An allo-octoploid strawberry (Fragaria × ananassa Duch.) is one of the most important vegetable crops in Korea. However, there were few genomic researches of strawberry due to polyploidy and complexity of its genome. In this study, we aimed to construct a genetic linkage map of strawberry using single nucleotide polymorphism (SNP) markers that were developed through a next-generation sequencing (NGS) analysis. Two strawberry varieties, ‘Sulhyang’ and ‘Senga-sengana’, were used as a maternal and a paternal parent, respectively, and their F1 generation consisting of 94 individuals was used for construction of a genetic linkage map. A total of 19.0 Gbp (‘Sulhyang’) and 21.8 Gbp (‘Senga-sengana’) of genomic sequences were obtained through NGS analysis. Subsequently, approximately 87,000 SNPs were identified and 1,154 primer sets for high-resolution melting (HRM) analysis were designed through bioinformatic analysis. In result, a total of 224 polymorphic HRM markers were developed and 205 markers were mapped on the genetic linkage map of strawberry, which total length was 800.8 cM and the number of linkage groups were 30. This SNP-based genetic linkage map and the 224 SNP markers will be very helpful for the genomic and genetic researches of allo-octoploid strawberry.

Recently, many breeders have preferred to use molecular markers for introgression backcross programs enabling foreground and background selection to cope with rapid cultivar changing of seed markets. In accumulation of target traits with marker-assisted selection, larger numbers of markers should give better resolution. For the analysis of quantitative traits, a high-density genetic map with a large number of markers is required for discovering more accurately linked markers with traits. Watermelon is a recalcitrant plant to generate a high-density genetic map with conventional molecular markers including simple sequence repeats (SSRs), since watermelon has narrow genetic diversity background and severe segregation distortions of those SSR markers. Thus, we have developed efficient and valid way to assemble genetic map and markers by next-generation sequencing coupled with genotyping by sequencing in F2 generation. After crosses between Citurullus lanatus ssp. citroides (PI254744 and PI189225) and C. lanatus ssp. lanatus (TS34, Korean cultigen), 163 of F2 progeny were sequenced through Illumina's Hi-Seq GAII platform. From sequence information of those variant call files, the SNPs were indexed and filtered by sequencing depth with genotype converter (SNP Genotyper), and optimized by heuristic physical bin mapping to construct more reliable genetic linkage map. Reliable SNP loci were determined and compared to sequences of physical reference map. Using the genetic map, we determined QTLs in F2:3 population and found major loci corresponding to seed size and powdery mildew race1 resistance in watermelon.

Based on double pseudo-testcross theory, a population of 76 F1 clones, which were derived from a cross of China type tea plants (Camellia sinensis var. sinensis) with a Korean tea cultivar, ‘Kemsull’ for female parent and a Japanese tea cultivar, ‘Houshun’ for male parent, was used to construct a genetic linkage map with AFLP markers. Totally, 2,360 markers were detected by 26 pairs of primers and 90.8 markers for each pair on average. Among these, 481 markers (20.3%) were polymorphic, 392 markers (81.5%) of which showed Mendelian segregation ratio (p=0.01). Of these Mendelian segregated markers, 139 (35.5%) were segregated in 3:1 ratio and 253 (65.5%) were segregated in 1:1 ratio. The construction of AFLP molecular marker based linkage map were carried out by Joinmap 4.0 version. The linkage map of ‘Kemsull’ contained 227 markers which distributed into 18 linkage groups. The linkage map of ‘Kemsull’ covered 1,382.2 cM with the average distance between two markers of 6.0 cM. The linkage map of ‘Houshun’ contained 154 markers which were distributed into 17 linkage groups and were spanned with the total map length of 1,540.9 cM and the average distance between two markers of 10 cM. However, these AFLP markers were not distributed evenly and further even saturation is additionally required.

Clubroot is a devastating disease caused by Plasmodiophora brassicae and results in severe losses of yield and quality in Brassica crops including Brassica oleracea. Therefore, it is important to identify resistance gene for CR disease and apply it to breeding of Brassica crops. In this study, we applied genotyping-by-sequencing (GBS) technique to construct high resolution genetic map and mapping of clubroot resistance (CR) genes. A total of 18,187 GBS markers were identified between two parent lines resistant and susceptible to the disease, of which 4,103 markers were genotyped in all 78 F2 plants generated from crossing of both parent lines. The markers were clustered into nine linkage groups spanning 879.9 cM, generating high resolution genetic map enough to refine reported reference genome of cabbage. In addition, through QTL analysis using 78 F2:3 progenies and mapping based on the genetic map, two and single major QTLs were identified for resistance of race 2 and race 9 of P. brassicae, respectively. These QTLs did not show collinearity with CR loci found in Chinese cabbage (Brassica rapa) but roughly overlapped with CR loci identified in cabbage for resistance to race 4. Taken together, genetic map and QTLs obtained in this study will provide valuable information to improve reference genome and clubroot resistance in cabbage.

Quantitative trait locus (QTL) mapping is a highly effective approach for studying genetically complex forms of plant shattering. With QTLs mapping, the shattering loci can be described. SSR marker is based on the imformation of Simple Sequence Repeat and easy to analyze using PCR and has high reproducibility. For analyzing QTLs associated with shattering, we selected 219 SSR markers from 254 SSR markers and used them for implementing Mapmaker(Ver. 3.0) and Mapchart(Ver. 2.2). Mapmaker help to calculate distances between each markers and Mapchart is a program for drawing Genetic map. This Genetic map of rice (Oryza sativa L.) covering 2082.4 cM with 9.5 cM between makers in the Kosambi function has been constructed using 120 F1 DH plants from a single cross between the indica variety Chungchung and the japonica variety Nagdong.

밀양23호/기호벼 재조합자식 유전집단을 대상으로 PCR 기반 DNA 마커들로 구성된 분자유전자지도를 만들고자, 주로 아가로스 젤 상에서 분석이 가능한 마커들을 위주로 STS, InDel, RTM, SSR 마커들을 선발하여 분석하였다. InDel 마커 37개, STS 마커 88개, RTM 마커 8개, SSR 마커 91개를 포함한 224개의 마커로 구성된 유전지도를 만들었는데, 총 유전거리는 1,425 cM이었으며, 마커간 평균거리는 6.7 cM이었다. 이들 DNA 마커들의 프라이머 시퀀스 정보를 바탕으로 e-PCR프로그램을 이용하여 각 마커들의 벼 유전체상에서의 물리적인 위치를 파악하고 물리지도를 작성하였다. 이 물리지도에서 마커간의 물리적 거리의 합은 356.8 Mbp이었으며, 총 유전거리에서 이를 나누어 구한 1 cM당 평균 물리적 거리는 250 kbp이었다. 5% 유의수준에서 분리비 편의(segregation distortion) 현상을 보인 마커는 전체 마커의 22.8%인 51개이었으며, 주로 3번 염색체의 중간부위, 6번 염색체의 거의 모든 영역, 7번 염색체의 상단부위, 8번 염색체의 하단부위, 12번 염색체의 상단부위에 분포하였다. 이 분자유전자지도는 자포니카형 품종과 통일형 품종 또는 인디카 품종간의 교배후대 집단에서 유용형질의 유전자 위치를 분석하고자 할 때 이용 가능한 마커들에 대한 정보를 제공할 것이다.

A core genetic map of the legume Medicago truncatula has been established by analyzing the segregation of 288 sequence-characterized genetic markers in an F2 population composed of 93 individuals. These molecular markers correspond to 141 ESTs, 80 BAC end sequence-tags, and 67 resistance gene analogs, covering 513 cM. In the case of EST-based markers we used an intron-targeted marker strategy, with primers designed to anneal in conserved exon regions and amplify across intron regions. Polymorphisms were significantly more frequent in intron vs exon regions, thus providing an efficient mechanism to map transcribed genes. Genetic and cytogenetic analysis produced eight well-resolved linkage groups, which have been previously correlated with eight chromosomes by means of FISH with mapped BAC clones. We anticipated that mapping of conserved coding regions would have utility for comparative mapping among legumes; thus 60 of the EST-based primer pairs were designed to amplify orthologous sequences across a range of legume species. As an initial test of this strategy, we used primers designed against M. truncatula exon sequences to rapidly map genes in Medicago sativa. The resulting comparative map, which includes 68 bridging markers, indicates that the two Medicago genomes are highly similar, and establishes the basis for a “Medicago” composite map.

Genetic map provides basic and important informations for breeding. Therefore, genetic map construction is a essential process in plant research. Panax ginseng is one of the most famous medical plant in the world. However, genetic informations of this medical plant for breeding are not enough. Because of little informations, genetic map construction of panax ginseng provides very useful information for breeding. Using Solexa next generation sequencing (NGS) technology, we have been produced a lot of expressed sequence tags (ESTs) and whole genome sequences from Chunpoong (368 Gb) and Yunpoong (6 Gb) cultivar. To develop large amount of DNA markers and thus construct high resolution genetic map, we inspect large scale of SSR motif and putative SNP sites which can be used as dCAPs markers using produced ginseng’s sequence data. As a result, we can find a number of DNA markers that have polymorphism between Yunpoong and Chunpoong cultivar. These developed DNA markers were analyzed for F2 population of Yunpoong x Chunpoong to find markers showing Mendelian segregation ratio 1:2:1.

Molecular genetic markers have wide applicability for a various genetic analyses, and genetic mapping with PCR-based markers has identified many loci in the rice genome. This study was conducted to develop a genetic map of rice based on SSR and MITE-AFLP

Genetic linkage maps serve the plant geneticist in a number of ways, from marker assisted selection in plant improvement to map-based cloning in molecular genetic research. Genetic map based upon DNA polymorphism is a powerful tool for the study of qualitative and quantitative traits in crops. The objective of this study was to develop genetic linkage map of soybean using the population derived from the cross of Korean soybean cultivar 'Kwangkyo, and wild accession 'IT182305'. Total 1,000 Operon random primers for RAPD marker, 49 combinations of primer for AFLP marker, and 100 Satt primers for SSR marker were used to screen parental polymorphism. Total 341 markers (242 RAPD, 83 AFLP, and 16 SSR markers) was segregated in 85 ~textrmF2 population. Forty two markers that shown significantly distorted segregation ratio (1:2:1 for codominant or 3:1 for domimant marker) were not used in mapping procedure. A linkage map was constructed by applying the computer program MAPMAKER/EXP 3.0 to the 299 marker data with LOD 4.0 and maximum distance 50 cM. 176 markers were found to be genetically linked and formed 25 linkage groups. Linkage map spanned 2,292.7 cM across all 25 linkage groups. The average linkage distance between pair of markers among all linkage groups was 13.0 cM. The number of markers per linkage group ranged from 2 to 55. The longest linkage group 3 spanned 967.4 cM with 55 makers. This map requires further saturation with more markers and agronomically important traits will be joined over it.