/sem+I.” Ho is ho(胡), and i is a dependent noun that means person. If so, Hosami or Hosemi means shaman who came from the northern Tungusic region. If Hosemi had the meaning of a shaman flowing from Tungus culture, the meaning of Semi is originally a shaman in Hamgyeong Province. This is a word from the same line as Samma of the Goguryeo monk, Adusamma.&#x0D; If so, it is reasonable to understand the Sim of the Simbang as a sound of this series. Sambang is a form of adding the suffix bang(房) to sam, which is the root of shaman. If Bang is attached to Semi/Samma/Sami, which is used in Hamgyeong Province and Silla, it can be Semibang/Sammabang/Samibang, and if it is abbreviated to two syllables, it can be Sembang or Sambang. The currently used Simbang is a word in which Sembang or Sambang has settled on Jeju Island, and it is a way of expression that substitutes the shaman with the shaman’s house.&#x0D; The fact that Samadongi in Hwangchenhonsi and Samani in Samanibonpuri share the root sama suggests a relationship between sama and sam. This is because not only sama and sam have similar sounds but their roles and actions in mythology are the same as Hosemi and Simbang. These figures reflect the stories of Hosumi and Simbang becoming Shamans. Samadongi and Samani in shamanistic myth prove the relationship between Hosemi and Simbang.

HVDC 운영 전략에 따른 제주 전력 계통의 출력제어 및 운영비용 분석

The proportion of renewable power generation in power systems is rapidly increasing, resulting in frequent imbalances. This paper focuses on the impact of renewable energy penetration on power system stability in Jeju, South Korea, under the CFI 2030 policy. With the increase in renewable energy sources, power variability has also increased due to their intermittent nature, leading to supply and demand imbalances and system stability problems. Traditional methods of maintaining power balance, such as curtailment, result in cost and environmental losses for system operators. To address this issue, the paper proposes the use of HVDC power reversal transmission strategies to return excess power from Jeju to the mainland power system. The study analyzes the impact of three operational strategies of HVDC on unit commitment results, considering cost and environmental factors. The results suggest that using HVDC can mitigate curtailment and reduce oversupply, leading to improved power system stability in Jeju island.

A survey of the genome-wide genetic variation of &lt;i&gt;Hibiscus hamabo&lt;/i&gt; (Malvaceae)

&lt;i&gt;Hibiscus hamabo&lt;/i&gt; (Malvaceae) is a deciduous shrub mainly found in northeast Asia, including China, Japan, and Korea. Due to its limited distribution on Jejudo Island and at several sites in Jeollanam-do in Korea, &lt;i&gt;H. hamabo&lt;/i&gt; has been designated as an endangered species by the Ministry of the Environment and has been the subject of several restoration programs. In this study, we quantified genetic variations using double-digestion restrictionassociated DNA sequencing technology in 96 individuals of &lt;i&gt;H. hamabo&lt;/i&gt; from 13 distinct populations in Korea. We determined 3,352 genome-wide single nucleotide polymorphism loci after stringent filtering processes and analyzed the level of genetic variation within and among populations as well as the population differentiation and genetic ancestry with various assumptions pertaining to the population origin. Our results indicated weak differentiations among populations surveyed in this study but clearly suggested that most of the &lt;i&gt;H. hamabo&lt;/i&gt; populations maintain a relatively high level of genetic diversity as evidence of frequent genetic exchanges among populations via outcrossing or sequential gene flows. For a more detailed analysis of the origin of Korean &lt;i&gt;H. hamabo&lt;/i&gt; and its demographic history, it will be necessary to expand sampling in China and Japan.

Rapid Identification of Diaporthe citri by Gene Sequence Analysis

Citrus melanoses caused by &lt;i&gt;Diaporthe citri&lt;/i&gt;, has been one of the serious diseases in many citrus orchards of Jeju Island. To protect melanose in citrus farms, a fast and exact diagnosis method is necessary. In this study, diseased leaves and dieback twigs were collected from a total of 49 farms within March to April in 2022. A total of 465 fungal isolates were obtained from a total of 358 isolated plant samples. Among these fungal isolates, 40 representatives of &lt;i&gt;D. citrii&lt;/i&gt; isolates which were isolated from 22 twigs and 18 leaves on 23 farms were found based on cultural characteristics on potato dextrose agar and conidial morphology. Additionally, the molecular assay was carried out and compared with those by morphological diagnosis. All isolates were identified as &lt;i&gt;D. citrii&lt;/i&gt; by analyzing the sequences at the internal transcribed spacer (ITS) rDNA region using primers of ITS1/ITS4 or at β-tubulin using primer Btdcitri-F/R. Therefore, based on the present study, where the results of morphological identification of conidial type were consistent with DNA sequence analysis of certain gene, choosing a suitable method for a fast diagnosis of citrus melanose was suggested.

빅데이터 기법을 활용한 외식관광이동패턴 연구

This study explored the movement patterns of tourists’ behavior concerning their food and beverage product choices, which differs from previous studies focusing on tourist movement patterns related to tourist products such as tourist attractions or accommodations. Navigation data of Jeju Island tourists visiting restaurants and cafes were analyzed through descriptive analysis, heatmap analysis, and social network analysis, which helped identify the movement patterns of tourists related to their food and beverage product choices. The heatmap analysis revealed that the movement patterns of tourists who visited restaurants were mostly centered around the urban areas of Jeju-si and Seogwipo-si, while the movement patterns of tourists who visited cafes were observed mostly in outlying areas such as along seasides or mountain areas. Additionally, the social network analysis revealed that the central nodes of restaurant networks were located near urban areas, while the central nodes of cafe networks were located further away from urban areas. This study can contribute to the theoretical understanding of differences in tourist movement patterns based on the purpose of the tourists’ visits. Furthermore, the study provides important insights for DMOs to efficiently operate and effectively develop and promote food and beverage products at destinations.

데이터와 서비스 대범람의 시대, DR 데이터센터 원거리 배치를 위한 기술 및 정책 방안

Recently, in late 2022, Disaster Recovery Data Center is recognized as important due to the disruption issue of Kakao, the Korea' s #1 SNS service provider caused by a fire at their separated operating data center. In this response; the needs of establishing the Disaster Reovery Data Center, this paper is examining the brief current status of domestic and foreign data centers and D.R. data centers and analyzing the related problems. Moreover, according to three requirements (environment, communication and power infrastructure) and two criteria (site level, socio-economic/manpower/government) to find the r ight location for the data center, Jeju's strengths and weaknesses were examined, and considered with the technical and policy measures for Jeju Island to encourage for the attraction of private sector's data centers/DR data centers.

Baseline Study on Microplastic Distribution in the Open Surface Waters of the Korean Southwest Sea

This study investigated microplastic distribution characteristics by collecting surface seawater from sea areas to the south of Jeju Island in August 2020. The average microplastic abundance was 0.46 ± 0.27 particles/L (n = 23), and PE had a high ratio, averaging 53%. The levels of fragments and fibers were observed to be 69% and 31% on average, respectively. The most common size of the microplastics was on average 0.02–0.30 mm at a level of 69%. We found a higher abundance of microplastics in the study area than in other open waters such as the Arctic Central Basin and the Atlantic Ocean, whereas the abundance was lower than that in previous studies on coastal areas. We studied an area of open sea connecting China, Japan, and the Pacific Ocean, and, in this region, the microplastic distribution varies depending on sea currents in the surrounding areas. In the summer, the western and central regions of the study sea area have low salinity levels due to discharge from China’s Yangtze River. This generally indicates that high-density plastic deposits are found in the Yangtze River estuary, and low-density plastics are found in the study area. Furthermore, this implies that low- and high-density plastics are transported in water for long periods of time due to the Taiwan Warm Current and because the eastern sea area has high salinity.

Thirty-year Trend in Inflammatory Bowel Disease on Jeju Island, South Korea.

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is increasing in South Korea. On the other hand, there are no reports of the incidence and prevalence of IBD specific to Jeju Island, prompting the necessity of this study. In this retrospective design, the medical records of 453 patients diagnosed with IBD at Jeju National University Hospital from January 1990 to December 2019 were analyzed. Of the 453 IBD subjects (165 CD, 288 UC) included, the UC: CD ratio was 1.75:1. The incidence of IBD increased continuously from 0.19/105 in 1990 to 6.39/105 in 2017 and after that decreased to 4.92/105 in 2019. The male:female ratio was 2.24:1 for CD and 1.29:1 for UC. In the CD subjects, the disease activity included remission (33.3%), mild (25.5%), moderate (30.9%), and severe (6.1%). In UC subjects, the disease activity included remission (24.0%), mild (35.4%), moderate (28.8%), and severe (6.2%). According to the Montreal classification, the cases were as follows: CD: terminal ileum (22.4%), colon (9.7%), ileocolon (66.1%), and upper gastrointestinal involvement (27.3%), and perianal fistula/abscess was present in 43.6% of subjects before or at diagnosis: UC: proctitis (43.4%), left-sided colitis (29.1%), and pancolitis (23.3%) at diagnosis. The incidence of IBD on Jeju Island has increased steadily for approximately 30 years but has exhibited a decline since 2017. Therefore, the incidence of IBD in Jeju is believed to have plateaued. Further study will be needed for clarification.

‘Safety in Numbers’ for Walkers: Effects of Pedestrian Volume on Per-Pedestrian Crash Rate and Severe Injury Probability

The ‘safety in numbers’ phenomenon is very intriguing to many walking advocates. Some studies have examined the phenomenon for walkers, but they mostly focused on the relationship between pedestrian volume and the likelihood of vehicle–pedestrian crash occurrences. This study evaluated the effects of the ‘safety in numbers’ phenomenon not only on the risk of crash occurrences, but also on the probability of severe or fatal injuries. Pedestrian volume and crash data obtained from the six districts in Seoul Metropolitan City and Jeju Island were jointly analyzed to examine the expected pedestrian crash rate and the probability of severe or fatal injury as a function of pedestrian volume. The analysis confirmed that the expected pedestrian crash rate and the probability of severe or fatal injuries decline as pedestrian volume increases, although the absolute number of crashes and injuries increases. The increase in the number of pedestrian crashes is less than the increase in pedestrian volume. In addition, the probability of severe or fatal injuries tends to diminish with a larger pedestrian volume. These findings can be used as logical evidence to support future policies promoting walking trips, and they suggest that policy measures encouraging walking trips can deliver additional benefits beyond the well-known economic, health, and environmental benefits.

The Liverwort and Hornwort Flora of Jeju Island, Republic of Korea: A Volcanic Island with a Unique Mixture of Subtropical, Temperate, Boreal, and Arctomontane Taxa.

Jeju Island, due to its position at the southern tip of the Korean Peninsula in Northeast Asia, is a on the unique enclave of the many southern elements in the area and features a mixture of subtropical, temperate, boreal, and arctomontane taxa. Among the arctomontane species recorded in this study was Anthelia juratzkana; among the temperate species was Dactyloradula brunnea, and subtropical species were Cavicularia densa, Pallavicinia subciliata, Wiesnerella denudata, and Megaceros flagellaris. A valuable species as first recorded for the Jeju Island is Cryptocoleopsis imbricata. The distribution patterns of these species suggest that the flora of Jeju Island is a meeting place between boreal and subtropical floras. We recorded 222 taxa belonging to 45 families, 80 genera, 209 species, 9 subspecies, and 4 varieties. Among these, 86 species are reported as new to the flora of Jeju Island. A checklist based on a study of 1697 specimens is also provided.