• Korean Journal of Environmental Agriculture
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• v.41 no.4
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• pp.318-327
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• 2022

BACKGROUND: The mean annual temperature of the Korean Peninsula will continue to rise due to global warming. 'Shiranuhi' mandarin-a late-harvest cultivar-is primarily cultivated in plastic greenhouses where high temperatures cannot be directly avoided. Therefore, growth and fruit quality changes under elevated temperatures must be investigated. METHODS AND RESULTS: Elevated temperatures were divided into three groups [2℃ (T-I), 4℃ (T-II), and 6℃ (T-III) above the ambient temperature] during the 2019-2020 season. Mean temperatures were 17.1℃, 18.6℃, and 20.2℃ in T-I, T-II, and T-III, respectively. The bud bursts in T-II and T-III were earlier than that in T-I at 7 days and 11 days, respectibely. And the full blooms in T-II and T-III were earlier than that in T-I at 11 days and 23 days, respectively. Fruit size significantly increased with increased temperature. The citrus color index in the coloring phase markedly differed across treatments. Further, total soluble solid and acid contents markedly changed with temperature rise but the sugar-to-acid ratio did not. Sucrose content tended to decrease with increase in temperature, but citric acid content remained unaffected. CONCLUSION(S): Elevated temperature accelerated plant growth and development but delayed rind color development in 'Shiranuhi' mandarin. Therefore, rise in ambient temperature by >4.6℃ may negatively affect yield and fruit quality.

• Horticultural Science & Technology
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• v.34 no.5
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• pp.665-676
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• 2016

As high temperature during citrus growing season has caused a serious problems including inferior coloration in production of mandarins in Korea, we were to investigate the expression pattern of several genes related with coloration during the ripening in high temperature condition of citrus fruits. The expression of genes related with sugar metabolism, cell wall degradation, and flavonoid synthesis in high temperature conditions was investigated in fruits of 'Haryejosaeng' (Citrus unshiu) and 'Shiranuhi' mandarin (C. reticulata). While the expression of beta-amylase (BMY), phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), and flavanone 3-hydroxylase (F3H) was differently induced, expression of polygalacturonase (PG) decreased dependently on temperature conditions. In 'Haryejosaeng' mandarin, while the expression of genes related to the skin coloration, such as CHS and F3H genes increased at $25^{\circ}C$, the expression of PAL and stilbene synthase (STS) genes were induced at $30-35^{\circ}C$ in all ripening stages. In 'Shiranuhi' mandarin, the expression of the BMY gene decreased at early time point in all temperature condition and then increased at $30-35^{\circ}C$ than at $25^{\circ}C$ in the ripening stage 2 to 3 of fruits. F3H and STS genes also showed the tendency to decrease at $30-35^{\circ}C$. Although the expression levels of genes in ripening stage 1 and stage 2 of fruits showed similar patterns in both 'Haryejosaeng' and 'Shiranuhi', the expression levels of genes were down-regulated in late ripening stage of 'Shiranuhi' fruits compared to 'Haryejosaeng'. In general, the mRNA levels of seven tested genes were higher in 'Haryejosaeng' than in 'Shiranuhi' mandarin, and expression of genes by high temperature was regulated sensitively in 'Haryejosaeng' compared to 'Shiranuhi' mandarin. Further investigations of expression of various genes based on transcriptome analysis in early ripening stage can provide valuable information about the responses to climatic changes in ripening citrus fruits.

• Korean journal of applied entomology
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• v.59 no.2
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• pp.153-163
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• 2020

This study was conducted to evaluate the fitness of Tetranychus kanzawai Kishida on different host plants: young and old leaves of the mandarin orange 'shiranuhi' ((Citrus unshiu × C. sinensis) × C. reticulata), Japanese violet (Viola japonica Langsd.) and kidney bean (Phaseolus vulgaris L.). The development and oviposition experiments were conducted at constant temperatures (20, 25 and 30℃) and a life table parameters were estimated. T. kanzawai could complete it's development on 'shiranuhi' young leaves, japanese violet and kidney bean, while all died during the immature period on 'shiranuhi' old leaves. The total developmental period of T. kanzawai feeding on 'shiranuhi' young leaves was 17.4, 13.4 and 10.2 days at each temperature, respectively, which was longer than 16.1, 9.5 and 7.0 days of kidney bean. The female longevity of T. kanzawai on young leaves of 'shiranuhi' were 19.1, 15.0 and 12.3 days at each temperature, respectively, and there was no significant difference from 22.1, 14.1 and 10.9 days investigated from kidney bean. The fecundity was 18.1, 23.9 and 17.8 eggs per female, which was less than them of japanese violet and kidney bean at each temperature, respectively. As a result of estimating the life table parameters based on the experimental data, intrinsic rate of increase (r_m) were significantly different from each other, and appeared in the following order: kidney (0.1542, 0.2563 and 0.3251), japanese violet (0.1087, 0.2007 and 0.2673) and 'shiranuhi' young leaves (0.0868, 0.1002 and 0.1217) at each temperature, respectively. Finally, the management strategy against T. kanzawai in citrus orchards was discussed based on the results.

• 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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• 2003.10a
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• pp.120.3-121
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• 2003

Relative degree of resistance of citrus to Xanthomonas axonopodis pv. citri, the causal bacterium of canker, was investigated. Growth rate of a bacterium in leaf tissues after infiltration, disease incidence, and percent of lesion area were compared. By using growth rate[(GR=(At - A$\sub$t-1/)/A$\sub$t-1] host plants were differentiated into susceptible and resistant. Growth rates reached to peak at 40 hrs after inoculation and then declined. The growth rate in leaf tissues of a moderately susceptible cultivar, Citrus sinensis vu. Lane late(sweet orange), was the highest, and those of C. unshiu ${\times}$ C. sinensis(kiyomi), C. junos(yuzu), [(Citrus. unshiu x C. sinensis) x C. reticulata] (shiranuhi), and C. unshiu(satuma mandarin) were similar. This result indicates that the growth rate of the bacterium in leaf tissues can be effectively used for evaluation of disease resistance for citrus plants to X. axonopodis pv. citri. The disease on sweet orange occurred earlier than relatively resistant citrus plants tested. The percent of lesion area on leaf was also higher in sweet orange than those of satsuma mandarin, shiranuhi and kiyomi, and yuzu. The disease severity was highest on sweet orange and followed by kiyomi, shiranuhi, satsuma mandarin, and yuzu.

• Korean Journal of Agricultural and Forest Meteorology
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• v.19 no.4
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• pp.215-222
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• 2017

The potential change of the cultivation area of main citrus cultivars, satsuma mandarin (Citrus unshiu Marc.) and 'Shiranuhi' mandarin hybrid [(Citrus unshiu ${\times}$ C. sinensis) ${\times}$ C. reticulata] were determined with base year (1981 to 2010) to 2090. The meteorological data provided by the Korea Meteorological Administration (KMA), and the digital agricultural climate map of 30m-solution based on the Representative Concentration Pathways (RCP) 8.5 was used for projection of potential cultivation area. As a result, the potential suitable region of satsuma mandarin included almost Jeju region during base year. At the 2030s, the potential suitable region of satsuma mandarin increased and the cultivable region also increased focused on the coast region of Jeonnam province. From the 2060s, the suitable area spread out to mountain area of Jeju, Jeonnam, Gyeongnam, and the coast region of Kangwon, and the cultivable region expanded to the area of Gyeongbuk, Chungnam, and Jeonbuk. In the case of 'Shiranuhi' mandarin hybrid, the suitable region included only the partial coast area of Jeju, and cultivable area covered Jeju region and the partial southern coast of Jeonnam during the standard period. At the 2030s, the suitable region of 'Shiranuhi' included the current cultivation area of satsuma mandarin, and the cultivable region moved to northward by the partial southern coast region. At the 2090s, the slightly increased suitable region covered all Jeju regions, Jeonnam, Gyeongnam, and the coast area of Kangwon, and the cultivable region proceeded northward focusing on the coastline. In conclusion, the prediction of the potential land for citrus cultivation based on the RCP 8.5 showed that the suitable region of satsuma mandarin decreased, whereas that of cultivation of 'Shiranuhi' increased. Moreover, it was forecasted that citrus cultivation area would extend to Kangwon region at the end of the $21^{st}$ century.

• Horticultural Science & Technology
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• v.31 no.3
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• pp.269-274
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• 2013

To further our understanding of sugar accumulation in 'Shiranuhi' mandarin [(C. unshiu ${\times}$ C. sinensis) ${\times}$ C. reticulate], we investigated the patterns of sugar uptake in juice sacs exposed to different concentrations of sucrose, fructose and glucose in vitro. Data was also collected on the change in weight and shape of the in vitro juice sacs over time. Soluble solids content, sugar content and acidity content were highest at 20% sucrose, fructose and glucose solution content; while fructose content was highest at 5% sucrose concentration. Furthermore, the juice sac's fresh weight was highest at 5% sucrose and lowest at 20% fructose content. The shape of the juice sacs also differed in different sugar concentration and type. Overall, sucrose, fructose and glucose content in juice sacs increased with the sugar concentration. These results suggest that sugar translocation into juice sacs is actively induced by high sugar concentration in the medium. Thus, it can be concluded that sugar and acid accumulation in juice sacs increased with sugar concentration in vitro culture.

• Horticultural Science & Technology
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• v.33 no.4
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• pp.459-469
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• 2015

The effects of elevated spring temperatures on the growth and fruit quality of the mandarin hybrid 'Shiranuhi' [(Citrus unshiu ${\times}$ C. sinensis) ${\times}$ C. reticulata] were investigated in plastic greenhouses, to develop a cropping system to improve the quality of the fruit and increase the income of growers on Jeju Island, South Korea. Under conditions of elevated temperature I ($25/15^{\circ}C$, day/night) and elevated temperature II ($28/18^{\circ}C$, day/night) during early spring, budburst was advanced by 11 and 15 d, and full bloom by 22 and 45 d, respectively, compared to those of the plants grown at ambient air temperature in a plastic greenhouse. Elevated temperatures decreased the number of spring shoots but increased mean spring shoot length and leaf area. Growing 'Shiranuhi' trees at elevated temperatures resulted in increases in mean fruit weight and fruit L/D ratio (> 1.0). In addition, fruit color development was significantly advanced in trees grown under elevated temperatures during early spring, which allowed the fruit to be harvested 1-2 months earlier than trees grown under ambient air temperature. Fruit soluble solids content (SSC) and titratable acidity (TA) at harvest were similar between elevated temperature I and ambient air temperature, but were significantly higher than at elevated temperature II. Considering fruit quality, harvest time, and yield, the elevated temperature treatment regime of $25/15^{\circ}C$ (day/night) during early spring could be useful for cultivation of the mandarin hybrid 'Shiranuhi' to increase the income of growers.

• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2005.11a
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• pp.276-276
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• 2005

• Korean Journal of Plant Resources
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• v.35 no.2
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• pp.192-200
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• 2022

Nitrogen is the most essential macronutrient for the growth of fruit trees and is important factor determining the fruit yield. In order to produce high-quality fruits, it is necessary to supply the appropriate nitrogen fertilizer at the right time. For this, it is a prerequisite to accurately diagnose the nitrogen status of fruit trees. The fastest and most accurate way to determine the nitrogen deficiency of fruit trees is to measure the nitrogen concentration in leaves. However, it is not easy for citrus growers to measure nitrogen concentration through leaf analysis. In this study, several machine learning models were developed to classify the nitrogen deficiency based on the concentration measurement of mineral nutrients in the leaves of tangor Shiranuhi (Citrus unshiu × C. sinensis). The data analyzed from the leaves were increased to about 1,000 training dataset through the bootstrapping method and used to train the models. As a result of testing each model, gradient boosting model showed the best classification performance with an accuracy of 0.971.