The study was performed to investigate basic tree growth and fruit characteristics of ‘Nero’ black chokeberry (Aronia melanocarpa) depending on the different cultivation regions and altitudes in 2014, 2015. Tree growth and change of developmental stages of ‘Nero’ were similar regardless of meteorological environment of the four cultivation regions (Danyang, Okcheon, Yeongdong, and Geumsan) in 2014. Fruit characteristics of ‘Nero’ were significant differences in berry weight and anthocyanin content among the four orchards due to difference in cultivation techniques and relatively wide daily temperature range just before harvest, respectively. Tree growth and change of developmental stages of ‘Nero’ grown at the two orchards with different altitudes appeared to be similar during the successive years 2014 and 2015. Soluble solids content of the berries cultivated at low altitude (117 m) was higher than at high altitude (342 m). Acidity showed an inverse pattern with soluble solids content. Anthocyanin content increased progressively until at the middle of August, 2014-15 and then it decreased. Our results showed that black chokeberry is a species adaptive to the domestic environment as there were no differences in tree growth and change of developmental stages of ‘Nero’. Considering fruit quality of black chokeberry such as soluble solids content, acidity, and anthocyanin content, our results suggest that optimal harvest period of black chokeberry ‘Nero’ is August 8 to 19.

Effects of different soil water conditions on fruit characteristics were investigated in 5-year-old ‘Nero’ black chokeberry trees (Aronia melanocarpa). Three kinds of drought stresses, including low water deficit, severe water deficit, and very severe water deficit, due to decline of soil water decreased the fruit quality of weight of 10 berries, soluble solid content, and anthocyanin, compared with the control (consistent water supply) during the harvest period. After longer drought stress, supply of soil water could induce berry cracking because cell size of epidermis of fruits contracted, whereas cell size of sub-epidermis and flesh expanded. Thus periodic water supply using water supply facility is needed for yield and quality of ‘Nero’ black chokeberry fruits.

The objective of the study was to identify 52 Asian pear accessions, two primary pear species, and one reference pear Asian pear with 12 microsatellite markers to maintain pear germplasm collection. The number of alleles of 12 microsatellites detected ranged from eight at CH03d12 to 18 at CH01f07. Gene diversity ranged from 0.7053 at CH01d08 to 0.9224 at CH01f07. The lowest value of PIC was 0.6600 at CH01d08 and the highest was 0.9171 at CH01f07. A group consisting of ‘Ooharabeni,’ ‘Bartlett,’ and P. calleryana was out-grouped and served as a reference to determine the relationship among Asian pear accessions. Except for the out-group, 50 Asian pears were segregated into two groups. Group I was divided in two small groups. Each small group was characterized by P. bretschneideri and P. ussuriensis, respectively. Group II was characterized as P. pyrifolia, and the group was divided in four small groups. The eigenvalue, difference, proportion, and cumulative of six principal components based on PCA to 12 microsatellite. The eigenvalue of the first principal components was 5.5850. The proportion of the first principal component was 0.9308. The cumulative value of the first two principal components was 0.9801. Consequently, nearly all of the results were elucidated by the two principal components. The results from analysis of the standard set of microsatellites in this study may be used as basic materials for the management of Asian pear germplasm collections, and the data might be useful in the development of a core collection.

Proline has been shown to accumulate in plant under various type of stresses. In our previous study, changes in cold hardiness and proline content showed contrasting patterns during a constant deacclimation. This study was performed to investigate the proline accumulation and related gene expression in response to repeated deacclimation and reacclimation in peach cultivar ‘Daewol’. Proline content was analyzed using the ninhydrin method and related gene expressions were examined using quantitative real-time RT-PCR. Proline contents of ‘Daewol’ increased during the repeated deacclimation treatments. Interestingly, during the twice deacclimation, expressions of P5CS (Δ1-pyrroline-5-carboxylatesynthase) constantly decreased, whereas expressions of P5CR (Δ1-pyrroline-5-carboxylatereductase) increased. Expressions of OAT (ornithine-δ-aminotransferase) indicated up- and down- pattern in response to repeated deacclimation and reacclimation. Our results indicated that proline responds positively to higher temperature in the shoots of peach cultivar ‘Daewol’ and expressions of both P5CS and P5CR genes could show contrasting patterns during the deacclimation. Moreover, our results suggest that ornithine pathway could serve as an alternative pathway in proline synthesis process during deacclimation in peach.

Proline (Pro) accumulation is a common physiological reaction in response to abiotic stresses in many plants. Accumulation of Pro is believed to play the important role in protecting cellular components from dehydrating effects due to such stresses. The study was performed to investigate the relationship between cold hardiness and Pro content or expression of related genes in peach cultivars during a constant experimental deacclimation. Changes in cold hardiness were determined using electrolyte leakage method in the shoots of 10 peach cultivars (Prunus persica ‘Aikawanakajima’, ‘Chiyomaru’, ‘Daewol’, ‘Janghowon Hwangdo’, ‘Kiraranokiwami’, ‘Mihong’, ‘Misshong’, ‘Soomee’, ‘Suhong’, and ‘Sun Gold’). Pro content was analyzed using the ninhydrin method and related gene expressions were examined using quantitative real-time RT-PCR. While cold hardiness of 10 peach cultivars decreased, Pro contents of those increased during the deacclimation. Notably, at the same time, expression of P5CS (Δ1-pyrroline-5-carboxylatesynthase) decreased in 10 peach cultivars, whereas expressions of P5CR (Δ1-pyrroline-5-carboxylatereductase) and OAT (ornithine-δ-aminotransferase) increased. Our results demonstrate that Pro responds positively to higher temperature in the shoots of 10 peach cultivars and expression of both P5CS and P5CR genes could show contrasting patterns during the deacclimation. Furthermore, our results suggest that ornithine pathway, which has been suggested to be important during seedling development, could serve as an alternative pathway in Pro synthesis process during the deacclimation in peach.

In this study, we sought to identify primary pears species and Korean native pears, without the use of morphological characteristics. In addition, this study was to establish pear DNA fingerprinting data for Korean native pears using 12 microsatellite markers, and to accurately classify a database for management of the Korean pear collection. Forty two pear accessions (7 primary pears, 5 Asian pears, 29 Korean pears, and 2 reference pears) were analyzed with twelve primers covering whole pear genome. In the present study, all pear accessions were successfully classified along with their pedigrees, and the distribution of primary pears was parallel to those of the previous taxonomic results. Korean pears were divided into 3 groups. Group I was characterized by Pyrus calleryana, and included Korean pea pears. Group II was characterized by P. pyrifolia, and was classified into 2 small groups. The first small group comprised of ‘Najucheongbae’, ‘Sunchanggulimdolbae’, ‘Andongmookbae’, ‘Andongdangsilri’, and ‘Najucheongbae’ and was presumed to be cultivars of P. pyrifolia. The second small group consisted of ‘Cheongdangrori’ and ‘Pyeongchangsuhyangri’. These two accessions were assumed to be a hybrid of P. pyrifolia and the other cultivar. Group III was characterized by P. ussuriensis. ‘Goesanhwangbae’, ‘Andongcheongsilri’, ‘Gongjucheongsilri’, and ‘Yecheoncheongbae’ were assumed to be cultivars of P. ussuriensis. Contrary to ‘Ulreungdocheongbae A’, ‘Ulreungdocheongbae B’ was classified as belonging to the P. ussuriensis group. It is possible that this is a consequence of, P. ussuriensis genes being transferred into ‘Ulreungdocheongbae B’. The result of this research reaffirmed the efficiency of a standard set of microsatellite markers and provides data, which will be useful for developing a core collection of pears.

Korea is a origin of three basic species, P. ussuriensis, P. pyrifolia and P. fauriei. Genetic relationship among Korean pear cultivars compared with their parents were also identified that they are closely related P. pyrifolia, P. ussuriensis and/or hybrid between two species. SSRs or Microsatellites are co-dominant and typically neutral inheritance showing high degree of polymorphism, large number of alleles per locus, abundance in genomes, and suitability for automation. SSR markers were developed in apple and pear where they were used for construction of genetic linkage maps, evaluation of the genetic diversity, cultivar identification, genotype identification, and in the determination of genetic relatedness. Many apple (Malus × domestica Borkh.) SSRs would be useful for genetic mapping in European and Asian pears in previous experiments and cross-species amplification was observed between apple and pear. The objectives of this study were to develop polymorphic SSR markers in ‘Whangkeumbae’ and ‘Minibae’, which were chosen as the representative cultivars of P. pyrifolia and P. ussuriensis in each among Korean pears, from ‘Golden Delicious’ genomic sequences generated by next generation sequencing technology and to evaluate the utility of the SSR markers based on ‘Golden Delicious’ sequences. Of 51 SSR markers, 18 were polymorphic in ‘Whangkeumbae’ and ‘Minibae’. The cross-species transportability of primers designed in ‘Golden Delicious’ sequences makes SSR markers more useful, given the current high level of investment in mapping the genomes of related Rosaceae.

Currently, the type of short insertions and deletions (InDels) polymorphisms are increasingly focused in genomic research. InDels have been known as a source of genetic markers that are widely spread across the genome. Genetic relationship among Korean pear cultivars compared with their parents was also identified that they are closely related P. pyrifolia, P. ussuriensis and/or hybrids between two species. Lack of genetic resources including molecular markers has made it difficult to study pears severely. Recently developed next generation sequencing (NGS) platforms offer opportunities for high-throughput and inexpensive genome sequencing and rapid marker development. The main goal of this study was to develop polymorphic InDel markers in ‘Whangkeumbae’ and ‘Minibae’, which were chosen as the representative cultivars of P. pyrifolia and P. ussuriensis × pyrifolia in each among Korean pears using genomic sequences generated by NGS technology. In this study, more than 18.6 Gbp and 15.8 Gbp sequences were obtained from NGS of ‘Whangkeumbae’ and ‘Minibae’, respectively. ‘Whangkeumbae’ contained 197,210 InDels and 197,272 InDels in ‘Minibae’. In InDels validations between ‘Whangkeumbae’ and ‘Minibae’, the number of polymorphic InDels were 149,338 and non-polymorphic InDels were 122,572. For InDel primer set designing, 11,308 of primers were designed from polymorphic InDels and 10,919 of InDel primers were recommended. The study shows that the utility of NGS technology to design amount of efficient InDels and the developed InDel primers will be used for genetic mapping, breeding by marker assisted selection (MAS) and QTL mapping of Korea native pear as well as further genetic studies.

Single nucleotide polymorphisms (SNPs) are the most frequent type among variations found in genomic regions and are valuable markers for genetic mapping, genetic diversity studies and association mapping in plants. There are three basic species known as Korean native which are Pyrus ussuriensis, P. pyrifolia, and P. fauriei. Genetic relationship among Korean pear cultivars compared with their parents was identified that they are closely related P. pyrifolia, P. ussuriensis and/or hybrids between two species. Lack of genetic resources, including molecular markers to study pears are very severe. Recently developed next generation sequencing (NGS) platforms offer opportunities for high-throughput and inexpensive genome sequencing and rapid marker development. The objective of this study was to develop polymorphic SNP markers in ‘Whangkeumbae’ and ‘Minibae’, which were chosen as the representative cultivars of P. pyrifolia and P. ussuriensis × pyrifolia in each among Korean pears, using genomic sequences generated by NGS technology. In this study, more than 18.6 Gbp and 15.8 Gbp sequences were obtained from NGS of ‘Whangkeumbae’ and ‘Minibae’, respectively. ‘Whangkeumbae’ and ‘Minibae’ contained 2,712,288 and 2,747,224 SNPs, respectively. In SNPs validations between ‘Whangkeumbae’ and ‘Minibae’, the number of polymorphic SNPs were 2,516,438 and non-polymorphic SNPs were 1,179,391. For HRM primer design, 2,125,479 HRM candidate primers were obtained from polymorphic SNPs and 343,731 SNP primers were developed. This study shows that the utility of NGS technology to discover efficiently a large number of SNPs and SNP primers can provide valuable information in the genome study of Pyrus spp.

Recent climate changes due to global warming are gradually introducing adverse circumstances for winter survival of temperate fruit trees. Particularly, late winter or early spring thaws followed by hard freezes can cause severe injury to deacclimated flower buds. Thus, the selection of later or slower deacclimating cultivars is needed to avoid frost injury in late winter or early spring. This study was performed to investigate relationship between cold hardiness and bud development under an experimental deacclimation condition for 10 Prunus persica cultivars (Aikawanakajima, Daewol, Izumi Hakuto, Janghowon Hwangdo, Kiraranokiwami, Mihong, Misshong, Soomee, Suhong, and Sun Gold). The rate of deacclimation was not correlated with hardiness before the deacclimation treatment. On the other hand, a strong positive correlation was found between cold hardiness and stage of bud opening.