• Korean Journal Plant Pathology
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• v.11 no.3
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• pp.210-216
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• 1995

Alternaria spp.were predominantly isolated from the abnormal leaf spot lesions of pear cultivars Niitaka and Nijiiseiki. Alternaria isolates from the cultivar Niitaka were not pathogenic to both cultivars, but the isolates from the cultivar Nijiiseiki developed typical lesions of black leaf spots and were identified as A. kikuchiana. However, no typical abnormal leaf spot lesions were produced by the Alternaria isolates. Foliar spray of twelve different agrochemicals including lime sulfur, either alone or in combinations, with 7 times applications from April to July failed to reduced the disease development. Application of 17 different pesticides including fungicides, insecticides and herbicides currently used in pear orchards did not cause leaf injury similar to the abnormal leaf spot. Simulated acid rain of as low as pH 3.0 did not incite any leaf lesions alike the abnormal spot lesions. Mineral contents in the leaves of both cultivars did not differ significantly between the healthy leaves and those with abnormal leaf spots. When cuttings of pear tree were obtained in February from newly emerged twigs of the healthy or the diseased trees of Niitaka and planted in sand in the greenhouse, only those from the diseased trees developed typical leaf lesions of the abnormal spot. These results indicate that abnormal leaf spots are caused by unknown systemic agents in pear trees, rather than by Alternaria spp., chemical injury or acid rain.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11c
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• pp.533-542
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• 2000

Instrumentation and technologies are described for determining the vibration response characteristics of the pear with frequency range 5 to 320Hz. The computer program for controlling the vibration exciter and the function generator and for measuring the vibration response characteristics of the pear was developed. Mechanical properties such bioyield deformation, rupture deformation and apparent elastic modulus etc. were compared with the vibration response characteristics of the pear. The resonant frequency of the pear ranged from 53 to 102Hz and the amplitude at resonance was between 1.08 and 2.48g-rms. The resonant frequency and amplitude at resonance decreased with the increase of the sample mass, and they were slightly affected by mechanical properties such as bioyield deformation and rupture deformation. Regression analysis was performed among the relatively high correlated parameters from the results of correlation coefficient analysis.

• Nutrition Research and Practice
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• v.8 no.1
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• pp.33-39
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• 2014

Obesity occurs when a person's calorie intake exceeds the amount of energy burns, which may lead to pathologic growth of adipocytes and the accumulation of fat in the tissues. In this study, the effect and mechanism of pear pomace extracts on 3T3-L1 adipocyte differentiation and apoptosis of mature adipocytes were investigated. The effects of pear pomace extract on cell viability and the anti-adipogenic and proapoptotic effects were investigated via MTT assay, Oil red O staining, western blot analysis and apoptosis assay. 3T3-L1 preadipocytes were stimulated with DMEM containing 10% FBS, 0.5 mM 3-isobutyl-1-methylxanthine (IBMX), $5{\mu}g/ml$ insulin and $1{\mu}M$ dexamethasone for differentiation to adipocytes. 3T3-L1 cells were cultured with PBS or water extract of pear pomace. Water extract of pear pomace effectively inhibited lipid accumulations and expressions of PPAR-${\gamma}$ and $C/EBP{\alpha}$ in 3T3-L1 cells. It also increased expression of p-AMPK and decreased the expression of SREBP-1c and FAS in 3T3-L1 cells. The induction of apoptosis was observed in 3T3-L1 cells treated with pear pomace. These results indicate that pear pomace water extract inhibits adipogenesis and induces apoptosis of adipocytes and thus can be used as a potential therapeutic substance as part of prevention or treatment strategy for obesity.

• Korean Journal of Agricultural Science
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• v.44 no.1
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• pp.23-29
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• 2017

This study was conducted to explore which pollen type could be an effective pollen source for self-incompatible 'Niitaka' pear (Pyrus pyrifolia Nakai), when different pollinizers were to be applied. The pollens of five different pears with similar flowering times were applied to bagged 'Niitaka' flowers grown in Cheonan city, Korea. Pollen types used were of different origins including Korean pears ('Wonhwang' and 'Chuhwangbae'), Japanese pears ('Chojuuro' and 'Okusankichi'), and Chinese pear ('Yali'). Results show that the amount of pollen produced by flowers of each cultivar was the largest in Korean pear 'Wonhwang' (234 g/100 flowers) and the smallest in Japanese pear 'Okusankichi' (126 g/100 flowers). A high proportion of large fruits (> 600 g), 71.4% of total production, was found in the fruits treated with 'Yali' pollen. However, these fruits showed an unfavorable external appearance. Based on individual fruit width differences, 'Chojuuro' treatment produced the smallest difference in fruit diameters (3.2 mm) and 'Yali' treatment' gave the largest (4.8 mm). Also, the difference in fruit length was the largest in 'Yali' (7.5 mm), which also produced the most uneven fruits among the pollinizers used. Meanwhile, the use of pollens of 'Wonhwang' and 'Chuhwangbae' improved productivity by increasing the fruit shape index and the ratio of bigger fruits in total production. Moreover, those pollens also decreased the development of lenticels on fruit skins which gave them a smoother appearance.

• Journal of the Korean Society of Food Science and Nutrition
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• v.32 no.5
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• pp.700-705
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• 2003

Oriental pear was used as treatment of asthma, control of blood pressure tonic medicine vasoactio, diabetes in oriental medicine. In this study, it was investigated that pear pectin effects on cardiovascular system as blood pressure and renin and atrial natriuretic peptide (ANP) in plasma, cardiac hypertrophy. The experiments were performed on Sprague-Dawley rats, 2K1C hypertension model was prepared by constricting the left renal artery with a sliver clip. Animals were then divided into four groups, 5 mg/kg, 10 mg/kg, 15 mg/kg and the control, pear pectin and apple pectin solutions were supplied with them. The blood pressure was more decreased in pear pectin 10 mg/kg than in apple pectin. The plasma ANP was decreased in pear pectin 10 mg/kg, and renin was increased in same concentration of drug. Cardiac hypertrophy had a tendency to decrease in pear pectin 15 mg/kg, but was not statistically significant compared to control group.

• Food Science and Preservation
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• v.20 no.2
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• pp.222-226
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• 2013

This study was performed to confirm physiological activities according to parts of new pear cultivars (Gamcheonbae, Manpungbae, Chuwhangbae, Hanareum) and Niitaka pear. The total polyphenol compound contents of pear peel, flesh and core were 178~235, 95~113, 177~229 mg/100 g as tannic acid equivalent, respectively. There were differences in the contents by cultivars, Chuwhangbae and Hanareum cultivars showed high contents. The total flavonoid contents of the pear peel, flesh and core were 29.2~40.2, 24.3~34.3, 26.9~38.8 mg/100 g, respectively and those of Chuwhangbae and Gamcheonbae cultivars showed comparatively high values. The electron-donating ability was high in Chuwhangbae, Gamcheonbae and in the pear peel (29.7~57.7%), core (29.1~38.2%), flesh (7.6~17.7%), in that order. The nitrate scavenging activity was highest in that pear peel (21.0~49.8%), followed by the core (11.8~16.2%) and flesh (7.8~9.7%), but there was little difference by cultivar.

• Mycobiology
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• v.47 no.1
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• pp.76-86
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• 2019

Scab disease caused by Venturia nashicola is of agroeconomic importance in cultivation of Asian pear. However, little is known about the degree of genetic diversity in the populations of this pathogen. In this study, we collected 55 isolates from pear scab lesions in 13 major cultivation areas in Korea and examined the diversity using sequences of internal transcribed spacer (ITS) region, ${\beta}$-tubulin (TUB2), and translation elongation factor-$1{\alpha}$ ($TEF-1{\alpha}$) genes as molecular markers. Despite a low level of overall sequence variation, we found three distinctive subgroups from phylogenetic analysis of combined ITS, TUB2, and $TEF-1{\alpha}$ sequences. Among the three subgroups, subgroup 1 (60% of isolates collected) was predominant compared to subgroup 2 (23.6%) or subgroup 3 (16.4%) and was distributed throughout Korea. To understand the genetic diversity among the subgroups, RAPD analysis was performed. The isolates yielded highly diverse amplicon patterns and none of the defined subgroups within the dendrogram were supported by bootstrap values greater than 30%. Moreover, there is no significant correlation between the geographical distribution and the subgroups defined by molecular phylogeny. Our data suggest a low level of genetic diversification among the populations of V. nashicola in Korea.

• Korean Journal of Environmental Agriculture
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• v.35 no.3
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• pp.175-183
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• 2016

BACKGROUND: There's a long rainy season during the Summer in Northeast Asia, including Korea. Heavy rainfall during this season causes harm to tree's root, and damped injury in the pear has been continuously reported. Pear Research Institute is breeding damp resistant rootstocks and investigating their mechanisms to relieve damped damages in the pear.METHODS AND RESULTS: Seedlings of Pyrus betulaefolia and P. calleryana were divided into two groups: control and damped, respectively. Damped group was treated by constant irrigation for 77 days and control group was maintained to keep the soil moisture pressure between 0 and -10 kPa. After the treatment, we analysed trees' growth rate, chlorophyll content, amino acids and total phenolic compounds. As a result, P. betulaefolia was sensitive to damped treatment while P. calleryana did not have significant differences between the control and damped treatment. It was observed that total contents for phenolic compounds were dramatically increased in P. betulaefolia while trees' growth rate, chlorophyll b and general amino acid contents were lowered by damping treatment.CONCLUSION: In some pear cultivars, growth habit is suppressed by damped damage. Pyrus calleryana displayed tolerances to damped damage in growth rate and some organic compound contents compared to P. betulaefolia. So we recommend to exploit P. calleryana as a pear rootstock rather than using P. betulaefolia.

• Journal of the Korean Society of International Agriculture
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• v.23 no.5
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• pp.491-496
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• 2011

Breeding for pear resistance to pear psylla (Cacopsylla pyricola) is one of important objective of the National Institute of Horticultural and Herbal Science breeding program. One hundred thirty three accessions from 15 Asian, Chinese and European pear species were investigated for their resistance against pear psylla. The pear psylla resistance was determined based on the following four characteristics: overwintering adult population, the number of eggs and nymphs, and the degree of soot. The different pear species showed varied resistance to pear psylla. Pyrus calleryana and P. betulaefolia indicated the highest antixenosis as ovipositional preference and antibiosis as nymphal feeding and were the most resistant genetic resources. Likewise the European pears (P. communis), 'Conference' and 'Cascade', exhibited little occurrence and damage by pear psylla. These were proved to be promising genetic materials for breeding resistant cultivars because they had good fruit quality and showed resistance to pear paylla. The observed population of overwintering adult, the number of eggs and nymphs of psylla had significant correlation each other.

• Korean Journal of Environmental Agriculture
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• v.14 no.2
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• pp.144-154
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• 1995

This study was conducted for the evaluation of air-pollution using pear plant. Twenty-three sites around the Ulsan Industrial Complex Area were selected for the study. The water soluble sulfur content, photosynthetic rate and the visible injured index of pear leaves were evaluated and the results are summarized as follows: 1. Water-soluble sulfur content of pear leaves at survey sites was shown to be an average of 0.201%. The content of their leaves at polluted sites ranged from 0.220 to 0.496%. Water-soluble sulfur content of the pear leaves decreased as the distance became far from the Industrial Complex. 2. The photosynthetic rate of pear leaves decreased with an accumulation of water-soluble sulfur content. However it increased as the distance became greater within the five-kilometer radius of the pollutant. 3. More than 60% of injured rate was shown in pear plant within the five-kilometer radius of the pollutant in 1993. There were high correlations between the visible injured index items. Compared with 1988, the most severely injured sites in 1988 were Yochon-dong and Yaum-dong. But in 1993, they moved to the Yongcham-dong and Bugok-dong area. 4. Water-soluble sulfur content of pear leaves was correlated with the photosynthetic rate of pear leaves. The same tendency was shown between water-soluble sulfur and total injured index. This method using pear plant will be applied to the evaluation of air pollution.