• Korean Journal of Plant Resources
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• v.36 no.6
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• pp.571-579
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• 2023

In this study, cryopreservation by droplet-vitrification was applied to pear (Pyrus spp.) germplasm. We focused on the development and assessment of various strategies for the selection of suitable tissue, osmoprotection, and dehydration. We also evaluated post-thaw recovery of cryopreserved explants by droplet-vitrification. Preferentially, we tested the effects of preculture and loading treatments to determine which tissues were more suitable, either the apical shoot tips or the axillary buds. Apical shoot tips showed the better regrowth rate than in vitro axillary buds. The most effective techniques for cryopreservation were as follows. Shoots from in vitro seedlings which had been cultured for about 5-6 weeks were cold-hardened at 4℃ for one week, excised shoot tips were precultured on liquid MS medium including 0.3 M sucrose for 31 hours and 0.7 M sucrose for 17 hours, osmoprotected in loading solution (LS) for 40 min, and then cryoprotected in dehydration solution (PVS3) for 90 min. In addition, we found that regrowth rates of explants on regrowth medium after exposure to liquid nitrogen (LN) were higher than those on MS medium. Results indicated that the highest regrowth percentage was 95.6% for 'Bartlett' cultivar and 68.9% for 'BaeYun No.3' cultivar. Consequently, apical shoot tips of two pear cultivars, 'Bartlett' (P. communis) and 'BaeYun No.3' (P. pyrifolia), were successfully cryopreserved by droplet-vitrification. Results of this study show that the enhanced droplet-vitrification method described in the present study could be used as an effective means for long-term storage of pear genetic resources.

• Horticultural Science & Technology
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• v.33 no.4
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• pp.486-491
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• 2015

In this study, we evaluated the differences in fruit development and quality indices of fruits subjected to blossom thinning before full bloom in 'Hanareum' and 'Niitaka' pears (Pyrus pyrifolia Nakai). We carried out a thinning treatments at 5 days before full bloom, targeting the blossoms at the 1st and 2nd position (T1) or the blossoms at the 6th and 7th position (T2) from the basal part of the flower cluster in both cultivars. Blossom thinning treatments increased the average fruit weight of early-season Asian pear 'Hanareum' up to 10.5% (T1) and 11.0% (T2) at harvest time (110 days after full bloom). The mid-season 'Niitaka' pear showed increased fruit weight of up to 12.6% (T1) and 16.8% (T2) at harvest time (170 days after full bloom). Moreover, these treatments increased the production rate of bigger sized fruits in both cultivars. Removal of blooms also affected fruit quality indices; the bloom-thinned fruits showed higher soluble solids contents (about $1^{\circ}Brix$) and higher skin color redness ($a^*$) especially in 'Niitaka' pears when compared to the non-thinned controls. Overall, the treatments increased the fruit size and weight as well as fruit quality including soluble solids and skin color. Bloom thinning treatment targeting the 6th to 7th blossom from the basal part of the flower cluster may be recommended as the practical thinning method in Asian pear 'Hanareum' and 'Niitaka'.

• Korean Journal of Food Science and Technology
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• v.34 no.2
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• pp.180-185
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• 2002

Volatile flavor components in three pear varieties (Pyrus pyriforia N.) of traditional cultivar, Bongri, Hwangsilri and Yongmokri, were collected by SDE method using the mixture of n-pentane and diethylether as an extract solvent and were identified by GC/MS. Among 97 compounds identified from all varieties, there were 72, 58 and 66 components in Bongri, Hwangsilri and Yongmokri, respectively. Ethyl acetate was the dominant constituent in all cultivars and also volatile profiles contained large quantity of ethanol and acetic acid. Butyl acetate identified as a main component in Bongri was not found in other pears, but in Hwangrilri and Yongmokri only 4 to 5 esters played important role in total volatile flavor composition. The volatile profiles of these three varieties were characterized by compounds in group of aldehydes, esters, alcohols, acids and ketones. As classified by functional group of separated and identified components, esters and alcohols in Bongri, alcohols in Hwangsilri, and esters in Yongmokri were roled as the title in composition of volatile flavor components. Although small amount, Yongmokri had the highest rate of volatile production at 6.552 mg/kg of pear while Hwangsilri produced the lowest at 4.175 mg/kg of pear.

• Korean Journal of Food Science and Technology
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• v.39 no.1
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• pp.7-13
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• 2007

The changes in phenolic compounds and pectin content were investigated during the growth of 3 cultivars (Hosui, Niitaka and Chuwhangbae) of Asian pear (Pyrus pyrifolria) fruits. The amounts of total phenolic compounds in peel, flesh and core was 20.61-22.98mg/g, 0.87-1.23mg/g and 6.39-37.96mg/g during early growth, respectively, and decreased with pear growth. Arbutin, chlorogenic acid and epicatechin were detected in each part of all three cultivars during early growth; of these, arbutin content was the highest. Caffeic acid, catechin and 4-hydroxymethyl benzoic acid were detected in the peel and core during the ripening process. The total pectin content in the flesh of Hosui, Niitaka, and Chuwhangbae cultivars decreased from 5.93mg/g, 5.99mg/g and 5.40mg/g to 1.07mg/g, 1.60mg/g and 1.63mg/g, respectively. Of the soluble pectins, the hydrochloric acid-soluble pectin content was the highest, 3.21-3.45mg/g, and decreased during growth.

• Korean Journal of Food Science and Technology
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• v.40 no.5
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• pp.491-496
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• 2008

Properties of pectin extracted from flesh of Asian pear in 3 cultivars were investigated at different growth stages. The extraction yields of pectin by the acidic treatment decreased during the growth. The $L^*$ value of young fruit was lower than unripe and ripe fruit, and $a^*$ and $b^*$ value were higher in the same cultivars. The degree of esterification (DE) and intrinsic viscosity of pectin were 21.1-41.3% and 1.90-3.81 dL/g, respectively. The pectin extracted from flesh of pear showed about 30% glucose retarding effect. The DE value had a high correlation with retarding effect on glucose transport and intrinsic viscosity (p<0.01 and p<0.05). The intrinsic viscosity of the pectin seems to affect the retardation of glucose transport in blood. Pectin extracted from flesh of Asian pear by acidic treatment could be a good source to develop low calorie and functional food.

• 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.

• Journal of Plant Biotechnology
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• v.42 no.1
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• pp.25-33
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• 2015

A PyrcpPR-10 gene with differentially expressed was isolated by using the suppression subtractive hybridization assay between '93-3-98' (highly resistant against scab caused by Venturia nashicola) and 'Sweat Skin'(highly susceptible) and analyzed the expression pattern according to organs and cultivars. The full length of PyrcpPR-10 was cloned as 743bp with 480bp's ORP, and was determined to encode a protein of 159 amino acid residues. On analyzing PyrcpPR-10 gene sequence compared with resistant and susceptible cultivars, 'Hwangsilri' (resistant), 'Gamcheonbae' (moderately resistant), 'Wonhwang' (moderately susceptible), 'Niitaka' (highly susceptible), and 'Sweat Skin' (highly susceptible) had identical gene sequence but 'Bartlett' (highly resistant) showed partly different sequences. The deduced amino acid sequence showed 64 ~ 98% homology and had the GXGGXG motif to known amino acid of other plants PR-10 by the BLAST X analysis. Among several organs or tissues, petal was showed highest expression level of PyrcpPR-10 gene followed by leaf, floral axis, bud, and bark. The expression level of PyrcpPR-10 gene was dramatically increased at 24 hr after inoculation in all cultivars and also up-regulated in accordance with resistant degree of cultivars. While resistant cultivars ('Bartlett', '93-3-98', and 'Hwangsilri') induced relatively high expression level of PyrcpPR-10 gene, susceptible cultivars ('Niitaka', and 'Sweat Skin') showed low expression level. PyrcpPR-10 gene is assumed that it is directly connected with defense mechanisms to pear scab.

• Horticultural Science & Technology
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• v.35 no.1
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• pp.98-107
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• 2017

A DNA profile database was constructed to investigate the genetic relatedness of 72 germplasm samples of Pyrus and related cultivars using microsatellite markers. Three P. pyrifolia, four P. commus, and one P. betulifolia cultivars with different morphological traits were screened using 387 pairs of microsatellite primers. A core set of 11 primer pairs was selected to obtain 133 polymorphic amplified fragments meeting three criteria: high polymorphism information contents (PIC), high repeatability, and distinct allele patterns. The number of alleles per locus ranged between 4 and 22. Average PIC was 0.743 (range: 0.557 - 0.879). Cluster analysis using the unweighted pair - group method with arithmetical average (UPGMA) separated the 72 pear cultivars and germplasm samples into four major groups: Chinese, European pears, and a cluster of 55 Asian pears that could be reclassify into two subcluster, I - $1^{st}$ and II - $2^{nd}$, according to pedigree information. Almost all of the cultivars were discriminated by 11 microsatellite marker genotypes. The microsatellite DNA profile database may be utilized as tool to verify distinctness, uniformity, and stability between candidate cultivar, and to verify in the distinctness of existing cultivars.

• Horticultural Science & Technology
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• v.31 no.4
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• pp.512-516
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• 2013

Pear cultivar 'Sinhwa' (Pyrus pyrifolia var. culta Nakai) was originated from a cross between 'Niitaka' and Whasan' with the aims of improving the fruit quality and the traits of cultivation and of early maturing more than 'Whasan' cultivar at Pear Research Station of National Institute of Horticultural & Herbal Science, Rural Development Administration in 1995. 'Sinhwa' was preliminarily selected in 2004 and named in 2009. The tree shows vigorous growth habit and semi-spread characters like 'Niitaka'. Furthermore, it has a sufficient and well upkeep of the flower bud, so it can be more easily cultivated in orchards. In the flower characteristics, flowering time of 'Sinhwa' is $11^{th}$ April like as maternal parent 'Niitaka'. Also 'Sinhwa' has short of pollen grains, so it is need above two pollinizer cultivars. 'Sinhwa' is highly resistant to black leaf spot (Alternaria kikuchiana) and relatively strong to pear scab (Venturia nashicola) in field condition. The optimum harvest time is around Sep. $15^{th}$ in Naju, which is ahead of 'Whasan' about 10 days in the harvest period. The fruit shape is oblate and fruit skin color is yellowish-brown during harvesting time. The average weight of fruit is 627 g, and the soluble solids content is $13.0^{\circ}Brix$. The flesh is very soft and juicy, and renders good eating quality. Shelf life is about 30 days under the room temperature condition.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2022.09a
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• pp.36-36
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• 2022

The molecular understanding of resistance and susceptibility of host plants to scab, a most threatful disease to pome fruit production worldwide, is very limited. Comparing resistant line '93-3-98' to susceptible one 'Sweet Skin' at seven time points of 0, 0.5, 1, 2, 3, 4, 8 days post inoculation, RNA-sequencing data derived from infected and mock-inoculated young leaves were analyzed to evaluate the tolerant response and to mine candidate genes of pear to the scab pathogen Venturia nashicola. Analysis of the mapped reads showed that the infection of V. nashicola led to significant differential expression of 17,827 transcripts with more than 3-fold change in the seven pairs of libraries, of which 9,672 (54%) are up- and 8,155(46%) are down-regulated. These included mainly receptor (NB-ARC domains-containing, CC-NBS-LRR, TIR-NBS-LRR, seven transmembrane MLO family protein) and transcription factor (ethylene responsive element binding, WRKY DNA-binding protein) related gene. An arsenal of defense response of highly resistant pear accessions derived from European pear was probably supposed no sooner had V. nashicola infected its host than host genes related to disease suppression like Polyketide cyclase/dehydrase and lipid transport protein, WRKY family transcription factor, lectin protein kinase, cystein-rich RLK, calcium-dependent phospholipid-binding copine protein were greatly boosted and eradicated cascade reaction induced by pathogen within 24 hours. To identify transcripts specifically expressed in response to V. nashicola, RT-PCRs were conducted and compare to the expression patterns of seven cultivars with a range of highly resistant to highly susceptible symptom. A DEG belonging to the PR protein family genes that were higher expressed in response to V. nashicola suggesting extraordinary role in the resistance response were led to the identification. This study provides the first transcriptional profile by RNA-seq of the host plant during scab disease and insights into the response of tolerant pear plants to V. nashicola.