• Korean Journal of Plant Tissue Culture
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• v.24 no.4
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• pp.239-256
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• 1997

Plants belonging to the category of 2n apomixis or agamospermy form embryos and seeds without the processes of normal meiosis and syngamy. Seeds produced in this way have identical genotype of their maternal parent. Three different types of agamospermy are recognized: diplospory, apospory, and adventitious (adventive) embryony. $F_1$ hybrid cultivars cannot be used as seed sources in the next ($F_2$) generation because this generation would be extremely variable as a result of genetic segregation. Hybrid vigor is also reduced in the $F_2$ generation. Therefore, parental stocks for hybrid seed production need to be maintained and cross must be continuously repeated. Agamospermic 2n apomixis would make it possible to fix the genotype of a superior variety so that clonal seeds faithfully representing that genotype could be continuously and cheaply produced independent of pollination. That is, $F_1$ hybrid seeds could be produced for many generations without loss of vigor or genotype alteration. Production of apomictic $F_1$ hybrid seed would be simplified because line isolation would not be necessary to produce seed or to maintain parental lines, and the use of male-sterile lines could be avoided. Overall, apomixis would enable a significant reduction in hybrid seed production costs. Additionally, the production of clonal seed is not only important for seed propagated crops, but also for the propagation of heterozygous fruit trees and timbers. Clonal seed would help avoid costly and time-consuming vegetative propagating methods that are currently used to ensure the large-scale production of these plants. Apomixis is scattered throughout the plant kingdom, but few important agricultural crops possess this trait Therefore, most research to date has centered on introgressing the trait of apomixis into agricultural crops such as wheat, maize, and some forage grasses from wild distant relatives by traditional cross breeding. The classical breeding approach, however is slow and often impeded by many breeding barriers. These problems could be surmounted by taking mutagenesis or molecular approach. Arabidopsis thaliana is a tiny sexually reproducing plant and is convenient in constructing and screening in molecular researches. Male-sterile mutants of Arabidopsis are particularly suitable genetic background for mutagenesis and screening for apomictic mutants. Molecular approaches towards isolating the genes controlling the apomictic process are feasible. Direct isolation of genes conferring apomixis development would greatly facilitate the transfer of this trait to wide variety of crops. Such studies are now in progress.

• Korean Journal of Breeding Science
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• v.43 no.1
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• pp.62-67
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• 2011

This study was carried out to gain basic informations about amylogram, antioxidant activity function and physicochemical properties for kernel of the newly developed waxy corn hybrids. The used materials were produced in 2008 and cultivated at breeding farm of CNU in 2009. From amylogram analysis, peak and minimum viscosity of the used hybrids were appeared in CNU08H-71 and CNU08H-69 hybrid, respectively. DPPH free radical scavenging effect marked as election donating ability was highly appeared in CNU08H-15 and CNU08H-69 hybrid, while CNU08H-h102 hybrid was the lowest. Hardness of kernel was highly appeared in CNU08H-35 hybrid, and chewiness and gumminess were also the highest in this hybrid, but those of CNU08H-h105 hybrid were the lowest. In these facts, we confirmed that the used hybrids were very different among traits related to amylogram, functions and table qualities. Accordingly, development of the new waxy corn hybrid will be profitable to select and develop as a crossing combination including many excellent traits.

• Asian-Australasian Journal of Animal Sciences
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• v.21 no.7
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• pp.917-922
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• 2008

A disintegrin-like and metalloprotease (reprolysin type) with thrombospondin type 1 motif (ADAMTS1) plays a critical role in follicular rupture and represents a major advance in the proteolytic events that control ovulation. In this study, a 9,026-bp DNA sequence containing the full coding region, all 8 introns and part of the 5'and 3' untranslated region of the porcine ADAMTS1 gene was obtained. Analysis of the ADAMTS1 gene using the porcine radiation hybrid panel indicated that pig ADAMTS1 is closely linkage with microsatellite marker S0215, located on SSC13q49. The open reading frame of its cDNA covered 2,844 bp and encoded 947 amino acids. The coding region of porcine ADAMTS1 as determined by sequence alignments shared 85% and 81% identity with human and mouse cDNAs, respectively. The deduced protein contained 947 amino acids showing 85% sequence similarity both to the human and mouse proteins, respectively. Comparative sequencing of three pig breeds revealed one single nucleotide polymorphism (SNP) within exon 7 of which a G-C substitution at position 6006 changes a codon for arginine into a codon for proline. The substitution was situated within a PvuII recognition site and developed as a PCR-RFLP marker for further use in population variation investigations and association analysis with litter size. Allele frequencies of this SNP were investigated in seven pig breeds/lines. An association analysis in a new Qingping female line suggested that different ADAMTS1 genotypes have significant differences in litter size (p<0.01).

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.5
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• pp.682-685
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• 2005

Large White, an introduced European pig breed, and Meishan, a Chinese indigenous pig breed, were hybridized directly and reciprocally and a total of 260 pigs, including purebreds, Large White and Meishan, and their hybrids, White${\times}$Meishan (LM) and Meishan${\times}$Large White (ML) pigs, were bred in our laboratory. The mRNA differential display PCR (DD-PCR) was used to detect the age-dependent changes of differential gene expression in backfat tissue between hybrids and parents. Some measures were taken to reduce the false positives in our experiment. Among the total of 2,686 bands obtained, 1,952 bands (about 72.67%) were reproducible and eight patterns (fifteen kinds) of gene expression were observed. The percentage of differentially expressed genes between hybrids and parents is 56.86% at the age of four months and 57.71% at the age of six months. This indicated that the differences of gene expression between hybrids and their parents were very obvious. U-test was used to compare the patterns of gene expression between the age of four and six months, and results showed that bands occurring in only one hybrid and bands displayed in one hybrid and one parent were significantly different at p<0.05, and bands visualized in only two hybrids were significantly different at p<0.01. These indicated that differential gene expression between hybrids and parents changed at different ages.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.7
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• pp.931-937
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• 2006

The full-length cDNA of the porcine SMPX gene was obtained by the rapid amplification of cDNA ends (RACE). The nucleotide sequences and the predicted protein sequences share high sequence identity with both human and mouse. The promoter of SMPX was sequenced and then analyzed to find the promoter binding sites. The reverse transcriptase-polymerase chain reaction (RT-PCR) revealed that SMPX has a high level of expression in heart and skeletal muscle, a very low expression in lung and spleen and no expression in liver, kidney, fat and brain. Moreover, SMPX has a differential expression level in skeletal muscle, the expression in 65-day embryos being higher than other stages. The porcine SMPX was mapped to SSCXp24 by using a somatic cell hybrid panel (SCHP) and was found closely linked to SW1903 using the radiation hybrid panel IMpRH. An A/G single nucleotide polymorphism (PCR-RFLP) in the 3'-untranslated region (3'-UTR) was detected in eight breeds. The analysis of allele frequency distribution showed that introduced pig breeds (Duroc and Large White) have a higher frequency of allele A while in the Chinese indigenous pig breeds (Qingping pig, Lantang pig, YushanBlack pig, Large Black-White pig, Small Meishan) have a higher frequencies of allele G. The association analysis using an experimental population (188 pigs), which included two cross-bred groups and three pure-blood groups, suggested that the SNP genotype was associated with intramuscular fat content.

• Journal of Crop Science and Biotechnology
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• v.11 no.4
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• pp.257-262
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• 2008

Genetic diversity of cultivated wheat is narrowing down and is increasingly becoming non-complacent in tackling new pathogenic races and adverse environmental situations. Wild relatives of wheat are rich repositories of beneficial genes that are capable of defying adverse situations. However, these wild species are not readily crossable with cultivated ones. The present study attempted to cross three wild wheat species as females with three cultivated species of varying ploidy to understand the intricate behaviour of hybrids in relation to cytology, morphology, and molecular recombination. Post-fertilization barriers caused hybrid recovery in wild species in contrast to cultivated species. Triticum monococcum did not produce hybrids in any of the crosses. Various degrees of chromosome anomalies and hybrid sterility were seen with hybrids of T. timopheevi and T. sphaerococcum. Cytoplasmic factors were suspected to add more to the abnormality. G genome from T. timopheevi could enhance more pairing between Band D of cultivated species. Precocity of certain chromosomes in laggard formation was evident, pointing towards evolutionary self balance of the genomes which prevented homeologous pairing. They are eliminated in hybrids. Molecular diversity clearly corroborated with genetic proximity of the species, which distinguished themselves by maintaining the genome homeology.

• Korean Journal of Breeding Science
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• v.40 no.3
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• pp.250-257
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• 2008

Knowledge of genetic diversity and of the genetic relationships among elite breeding materials has had a significant impact on the improvement of crops. In maize, this information is particularly useful in i) planning crosses for hybrid and line development, ii) in assigning lines to heterotic groups and iii) in plant variety protection. We have used the SSR technique to study the genetic diversity and genetic relationships among 76 Korean waxy corn accessions, representing a diverse collection from throughout Korea. Assessment of genetic diversity among members of this group was conducted using 30 microsatellite markers. Among these 30 microsatellite markers, we identified a total of 127 alleles (with an average of 4.2 and a range of between 2 and 9 alleles per locus). Gene diversity at these 30 microsatellite loci varied from 0.125 to 0.795 with an average of 0.507. The cluster tree generated with the described microsatellite markers recognized two major groups with 36.5% genetic similarity. Group I includes 63 inbred lines, with similarity coefficients of between 0.365 and 0.99. Group II includes 13 inbred lines, with similarity coefficients of between 0.45 and 0.85. The present study indicates that the 30 microsatellite loci chosen for this analysis are effective molecular markers for the assessment of genetic diversity and genetic relationships between Korean waxy corn accessions. Specifically, this study's assessment of genetic diversity and relationships between a set of 76 Korean waxy corn inbred lines will be helpful for such activities as planning crosses for hybrid and line development and association mapping analyses of maize breeding programs in Korea.

• Weed & Turfgrass Science
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• v.6 no.4
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• pp.283-291
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• 2017

Zoysiagrass has been used in Korea as a native grass. Informations on distributions, classifications, breeding efforts and outputs, current production and uses of zoysiagrasses in Korea are summarized. During past a few decades, collection of naturally growing zoysiagrass ecotypes has been continued, followed by evaluation, selection and cross-pollination. Classification efforts using important morphological, biochemical traits and DNA polymorphisms resulted in the several suggestions of grouping zoysiagrass species and varieties. Zoysia japonica consistently form separate group, while Zoysia sinica and Zoysia macrostackya have been separately or inter-mixed. Z. matrella with some variations frequently grouped separately but with some similarity with Z. tenuifolia, which was recently renamed as Z. pacifica. Hybrid types of zoysiagrasses were frequently found in Korea. New varieties such as 'Kunhee' and 'Green Ever' etc. were bred by ecotype selections, while 'Senock', 'Semil', 'Millock' were bred through pollination. Molecular approaches were also used to introduce beneficial genes into zoysiagrasses with no practical outputs by legal regulations. Currently popular varieties are inter-specific hybrid types such as 'Anyang' and other local zoysiagrasses as well as common zoysiagrass (Zoysia japonica) Production area in Korea was estimated as 2,947 ha with increasing problems of mixed or contaminated species and varieties.

• Korean Journal of Breeding Science
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• v.43 no.2
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• pp.120-125
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• 2011

A field experiment was conducted to examine the fruit quality characters in second generation ($F_2$) hybrid cultivar and to compare the fruit characters with original $F_1$ hybrid cultivar of minipaprika (yellow and orange type) at the Research Farm, Hwacheon in July, 2010. Fruit characters varied within $F_2$ population of each minipaprika type. In minipaprika yellow, fruit weight varied from 12.2 g to 50.8 g (average 28.5 g) and fruit length/width varied from 1.4 to 2.8 (average, 2.0). Pericarp thickness ranged from 1.8 mm to 4.1 mm (average, 2.9 mm). Total soluble solid (TSS) varied from $6.2^{\circ}Brix$ to $13.5^{\circ}Brix$ with an average of $8.7^{\circ}Brix$. Fruit volume varied from 10.3 cc to 46.7 cc with an average of 24.4 cc. In minipaprika orange type, fruit weight ranged from 19.7 g to 42.4 g (average, 29.0 g) and fruit length/width varied from 1.5 to 2.6 (average, 2.0). Pericarp thickness varied from 2.1 mm to 4.1 mm with an average of 3.0 mm. TSS varied from $5.0^{\circ}Brix$ to $12.2^{\circ}Brix$ (average, $7.9^{\circ}Brix$) and average fruit volume was 24.6 cc ranging from 10.7 cc to 35.0 cc. The average fruit quality characters in $F_2$ population in both yellow and orange minipaprika did not differ from their $F_1$ hybrid parent and $F_2$ seed can be an additional way to supply high yielding hybrid cultivars at lower cost to the minipaprika growers.

• Nuclear Engineering and Technology
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• v.50 no.8
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• pp.1339-1348
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• 2018

The aim of this paper is to determine neutronic performances of the light water reactor (LWR) spent fuel mixed with fertile thorium fuel in a FFHR. Time dependent three dimensional calculations for major technical data, such as blanket energy multiplication, tritium breeding ratio, cumulative fissile fuel enrichment and burnup have been performed by using Monte Carlo Neutron-Particle Transport code MCNP5 1.4, coupled with a novel interface code MCNPAS, which is developed by our research group. A self-sustaining tritium breeding ratio (TBR>1.05) has been kept throughout the calculations. The study has shown that the fissile fuel quality will be improved in the course of the transmutation of the LWR spent in the FFHR. The latter has gained the reusable fuel enrichment level conventional LWRs between one and two years. Furthermore, LWR spent fuel - thorium mixture provides higher burn-up values than in light water reactors.