• Korean Journal of Animal Reproduction
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• v.25 no.4
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• pp.295-304
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• 2001

Characterization of quantitative trait loci (QTL) was investigated in the experimental crosses between Berkshire and Yorkshire breed. A total of 525 F$_2$ progenies from 65 matting of F$_1$ Parents were produced. Phenotypic measurements included average daily gain (ADG), average back fat thickness (ABF), and loin eye area (LEA). To identify the presence of QTL for reproductive performance, birth weight (BWT) and body weight at 16 days (16DAY) were included as indirect trait. QTL segregation was deduced using 8 markers assigned to chromosome 2 (SSC2). Quantitative trait locus analyses were performed using interval mapping by regression under line-cross model. Presence of imprinting was tested under the statistical model that separated the expression of paternally and maternally inherited alleles. To set the evidence of QTL presence, significance thresholds were derived by permutation following statistical tests, respectively. Genome scan revealed significant evidence for three quantitative trait loci (QTL) affecting growth and body compositions, of which two were identified to be QTL with imprinting expression mode near the ICF II gene region. For average back fat thickness (ABF), a paternally expressed QTL was found on chromosome 2 (SSC2). A paternally expressed QTL affecting loin eye area (LEA) was found in the region of SSC2 where evidence of imprinted QTL was found for average back fat thickness (ABF). For average daily gain (ADG), QTL expressed with Mendelian mode was found on chromosome 2 (SS2). Also, QTL affecting average daily gain (ADC), was identified to be expressed with Mendelian express mode.

• The Korean Journal of Applied Statistics
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• v.18 no.3
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• pp.533-541
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• 2005

We identify the correct chromosome and locate the corresponding markers close to the QTL in the linkage analysis of a quantitative trait by using the SSVS method. We consider several markers linked to the QTL, as well as to each oyher and thus the i.b.d. values at these loci generate collinear predictors to be evaluated when using the SSVS approach. The results on considering only closely linked markers to two QTL simultaneously showed clear evidence in favor of the closest marker to the QTL considered over other markers. The results of the analysis of collinear markers with SSVS showeed high concordance to those obtained using traditional multiple regression. We conclude based on this simulation study that the SSVS is quite useful to identify linkage with multiple linked markers simultaneously for a complex quantitative trait.

• Korean Journal of Breeding Science
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• v.41 no.3
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• pp.236-243
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• 2009

This study was conducted to develop a japonica-type rice cultivar with brown planthopper (BPH) resistance using DNA markers. A doubled haploid (DH) population consisting of 120 pure-lines was established by anther culture of $F_1$ hybrids between 'Samgang', a Tongil type BPH resistance cultivar, and 'Nagdong', a japonica cultivar. To determine the map position of genes responsible for BPH resistance in rice, a genetic map was constructed based on 120 DH lines. A total of 162 molecular markers were classified into 12 linkage groups, covering 1,884 Kosami centimorgan (cM) with an average of 11.6 cM. Five QTLs (qBPR3, qBPR6, qBPR7, qBPR8, and qBPR12) associated with BPH resistance were identified and mapped on chromosomes 3, 6, 7, 8, and 12, respectively, using the genetic map constructed in this study. To analyze the relationship between BPH resistance and agronomic traits, a total of eight QTLs related to the agronomic traits were detected on 12 rice chromosomes. In an analysis of relationships, three QTLs (qBPR3, qBPR7, and qBPR8) showed a linkage with tested agronomic traits. A QTL (qBPR3) located on chromosome 3 (RM282-3023) was closely linked to culm length (qCL3). The QTL (qBPR8) for BPH resistance on the short arm of chromosome 8 also overlapped the region detected in culm length (qCL8).

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.6
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• pp.539-545
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• 2004

The purpose of this study was to locate the quantitative trait loci (QTL) associated with quality properties in the recombinant inbred lines derived from the 'Milyang 23' and 'Gihobyeo' cross. Four quality-related traits; protein content, amylose content, fat acid content and sensory value were measured. Eight QTLs for protein content were detected on chromosomes 1 (two loci), 3, 6, 7 and 8 (three loci), each accounting for $6.0\%\~15.2\%$ of the phenotypic variation. Three QTLs for amylose content were detected on chromosomes 6 and 7 (two loci), each explaining from $7.3\%\;to\;24.4\%$ of the phenotypic variation. Six QTLs for fat acid content were detected on chromosomes 2 (two loci), 3, 6 (two loci) and 7, each explaining form $5.5\%\;to\;14.0\%$ of the phenotypic variation. Six QTLs for sensory value were detected on chromosomes 2, 6, 7(two loci) and 8 (two loci), each accounting for $5.5\%\~10.3\%$ of the phenotypic variation.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.55 no.2
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• pp.105-110
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• 2010

This study was conducted to analyze the relationships between resistance of brown planthopper and traits related to the lodging in rice. For the linkage analysis of traits tested in this study, a genetic linkage map was created with 162 DNA markers spanning 12 rice chromosomes based on 120 doubled haploid (DH) lines, which were derived from a cross between Samgang', a Tongil type cultivar with BPH resistance, and ‘Nagdong’, a japonica cultivar. QTLs were identified to analyze the agronomic traits including lodging by composite interval mapping. Thirteen QTLs were detected for five traits comprised of plant length (PL), 3rd internode length (3rdIL), moments (Mo), lodging index (LI), and breaking weight (BW). The relationships between the BPH resistance and agronomic traits including lodging revealed that two QTLs (qBPR7, qBPR8) were linked to traits related to lodging. Two QTLs, qBPR7 and qBPR8 on chromosome 7 (RM531-7042) and 8 (RM1148- RM544) showed associations with moments and 3rd internode length, respectively.

• Journal of Embryo Transfer
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• v.19 no.3
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• pp.291-299
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• 2004

Characterization of quantitative trait loci (QTL) was investigated in the experimental cross population between Berkshire and Yorkshire breed. A total of 512 F$_2$ offspring from 65 matting of F$_1$ parents were phenotyped the carcass traits included average daily gain (ADG), average backfat thickness (ABF), tenth rip backfat thickness (TRF), loin eye area (LEA), and last rip backfat thickness (LRF). All animals were genotyped for 125 markers across the genome. Marker linkage maps were derived and used in QTL analysis based on line cross least squares regression interval mapping. A decision tree to identify QTL with imprinting effects was developed based on tests against the Mendelian mode of QTL expression. To set the evidence of QTL presence, empirical significance thresholds were derived at chromosome-wise and genome-wise levels using specialized permutation strategies. Significance thresholds derived by the permutation test were validated in the data set based on simulation of a pedigree and data structure similar to the Berkshire-Yorkshire population. Genome scan revealed significant evidences for 13 imprinted QTLs affecting growth and body compositions of which nine were identified to be QTL with paternally expressed inheritance mode. Four of QTLs in the loin eye area (LEA), and tenth rip backfat thickness (TRF), a maternally expressed QTL were found on chromosome 10 and 12. These results support the useful statistical models to analyse the imprinting far the QTLs related carcass trait.

• Journal of Korean Society of Forest Science
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• v.95 no.4
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• pp.483-494
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• 2006

We conducted QTL mapping for 6-year growths of open-pollinated half-sib progenies from a selected clone 7-1037 in Pinus taeda. With an AFLP marker analysis on haploid DNA samples from the megagametophytes of the open-pollinated seeds, we constructed 20 framework maps spanning a total of 1,869 cM in total length and 18.5 cM in an average interval length between markers. Composite interval mapping reveals that one QTL explains 5.9% of the total phenotypic variation of height, and three QTLs account for 3.9~5.6% of the variation of diameter at breast height (DBH). There are no correlations between the QTLs. The genetic effects of the QTLs are 39.6 cm in height and 7.20~9.41 mm in DBH, respectively, The average effects of gene substitution of the markers closely linked with the QTLs are 44.3 cm in height and 8.38~11.81 m in DBH. Under an assumption that the within-family heritability for the growth traits of loblolly pine is less than 0.2, the QTLs account for 26.8% of the additive genetic variance of the progenies. In terms of relative selection efficiency, the individual selection based on QTL markers could be 5 times as high as phenotypic selection. The results in this study indicate that the QTL mapping method with open-pollinated half-sib family could be more practical and applicable to the conventional seed orchard-based selection work than other mapping methods with a single full-sib family, in particular from the viewpoint that it can provide crucial information for within-family individual selection such as breeding value.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.65 no.4
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• pp.303-313
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• 2020

Rice grain shape is one of the key components of grain yield and market value. An understanding of the genetic basis of the variation in grain shape could be used to improve grain shape. In this study, we developed a total of 265 F₂ individuals derived from a cross between japonica cultivars (Josaeng-jado and Langi) and used this population for quantitative trait locus (QLT) analysis. Correlation analysis was performed to identify relationships between grain traits (GL: grain length, GW: grain width, L/W: ratio of length to width, TGW: 1,000 grain weight). The grain shape was positively correlated with GL and TGW, and negatively correlated with GW. In QTL analysis associated with grain shape, one QTL for GL, qGL5, detected on chromosome 5, explained 20.3% of the phenotypic variation (PV), while two QTLs, qGW5 (PV=36.1) and qGW7 (PV=26.1), for GW were identified on chromosomes 5 and 7, respectively. Evaluation of the effects of each of the QTLs on the grain shape in the population showed a significant difference in the grain size in positive lines compared with the lines without the QTLs. According to the QTL combination of the allelic-types, the grain shape of the tested lines varied from semi-round type to long spindle-shaped type. The results of this study extend our knowledge about the genetic pool governing the diversity of grain shape in japonica cultivars and could be used to improve the grain shape of this species through marker-assisted selective breeding in Korea.

• Journal of Life Science
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• v.25 no.8
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• pp.925-931
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• 2015

We performed a molecular marker-based analysis of quantitative trait loci (QTLs) for traits that determine the quality of the appearance of grains, using 120 doubled-haploid (DH) lines developed by another culture from the F1 cross between ‘Cheongcheong’ (Oryza sativa L. ssp. Indica) and ‘Nagdong’ (Oryza sativa L. ssp. Japonica). The traits studied included length, width, and thickness of the grains, as well as length-to-width ratio and 1,000-grain weight. The objective of this study was to determine the genetic control of these traits in order to formulate a strategy for improving the appearance of this hybrid. Within the DH population, five traits exhibited wide variation, with mean values occurring within the range of the two parents. Three QTLs were identified for grain length on chromosomes 2, 5, and 7. Three QTLs were mapped for grain width on chromosome 2: qGW2-1, qGW2-2, and qGW2-3. Six chromosomes were identified for the grain length-to-width ratio; four of these were on chromosome 2, whereas the other two were on chromosomes 7 and 12. One QTL influencing 1,000-grain weight was identified and located on chromosome 8. The results presented in the present study should facilitate rice-breeding, especially for improved hybrid-rice quality.

• Journal of Animal Science and Technology
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• v.44 no.1
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• pp.31-38
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• 2002

Interval mapping using microsatellite markers was employed to detect quantitative trait loci (QTL) in the experimental cross between Berkshire and Yorkshire pigs. In order to derive critical values (CV) for test statistics for declaring significance of QTL, permutation test (PT) of Churchill and Doerge method(1994) and the analytical method(LK) of Lander and Kruglyak(1995) were used by each trait and chromosome. 525 $F_2$ progeny phenotypes of five traits(carcass weight, loin eye area, marbling score, cholesterol content, last back fat thickness) and genotypes of 125 markers covering the genome were used. Data were analyzed by line cross regression interval mapping with an F-test every by 1cM. PT CV were based on 10,000 permutations. CV at genome-wise test were 10.5 for LK and ranged from 8.1 to 8.3 for PT, depending on the trait. CV, differed substantially between methods, led to different numbers of quantitative trait loci (QTL) to be detected. PT results in the least stringent CV compared at the same % level.