• Horticultural Science & Technology
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• v.34 no.4
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• pp.537-548
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• 2016

The objective of this study was to evaluate the antimicrobial activities of 9 kinds of medicinal plants against crown gall in grapevine. The medicinal plants extracted with several solvent systems were screened for in vitro antibacterial activity by the disc diffusion method. The ethanol and ethyl acetate extracts from magic lily flowers, tachys roots, asian plantain flowers and seeds, sweet wormwood leaves, stems and flowers, immature bitter melon fruits, cockscomb flowers, and peach tree resin showed in vitro antimicrobial activities against Rhizobium vitis with growth inhibition zones ranging from 10 to 27 mm in diameter. The minimum inhibitory concentration values of extracts against R.vitis ranged from 10,000 in Asian plantain flower and 50,000 fold diluted extracts in sweet wormwood flowers, stems, leaves, cockscomb leaves and immature bitter melon fruits. The active fractions of ethyl acetate and ethanol extracts from the medicinal plants were partially separated through silica gel column chromatography and thin layer chromatography (TLC). The active fractions were separated at Rf 0.36, 0.69, 0.75, 0.84, and 0.94 in sweet wormwood extracts, Rf 0.96 and 0.99 in cockscomb flower extracts, Rf 0.92 and 0.97 in cockscomb leaf extracts, and Rf 0.85 in immature bitter melon fruit extracts in TLC analysis developed with hexane:ethyl acetate (20:80, v/v) and methanol:chloroform (20:80, v/v). Among extracts from plants with in vitro antimicrobial activities, sweet wormwood, cockscomb leaves, and immature bitter melon fruits showed in vivo antimicrobial activities with inhibition activity of 100, 67, and 83.3%, respectively, in 'Kyoho' grapevine inoculated with R. vitis compared with the untreated control. These findings indicate that extracts of medicinal plants could be used as sustainable candidates to control crown gall disease caused by R. vitis in grapevines.

• Journal of Bio-Environment Control
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• v.24 no.3
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• pp.161-166
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• 2015

To determine the adequate levels of light intensity and $CO_2$ concentration for mango grown in greenhouses, quantitative measurements of photosynthetic rates at various leaf positions in the tree are required. The objective of this study was to develop two-variable leaf photosynthetic models of Irwin mango (Mangifera indica L. cv. Irwin) using light intensity and $CO_2$ concentration at different leaf positions. Leaf photosynthetic rates at different positions (top, middle, and bottom) were measured by a leaf photosynthesis analyzer at light intensities (0, 50, 100, 200, 300, 400, 600, and $800{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$) with $CO_2$ concentrations (100, 400, 800, 1200, and $1600{\mu}mol{\cdot}mol^{-1}$). The two-variable model consisted of the two leaf photosynthetic models expressed as negative exponential functions for light intensity and $CO_2$ concentrations, respectively. The photosynthetic rates of top leaves were saturated at a light intensity of $400{\mu}mol{\cdot}^{-2}{\cdot}s^{-1}$, while those of middle and bottom leaves saturated at $200{\mu}mol{\cdot}^{-2}{\cdot}s^{-1}$. The leaf photosynthetic rates did not reach the saturation point at a $CO_2$ concentration of $1600imolmol^{-1}$. In validation of the model, the estimated photosynthetic rates at top and bottom leaves showed better agreements with the measured ones than the middle leaves. It is expected that the optimal conditions of light intensity and $CO_2$ concentration can be determined for maximizing photosynthetic rates of Irwin mango grown in greenhouses by using the two-variable model.

• The Plant Pathology Journal
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• v.19 no.5
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• pp.248-252
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• 2003

This study was carried out to evaluate potential of Shiranuhi cultivar against inoculation of causal pathogen of citrus canker, Xanthomonas axonopodis pv. citri in Jeju Island by comparing degree of susceptibility of fruits and leaves/twigs, and analysis of incidence of canker disease. Progression of symptom, disease incidence, and percent area of lesion were surveyed for evaluation of resistance. In greenhouse condition, symptoms of bacterial citrus canker progressed more rapidly in sweet orange, a moderately susceptible cultivar, than in other four cultivars (satsuma mandarin, 'Kiyomi', 'Shiranuhi' and 'Yuzu'). At 20 days after inoculation, disease severity was the highest in sweet orange (5.0$\pm$0.0), and all tested leaves were distorted or had dropped. On the other hand, 'Yuzu' showed the lowest disease severity (2.6$\pm$0.47), followed by 'Kiyomi' (4.0$\pm$0.0), 'Shiranuhi' (4.0$\pm$0.82), and satsuma mandarin (4.3$\pm$0.47). Percent area of lesion per leaf 30 days after inoculation was the highest in sweet orange (8.31$\pm$1.78), followed by satsuma mandarin (1.51$\pm$1.25), 'Shiranuhi' (1.39$\pm$0.94), and 'Kiyomi' (1.1$\pm$0.9), while the lowest was in 'Yuzu' (0.26$\pm$0.17). Infield condition, percentage of diseased leaf in 'Shiranuhi' was very low, 5.2$\pm$2.9, compared with sweet orange, 71.0$\pm$ 11.5, while that of satsuma mandarin and 'Kiyomi' were 6.9$\pm$7.0 and 4.3$\pm$2.0, respectively. Percentages of diseased leaf was higher (17.4$\pm$7.1) than that of diseased fruit (3.2$\pm$2.5) in severely diseased trees of Shiranuhi cultivar, and the disease was not observed on twig in open field condition. Lesion sizes on leaves and fruits in open field condition were 4.1$\pm$2.2 mm2 and 5.1$\pm$5.6 mm2, respectively, while those in greenhouse condition were 8.7$\pm$5.7 mm2, 10.4$\pm$9.2 mm2 and 5.6$\pm$2.6 mm2 on leaves, fruits and twigs, respectively. The disease was observed in 5.6% out of total 107 farmers Shiranuhi fields under polyethylene film house, and average percentages of diseased tree in 31 fields of Shiranuhi cultivar and adjacent satsuma mandarin fields were 0.02% and 14.8%, respectively. Average percentage of diseased fruit was 1.6% in satsuma mandarin which was not observed in anyone of all the 31 Shiranuhi farmers fields. Therefore, it was concluded that 'Shiranuhi' cultivar is not potential against causal pathogen of citrus canker disease in Jeju Island because the cultivar has similar resistance as satsuma mandarin which occupies over 95% of total 25,000 ha in Jeju Island in polyethylene film houses protected from outside.

• Korean Journal of Microbiology
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• v.33 no.4
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• pp.262-266
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• 1997

Total, direct viable count, and acid-tolerant epiphytic bacterial population sizes were quantified on leaves of chestnut tree (Castanea crenata S. et Z.) near Taejon Industrial Estate affected by acid precipitation and deposition as well as in the clean natural forest area, Mt. Kyejok, in Taejon city from August 1996 to August 1997. Geometric mean numbers of total, direct viable count, and acid-tolerant epiphytic bacteria were $9.9{\times}10^5cell/cm^2$, $1.6{\times}10^6cell/cm^2$, and $7.1{\times}10^3cfu/cm^2$ respectively, being 1.5, 2, and 2.6 times those in the clean area. Acid-tolerant epiphytic bacterial numbers at pH 5.6 by MPN method were $3.3{\times}10^4$ in the industrial area, about the same as the number, $3.4{\times}10^4MPN/cm^2$, of the clean area. Acid-tolerant bacterial number at pH 4.0 was $1.9{\times}10^{-1}MPN/cm^2$ in the industrial area, whereas none was detected in the clean area. Acid-tolerant bacteria at pH 3.0 were not detected at all in the industrial area as well as in the clean area. Epiphytic bacterial population sizes were generally the greatest in May when leaves are emerged and grew hut the lowest in November when defoliation occurs. These results showed that air pollutant deposition on leaves did not cause a decrease of epiphytic bacteria at least and acid deposition on leaves did cause an increase of acid-tolerant bacteria.

• Journal of Korean Society of Forest Science
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• v.47 no.1
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• pp.1-15
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• 1980

The occurrence of witches' broom of Rhus javanica was first noticed in Korea by the author in 1979. Subsequently, studies were made on the symptomatology, etiology, and transmission of the disease, as well as the effect of some antibiotics on the disease development. The results of these studies are summarized as follows: 1. Symptoms of the infected plant were characterized by dwarfing of the tree accompanied by yellowing and brooming of the foliage. 2. Electron microscopy of witches' broom diseased Rhus javanica plant revealed the occurrence of numerous mycoplasma-like organisms (MLO's) in the phloem tissue cells (sieve tube elements and phloem parenchyma cells) of the rachis and midribs of infected leaves. 3. The MLO's were bounded by a single unit membrane and contained ribosome-like granules and strands presumed to be DNA. It also appears that the MLO multiply possibly by budding as well as binary and plurinary fission. 4. In the midrib of healthy leaves, vascular bundles were collaterally discontinuous. In the diseased leaves, however, xylems were connected to each other and phloem cells showed an atrophy. Granules, which were prominent in the normal abaxial epidermis, were not observed in the peidermis of diseased leaves. 5. Electron microscopy revealed crystals or osmopholic granules in the phloem parenchyma cells, and that normal stacks of grana were not developed in the chloroplasts of infected levels. 6. The disease was experimentally transmitted by grafting. Budding was more effective than crown grafting for transmitting the disease. The disease has been transmitted by grafting even when complete union of stocks and scions has not taken place. The disease agent was not transmitted by sap inoculation. Insect transmission has not been confirmed. 7. Dipping the roots of infected plants into the 500 ppm and 1,000 solutions of either tetracycline HCI or oxytetracycline, HCI was more effective on temporary remision of the symptoms than spraying the 100 ppm and 200 ppm solutions of the same antibiotics. A greater effect was achieved through dipping into 1,000 ppm than into 500 ppm.

• Fire Science and Engineering
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• v.26 no.1
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• pp.49-60
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• 2012

The change in fuel moisture in accordance with the number of days after rainfall is an important factor in predicting forest fire dangers and supporting forest fire rangers. Therefore, in order to clear up these forest fire occurrence conditions, forest fire danger levels for surface fuel 0.6 cm or lower, 0.6~3.0 cm, 3.0~6.0 cm, and 6.0 cm or above by fallen leaves layer, humus layer, soil layer, and diameter after rainfall of 5.0 mm and higher in accordance with tree density in 2008, 2009 Spring/Autumn Young Dong region have been analyzed. Research showed an approximate 17 % fuel moisture which is a dangerous forest fire occurrence level after 5 days from rainfall in medium-density areas and 3 days after rainfall in loose-density areas of Spring time in the fallen leaves layer. On the other hand, the humus layer showed a 40 % or higher fuel humidity even after 6 days from rainfall regardless of the season, while the upper and lower parts of the soil layer had a little change. In loose-density areas with 0.6 cm or less surface fuel per diameter in Spring time, the fuel humidity displayed a dangerous level in fire forest occurrence after 3 days, and 4days in medium-density areas, and for loose-density areas with 0.6~3.0 cm surface fuel per diameter in Autumn time it showed a dangerous level in forest fire occurrence after 3 days, and for medium-density areas, 5 days. In the case of 3.0~6.0 cm of fuel moisture per diameter in both Spring and Autumn times, even after 6 days, low and medium-density areas showed that they maintain fuel moisture and therefore the dangers of forest fires were very low, and in the case of 6.0 cm or higher, it showed 25 % or higher fuel moisture even after 6 days from rainfall regardless of the season.

• Korean journal of applied entomology
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• v.36 no.1
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• pp.111-117
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• 1997

Occurrence status of Tetranychus viennensis Zacher was investigated in Kyonghuk province. Its ecological studies were carried out and chemical control efficacy against females and eggs was examined. And the results ohtained are as follows. T. viennensis occurred from mid April through mid November with the peak time in June on cherry tree. Population level of T. viennensis was varied from 0 to 160 individuals per 100 peach leaves in different peach orchards, and its occurrence rate was 35% out of 20 ochards. However no T. viennensis was observed from 25 apple orchards in 5 districts of Kyongbuk province. Overwintering stage of T. viennensis females appeared in mid October, and most of them moved into under the rough hark in early November. The overwintered adult females moved out from the rough bark to leaves in early April. Mortality during overwintering was about 55%. Under four constant temperatures of 16, 19, 22, 25$^{\circ}$C. egg periods were 14. 3, 9.2, 6.8, and 4.0 days ; larva -nymph periods were 20.2, 13.9, 8.7, and 6.6 days. Female longevity was 67. 7, 60.7, 46.4, and 34.0 days : mean tota: fecundities per female were 21.2, 44.3, 54.4, and 64.7 eggs. Some acaricides, azocyclotin, pyridaben, propargite, tehufenpyrad and fenpyroximate were highly effective against females, while hexythiazox and clofentezine showed very low control effect from 3.6 to 14.4%. Whereas, all of 7 acaricides tested highly effective against the eggs.

• Korean Journal of Agricultural and Forest Meteorology
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• v.16 no.4
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• pp.267-273
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• 2014

This study is to compare drought-resistance and to find the permanent wilting coefficient of Syringa Dilatata, Euonymus Japonica, Ligustrum Obtusifolium, Nandina Domestica, which are commonly used for rooftop garden due to their relatively strong drought resistance To compare the drought resistance precipitation was blocked from June 4, 2013 to July 20, 2013. During this time, the relative water content, specific electrical conductance, and water potential were measured every seven days and permanent wilting coefficients were investigated. Two days after precipitation was blocked, the relative water content in leaves were measured as follows: Ligustrum Obtusifolium 91.3%, Syringa Dilatata 92.9%, Nandina Domestica 91.2%, and Euonymus Japonica 90.1% respectively. After 28 days, relative water contents of leaves were reduced greatly 60.2% for Ligustrum Obtusifolium and 67.8% for Syringa Dilatata, but Nandina Domestica and Euonymus Japonica's reduced to 80.1% and 81.7% respectively. Permanent wilting coefficient was Ligustrum Obtusifolium 3.1%, Syringa Dilatata 2.1%, Nandina Domestica 1.6% and Euonymus Japonica 0.7%. In other words, the above four tree species are strong in drought resistance and Euonymus Japonica's drought resistance is the strongest while Nandina Domestica, Syringa Dilatata, Ligustrum Obtusifolium follow in that order.

• Journal of Bio-Environment Control
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• v.18 no.4
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• pp.481-491
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• 2009

This study was conducted to observe some characteristics of aneuploid trees obtained from the crosses between diploid and triploid in the first experiment. The results showed that the difference among the percentage of aneuploid's pollen grain germination was large, and all of them were lower than that of diploid 'Hongro' (82.4%). The average weight and size of each aneuploid's fruit was far lighter and smaller than that of diploid 'Hongro'. According to the width and length, all of the fruits shape was flat or short-globose conical shape except for JF3942. Almost all the aneuploid had higher sugar content than 'Hongro', nearly half of aneuploid fruits were firmer than that of diploid 'Hongro'. As for the acid contents of aneuploid fruits, the results were greatly different from those of previous studies on diploid apples, in present study the citric acid and tartaric acid contents were more than the malic acid which are dominant acid in most cultivars of apples. Both the length and width of aneuploid tree were shorter than that of diploid 'Hongro'. Most aneuploid trees' height was longer than width, but there were 4 exceptions. The size of leaves was smaller than that of diploid 'Hongro' according to the length and width of leaves measured. In all, aneuploid's vegetative growth is not as vigorous as diploid.

• Korean Journal Plant Pathology
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• v.13 no.3
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• pp.145-151
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• 1997

An unusual young fruit rot of apple caused by two species of Phytophthora was epidemic from late May to early July of 1996 in Andong, Uisung and Chungwon areas of Korea. The disease spread to over 30 apple orchards in the areas and percent of the infected tree and fruit was ca. 10~90% and 1`15%, respectively. Water soaking lesions or spots on leaves and shoot blight were also developed by the pathogen. Among 39 isolates collected, 25 were identified as P. cactorum and the others were as zp. cambivora on the basis of their distinctive morphological characters. While the former fungus was homothallic, all isolates of the latter were A1 mating types. Koch's postulate was fulfilled. Both fungi showed strong pathogenicity not only to young fruits, leaves and shoots of apple but also to those of pear and peach. Several vegetables tested did not show symptoms even by wound inoculation. An Occurrence of young fruit rot of apple caused by Phytophthora has not been reported in Korea, especially, P. cambivora has not been recorded previously as the causal agent of the disease in the world.