• 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 Breeding Science
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• v.41 no.4
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• pp.444-450
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• 2009

Amplified fragment length polymorphism (AFLP) marker was utilized for evaluation of genetic diversity of 60 pear germplasms. Twenty selective AFLP primer pairs generated a total of 522 polymorphic amplification products. From UPGMA (unweighted pair-group method arithmetic average) cluster analysis by using polymorphic bands, the pear germplasms were divided into four clusters by similarity index of 0.691. The first cluster (I) included European pears belonging to Pyrus communis and wild species such as P. nivalis and P. cordata. The second cluster (II) included Ussurian pea pears belonging to P. betulaefolia and P. fauriei. The third cluster (III) included pea pears belonging to P. calleryana and P. koehnei. Most of germplasms belonging to P. pyrifolia and P. ussuriensis, and interspecific hybrids were included in the fourth (IV) cluster. Therefore pear germplasms originated from East Asia were closely related to P. pyrifolia and P. ussuriensis. Similarity values among the tested pear germplasms ranged from 0.584 to 0.879, and the average similarity value was 0.686.

• Journal of Plant Biotechnology
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• v.43 no.4
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• pp.466-472
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• 2016

This study analyzed the genetic diversity of 115 pear germplasms using 15 SSR markers. Three to forty-one SSR alleles were detected for each locus with an average of 16 alleles per locus. The average availability of markers was 0.966. The average observed heterozygosity ($H_{obs}$) was 0.603 (range: 0.140 to 0.929). The average expected heterozygosity ($H_{exp}$) was 0.718 (range: 0.463 to 0.904). The average polymorphism information content (PIC) was 0.692 (range: 0.403 to 0.897). The genetic relationships of pear germplasms were classified into two major groups by geographic origins and genetic characteristics according to genetic distance. The first group was composed of European pear belonging to Pyrus communis. The second group consisted of P. pyrifolia, P. ussuriensis, P. bretschneideri, P. betulaefolia, P. calleryana, interspecific hybrids, and unclear germplasms. The results of this study suggest that genotype analysis of pear germplasms using SSR markers can identify the genetic diversity of germplasms, and can be used to provide basic information for pear breeding.