• Molecules and Cells
• /
• v.25 no.4
• /
• pp.467-478
• /
• 2008

Simple sequence repeats (SSRs) and interSSR (ISSR) marker systems were used in this study to reveal genetic changes induced by artificial selection for short/long larval duration in the tropical strain Nistari of the silkworm Bombyx mori. Artificial selection separated longer larval duration (LLD) ($29.428{\pm}0.723days$) and shorter larval duration (SLD) ($22.573{\pm}0.839days$) lines from a base, inbred population of Nistari (larval span of $23.143{\pm}0.35days$). SSR polymorphism was observed between the LLD and SLD lines at one microsatellite locus, Bmsat106 ($CA_7$) and at two loci of 1074 bp and 823 bp generated with the ISSR primer UBC873. Each of these loci was present only in the LLD line. The loci segregated in the third generation of selection and were fixed in opposite directions. In the $F_2$ generation of the $LLD{\times}SLD$ lines, the alleles of Bmsat106 and $UBC873_{1074bp}$ segregated in a 1:1 ratio and the loci were present only in the LLD individuals. $UBC873_{823bp}$ was homozygous. Single factor ANOVA showed a significant association between the segregating loci and longer larval duration. Together, the two alleles contributed to an 18% increase in larval duration. The nucleotide sequences of the $UBC873_{1074bp}$ and $UBC873_{823bp}$ loci had 67% A/T content and consisted of direct, reverse, complementary and palindromic repeats. The repeats appeared to be "nested" (59%) in larger repeats or as clustered elements adjacent to other repeats. Of 203 microsatellites identified, dinucleotides (67.8%) predominated and were rich in A/T and T/A motifs. The sequences of the $UBC873_{1074bp}$ and $UBC873_{823bp}$ loci showed similarity (E = 0.0) to contigs located in Scaffold 010774 and Scaffold 000139, respectively, of the B. mori genome. BLASTN analysis of the $UBC873_{1074bp}$ sequence showed significant homology of (nt.) 45-122 with upstream region of three exons from Bombyx. The complete sequence of this locus showed ~49% nucleotide conservation with transposon 412 of Drosophila melanogaster and the Ikirara insertions of Anopheles gambiae. The A + T richness and lack of coding potential of these small loci, and their absence in the SLD line, reflect the active process of genetic change associated with the switch to short larval duration as an adaptation to the tropics.

• Horticultural Science & Technology
• /
• v.35 no.2
• /
• pp.149-164
• /
• 2017

Next generation sequencing (NGS) technologies have led to the rapid accumulation of genome sequences through whole-genome sequencing and re-sequencing of crop species. Genomic resources provide the opportunity for a new revolution in plant breeding by facilitating the dissection of complex traits. Among vegetable crops, reference genomes have been sequenced and assembled for several species in the Solanaceae and Cucurbitaceae families, including tomato, pepper, cucumber, watermelon, and melon. These reference genomes have been leveraged for re-sequencing of diverse germplasm collections to explore genome-wide sequence variations, especially single nucleotide polymorphisms (SNPs). The use of genome-wide SNPs and high-throughput genotyping methods has led to the development of new strategies for dissecting complex quantitative traits, such as genome-wide association study (GWAS). In addition, the use of multi-parent populations, including nested association mapping (NAM) and multiparent advanced generation intercross (MAGIC) populations, has helped increase the accuracy of quantitative trait loci (QTL) detection. Consequently, a number of QTL have been discovered for agronomically important traits, such as disease resistance and fruit traits, with high mapping resolution. The molecular markers for these QTL represent a useful resource for enhancing selection efficiency via marker-assisted selection (MAS) in vegetable breeding programs. In this review, we discuss current genomic resources and marker-trait association analysis to facilitate genome-assisted breeding in vegetable species in the Solanaceae and Cucurbitaceae families.

• Asian-Australasian Journal of Animal Sciences
• /
• v.19 no.12
• /
• pp.1702-1705
• /
• 2006

A simulation study was conducted to evaluate a fine-mapping method exploiting population-wide linkage disequilibrium. Data were simulated according to the pedigree structure based on a large paternal half-sib family population with a total of 1,034 or 2,068 progeny. Twenty autosomes of 100 cM were generated with 5 cM or 1 cM marker intervals for all founder individuals in the pedigree, and marker alleles and a number of quantitative trait loci (QTL) explaining a total of 70% phenotypic variance were generated and randomly assigned across the whole chromosomes, assuming linkage equilibrium between the markers. The founder chromosomes were then descended through the pedigree to the current offspring generation, including recombinants that were generated by recombination between adjacent markers. Power to detect QTL was high for the QTL with at least moderate size, which was more pronounced with larger sample size and denser marker map. However, sample size contributed much more significantly to power to detect QTL than map density to the precise estimate of QTL position. No QTL was detected on the test chromosomes in which QTL was not assigned, which did not allow detection of false positive QTL. For the multiple QTL that were closely located, the estimates of the QTL positions were biased, except when the QTL were located on the right marker positions. Our fine mapping simulation results indicate that construction of dense maps and large sample size is needed to increase power to detect QTL and mapping precision for QTL position.

• Korean Journal of Breeding Science
• /
• v.43 no.4
• /
• pp.273-281
• /
• 2011

Fusarium head blight (FHB), also known as scab, caused mainly by Fusarium graminearum is a devastating disease of wheat in regions that are warm and humid during flowering. In addition to significant yield and quality losses, the mycotoxin deoxynivalenol produced by the pathogen in infected wheat kernels is a serious problem for food and feed safety. Twenty- three Korean cultivars and "Sumai 3", which is a FHB-resistant Chinese cultivar were tested for Type I, Type II resistances of FHB. Three cultivars were identified as resistant in Type I assessment, and two cultivars were resistant in Type II assessment. Genetic variation and relationship among the cultivars were evaluated on the basis of 11 Simple Sequence Repeat (SSR) and 29 Sequence Tagged Site (STS) markers that were linked to FHB resistance Quantitative Trait Loci (QTL) on chromosome 3BS. One SSR and 7 STS markers detected polymorphisms. Especially, using a STS marker (XSTS3B-57), 32.4% of the variation for Type II FHB resistance could be explained. Genetic relationship among Korean wheat cultivars was generally consistent with their released year. These markers on chromosome 3BS have the potential for accelerating the development of Korean wheat cultivars with improved Fusarium head blight resistance through the use of marker-assisted selection.

• Animal Systematics, Evolution and Diversity
• /
• v.36 no.4
• /
• pp.347-353
• /
• 2020

Although sea slaters Ligia have a significant role in rocky shore habitats, their taxonomic entities have not been clearly understood. In this study, we investigated whether genetic variation inferred from a nuclear genetic marker, namely amplified fragment length polymorphism (AFLP), would conform to that of a mitochondrial DNA marker. Using both the mitochondrial DNA marker and the AFLP marker amplified by the six selective primer sets, we analyzed 95 Ligia individuals from eight locations from East Asia. The direct sequencing of mitochondrial 16S rRNA gene revealed three distinct genetic lineages, with 9.8-11.7 Kimura 2-parameter genetic distance. However, the results of AFLP genotyping analysis with 691 loci did not support those of mitochondrial DNA, and revealed an unexpectedly high proportion of shared polymorphisms among lineages. The inconsistency between the two different genetic markers may be explained by difference in DNA evolutionary history, for example inheritance patterns, effective population size, and mutation rate. The other factor is a possible genomic island of speciation, in that most of the genomic parts are shared among lineages, and only a few genomic regions have diverged.

• Food Science of Animal Resources
• /
• v.31 no.3
• /
• pp.325-338
• /
• 2011

Investigations into fatty acid composition in meats are becoming more important due to consumer demand for high quality healthy food. Marker-assisted selection has been applied to livestock to improve meat quality by directly selecting animals for favorable alleles that affect economic traits. Quantitative trait loci affecting fatty acid composition in cattle and pigs were investigated, and five candidate genes (ACACA, FASN, SCD, FABPs, and SREBP-1) were significantly associated with fatty acid composition. The information presented here should provide valuable guidelines to detect causative mutations affecting fatty acid composition in cattle and pigs.

• Journal of Plant Biotechnology
• /
• v.33 no.4
• /
• pp.289-295
• /
• 2006

This study was carried out to evaluate the suitability of simple sequence repeat (SSR) markers for varietal identification and genetic diversity in 28 commercial tomato varieties. The relationship between marker genotypes and 28 varieties was analyzed. Of the 219 pairs of SSR primers screened against ten tomato varieties, 18 pairs were highly polymorphic with polymorphism information content (PIC) ranging from 0.467 to 0.800. Among the polymorphic loci, two to nine SSR alleles were detected for each locus with an average of 3.3 alleles per locus. Genetic distances were estimated according to Jaccard's methods based on the probability that the amplified fragment from one genotype would be present in another genotype. These varieties were categorized into cherry and classic fruit groups corresponding to varietal types and genetic distance of cluster ranging from 0.35 to 0.97. The phonogram discriminated all varieties by marker genotypes. The SSR markers proved to be useful variety identification and genetic resource analysis of tomato.

• Molecules and Cells
• /
• v.24 no.1
• /
• pp.83-94
• /
• 2007

During monocarpic senescence in higher plants, functional stay-green delays leaf yellowing, maintaining photosynthetic competence, whereas nonfunctional stay-green retains leaf greenness without sustaining photosynthetic activity. Thus, functional stay-green is considered a beneficial trait that can increase grain yield in cereal crops. A stay-green japonica rice 'SNU-SG1' had a good seed-setting rate and grain yield, indicating the presence of a functional stay-green genotype. SNU-SG1 was crossed with two regular cultivars to determine the inheritance mode and identify major QTLs conferring stay-green in SNU-SG1. For QTL analysis, linkage maps with 100 and 116 DNA marker loci were constructed using selective genotyping with $F_2$ and RIL (recombinant inbred line) populations, respectively. Molecular marker-based QTL analyses with both populations revealed that the functional stay-green phenotype of SNU-SG1 is regulated by several major QTLs accounting for a large portion of the genetic variation. Three main-effect QTLs located on chromosomes 7 and 9 were detected in both populations and a number of epistatic-effect QTLs were also found. The amount of variation explained by several digenic interactions was larger than that explained by main-effect QTLs. Two main-effect QTLs on chromosome 9 can be considered the target loci that most influence the functional stay-green in SNU-SG1. The functional stay-green QTLs may help develop low-input high-yielding rice cultivars by QTL-marker-assisted breeding with SNU-SG1.

• Journal of Life Science
• /
• v.19 no.2
• /
• pp.169-173
• /
• 2009

To assist in selection schemes we estimate the genetic diversity of the horse breeds. Genetic diversity at 13 microsatellite loci was compared in six horse breeds : Jeju Native Horse, American Quarter, Jeju Racing Horse, Mongolian Horse, Japanese Horse and Thoroughbred. All of the equine microsatellite used in this study were amplified and were polymorphic. The expected total heterozygosity over all the populations varied between 0.669 and 0.869 and the expected heterozygosity within population range from 0.569 to 0.219 in this study. The low coefficient of gene differentiation value showed that only 0.118 of the diversity was between horses breeds. The constructed dendrogram from the genetic distance matrix showed little differentiation between horse breeds using DISPAN program. The genetic distance using 13 microsatellites ranged between 0.137 and 0.414 for the six horse breeds. These results confirm the potential use of equine microsatellite loci as a tool for genetic studies in horse populations. The genetic diversity of the six horse breeds to each other closed to their geographical distribution. Suggesting that the loci would be suitable for horse breeds parentage testing. Therefore, Microsatellite marker seems to be very useful for clarifying the evolutionary relationships of closely related populations.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.26 no.4
• /
• pp.337-344
• /
• 2000

Germ-line mutations at DNA repair loci confer susceptibility to colon cancer in hereditary non-polypopsis colorectal cancer. Somatic loss of DNA mismatch repair gene has been reported in a large variety of other tumor types. Replication errors(RERs) judged by microsatellite instability(MSI) and its associated mutations have been recognized as an important mechanism in various tumor types. To investigate associations between MSI and oral squamous cell carcinoma, the frequency of MSI using 12 microsatellite markers were analyzed for the series of oral tumors. Of 17 tumors, 8 cases(47%) did not show instability at any of the 12 loci; 5(29%) showed instability at $2{\sim}3$ loci; and 4(24%) showed instability above 4 loci. The 4 cases showing widespread MSI did not differ from those without evidence of instability in terms of age at diagnosis, degree of differentiation, metastasis to lymph node, tumor location or the presence of mutations in the p53 tumor suppressor gene. DCC and D17S 796 were the most frequently detected in MSI analysis. There were no correlation between smoking and MSI frequency, instead, smoking was suggested to increase the mutation rate of p53 and development of oral carcinomas.