Barley systematics and taxonomy foreseen by seed morphometric variation.

Since its Neolithic domestication in the Fertile Crescent, barley has spread to all continents and represents a major cereal in many modern agrarian systems. Current barley diversity includes thousands of varieties divided into four main categories corresponding to 2-row and 6-row subspecies and naked and hulled types, each of them with winter and spring varieties. This diversity is associated to different uses and allow cultivation in diverse environments. We used a large dataset of 58 varieties of French origin, (1) to assess the taxonomic signal in barley grain measurements comparing 2-row and 6-row subspecies, and naked and hulled types; (2) to test the impact of the sowing period and interannual variation on the grains size and shape; (3) to investigate the existence of morphological differences between winter and spring types; and finally (4) to contrast the relationship between the morphometric and genetic proximity. Size and shape of 1980 modern barley caryopses were quantified through elliptic Fourier Transforms and traditional size measurements. Our results indicate that barley grains record morphological diversity of the ear (89.3% classification accuracy between 2-row/6-row subspecies; 85.2% between hulled and naked type), sowing time of the grains (from 65.6% to 73.3% within barley groups), and environmental conditions during its cultivation and varietal diversity. This study opens perspectives for studying archaeological barley seeds and tracing the barley diversity and evolution since the Neolithic.

Breeding for Economically and Environmentally Sustainable Wheat Varieties: An Integrated Approach from Genomics to Selection.

There is currently a strong societal demand for sustainability, quality, and safety in bread wheat production. To address these challenges, new and innovative knowledge, resources, tools, and methods to facilitate breeding are needed. This starts with the development of high throughput genomic tools including single nucleotide polymorphism (SNP) arrays, high density molecular marker maps, and full genome sequences. Such powerful tools are essential to perform genome-wide association studies (GWAS), to implement genomic and phenomic selection, and to characterize the worldwide diversity. This is also useful to breeders to broaden the genetic basis of elite varieties through the introduction of novel sources of genetic diversity. Improvement in varieties particularly relies on the detection of genomic regions involved in agronomical traits including tolerance to biotic (diseases and pests) and abiotic (drought, nutrient deficiency, high temperature) stresses. When enough resolution is achieved, this can result in the identification of candidate genes that could further be characterized to identify relevant alleles. Breeding must also now be approached through in silico modeling to simulate plant development, investigate genotype × environment interactions, and introduce marker-trait linkage information in the models to better implement genomic selection. Breeders must be aware of new developments and the information must be made available to the world wheat community to develop new high-yielding varieties that can meet the challenge of higher wheat production in a sustainable and fluctuating agricultural context. In this review, we compiled all knowledge and tools produced during the BREEDWHEAT project to show how they may contribute to face this challenge in the coming years.

Association between SNP Markers and 11 Vitamin Contents in Grains of a Worldwide Bread Wheat Core Collection.

The metabolomic profiling analyses of 11 vitamins' statuses of wheat grain in a subsample of 167 accessions from the INRAE worldwide bread wheat core collection planted in two contrasting environments in France (Le Moulon and Clermont-Ferrand) have been evaluated using a high-throughput liquid chromatography-tandem mass spectrometry (LC-MS/MS) procedure. This has allowed us to perform a genome-wide association study (GWAS) for these nutritional traits of interest combining the phenotypic data with the genotypic data derived from the TaBW280K SNP chip. Considering both thresholds (P < 0.0003 and R2 ≥ 8%), the GWAS identified between 1 and 22 marker-trait associations (MTAs) for the individual vitamins at the individual locations, and 12 SNP markers were stable and associated with vitamin contents across two environments. Desirable alleles and superior genotypes identified in the current analysis provide novel genetic data that can be used for future research on the genetics of vitamins and their application in wheat breeding.

Structural Variations Affecting Genes and Transposable Elements of Chromosome 3B in Wheats.

Structural variations (SVs) such as copy number and presence-absence variations are polymorphisms that are known to impact genome composition at the species level and are associated with phenotypic variations. In the absence of a reference genome sequence, their study has long been hampered in wheat. The recent production of new wheat genomic resources has led to a paradigm shift, making possible to investigate the extent of SVs among cultivated and wild accessions. We assessed SVs affecting genes and transposable elements (TEs) in a Triticeae diversity panel of 45 accessions from seven tetraploid and hexaploid species using high-coverage shotgun sequencing of sorted chromosome 3B DNA and dedicated bioinformatics approaches. We showed that 23% of the genes are variable within this panel, and we also identified 330 genes absent from the reference accession Chinese Spring. In addition, 60% of the TE-derived reference markers were absent in at least one accession, revealing a high level of intraspecific and interspecific variability affecting the TE space. Chromosome extremities are the regions where we observed most of the variability, confirming previous hypotheses made when comparing wheat with the other grasses. This study provides deeper insights into the genomic variability affecting the complex Triticeae genomes at the intraspecific and interspecific levels and suggests a phylogeny with independent hybridization events leading to different hexaploid species.

Worldwide phylogeography and history of wheat genetic diversity.

Since its domestication in the Fertile Crescent ~8000 to 10,000 years ago, wheat has undergone a complex history of spread, adaptation, and selection. To get better insights into the wheat phylogeography and genetic diversity, we describe allele distribution through time using a set of 4506 landraces and cultivars originating from 105 different countries genotyped with a high-density single-nucleotide polymorphism array. Although the genetic structure of landraces is collinear to ancient human migration roads, we observe a reshuffling through time, related to breeding programs, with the appearance of new alleles enriched with structural variations that may be the signature of introgressions from wild relatives after 1960.

Tracing the ancestry of modern bread wheats.

For more than 10,000 years, the selection of plant and animal traits that are better tailored for human use has shaped the development of civilizations. During this period, bread wheat (Triticum aestivum) emerged as one of the world's most important crops. We use exome sequencing of a worldwide panel of almost 500 genotypes selected from across the geographical range of the wheat species complex to explore how 10,000 years of hybridization, selection, adaptation and plant breeding has shaped the genetic makeup of modern bread wheats. We observe considerable genetic variation at the genic, chromosomal and subgenomic levels, and use this information to decipher the likely origins of modern day wheats, the consequences of range expansion and the allelic variants selected since its domestication. Our data support a reconciled model of wheat evolution and provide novel avenues for future breeding improvement.

High throughput SNP discovery and genotyping in hexaploid wheat.

Because of their abundance and their amenability to high-throughput genotyping techniques, Single Nucleotide Polymorphisms (SNPs) are powerful tools for efficient genetics and genomics studies, including characterization of genetic resources, genome-wide association studies and genomic selection. In wheat, most of the previous SNP discovery initiatives targeted the coding fraction, leaving almost 98% of the wheat genome largely unexploited. Here we report on the use of whole-genome resequencing data from eight wheat lines to mine for SNPs in the genic, the repetitive and non-repetitive intergenic fractions of the wheat genome. Eventually, we identified 3.3 million SNPs, 49% being located on the B-genome, 41% on the A-genome and 10% on the D-genome. We also describe the development of the TaBW280K high-throughput genotyping array containing 280,226 SNPs. Performance of this chip was examined by genotyping a set of 96 wheat accessions representing the worldwide diversity. Sixty-nine percent of the SNPs can be efficiently scored, half of them showing a diploid-like clustering. The TaBW280K was proven to be a very efficient tool for diversity analyses, as well as for breeding as it can discriminate between closely related elite varieties. Finally, the TaBW280K array was used to genotype a population derived from a cross between Chinese Spring and Renan, leading to the construction a dense genetic map comprising 83,721 markers. The results described here will provide the wheat community with powerful tools for both basic and applied research.

High-Resolution Mapping of Crossover Events in the Hexaploid Wheat Genome Suggests a Universal Recombination Mechanism.

During meiosis, crossovers (COs) create new allele associations by reciprocal exchange of DNA. In bread wheat (Triticum aestivum L.), COs are mostly limited to subtelomeric regions of chromosomes, resulting in a substantial loss of breeding efficiency in the proximal regions, though these regions carry ∼60-70% of the genes. Identifying sequence and/or chromosome features affecting recombination occurrence is thus relevant to improve and drive recombination. Using the recent release of a reference sequence of chromosome 3B and of the draft assemblies of the 20 other wheat chromosomes, we performed fine-scale mapping of COs and revealed that 82% of COs located in the distal ends of chromosome 3B representing 19% of the chromosome length. We used 774 SNPs to genotype 180 varieties representative of the Asian and European genetic pools and a segregating population of 1270 F6 lines. We observed a common location for ancestral COs (predicted through linkage disequilibrium) and the COs derived from the segregating population. We delineated 73 small intervals (<26 kb) on chromosome 3B that contained 252 COs. We observed a significant association of COs with genic features (73 and 54% in recombinant and nonrecombinant intervals, respectively) and with those expressed during meiosis (67% in recombinant intervals and 48% in nonrecombinant intervals). Moreover, while the recombinant intervals contained similar amounts of retrotransposons and DNA transposons (42 and 53%), nonrecombinant intervals had a higher level of retrotransposons (63%) and lower levels of DNA transposons (28%). Consistent with this, we observed a higher frequency of a DNA motif specific to the TIR-Mariner DNA transposon in recombinant intervals.

Exploiting the Repetitive Fraction of the Wheat Genome for High-Throughput Single-Nucleotide Polymorphism Discovery and Genotyping.

Transposable elements (TEs) account for more than 80% of the wheat genome. Although they represent a major obstacle for genomic studies, TEs are also a source of polymorphism and consequently of molecular markers such as insertion site-based polymorphism (ISBP) markers. Insertion site-based polymorphisms have been found to be a great source of genome-specific single-nucleotide polymorphism (SNPs) in the hexaploid wheat ( L.) genome. Here, we report on the development of a high-throughput SNP discovery approach based on sequence capture of ISBP markers. By applying this approach to the reference sequence of chromosome 3B from hexaploid wheat, we designed 39,077 SNPs that are evenly distributed along the chromosome. We demonstrate that these SNPs can be efficiently scored with the KASPar (Kompetitive allele-specific polymerase chain reaction) genotyping technology. Finally, through genetic diversity and genome-wide association studies, we also demonstrate that ISBP-derived SNPs can be used in marker-assisted breeding programs.

Predictions of heading date in bread wheat (Triticum aestivum L.) using QTL-based parameters of an ecophysiological model.

Prediction of wheat phenology facilitates the selection of cultivars with specific adaptations to a particular environment. However, while QTL analysis for heading date can identify major genes controlling phenology, the results are limited to the environments and genotypes tested. Moreover, while ecophysiological models allow accurate predictions in new environments, they may require substantial phenotypic data to parameterize each genotype. Also, the model parameters are rarely related to all underlying genes, and all the possible allelic combinations that could be obtained by breeding cannot be tested with models. In this study, a QTL-based model is proposed to predict heading date in bread wheat (Triticum aestivum L.). Two parameters of an ecophysiological model (V sat and P base , representing genotype vernalization requirements and photoperiod sensitivity, respectively) were optimized for 210 genotypes grown in 10 contrasting location × sowing date combinations. Multiple linear regression models predicting V sat and P base with 11 and 12 associated genetic markers accounted for 71 and 68% of the variance of these parameters, respectively. QTL-based V sat and P base estimates were able to predict heading date of an independent validation data set (88 genotypes in six location × sowing date combinations) with a root mean square error of prediction of 5 to 8.6 days, explaining 48 to 63% of the variation for heading date. The QTL-based model proposed in this study may be used for agronomic purposes and to assist breeders in suggesting locally adapted ideotypes for wheat phenology.

Structural and functional partitioning of bread wheat chromosome 3B.

We produced a reference sequence of the 1-gigabase chromosome 3B of hexaploid bread wheat. By sequencing 8452 bacterial artificial chromosomes in pools, we assembled a sequence of 774 megabases carrying 5326 protein-coding genes, 1938 pseudogenes, and 85% of transposable elements. The distribution of structural and functional features along the chromosome revealed partitioning correlated with meiotic recombination. Comparative analyses indicated high wheat-specific inter- and intrachromosomal gene duplication activities that are potential sources of variability for adaption. In addition to providing a better understanding of the organization, function, and evolution of a large and polyploid genome, the availability of a high-quality sequence anchored to genetic maps will accelerate the identification of genes underlying important agronomic traits.

Association study of wheat grain protein composition reveals that gliadin and glutenin composition are trans-regulated by different chromosome regions.

Wheat grain storage protein (GSP) content and composition are the main determinants of the end-use value of bread wheat (Triticum aestivum L.) grain. The accumulation of glutenins and gliadins, the two main classes of GSP in wheat, is believed to be mainly controlled at the transcriptional level through a network of transcription factors. This regulation network could lead to stable cross-environment allometric scaling relationships between the quantity of GSP classes/subunits and the total quantity of nitrogen per grain. This work conducted a genetic mapping study of GSP content and composition and allometric scaling parameters of grain N allocation using a bread wheat worldwide core collection grown in three environments. The core collection was genotyped with 873 markers for genome-wide association and 167 single nucleotide polymorphism markers in 51 candidate genes for candidate association. The candidate genes included 35 transcription factors (TFs) expressed in grain. This work identified 74 loci associated with 38 variables, of which 19 were candidate genes or were tightly linked with candidate genes. Besides structural GSP genes, several loci putatively trans-regulating GSP accumulation were identified. Seven candidate TFs, including four wheat orthologues of barley TFs that control hordein gene expression, were associated or in strong linkage disequilibrium with markers associated with the composition or quantity of glutenin or gliadin, or allometric grain N allocation parameters, confirming the importance of the transcriptional control of GSP accumulation. Genome-wide association results suggest that the genes regulating glutenin and gliadin compositions are mostly distinct from each other and operate differently.

Rht-1 and Ppd-D1 associations with height, GA sensitivity, and days to heading in a worldwide bread wheat collection.

Reduced height (Rht)-1 and Photoperiod (Ppd) have major effects on the adaptability of bread wheat (Triticum aestivum) to specific environments. Ppd-D1a is a photoperiod insensitive allele that reduces time to flowering. The gibberellin (GA) insensitive alleles Rht-B1b and Rht-D1b shorten plant stature and were important components of the 'green revolution'. Two additional Rht-B1 alleles were recently identified that contain a 160 or 197 bp insertion upstream of the coding region and may affect plant height or GA sensitivity Wilhelm et al. (Theor Appl Gen doi: 10.1007/s00122-013-2088-7 , 2013b). We determined the frequency of the five alleles in a worldwide core collection of 372 wheat accessions (372CC) and estimated their effects on height, days to heading, and GA sensitivity when the collection was grown in pots outdoors or in the glasshouse. This revealed that each allele was widespread geographically with frequencies ranging from 0.12 to 0.25. Ppd-D1a was associated with significant (p ≤ 0.05) reductions in days to heading and height relative to photoperiod sensitive Ppd-D1b. Relative to wild type, Rht-B1b and Rht-D1b each resulted in significant reductions in height (approximately 30 %) and GA sensitivity. The 160 and 197 bp alleles were associated with significant height reductions of 18 and 12 %, respectively, and with non-significant reductions in GA sensitivity relative to wild type. Two statistical methods were developed and used to estimate GA sensitivity of the 372CC accessions, but novel GA insensitive alleles were not identified. Further characterization of the Rht-B1 insertion alleles is required, but our results suggest these may enable fine adjustments in plant height.

Haplotype dictionary for the Rht-1 loci in wheat.

The introduction of Reduced height (Rht)-B1b and Rht-D1b into bread wheat (Triticum aestivum) varieties was a key component of the 'green revolution' and today these alleles are the primary sources of semi-dwarfism in wheat. The Rht-1 loci encode DELLA proteins, which are transcription factors that affect plant growth and stress tolerance. In bread wheat, Rht-D1b and Rht-B1b influence resistance to the disease Fusarium Head Blight. To identify Rht-1 variants, locus specific primers were developed and used to sequence the entire open reading frame (ORF) and 1.7 kb of the 5' and 0.5 kb of the 3' flanking regions of Rht-A1 (Rht-A1+f), Rht-B1 (Rht-B1+f), and Rht-D1 (Rht-D1+f) in bread wheat (36 sequences from each genome) and tetraploid and diploid wheat (TDW) (one to three sequences from each genome). Among the bread wheat accessions, the Rht-A1+f and Rht-D1+f sequences contained relatively low genetic diversity and few haplotypes relative to the Rht-B1+f sequences. The TDW accessions were relatively rich in genetic diversity and contained the majority of the polymorphic sites. Novel polymorphisms, relative to 'Chinese Spring', discovered among the accessions include 160 and 197 bp insertions 5' of Rht-B1 and a frameshift in the Rht-B1 ORF. Quantitative real-time PCR using shoot and leaf tissue from 5-day-old seedlings of genotypes lacking or containing the 5' insertions revealed no major effect on Rht-B1 transcript accumulation. This research provides insights into the genetic diversity present at the Rht-1 loci in modern bread wheat and in relation to ancestral wheat accessions.

Association mapping and haplotype analysis of a 3.1-Mb genomic region involved in Fusarium head blight resistance on wheat chromosome 3BS.

A previous study provided an in-depth understanding of molecular population genetics of European and Asian wheat gene pools using a sequenced 3.1-Mb contig (ctg954) on chromosome 3BS. This region is believed to carry the Fhb1 gene for response to Fusarium head blight. In this study, 266 wheat accessions were evaluated in three environments for Type II FHB response based on the single floret inoculation method. Hierarchical clustering (UPGMA) based on a Manhattan dissimilarity matrix divided the accessions into eight groups according to five FHB-related traits which have a high correlation between them; Group VIII comprised six accessions with FHB response levels similar to variety Sumai 3. Based on the compressed mixed linear model (MLM), association analysis between five FHB-related traits and 42 molecular markers along the 3.1-Mb region revealed 12 significant association signals at a threshold of P<0.05. The highest proportion of phenotypic variation (6.2%) in number of diseased spikelets (NDS) occurred at locus cfb6059, and the physical distance was about 2.9 Kb between umn10 and this marker. Haplotype block (HapB) analysis using a sliding window LD of 5 markers, detected six HapBs in the 3.1-Mb region at r(2)>0.1 and P<0.001 between random closely linked markers. F-tests among Haps with frequencies >0.05 within each HapB at r(2)>0.1 and P<0.001 showed significant differences between the Hap carried by FHB resistant resources, such as Sumai 3 and Wangshuibai, and susceptible genotypes in HapB3 and HapB6. These results suggest that Fhb1 is located within HapB6, with the possibility that another gene is located at or near HapB3. SSR markers and Haps detected in this study will be helpful in further understanding the genetic basis of FHB resistance, and provide useful information for marker-assisted selection of Fhb1 in wheat breeding.

Strong presence of the high grain protein content allele of NAM-B1 in Fennoscandian wheat.

Grain protein content in wheat has been shown to be affected by the NAM-B1 gene where the wildtype allele confers high levels of protein and micronutrients but can reduce yield. Two known non-functional alleles instead increase yield but lead to lower levels of protein and micronutrients. The wildtype allele in hexaploid bread wheat is so far mainly known from historical specimens and a few lines with an emmer wheat introgression. Here we report a screening for the wildtype allele in wheats of different origin. First, a worldwide core collection of 367 bread wheats with worldwide origin was screened and five accessions carrying the wildtype NAM-B1 allele were found. Several of these could be traced to a Fennoscandian origin and the wildtype allele was more frequent in spring wheat. These findings, together with the late maturation of spring wheat, suggested that the faster maturation caused by the wildtype allele might have preserved it in areas with a short growing season. Thus a second set consisting of 138 spring wheats of a northern origin was screened and as many as 33 % of the accessions had the wildtype allele, all of a Fennoscandian origin. The presence of the wildtype allele in landraces and cultivars is in agreement with the use of landraces in Fennoscandian wheat breeding. Last, 22 spelt wheats, a wheat type previously suggested to carry the wildtype allele, were screened and five wildtype accessions found. The wildtype NAM-B1 accessions found could be a suitable material for plant breeding efforts directed towards increasing the nutrient content of bread wheat.

Application of direct calibration in multivariate image analysis of heterogeneous materials.

Many scientific instruments produce multivariate images characterized by three-way tables, an element of which represents the intensity value at a spatial location for a given spectral channel. A problem frequently encountered is to attempt estimating the contributions of some compounds at each location of these images. Usual regression methods of calibration, such as PLS, require having a matrix of calibration X (n×p) and the corresponding vector y of the dependent variable (n×1). X can be built up by sampling pixel-vectors in the images, but y is sometimes difficult to obtain, if the surface of the samples is formed by chemically heterogeneous regions. In this case, the quantitative analyses related to y may be difficult, if the pixels represent very small areas (for example on microscopic images) or very large ones (satellite images). This is for example the case when dealing with biological solid samples representing different tissues. Direct Calibration (DC), sometimes referred to as "spectral unmixing", do not require having such a calibration set. However, it is indeed needed to have both a matrix of "perturbing" pixel-vectors (noted K) and a vector of the "pure" component spectrum to be analyzed (p), which are more easily obtainable. For estimating the contribution, the unknown pixel vector x and the pure spectrum p are first projected orthogonally onto K giving the vectors x(⊥) onto p(⊥), respectively. The contribution is then estimated by a second projection of x(⊥) onto p(⊥). A method, based on principal component analysis, for determining the optimal dimensions of K is proposed. DC was applied on a collection of multivariate images of kernel of wheat to estimate the proportion of three tissues, namely out-layers, "waxy"endosperm and normal endosperm. The eventual results are presented as images of wheat kernels in false colors associated to the estimated proportions of the tissues. It is shown that DC is appropriate for estimating contributions in situations in which the more usual methods of calibration cannot be applied.

Deciphering the genetics of flowering time by an association study on candidate genes in bread wheat (Triticum aestivum L.).

Earliness is very important for the adaptation of wheat to environmental conditions and the achievement of high grain yield. A detailed knowledge of key genetic components of the life cycle would enable an easier control by the breeders. The objective of the study was to investigate the effect of candidate genes on flowering time. Using a collection of hexaploid wheat composed of 235 lines from diverse geographical origins, we conducted an association study for six candidate genes for flowering time and its components (vernalization sensitivity and earliness per se). The effect on the variation of earliness components of polymorphisms within the copies of each gene was tested in ANOVA models accounting for the underlying genetic structure. The collection was structured in five groups that minimized the residual covariance. Vernalization requirement and lateness tend to increase according to the mean latitude of each group. Heading date for an autumnal sowing was mainly determined by the earliness per se. Except for the Constans (CO) gene orthologous of the barley HvCO3, all gene polymorphisms had a significant impact on earliness components. The three traits used to quantify vernalization requirement were primarily associated with polymorphisms at Vrn-1 and then at Vrn-3 and Luminidependens (LD) genes. We found a good correspondence between spring/winter types and genotypes at the three homeologous copies of Vrn-1. Earliness per se was mainly explained by polymorphisms at Vrn-3 and to a lesser extent at Vrn-1, Hd-1 and Gigantea (GI) genes. Vernalization requirement and earliness as a function of geographical origin, as well as the possible role of the breeding practices in the geographical distribution of the alleles and the hypothetical adaptive value of the candidate genes, are discussed.

Variation in crossover rates across a 3-Mb contig of bread wheat (Triticum aestivum) reveals the presence of a meiotic recombination hotspot.

In bread wheat (Triticum aestivum L.), initial studies using deletion lines indicated that crossover (CO) events occur mainly in the telomeric regions of the chromosomes with a possible correlation with the presence of genes. However, little is known about the distribution of COs at the sequence level. To investigate this, we studied in detail the pattern of COs along a contig of 3.110 Mb using two F2 segregating populations (Chinese Spring × Renan (F2-CsRe) and Chinese Spring × Courtot (F2-CsCt)) each containing ~2,000 individuals. The availability of the sequence of the contig from Cs enabled the development of 318 markers among which 23 co-dominant polymorphic markers (11 SSRs and 12 SNPs) were selected for CO distribution analyses. The distribution of CO events was not homogeneous throughout the contig, ranging from 0.05 to 2.77 cM/Mb, but was conserved between the two populations despite very different contig recombination rate averages (0.82 cM/Mb in F2-CsRe vs 0.35 cM/Mb in F2-CsCt). The CO frequency was correlated with the percentage of coding sequence in Cs and with the polymorphism rate between Cs and Re or Ct in both populations, indicating an impact of these two factors on CO distribution. At a finer scale, COs were found in a region covering 2.38 kb, spanning a gene coding for a glycosyl transferase (Hga3), suggesting the presence of a CO hotspot. A non-crossover event covering at least 453 bp was also identified in the same interval. From these results, we can conclude that gene content could be one of the factors driving recombination in bread wheat.

Genetic diversity and linkage disequilibrium studies on a 3.1-Mb genomic region of chromosome 3B in European and Asian bread wheat (Triticum aestivum L.) populations.

Genetic diversity and linkage disequilibrium (LD) were investigated in 376 Asian and European accessions of bread wheat (Triticum aestivum L.). After a first and rapid screening about diversity and genetic structure at the whole genome scale using 70 simple sequence repeats (SSRs), we focused on a sequenced contig (ctg954) of 3.1 Mb located on the short arm of chromosome 3B of cv. Chinese Spring, using 32 SSRs and 10 single nucleotide polymorphisms. This contig is part of a multiple fungal resistance region. Mean polymorphism information content value on the 32 SSRs was slightly higher in the Asian genepool (0.396) than that for the European (0.329) pool. Compared with results at the whole genome scale, data from this 3.1-Mb region indicated similar trends in genetic diversity indices between both genepools. Population structure and molecular variance analyses demonstrated significant genetic differentiation and geographical subdivision in both groups of accessions. Concerning LD at the contig level, the European population had a significantly higher mean r(2) value (0.23) than the Asian population (0.18), indicating a stronger LD in the European material. With a mean of 1 marker every 74 kb, the resolution reached here allowed to perform a detailed comparative analysis of the LD and genetic diversity along the complete 3.1-Mb region in both genepools. A sliding-window approach revealed some interesting regions of the contig where LD is increasing when genetic diversity is decreasing. This study provides an in-depth understanding of molecular population genetics in European and Asian wheat gene pools, and prospects for association mapping of important sources of fungal disease resistance.