• Korean Journal of Environmental Agriculture
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• v.16 no.2
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• pp.181-186
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• 1997

Since volcanic ash soils in Cheju island have high capacities of adsorption and immobilization of phosphate, a relatively high rate of P application has been recommended in citrus orchards for many years and such a large amount of P application could be problematic both in agricultural and environmental point of view. The objective of this study was to test whether arbuscular-mycorrhizae can be used to improve P availability in Cheju citrus orchard soils. Soil, root and leaf samples were taken from 14 citrus orchards of different location and soil texture. Mycorrhizal spore distribution in the soils, mycorrhizal infection ratio on the citrus roots, and mineral nutrients in leaf samples were determined. Numbers of mycorrhizal spore were in the range of $9,000{\sim}40,000/100g$ soil. The population level was not correlated with any of the soil characteristics examined. Mycorrhizae were found in all of the examined orchards and root infection ratio varied between $14{\sim}60%$. The mycorrhizae infection ratio differed substantially in different soils. Although root infection was high at soils with low extractable P level, it was not significantly correlated with other soil factors measured. Since a positive correlation was observed between leaf P concentration and root infection, enhancement of P uptake seemed to be associated with mycorrhizal infection. These results indicate that mycorrhizae could be a useful method to reduce P applications in Cheju citrus orchards.

• The Plant Pathology Journal
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• v.33 no.3
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• pp.307-317
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• 2017

Satsuma dwarf virus (SDV) or Citrus mosaic sadwavirus (CiMV) were not consistently detected in RTPCR assay with the primer sets based on gene of Japan isolates. SDV and CiMV isolates were distinctively divided into two groups based on phylogenetic analysis of PP2 gene cloned from 22 Korean isolates, and the Korean CiMV and SDV isolates shared 95.5-96.2% and 97.1-97.7% sequence identity with Japanese isolate, respectively. We developed PP2-1 primer set based on the PP2 gene sequence of Korean isolates to simultaneously and effectively detect SDV and CiMV. And CTLV-2013 and CTV-po primer sets were newly designed for detection of Citrus tatter leaf virus (CTLV) and Citrus tristeza virus (CTV), respectively. Using these primer sets, a new multiplex PCR assay was developed as a means to simultaneously detect 4 citrus viruses, CTV, CTLV, SDV, and CiMV. The degree of detection by the multiplex PCR were consistent with those of uniplex RT-PCR for detection of each of the viruses. Therefore, the new multiplex PCR provides an efficient method for detecting 4 citrus viruses, which will help diagnose many citrus plants at the same time. We verified that 35.2% and 72.1% of 775 trees in 155 orchards were infected with SDV or CiMV (SDV/CiMV) and CTV by the multiplex-PCR assay, respectively, and CTLV was not detected in any of the trees tested.

• 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.

• Korean journal of applied entomology
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• v.42 no.3
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• pp.233-240
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• 2003

The effect of density suppression of Amblyseius fallacis (Garman) against Panonychus citri (McGregor) on citrus tree introduced with some different ratio was investigated. When it was introduced with over 16:1 (Panonychus citri: A. fallacis) ratio, Panonychus citri was suppressed very effectively. And in case of introduced once or two times with 20: 1 ratio when the density of Panonychus citri was reached 0.5 and 1.0 per leaf, the density of A. fallacis was formed highly, but the suppression effect against Panonychus citri was not effective. Also, the density changes of P. citri and A. fallacis on the citrus tree released with 10: 1 ratio (P. citri: A. fallacis) when the density of P. citri was reached about 0.1 per leaf in plastic film house were investigated. In case of released twice at the interval of 10 days, the density of A. fallacis was high and P. citri was suppressed so effectively over two month. On the inside of canopy of the citrus tree planted in plastic film house, the air temperature was much lower than on the outside of canopy, while relative humidity was much higher.

• The Plant Pathology Journal
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• v.19 no.5
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• pp.253-256
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• 2003

Citrus canker disease is caused by bacteria Xanthomonas axonopodis .pv. Citri. Shiranuhi cultivar, a hybrid of Kiyomi tangor and Nakano No.3 ponkan was evaluated for resistance to citrus canker based on initiation of disease, percent area of lesion infected and growth rate of bacteria in the leaf under growth chamber condition. Significant differences between susceptible plant and resistant plants were observed in these assays. Resistant plants showed delayed disease symptoms compared to the susceptible plants after spray inoculation of the pathogen. The resistant verities, satsuma, yuzu, and Shiranuhi showed symptoms after six days where as susceptible, mexican lime showed the symptoms just after three days of inoculation. 18 days after inoculation, percent area of lesions developed on leaf and disease severity differed significantly in susceptible and resistant plants, and were ranked as follows: mexican lime > early satsuma =Shiranuhi =yuzu (P <, 0.01). However, 30 days after inoculation, percent area of lesion was further differentiated into resistant and highly resistant plants. That was ranked as follows: sweet orange> early satsuma =Shiranuhi =Kiyomi > yuzu (P < 0.01). These results indicate that host reaction to the bacterial was more distinct when the disease developed for a longer period. Growth rates of a citrus canker bacterium during 16 40 h also were distinct after infiltration into leaves of susceptible and resistant plants, and were ranked as follows: sweet orange> early satsuma =Shiranuhi =Kiyomi =yuzu (P < 0.01). Based on these results, we concluded that Shiranuhi is resistant to citrus canker as compared to Kiyomi, early satsuma, and yuzu.

• Research in Plant Disease
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• v.11 no.2
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• pp.115-121
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• 2005

This studies were carried out to elucidate the control effect of copper fungicides against some citrus diseases, assess copper spray injury on leaf and fruit of citrus by spraying of copper fungicides according to growth stages and spray seasons and by tank mixing with paraffin oil in field experiments for 3 years (2003-2005 season). As results, the control value was approximately $75\%$ against scab disease in all tested copper fungicides, $85-88\%$ to canker and $75-86\%$ to melanose. In case of leaf, the copper injury was the severest in early stage of shooting, and the injury was gradually weakened according to growth of leaf. In fruit, the copper injury was more severe in midsummer (late of July and August) than early of summer and spring season (June and ealy of July). Among copper fungicides, the bordeaux mixture which made by level of farm induced more injury compared to other copper fungicides commercialized. Less copper spray injury was observed on treatments in which copper fungicide was sprayed as tank mixtures with paraffin oil when compared to treatment which sprayed with only copper fungicide.

• Journal of Plant Biotechnology
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• v.49 no.4
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• pp.271-291
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• 2022

Pectin methylesterase (PME) plays an important role in vegetative and reproductive development and biotic/abiotic stress responses by regulating the degree of methyl-esterification of pectic polysaccharides in the plant cell wall. PMEs are encoded by a large multigene family in higher land plant genomes. In general, the expression of plant PME genes shows tissue- or cell-specific patterns and is induced by endogenous and exogenous stimuli. In this study, we identified PME multigene family members (CsPMEs) from the sweet orange genome and report detailed molecular characterization and expression profiling in different citrus tissues and two fruit developmental stages. We also discussed the possible functional roles of some CsPME genes by comparing them with the known functions of PMEs from other plant species. We identified 48 CsPME genes from the citrus genome. A phylogenetic tree analysis revealed that the identified CsPMEs were divided into two groups/types. Some CsPMEs showed very close phylogenetic relationships with the PMEs whose functions were formerly addressed in Arabidopsis, tomato, and maize. Expression profiling showed that some CsPME genes are highly or specifically expressed in the leaf, root, flower, or fruit. Based on the phylogenetic relationships and gene expression profiling results, we suggest that some CsPMEs could play functional roles in pollen development, pollen tube growth, cross incompatibility, root development, embryo/seed development, stomata movement, and biotic/abiotic stress responses. Our results shed light on the biological roles of individual CsPME isoforms and contribute to the search for genetic variations in citrus genetic resources.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.121.1-121
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• 2003

Dispersal of Xanthomonas axonopodis pv. citri, causing citrus bacterial canker disease on Unshiu orange was investigated at previously infested plots at Seogwipo in Jeju island of Korea. The bacterial pathogen overwintered in lesions started to multiply at tate May, and disease firstly observed one month after detection of phage from lesions. The disease gradually increased, however, it dispersed non-directionally to nearby plants from inoculum sources. Diseased plants were aggregated to form a cluster throughout the experiment. Population dynamics of phage on symtomless leaf surface and the disease severity were compared in the nursery, Increase of phage population on symptomless leaf surface preceded one month to that of the disease severity Population of phage increased constantly from late July to October, however, the disease severity decreased from late August to late October. It was assumed that the decrease of disease severity might be due to disease-induced defoliation.

• Journal of Plant Biotechnology
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• v.32 no.1
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• pp.45-50
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• 2005

Virus-free stocks was produced by the combination of the heat treatment of virus infected plant and shoot-tip grafting (STS). To produce virus-free stocks, the plants infected with citrus viruses were used for virus-free stock production using the modified method of STG in thermotherapy at $40^{\circ}C$ for 16 hours in the light, and at $30^{\circ}C$ for 8 hours of darkness for 4 weeks. Trifoliate orange (P. trifoliata) were used as rootstock seedling for STG. Percentages of virus-free stocks against citrus tristeza virus (CTV), satsuma dwarf virus (SDV) and citrus tatter leaf virus (CTLV) were $75.7\%,\;100.0,\%\;82.6\%$ respectively. Shoot tip size for successful STG were as small as possible. Less than $0.3\;\cal{mm}$ of shoot tips gave the hight efficiency of virus free plants but survival rates were low. And, survival rate after shoot-tip culture was analyzed and the rates were dependant on the cultivars; Yuzu cultivar showed the hight survival rate ($74.6\%$) and early satsuma mandarin (Iwasagi) was $13.3\%$ as the lowest cultivar. But citrus trees were not succeed to grown, turned brown, and died.

• Korean journal of applied entomology
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• v.37 no.2
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• pp.193-198
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• 1998

Experiments were conducted to investigate the population fluctuation, developmental periods, fecundity, hatching rate and demage of Citrus red mite (Panonychus citri M.) on Yuzu trees (citrus junos T.) from 1996 to 1997. Citrus red mite occurred from May to November and made two peaks. The first peak was in July to August and the secondary peak was in October. Density of the second peak was higher (9.5 miteslleaf) than that of the first peak. In the constitution rate of each developmental stage of citrus red mite on Yuzu leaves, egg stage occupied 85%. At the four constant temperature (15, 20, 25, 30 + 1$^{\circ}$C, RH 60 + lo%, 14L- IOD) conditions, the developmental period from egg to adult was 41 .l, 15.5, 11.0 and 9.4 days ; Mean longevity of adult was 23.3, 8.3, 6.3, and 6.1 days; Mean number of egg laid per female per day was 1.6, 3.2, 4.5, 4.0 eggs; Mean hatching rate was 66.6, 85.7, 90.7 and 94.7% at above temperature, respectively. When sprayed acaricide at different density of Citrus red mite, the growth of young Yuzu tree were better at low density. Defoliation rate during winter was 13.5, 20.6, 53.1, 72.6% at 4 control density 1 , 3, 6 mites per leaf and uncontrolled (10 ( ). When every time spray acaricide under 3 mites per leaf, defoliation rate during winter suppressed above 50% compare to uncontrol 72.6%.