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Although understanding factors determining the genetic makeup of natural populations has long been an important goal of evolutionary biology, the effect of population position within the species range (i.e., interior vs. edge) on species genetic variation is still unclear. According to the ‘abundant center’ hypothesis, the range edge populations are expected to exhibit lower genetic variation and higher differentiation than core populations because of their greater spatial isolation and smaller size. We tested these predictions by comparing the extent and structure of neutral (SSR) and quantitative trait genetic variation in 20 populations of an annual grass Avena sterilis hierarchically sampled at the species range core and two opposite edges. Within-population genetic diversity was reduced at the desert range edge compared to the range core as assessed by six SSR markers but not by eight quantitative traits; no reduction was detected at the mountain edge. Genetic differentiation among populations was higher at the desert range edge than the range core in both molecular markers and quantitative traits, but not at the mountain edge. Our results imply that the pattern of population genetic variation at the species range edges largely depends on the steepness of the environmental cline that has a major effect on species fitness. The more gradual the environmental cline from the species interior towards the edge, the higher the probability of detecting reduced genetic diversity and increased differentiation of peripheral populations as predicted by the ‘abundant center’ hypothesis.

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W244: Climate change poses major challenge for global wheat production and thus food security. Drought, heat, salinity and recurrent rust, septoria and fusarium epidemic waves are among the most common abiotic and biotic stresses limiting wheat crop productivity and sustainability worldwide. If adequately characterized, natural variants present in underutilized plant genetic resources (PGRs) are potentially valuable for providing improvements on resilience to abiotic stress and durable resistance to plant pathogens. In this context, Golden-standard reference genomes as well as characterized PGRs are instrumental. Both Triticum aestivum and Triticum turgidum ssp. durum share BB and AA genomes inherited from wild and domesticated emmer throughout complex steps of domestication, spread and migration events from the Fertile Crescent to diverse environments and agro-ecological conditions. With the aim of facilitating germplasm characterization and use, we assembled two comprehensive and complementary tetraploid collections: i) the Global Durum Wheat Panel (GDP) and the Tetraploid wheat Global Collection (TGC, Maccaferri et al. Nature Genetics 2019). GDP was established through a cooperative effort in the frame of the Wheat Initiative. GDP, currently maintained by ICARDA, was assembled by bringing together the durum wheat cultivated germplasm from more than 50 countries worldwide, including ca. 500 cultivars and 400 landraces, pre-breeeding lines and emmer. The Tetraploid wheat Global Collection (TGC), of 1,856 single-seed descent derived-genotypes, represents 11 tetraploid BBAA wheat taxa covering the whole distribution range. The Illumina 90K wheat SNP array was used to characterize both collections. Ca. 20,000 unique, non-redundant, single Mendelian SNP markers that were both genetically and physically mapped were use to obtain a haplo-based map of germplasm. We provide a detailed dissection of the huge reservoir of genetic diversity available in these two tetraploid genetic resources and examples of successful utilization of these resource to conduct GWAS for traits related to improvement of wheat sustainability and adaptation to climate change effects.

Background The tetraploid durum wheat (Triticum turgidum L. ssp. durum Desf. Husnot) is an important crop which provides the raw material for pasta production and a valuable source of genetic diversity for breeding hexaploid wheat (Triticum aestivum L.). Future breeding efforts to enhance yield potential and climate resilience will increasingly rely on genomics-based approaches to identify and select beneficial alleles. A deeper characterisation of the molecular and functional diversity of the durum wheat transcriptome will be instrumental to more effectively harness its genetic diversity. Results We report on the de novo transcriptome assembly of durum wheat cultivar ‘Svevo’. The transcriptome of four tissues/organs (shoots and roots at the seedling stage, reproductive organs and developing grains) was assembled de novo, yielding 180,108 contigs, with a N50 length of 1121 bp and mean contig length of 883 bp. Alignment against the transcriptome of nine plant species identified 43% of transcripts with homology to at least one reference transcriptome. The functional annotation was completed by means of a combination of complementary software. The presence of differential expression between the A- and B-homoeolog copies of the durum wheat tetraploid genome was ascertained by phase reconstruction of polymorphic sites based on the T. urartu transcripts and inferring homoeolog-specific sequences. We observed greater expression divergence between A and B homoeologs in grains rather than in leaves and roots. The transcriptomes of 13 durum wheat cultivars spanning the breeding period from 1969 to 2005 were analysed for SNP diversity, leading to 95,358 non-rare, hemi-SNPs shared among two or more cultivars and 33,747 locus-specific (diploid inheritance) SNPs. Conclusions Our study updates and expands the de novo transcriptome reference assembly available for durum wheat. Out of 180,108 assembled transcripts, 13,636 were specific to the Svevo cultivar as compared to the only other reference transcriptome available for durum, thus contributing to the identification of the tetraploid wheat pan-transcriptome. Additionally, the analysis of 13 historically relevant hallmark varieties produced a SNP dataset that could successfully validate the genotyping in tetraploid wheat and provide a valuable resource for genomics-assisted breeding of both tetraploid and hexaploid wheats. Electronic supplementary material The online version of this article (10.1186/s12864-019-5645-x) contains supplementary material, which is available to authorized users.

Triticum turgidum genetic resources are a wide reservoir of diversity, valuable for both durum wheat and common wheat pre-breeding, as highlighted by the success of synthetic wheats. However, a comprehensive analysis of these resources is lacking. As part of the Svevo durum wheat genome sequencing, we assembled a Global Tetraploid wheat Collection (GTC) of 1,856 accessions from 11 tetraploid wheat taxa, including wild and domesticated emmer (WEW and DEW) durum landraces (DWL) and modern durum wheat cultivars (DWC). We used the iSelect 90K SNP array anchored to the Svevo genome to investigate population structure and selection/demography signatures. We traced: i) the inheritance of haplotype blocks from either the North-eastern or Southern Levantine Fertile Crescent (Turkey) WEW populations to whole DEW germplasm, with a 0.65/0.35 overall inheritance ration, ii) the two subsequent independent but similar star-like dispersal patterns associated to DEW and DWL evolution, with six main populations each. Durum wheat most probably originated from the Southern-levant DEW. Ethiopian emmer and durum, T. turanicum and T. carthlicum were the most differentiated with minimal contribution to modern durum. Modern durum originated mostly from the North-African and Transcaucasian DWL populations. WEW, with the highest genome-wide diversity, provided the reference for assessing the diversity reductions associated to domestication and breeding. Numerous strong diversity depletions signals were observed primarily for the WEW-to-DEW transition. These signals progressively consolidated through domestication and breeding. Specific DEW-to-DWL signals were also observed. Diversity reduction index (DRI), Fst, haplotype-based XP-EHH and hapFLK and spatial pattern of site frequency spectrum (XP-CLR) metrics were considered. Frequently two or more indexes occurred in overlapping regions (selection clusters). In total, 104 pericentromeric (average size of 107.7 Mb) and 350 non-pericentromeric (average size of 11.4 Mb) clusters were identified. WEW-to-DEW and DEW-to-DWL transitions mostly involved extended pericentromeric regions tagged by DRI and Fst, while the DEW-to-DWL and DWL-to-DWC transitions were mostly associated to numerous XP-EHH and XP-CLR signals. We carried out a comprehensive projection of the published tetraploid QTLome and investigated the genome-wide QTL distribution and co-location between meta-QTLs and demography/selection signals. The usefulness of the GTC to elucidate the evolutionary patterns associated to loci, haplotype blocks and causative sequence variants for traits of breeding interest like cadmium-cumulation in grains, grain size and disease resistance loci are reported.

The release of several wheat reference genome sequences lays the basis for accelerating wheat improvement. However, additional effort is require to capture/exploit native variability. Triticum turgidum genetic resources provide a rich diversity reservoir, valuable for both durum and common wheat. We collected iSelect 90K wheat SNP data for 1,856 accessions from 11 tetraploid wheat taxa, including wild and domesticated emmer wheat (WEW and DEW), durum landraces (DWL) and modern durum cultivars (DWC), known as Global Tetraploid wheat Collection (GTC). Infinium raw data were processed under a unique pipeline and over 23,000 SNPs were anchored to Svevo genome. WEW and DEW were highly structured while DWL showed high admixture already at low k values. WEW germplasm was split into North-Eastern and Southern Levant Fertile Crescent populations (WEW-NE and WEW-SL, respectively) and many subpopulations. DEW and DWL showed two similar but independent radial dispersal patterns including six main populations each following North/South and Fertile Crescent to Mediterranean basin and Greece-to-Balkans (Western), Iran-to-Transcaucasia and Oman-to-India, Ethiopia (Eastern) spread. Domestication bottlenecks and haplotype transmission rate were traced for the three main transitions (WEW-to-DEW early domestication, DEW-to-DWL and DWL-to-DWC evolution under domestication). WEW had the highest, evenly distributed diversity, thus providing the reference for assessing diversity reductions. Diversity reduction index (DRI), Fst, haplotype-based XP-EHH, hapFLK and XP-CLR metrics served to produce a selection/demography signal map. In total, 104 pericentromeric (average size of 107.7 Mb) and 350 non-pericentromeric (average size of 11.4 Mb) signal clusters were identified. Numerous strong diversity depletions characterized the WEW-to-DEW transition, for 2Gb in total. These signals progressively consolidated through domestication and breeding and novel signals were found, affecting up to 5Gb in DWC. WEW-to-DEW signals involved extended pericentromeric regions tagged by DRI and Fst while DEW-to-DWL and DWL-to-DWC were mostly associated to numerous XP-EHH and XP-CLR signals. Nevertheless, DEW-to-DWL-specific strong signals were observed in chromosomes 1A, 1B, 2B, 3B, 7A, 7B. Genome-wide haplo-blocks were transmitted from WEW-NE and WEW-SL to DEW with a 0.65/0.35 overall inheritance ratio. Based on haplo-block transmission rate in selected key-regions, durum wheat (DWL) most probably originated from the Southern-levant and SL-to-Europe DEW. Modern durum originated mostly from the North-African and Transcaucasian DWL. Ethiopian germplasm, T.turanicum and T.carthlicum were the most differentiated with minimal contribution to modern durum. Our results show the usefulness of the GTC to elucidate the evolutionary patterns associated to loci, haplotype blocks and causative sequence variants for traits of breeding interest.

The assembled Svevo durum wheat genome and the iSelect wheat 90K SNP array were used as a base to characterize a world-wide tetraploid wheat collection. We report on the diversity pattern of 1,854 non-redundant accessions from all known Triticum turgidum subspecies. The genetic diversity survey relied on a common genotype-calling pipeline from AgriBio supported by 17 tetraploid linkage maps. The pipeline yielded 17,416 informative single-locus SNPs anchored to the Svevo genome. Among the wild emmer (WEW), domesticated emmer (DEW), durum wheat landraces (DWL) and durum wheat cultivars (DWC), WEW showed the highest and uniform diversity across the whole genome, providing a reference for cross-comparison with DEW, DWL and DWC. Extended diversity depletions associated to domestication were found particularly in pericentromeric regions. Some 38.2% of DW genome was affected by strong genetic bottleneck/selection events leading to diversity depletions. Six extended regions showed increased genetic diversity associated to DEW-DWL and DWL-DWC transitions. Population structure revealed multiple subsequent events of population differentiation associated to human-driven dispersal routes. This analysis provides the basis for a more informative re-sequencing towards a tetraploid pan-genome. Sub-panels have already been used for GWAS analysis, allowing us to identify GWAS-QTL that can be readily used in breeding. GWAS-QTLs for grain yield components (grain size and grain number per spike) and resistance to diseases have been identified using a subpanel of Mediterranean DW landraces. These resources allowed us to map QTLs at an improved resolution (1 cM confidence interval) and readily scan the genome for underlying candidate genes.

PubMedID: 30962619 The domestication of wild emmer wheat led to the selection of modern durum wheat, grown mainly for pasta production. We describe the 10.45 gigabase (Gb) assembly of the genome of durum wheat cultivar Svevo. The assembly enabled genome-wide genetic diversity analyses revealing the changes imposed by thousands of years of empirical selection and breeding. Regions exhibiting strong signatures of genetic divergence associated with domestication and breeding were widespread in the genome with several major diversity losses in the pericentromeric regions. A locus on chromosome 5B carries a gene encoding a metal transporter (TdHMA3-B1) with a non-functional variant causing high accumulation of cadmium in grain. The high-cadmium allele, widespread among durum cultivars but undetected in wild emmer accessions, increased in frequency from domesticated emmer to modern durum wheat. The rapid cloning of TdHMA3-B1 rescues a wild beneficial allele and demonstrates the practical use of the Svevo genome for wheat improvement. © 2019, The Author(s), under exclusive licence to Springer Nature America, Inc. Western Grains Research Foundation Ministry of Agriculture - Saskatchewan Israel Science Foundation: 1137/17 031A536 FP7 Food, Agriculture and Fisheries, Biotechnology: DROPS ID244347 Natural Sciences and Engineering Research Council of Canada InterOmics PB05 Genome Prairie United States-Israel Binational Science Foundation: 2015409 Genome Canada Saskatchewan Canola Development Commission 2819103915 PIR01_00017 3060-21000-038-00-D We acknowledge the funding support of: the Italian Ministry of Education and Research with projects CNR Flagship InterOmics PB05 (L.M., A.C., G.S.), PON ELIXIR CNR-BiOmics PIR01_00017 (L.M., M.G., M.Mo.) and PON ISCOCEM (P.D.); CREA project Interomics (L.C.); Fondazione in rete per la ricerca agroalimentare AGER project From Seed to Pasta (R.T.); FP7-KBBE Project DROPS ID244347 (R.T.); Genome Canada (A.G.S., C.P.); the Western Grain Research Foundation (A.G.S., C.P.); the Manitoba Wheat and Barley Commission (A.G.S., C.P.); the Saskatchewan Wheat Development Commission (A.G.S., C.P.); the Alberta Wheat Development Commission (A.G.S., C.P.); the Saskatchewan Ministry of Agriculture (A.G.S., C.P.); the administrative support of Genome Prairie (A.G.S., C.P.); Canadian Triticum Applied Genomics -CTAG2-(A.G.S., C.P.); Binational Science Foundation grant no. 2015409 (I.H., A.D.); Israel Science Foundation grant no. 1137/17 (A.D.); USDA-Agricultural Research Service Current Research Information System project 3060-21000-038-00-D (J.D.F., S.S.X.); German Federal Ministry of Food and Agriculture grant no. 2819103915 (N.S., K.F.X.M.); German Ministry of Education and Research grant no. 031A536 (K.F.X.M.); and Natural Sciences and Engineering Council of Canada grant nos. SPG 336119-06 and RGPIN 92787 (G.J.T., C.P.). The authors are grateful to E. Elias (North Dakota State University) for providing nine DW cultivars, included in the Global Tetraploid Wheat Collection and E. Scarpella (University of Alberta, Edmonton, Canada) for assistance with confocal microscopy.

Gene flow at a fine scale is still poorly understood despite its recognized importance for plant population demographic and genetic processes. We tested the hypothesis that intensity of gene flow will be lower and strength of spatial genetic structure (SGS) will be higher in more peripheral populations because of lower population density. The study was performed on the predominantly selfing Avena sterilis and included: (1) direct measurement of dispersal in a controlled environment; and (2) analyses of SGS in three natural populations, sampled in linear transects at fixed increasing inter-plant distances. We found that in A. sterilis major seed dispersal is by gravity in close (less than 2 m) vicinity of the mother plant, with a minor additional effect of wind. Analysis of SGS with six nuclear SSRs revealed a significant autocorrelation for the distance class of 1 m only in the most peripheral desert population, while in the two core populations with Mediterranean conditions, no genetic structure was found. Our results support the hypothesis that intensity of SGS increases from the species core to periphery as a result of decreased within-population gene flow related to low plant density. Our findings also show that predominant self-pollination and highly localized seed dispersal lead to SGS at a very fine scale, but only if plant density is not too high.

The adaptive potential of populations and therefore their ability to cope with rapid environmental changes is a question of paramount fundamental and applied importance. However, what is still not clear is the effect of population position within the species range (i.e. core vs. edge) on population adaptive potential, and whether the adaptive potential can be predicted from extent of neutral molecular variation. In this study, we compared the extent and structure of neutral (SSR) and presumably adaptive quantitative trait genetic variation in populations of Triticum dicoccoides sampled at the species range core and two opposite edges, and related this information to multigenerational performance of plants experimentally introduced beyond the range edge. The plants from the species arid edge performed worse than plants from the more mesic core in extreme desert conditions. The core and edge populations did not differ in extent of SSR variation. In contrast to the neutral genetic variation, there was lower quantitative trait variation in the two edge as compared with the core population for many traits, and no trait in any edge population had higher variation than the core population or either of its habitats. Reduced variation in selectively important traits indicates a lower adaptive potential of the two edge as compared with the core population. Our results imply (1) that extent of variation in quantitative traits can predict plant performance in novel environments while extent of variation in molecular markers can not; and (2) caution in usage of peripheral populations in such conservation actions as relocation and creation of new populations. We also warn against usage of neutral molecular variation as a surrogate for selectively important quantitative variation in conservation decisions.

Evaluating the relative importance of neutral and adaptive processes as determinants of population differentiation across environments is a central theme of evolutionary biology. We applied the QST-FST comparison flanked by a direct test for local adaptation to infer the role of climate-driven selection and gene flow in population differentiation of an annual grass Avena sterilis in two distinct parts of the species range, edge and interior, which represent two globally different climates, desert and Mediterranean. In a multiyear reciprocal transplant experiment, the plants of desert and Mediterranean origin demonstrated home advantage, and population differentiation in several phenotypic traits related to reproduction exceeded neutral predictions, as determined by comparisons of QST values with theoretical FST distributions. Thus, variation in these traits likely resulted from local adaptation to desert and Mediterranean environments. The two separate common garden experiments conducted with different experimental design revealed that two population comparisons, in contrast to multi-population comparisons, are likely to detect population differences in virtually every trait, but many of these differences reflect effects of local rather than regional environment. We detected a general reduction in neutral (SSR) genetic variation but not in adaptive quantitative trait variation in peripheral desert as compared with Mediterranean core populations. On the other hand, the molecular data indicated intensive gene flow from the Mediterranean core towards desert periphery. Although species range position in our study (edge vs. interior) was confounded with climate (desert vs. Mediterranean), the results suggest that the gene flow from the species core does not have negative consequences for either performance of the peripheral plants or their adaptive potential.

Genetic architecture of adaptation is traditionally studied in the context of local adaptation, viz. spatially varying conditions experienced by the species. However, anthropogenic changes in the natural environment pose a new context to this issue, that is, adaptation to an environment that is new for the species. In this study, we used crossbreeding to analyze genetic architecture of adaptation to conditions not currently experienced by the species but with high probability of encounter in the near future due to global climate change. We performed targeted interpopulation crossing using genotypes from two core and two peripheral Triticum dicoccoides populations and raised the parents and three generations of hybrids in a greenhouse under simulated desert conditions to analyze the genetic architecture of adaptation to these conditions and an effect of gene flow from plants having different origin. The hybrid (F1) fitness did not differ from that of the parents in crosses where both plants originated from the species core, but in crosses involving one parent from the species core and another one from the species periphery the fitness of F1 was consistently higher than that of the periphery-originated parent. Plant fitness in the next two generations (F2 and F3) did not differ from the F1, suggesting that effects of epistatic interactions between recombining and segregating alleles of genes contributing to fitness were minor or absent. The observed low importance of epistatic gene interactions in allopolyploid T. dicoccoides and low probability of hybrid breakdown appear to be the result of permanent fixation of heterozygosity and lack of intergenomic recombination in this species. At the same time, predominant but not complete selfing combined with an advantage of bivalent pairing of homologous chromosomes appears to maintain high genetic variability in T. dicoccoides, greatly enhancing its adaptive ability.

Species can adapt to new environmental conditions either through individual phenotypic plasticity, intraspecific genetic differentiation in adaptive traits, or both. Wild emmer wheat, Triticum dicoccoides, an annual grass with major distribution in Eastern Mediterranean region, is predicted to experience in the near future, as a result of global climate change, conditions more arid than in any part of the current species distribution. To understand the role of the above two means of adaptation, and the effect of population range position, we analyzed reaction norms, extent of plasticity, and phenotypic selection across two experimental environments of high and low water availability in two core and two peripheral populations of this species. We studied 12 quantitative traits, but focused primarily on the onset of reproduction and maternal investment, which are traits that are closely related to fitness and presumably involved in local adaptation in the studied species. We hypothesized that the population showing superior performance under novel environmental conditions will either be genetically differentiated in quantitative traits or exhibit higher phenotypic plasticity than the less successful populations. We found the core population K to be the most plastic in all three trait categories (phenology, reproductive traits, and fitness) and most successful among populations studied, in both experimental environments; at the same time, the core K population was clearly genetically differentiated from the two edge populations. Our results suggest that (1) two means of successful adaptation to new environmental conditions, phenotypic plasticity and adaptive genetic differentiation, are not mutually exclusive ways of achieving high adaptive ability; and (2) colonists from some core populations can be more successful in establishing beyond the current species range than colonists from the range extreme periphery with conditions seemingly closest to those in the new environment.

Detecting local adaptation and its spatial scale is one of the most important questions of evolutionary biology. However, recognition of the effect of local selection can be challenging when there is considerable environmental variation across the distance at the whole species range. We analyzed patterns of local adaptation in emmer wheat, Triticum dicoccoides, at two spatial scales, small (inter-population distance less than one km) and large (inter-population distance more than 50 km) using several approaches. Plants originating from four distinct habitats at two geographic scales (cold edge, arid edge and two topographically dissimilar core locations) were reciprocally transplanted and their success over time was measured as 1) lifetime fitness in a year of planting, and 2) population growth four years after planting. In addition, we analyzed molecular (SSR) and quantitative trait variation and calculated the Q ST/F ST ratio. No home advantage was detected at the small spatial scale. At the large spatial scale, home advantage was detected for the core population and the cold edge population in the year of introduction via measuring life-time plant performance. However, superior performance of the arid edge population in its own environment was evident only after several generations via measuring experimental population growth rate through genotyping with SSRs allowing counting the number of plants and seeds per introduced genotype per site. These results highlight the importance of multi-generation surveys of population growth rate in local adaptation testing. Despite predominant self-fertilization of T. dicoccoides and the associated high degree of structuring of genetic variation, the results of the Q ST - F ST comparison were in general agreement with the pattern of local adaptation at the two spatial scales detected by reciprocal transplanting.

The adaptive potential of a population defines its importance for species survival in changing environmental conditions such as global climate change. Very few empirical studies have examined adaptive potential across species' ranges, namely, of edge vs core populations, and we are unaware of a study that has tested adaptive potential (namely, variation in adaptive traits) and measured performance of such populations in conditions not currently experienced by the species but expected in the future. Here we report the results of a Triticum dicoccoides population study that employed transplant experiments and analysis of quantitative trait variation. Two populations at the opposite edges of the species range (1) were locally adapted; (2) had lower adaptive potential (inferred from the extent of genetic quantitative trait variation) than the two core populations; and (3) were outperformed by the plants from the core population in the novel environment. The fact that plants from the species arid edge performed worse than plants from the more mesic core in extreme drought conditions beyond the present climatic envelope of the species implies that usage of peripheral populations for conservation purposes must be based on intensive sampling of among-population variation.

Background Stem rust (SR) is one of the most economically devastating barley diseases in Kazakhstan, and in some years it causes up to 50 % of yield losses. Routine conventional breeding for resistance to stem rust is almost always in progress in all Kazakhstan breeding stations. However, molecular marker based approach towards new SR resistance genes identification and relevant marker-assisted selection had never been employed in Kazakhstan yet. In this study, as a preliminary step the GWAS (genome-wide association study) mapping was applied in attempt to identify reliable SNP markers and quantitative trait loci (QTL) associated with resistance to SR. Results Barley collection of 92 commercial cultivars and promising lines was genotyped using a high-throughput single nucleotide polymorphism (9,000 SNP) Illumina iSelect array. 6,970 SNPs out of 9,000 total were polymorphic and scorable. 5,050 SNPs out of 6,970 passed filtering threshold and were used for association mapping (AM). All 92 accessions were phenotyped for resistance to SR by observing adult plants in artificially infected plots at the Research Institute for Biological Safety Problems in Dzhambul region of Kazakhstan. GLM analysis allowed the identification of 15 SNPs associated with the resistance at the heading time (HA) phase, and 2 SNPs at the seed’s milky-waxy maturity (SM) phase. However, after application of 5 % Bonferroni multiple test correction, only 2 SNPs at the HA stage on the same position of chromosome 6H can be claimed as reliable markers for SR resistance. The MLM analysis after the Bonferroni correction did not reveal any associations in this study, although distribution lines in the quantile-quantile (QQ) plot indicates that overcorrection in the test due to both Q and K matrices usage. Conclusions Obtained data suggest that genome wide genotyping of 92 spring barley accessions from Kazakhstan with 9 K Illumina SNP array was highly efficient. Linkage disequilibrium based mapping approach allowed the identification of highly significant QTL for the SR resistance at the HA phase of growth on chromosome 6H. On the other hand, no significant QTL was detected at the SM phase, assuming that for a successful GWASmapping experiment a larger size population with more diverse genetic background should be tested. Obtained results provide additional information towards better understanding of SR resistance in barley. Electronic supplementary material The online version of this article (doi:10.1186/s12870-015-0686-z) contains supplementary material, which is available to authorized users.

QSbm.ubo - 2BS=Sbm2, a major QTL controlling the response to Soil - Borne Cereal Mosaic Virus (SB CMV) in durum wheat, was c haracterized in two recombinant inbred line populations, namely Meridiano (resistant, R) x Claudio (moderately susceptible, MS) and Simeto (susceptible, S) x Levante (R). B y means of meta - QTL analysis QSbm.ubo - 2BS was mapped as a unique QTL within a 2 cM - wide interval (LOD - 2) in the distal region of chromosome arm 2BS (Maccaferri et al., 2012) . The addition of the Illumina 90K SNPs array to the durum linkage maps allowed to identify 36 transcripts - associated SNPs tightly associated with the Mendelized QTL (Maccaferri et al., 2014) . Nine SNPs from the Illumina 90K wheat array were converted to KASP markers, which provided fluorescent high - throughput assays spanning the QTL region. Marker - assisted selection (MAS) was performed on ∼ 2,000 RILs from the Svevo (R) x Ciccio (S) population (Gadaleta et al., 2009) with two KAS P markers flanking the QTL interval , KUBO 9 and KUBO 13. MAS identified 291 lines recombinant between the two markers. These lines were characterized for SBCMV response in the 2016 field nursery under severe and uniform SBCMV infection. The lines were scor ed for symptom severity (SS) on a 0 to 4 scale , where 0 = very res istant and 4 = very susceptible (Vallega and Rubies Autonell, 1985). They were also genotyped with seven KASP markers distributed along the QTL interval ( KUBO 1 , KUBO 3 , KUBO 27 , KUBO 29 , KU BO 38, KUBO 40 and KUBO 41 ) and with the DArT marker wPt - 2106 , the marker most associated with the phenotype in the Meridiano x Claudio RIL population (Maccaferri et al., 2012). The bimodal distribution of SS reflects the segregation of the resistance trai t in the QTL interval: frequency peaks were observed around values of 1.7 and 3.8. The fine - mapping allowed to narrow the most probable support interval to 0,2 cM between KUBO 27 and KUBO 1 based on the Svevo x Ciccio RILs population. Work is in progress to analyze other - 1,000 RILs of the same population in order to confirm the results obtained with the first part of the study and to improve the ongoing fine - mapping of the gene responsible for the resistance.