• The Plant Pathology Journal
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• v.17 no.4
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• pp.231-235
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• 2001

From April to May 1998, Phytophthora rot on pear, which has not been reported in Korea before, became an epidemic in the southeast part of the country under abnormally higher temperature and prolonged rainy days. Average temperature was about $3^{\circ}$ higher than in normal years, and 29 days were rainy during the 2 months in the areas surveyed. Over 1,000 orchards estimated at about 270 ha in 19 cultivation areas were infected by the disease, which occurred on all parts of the tree such as leaves, shoots, branches, stems, and flower clusters. Among 43 isolates collected from various locations and plant parts, 41 were identified as Phytophthora cactorum while 2 were identified as P. cambivora based on their mycological characteristics. The representative isolates revealed strong pathogenicity not only to pear but also to apple and peach. Among 23 pear cultivars tested, 7 were estimated as susceptible, 4 were moderate, and 11 were resistant to the pathogen. Results suggest that Phytophthora disease on pear is a potential threat to pear cultivation when environmental factors are favorable to disease development.

• Korean Journal of Plant Resources
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• v.37 no.1
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• pp.62-70
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• 2024

Fruit thinning rate and characteristics were investigated for three years on seven promising pear (Pyrus pyrifolia Nakai) cultivars, which were treated by lime-sulfur as an eco-chemical thinning substance. Lime-sulfur was treated twice at the second and third days after full bloom by cultivar. Most of pear cultivars were significantly thinned by lime-sulfur compounds. Especially 'Whangkeumbae', 'Supergold' and 'Hanareum' exhibited high flower thinning rates, 41.5%, 40.1% and 39.9%, respectively. As weather conditions at the lime-sulfur treatment, insolation and cloud amount were correlated with flower thinning rate but not significant (r = 0.49 and r = -0.45, respectively). These results suggest that lime-sulfur is suitable for reducing labor force for flower thinning of Korean pears but flower thinning effects of lime-sulfur can vary depending on other factors such as environmental conditions. This information will provide useful data for low labor force cultivation of Korean pear cultivars.

• Korean Journal Plant Pathology
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• v.10 no.3
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• pp.169-174
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• 1994

A new unidentified pear leaf spot disease presumed to first occur in the late 1970's has recently become prevalent over the pear growing areas, and caused the greatest problem for pear production in Korea. The disease began to develop on pear leaves at mid- to late May, peaked at mid- to late une, but stopped further development until September in cool climate. Leaf lesions are 0.9∼2.5 mm in diam., oval or irregular to rectangular in shape, first appeared reddish purple, later changed to dark brown, and to whitish grey in the late season. Lesions were limited to appear only on the mature, hardened leaves, initially from leaf margin or near the leaf veins, and later scattered over the leaf surface. Individual lesions usually did not enlarge, but often coalesced each other, commonly causing shot holes and eventual early falling. The disease was most severe on the major pear cultivars Niitaka and Okusankichi ranged with 4 to 100% infections in trees, depending on the orchards, but not on the cultivar Chojuro. Damages from the disease included lower fruit weight, and higher acid and less sugar content in fruits, resulting in lowering the overall fruit quality. Etiology of the disease including identification of the causal organism is in a separate paper.

• Horticultural Science & Technology
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• v.30 no.2
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• pp.208-213
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• 2012

This study was performed to compare antioxidant activities of 80% EtOH extracts from young and mature fruit of three pear cultivars ('Wonhwang', 'Whangkeumbae', and 'Chuwhangbae') classified by three parts (peel, core, and flesh) of mature fruit. The total phenolics compound and flavonoid contents of 80% EtOH extracts from young fruit were 1.5-2.5 times higher than the mature fruit with great cultivar difference. In particular, the contents of those compounds were highest in 'Chuwhangbae' pear. The total phenolics compound and flavonoid contents of 80% EtOH extracts from mature fruit were the most in the peel, core, and flesh respectively. DPPH radical scavenging and $ABTS^+$ radical scavenging of 80% EtOH extracts from the young fruit were higher than the mature fruit of 'Chuwhangbae' pear. DPPH radical scavenging and ABTS+ radical scavenging of 80% EtOH extracts from mature fruit were the highest in the peel, core, and flesh respectively.

• Food Science and Biotechnology
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• v.15 no.1
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• pp.44-50
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• 2006

Contents of phenolic compounds in peel, flesh, and core of three Asian pear cultivars, Hosui, Niitaka, and Chuwhangbae, were determined at different stages of maturity. Antioxidant properties of methanol extracts of peels at various fruit maturity stages were also evaluated. Total phenolic content decreased with maturity. Arbutin, chlorogenic acid, and epicatechin were major phenolic compounds in young fruits. Catechin, 4-hydroxymethyl benzoic acid, and caffeic acid were detected in peel and core of immature and mature pears. 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activities of methanol extracts were 16.30 and $15.73\;{\mu}g$ in peel of immature Hosui and Chuwhangbae pears, respectively, and $11.59\;{\mu}g$ in mature Niitaka pears, which was significantly higher than those of other maturity stage in the same cultivar. Inhibitory activities on lipid oxidation of methanol extracts of three cultivars at all maturity stages were similar to that of ${\alpha}$-tocopherol.

• Horticultural Science & Technology
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• v.33 no.5
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• pp.712-721
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• 2015

To improve the breeding efficiency of oriental pear, heritability, correlation and frequency distribution of fruit ripening date were analyzed using 4,035 seedlings obtained from 15 families between 13 parental cultivars. Although variation of fruit ripening time was higher in most early-ripening parental cultivars than in late-ripening parental cultivars, according to analysis of average, standard deviation, and coefficient of ripening variation for ten years, fruit ripening time obtained from all parental cultivars was inherited narrower and more stable variation than others fruit trait, with 0.92-3.41 in coefficient of variation. The heritability of fruit ripening time was calculated to be over 0.8 in almost all crosses and average fruit ripening time of seedlings from cross combinations could be predicted based on that of the parental cultivars due to its superior heritability relative to other fruit traits. The average ripening time was earlier than the mid-parental value in families obtained from cross combinations using at least one late-ripening cultivar as parent, indicating that the early-ripening trait was more likely to be dominant compared to the late-ripening trait. By contrast, average ripening time was clustered in families of crosses not only between mid-season and early-season cultivars, but also between mid-season and mid-season cultivars. There was highly significant relationship (at 0.68) between mid-parental and progeny mean fruit ripening time. The correlation between fruit ripening time and fruit weight was also highly positive and thus, the mid-parental fruit ripening time could be a potent criterion for indirect selection of fruit weight.

• Microbiology and Biotechnology Letters
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• v.37 no.3
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• pp.213-218
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• 2009

The goal of this study was to develop new functional pear wine using six Asian pears (Pyrus pyrifolia, Nakai), namely Wonhwang, Niitaka, Whangkeumbae, Whasan, Gamcheonbae and Chuwhangbae. To select optimal yeast and pear, we investigated the physicochemical properties of the pear wines from fermentation of musts of six pear cultivars at $25^{\circ}C$ for 7 days by several yeasts. $11.2%{\sim}12.4%$ of ethanol from musts of 'Wonhwang', 'Whangkeumbae' and 'Whasan' were produced by Saccharomyces cerevisiae K-7 and 12.8% of ethanol was also produced from 'Niitaka' by commercial Saccharomyces cerevisiae C-2. 9.9% and 11.4% of ethanol were produced from musts of 'Gamcheonbae' and 'Chuwhangbae' by Saccharomyces cerevisiae KCTC 7904, respectively. Among several pear wines, Niitaka pear wine showed the best acceptability in the sensory evaluation, and Niitaka pear wine and Whangkeumbae pear wine showed 31.1% and 27.8% of antihypertensive angiotensin I-converting enzyme(ACE) inhibitory activity, respectively. However, the other functionalities were not detected or very low. Furthermore, Niitaka-strawberry mixed fermentation wine was showed the excellent acceptability and high antihypertensive ACE inhibitory activity of 64.9%.

• Korean Journal of Agricultural Science
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• v.38 no.3
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• pp.405-411
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• 2011

In this study, we evaluated the changes of fruit quality indices during fruit development and ripening in Korean new pear cultivar 'Wonhwang' and 'Whasan' to determine appropriate harvest time and to enhance the marketability. The fruit of each cultivar harvested from 100 days after full bloom (DAFB) to 135 and 150 DAFB in 'Wonhwang' and 'Whasan', respectively. The fruit growth of both cultivars showed a typical single sigmoidal pattern. Flesh firmness of two cultivars decreased continuously with fruit development and ripening, reaching a final level of about 2.6 kgF at harvest stage. The starch content of fruit sap was much higher in the fruits of early development stage than the later stage of fruit ripening. In 'Wonhwang' pears, the starch level decreased coincide with fruit ripening (130 DAFB), while that of 'Whasan' decreased from very early stage of fruit development (120 DAFB), 30 days before full ripe. 'Whasan' pear showed much lower acidity level of about 0.13% during fruit development and ripening period compared with that of 'Wonhwang'. Therefore, the ratio of soluble solids to total acidity (TSS/acid) increased gradually with fruit development and ripening, reaching a final level of 80 and 98 in 'Wonhwang' and 'Whasan', respectively. There were no climateric rise of fruit respiration during fruit ripening periods in two oriental pear cultivar. The changes of skin color difference including hunter vale $a^*$ which means loss of green color occurred only after onset of ripening in two cultivars.

• Research in Plant Disease
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• v.16 no.3
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• pp.326-330
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• 2010

Three pome fruit viruses, Apple chlorotic leaf spot virus (ACLSV), Apple stem grooving virus (ASPV) and Apple stem pitting virus (ASGV) were detected in pear trees (Pyrus pyrifolia) using double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) in Ansung, Naju and Ulsan provinces of Korea. Infection rate of three viruses was 35.2% from 452 leaf samples of the three cultivars of pear trees. Also, each of three viruses was detected by reverse transcription polymerase chain reaction (RT-PCR) for a limited number of samples. Infection rate of three viruses was 86.3% from 233 leaf samples of the three pear cultivars. The virus infection rates by RT-PCR were much higher than ELISA. ASGV was prevailing on pear with 74.2%, whereas ASPV and ACLSV were found in 34.8% and 0.4% of tested samples, respectively. Symptoms caused by ASGV showed black spots of infected Niitaka cultivar leaves. The ACLSV, ASPV and ASGV isolates showed 83~94% sequence identity at a nucleotide level to other pome fruit virus isolates when analyzed by NCBI BLAST. Pome fruit viruses occurring in pear were ACLSV, ASPV and ASGV. This is the first report of pear trees infected ASPV in Korea.

• Horticultural Science & Technology
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• v.29 no.6
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• pp.645-650
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• 2011

Pear cultivar 'Supergold' (Pyrus pyrifolia var. culta Nakai) was originated from the cross between 'Chuwhangbae' and 'Manpungbae' with the aims of improving the fruit quality of 'Chuwhangbae' cultivar at Pear Research Station of National Institute of Horticultural & Herbal Science, Rural Development Administration in 1994. 'Supergold' was preliminarily selected in 2002 and named in 2008. The tree shows a vigorous growth habit and semi-spread characters like as 'Manpungbae'. Furthermore, it has sufficient flowers and carries abundant pollen grains, so it can also be used as a pollinator. 'Supergold' is highly resistant to black leaf spot (Alternaria kikuchiana) in the field condition. The optimum harvest time is around Sep. 11th, which is ahead of 'Whangkeumbae' about 5 days in the harvest period. The fruit shape is oblate and fruit skin color is greenish-white at harvesting time. The average weight of fruit is 570 g, and the soluble solids content is $13.6\;^{\circ}Brix$. The flesh is very soft and juicy, and renders good eating quality. Shelf life is about 6 months under the cold storage condition. To determine the self-incompatibility (SI) genotype of 'Supergold' pear cultivar, it was crossed with other cultivars of which SI genotypes have already known. The result of cross-pollinations of 'Supergold' with other cultivars showed relatively high rates of fruit set from 64.5% to 91.0%, except for the cross with pollens of 'Nijisseiki' that represented only 28.8% of fruiting rate. Although sometimes the stigma of 'Supergold' crossed with 'Hayatama', 'Chojuro', and 'Nijisseiki' showed malformed pollen tube tips, 'Supergold' is generally supposed to have cross-compatibility with all other pollen donor cultivars. It is considered that the S-allele of 'Supergold' is $S_3S_4$, which is based on the result of PCR-RFLP.