Elite Wheat Breeding Research Articles

Integrated genome-wide association and transcriptomic analysis to identify receptor kinase genes to stripe rust resistance in wheat germplasm from southwestern China

Stripe rust of wheat, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most important diseases of wheat worldwide. Identification of new and elite Pst-resistance loci or genes has the potential to enhance overall resistance to this pathogen. Here, we conducted an integrated genome-wide association study (GWAS) and transcriptomic analysis to screen for loci associated with resistance to stripe rust in 335 accessions from Yunnan, including 311 landraces and 24 cultivars. Based on the environmental phenotype, we identified 113 protein kinases significantly associated with Pst resistance using mixed linear model (MLM) and generalized linear model (GLM) models. Transcriptomic analysis revealed that 52 of 113 protein kinases identified by GWAS were up and down regulated in response to Pst infection. Among these genes, a total of 15 receptor kinase genes were identified associated with Pst resistance. 11 candidate genes were newly discovered in Yunnan wheat germplasm. Our results revealed that resistance alleles to stripe rust were accumulated in Yunnan wheat germplasm, implying direct or indirect selection for improving stripe rust resistance in elite wheat breeding programs.

Insights into breeding history, hotspot regions of selection, and untapped allelic diversity for bread wheat breeding.

Breeding has increasingly altered the genetics of crop plants since the domestication of their wild progenitors. It is postulated that the genetic diversity of elite wheat breeding pools is too narrow to cope with future challenges. In contrast, plant genetic resources (PGRs) of wheat stored in genebanks are valuable sources of unexploited genetic diversity. Therefore, to ensure breeding progress in the future, it is of prime importance to identify the useful allelic diversity available in PGRs and to transfer it into elite breeding pools. Here, a diverse collection consisting of modern winter wheat cultivars and genebank accessions was investigated based on reduced-representation genomic sequencing and an iSelect single nucleotide polymorphism (SNP) chip array. Analyses of these datasets provided detailed insights into population structure, levels of genetic diversity, sources of new allelic diversity, and genomic regions affected by breeding activities. We identified 57 regions representing genomic signatures of selection and 827 regions representing private alleles associated exclusively with genebank accessions. The presence of known functional wheat genes, quantitative trait loci, and large chromosomal modifications, i.e., introgressions from wheat wild relatives, provided initial evidence for putative traits associated within these identified regions. These findings were supported by the results of ontology enrichment analyses. The results reported here will stimulate further research and promote breeding in the future by allowing for the targeted introduction of novel allelic diversity into elite wheat breeding pools.

Response to Early Generation Genomic Selection for Yield in Wheat.

We investigated increasing genetic gain for grain yield using early generation genomic selection (GS). A training set of 1,334 elite wheat breeding lines tested over three field seasons was used to generate Genomic Estimated Breeding Values (GEBVs) for grain yield under irrigated conditions applying markers and three different prediction methods: (1) Genomic Best Linear Unbiased Predictor (GBLUP), (2) GBLUP with the imputation of missing genotypic data by Ridge Regression BLUP (rrGBLUP_imp), and (3) Reproducing Kernel Hilbert Space (RKHS) a.k.a. Gaussian Kernel (GK). F2 GEBVs were generated for 1,924 individuals from 38 biparental cross populations between 21 parents selected from the training set. Results showed that F2 GEBVs from the different methods were not correlated. Experiment 1 consisted of selecting F2s with the highest average GEBVs and advancing them to form genomically selected bulks and make intercross populations aiming to combine favorable alleles for yield. F4:6 lines were derived from genomically selected bulks, intercrosses, and conventional breeding methods with similar numbers from each. Results of field-testing for Experiment 1 did not find any difference in yield with genomic compared to conventional selection. Experiment 2 compared the predictive ability of the different GEBV calculation methods in F2 using a set of single plant-derived F2:4 lines from randomly selected F2 plants. Grain yield results from Experiment 2 showed a significant positive correlation between observed yields of F2:4 lines and predicted yield GEBVs of F2 single plants from GK (the predictive ability of 0.248, P < 0.001) and GBLUP (0.195, P < 0.01) but no correlation with rrGBLUP_imp. Results demonstrate the potential for the application of GS in early generations of wheat breeding and the importance of using the appropriate statistical model for GEBV calculation, which may not be the same as the best model for inbreds.

Marker-Trait Associations for Enhancing Agronomic Performance, Disease Resistance, and Grain Quality in Synthetic and Bread Wheat Accessions in Western Siberia

Exploiting genetically diverse lines to identify genes for improving crop performance is needed to ensure global food security. A genome-wide association study (GWAS) was conducted using 46,268 SNP markers on a diverse panel of 143 hexaploid bread and synthetic wheat to identify potential genes/genomic regions controlling agronomic performance (yield and 26 yield-related traits), disease resistance, and grain quality traits. From phenotypic evaluation, we found large genetic variation among the 35 traits and recommended five lines having a high yield, better quality, and multiple disease resistance for direct use in a breeding program. From a GWAS, we identified a total of 243 significant marker-trait associations (MTAs) for 35 traits that explained up to 25% of the phenotypic variance. Of these, 120 MTAs have not been reported in the literature and are potentially novel MTAs. In silico gene annotation analysis identified 116 MTAs within genes and of which, 21 MTAs were annotated as a missense variant. Furthermore, we were able to identify 23 co-located multi-trait MTAs that were also phenotypically correlated to each other, showing the possibility of simultaneous improvement of these traits. Additionally, most of the co-located MTAs were within genes. We have provided genomic fingerprinting for significant markers with favorable and unfavorable alleles in the diverse set of lines for developing elite breeding lines from useful trait-integration. The results from this study provided a further understanding of genetically complex traits and would facilitate the use of diverse wheat accessions for improving multiple traits in an elite wheat breeding program.

Wheat grain number and yield: The relative importance of physiological traits and source-sink balance in southern Australia

Grain number (GN) is determined by spike growth rate (SGR), fruiting efficiency (FE) and the duration of spike growth period (Ds). However, these three traits are not independent of each other and therefore quantifying their relative contribution to GN is important for improving yield potential. This study aimed to model GN as a function of SGR, FE and Ds in bread wheat and investigate the relative importance of these three traits in determining GN. A large number of commercial varieties, elite wheat breeding lines, and a Multiparent Advanced Generation InterCross population were evaluated for GN, SGR, Ds, and FE in six Australian environments in 2014 and 2015. The model explained 43–98% of the variation in GN in individual environments and 88% of the variation in GN across the six environments. The percentage of GN variance explained by the model was significantly higher than those explained by correlating GN to individual traits. The relative importance of the contribution of the three traits to GN was different and ranked as SGR > FE > Ds. The negative correlation between FE and spike dry weight at anthesis (SDWa) appears to be spurious, suggesting that there was no causality between high FE and low SDWa and vice versa. Thus, FE can be used as an independent trait to increase GN in addition to SGR and Ds. We also investigated if the wheat crop had enough source to fill the increased sink size in the southern Australian high rainfall environment. The source-sink balance analysis indicates that the available source, consisting of concurrent photosynthetic assimilate and stored water-soluble carbohydrate at anthesis, was sufficient to fill the established sink but no surplus assimilates were available to fill a larger sink in southwestern Australia. However, the opportunity to increase yield potential by further increasing grain number might exist in south-eastern Australia environments.

Genome-wide association study of resistance to stripe rust (Puccinia striiformis f. sp. tritici) in Sichuan wheat

BackgroundStripe rust (also called yellow rust) is a common and serious fungal disease of wheat (Triticum aestivum L.) caused by Puccinia striiformis f. sp. tritici. The narrow genetic basis of modern wheat cultivars and rapid evolution of the rust pathogen have been responsible for periodic and devastating epidemics of wheat rust diseases. In this study, we conducted a genome-wide association study with 44,059 single nucleotide polymorphism markers to identify loci associated with resistance to stripe rust in 244 Sichuan wheat accessions, including 79 landraces and 165 cultivars, in six environments.ResultsIn all the field assessments, 24 accessions displayed stable high resistance to stripe rust. Significant correlations among environments were observed for both infection (IT) and disease severity (DS), and high heritability levels were found for both IT and DS. Using mixed linear models, 12 quantitative trait loci (QTLs) significantly associated with IT and/or DS were identified. Two QTLs were mapped on chromosomes 5AS and 5AL and were distant from previously identified stripe rust resistance genes or QTL regions, indicating that they may be novel resistance loci.ConclusionsOur results revealed that resistance alleles to stripe rust were accumulated in Sichuan wheat germplasm, implying direct or indirect selection for improved stripe rust resistance in elite wheat breeding programs. The identified stable QTLs or favorable alleles could be important chromosome regions in Sichuan wheat that controlled the resistance to stripe rust. These markers can be used molecular marker-assisted breeding of Sichuan wheat cultivars, and will be useful in the ongoing effort to develop new wheat cultivars with strong resistance to stripe rust.

High-Density SNP Genotyping Array for Hexaploid Wheat and Its Relatives.

A lack of genetic diversity between wheat breeding lines has been recognized as a significant block to future yield increases. Wheat breeding and prebreeding strategies are increasingly using material from wheat ancestors or wild relatives to reintroduce diversity. Where molecular markers are polymorphic between the host and introgressed material, they may be used to track the size and location of the introgressed material through generations of backcrossing. To generate markers for this purpose, sequence capture targeted resequencing was carried out for a range of wheat varieties, wheat relatives, and wheat progenitors. From these sequences, putative SNPs were identified and used to generate the Axiom® Wheat HD array. A selection of varieties representing a selection of elite wheat breeding material, progenitor species, and wild relatives were used to validate the array. The procedures used are described here in detail.

Genome Wide Association Study of Seedling and Adult Plant Leaf Rust Resistance in Elite Spring Wheat Breeding Lines.

Leaf rust is an important disease, threatening wheat production annually. Identification of resistance genes or QTLs for effective field resistance could greatly enhance our ability to breed durably resistant varieties. We applied a genome wide association study (GWAS) approach to identify resistance genes or QTLs in 338 spring wheat breeding lines from public and private sectors that were predominately developed in the Americas. A total of 46 QTLs were identified for field and seedling traits and approximately 20–30 confer field resistance in varying degrees. The 10 QTLs accounting for the most variation in field resistance explained 26–30% of the total variation (depending on traits: percent severity, coefficient of infection or response type). Similarly, the 10 QTLs accounting for most of the variation in seedling resistance to different races explained 24–34% of the variation, after correcting for population structure. Two potentially novel QTLs (QLr.umn-1AL, QLr.umn-4AS) were identified. Identification of novel genes or QTLs and validation of previously identified genes or QTLs for seedling and especially adult plant resistance will enhance understanding of leaf rust resistance and assist breeding for resistant wheat varieties. We also developed computer programs to automate field and seedling rust phenotype data conversions. This is the first GWAS study of leaf rust resistance in elite wheat breeding lines genotyped with high density 90K SNP arrays.

Identification of high yielding wheat genotypes through evaluation of international nurseries

High yielding, stable wheat (Triticum aestivum L.) cultivars are needed for the diverse environments in West Asia to improve rural livelihoods. This study was conducted to determine the performance of elite wheat breeding lines developed by CIMMYT, to analyze their stability for grain yield across diverse environments, and to identify superior genotypes that could be valuable for varietal release. Genetically diverse 196 advanced breeding lines were evaluated across different sites in Afghanistan. Grain yield, days to heading and plant height were analyzed. Genotypic superiority for grain yield was determined using genotype and genotype × environment (GGE) biplot analysis. The experimental genotypes showed arrays of variation for grain yield in each year, with mean values ranging from 3908 to 7209 kg/ha. A set of 20 experimental genotypes superior to the check based on their high mean yield and stability across environments as assessed by the GGE rank was identified. The most stable high yielding genotypes were HD 2687; Elvia/5/Cndo/R143//Ente/Mexi75/3/AE. sq./4/2*Oci; Quaiu; Whear/Vivitsi//Whear; Kiritati/2*Trch; Waxwing; Munal#1; Whear//Inqalab 91*2/Tukuru and Snb//Cmh79A.955/3*Cno79/3/Attila/4/Chen/A.sq.(Taus)//Bcn/3/2*Kauz. These superior genotypes also had acceptable maturity and plant height. The findings of this study provides information on adaptation of the internationally important wheat genotypes, valuable for wheat improvement program in Afghanistan and its neighbouring countries in West, Central and South Asia.

Simultaneous transfer, introgression, and genomic localization of genes for resistance to stem rust race TTKSK (Ug99) from Aegilops tauschii to wheat

Wheat production is currently threatened by widely virulent races of the wheat stem rust fungus, Puccinia graminis f. sp. tritici, that are part of the TTKSK (also known as 'Ug99') race group. The diploid D genome donor species Aegilops tauschii (2n = 2x = 14, DD) is a readily accessible source of resistance to TTKSK and its derivatives that can be transferred to hexaploid wheat, Triticum aestivum (2n = 6x = 42, AABBDD). To expedite transfer of TTKSK resistance from Ae. tauschii, a direct hybridization approach was undertaken that integrates gene transfer, mapping, and introgression into one process. Direct crossing of Ae. tauschii accessions with an elite wheat breeding line combines the steps of gene transfer and introgression while development of mapping populations during gene transfer enables the identification of closely linked markers. Direct crosses were made using TTKSK-resistant Ae. tauschii accessions TA1662 and PI 603225 as males and a stem rust-susceptible T. aestivum breeding line, KS05HW14, as a female. Embryo rescue enabled recovery of F1 (ABDD) plants that were backcrossed as females to the hexaploid recurrent parent. Stem rust-resistant BC1F1 plants from each Ae. tauschii donor source were used as males to generate BC2F1 mapping populations. Bulked segregant analysis of BC2F1 genotypes was performed using 70 SSR loci distributed across the D genome. Using this approach, stem rust resistance genes from both accessions were located on chromosome arm 1DS and mapped using SSR and EST-STS markers. An allelism test indicated the stem rust resistance gene transferred from PI 603225 is Sr33. Race specificity suggests the stem rust resistance gene transferred from TA1662 is unique and this gene has been temporarily designated SrTA1662. Stem rust resistance genes derived from TA1662 and PI 603225 have been made available with selectable molecular markers in genetic backgrounds suitable for stem rust resistance breeding.

Genetic Diversity, Population Structure, and Linkage Disequilibrium in U.S. Elite Winter Wheat

Information on genetic diversity and population structure of elite wheat (Triticum aestivum L.) breeding lines promotes effective use of genetic resources. We analyzed 205 elite wheat breeding lines from major winter wheat breeding programs in the USA using 245 markers across the wheat genomes. This collection showed a high level of genetic diversity as reflected by allele number per locus (7.2) and polymorphism information content (0.54). However, the diversity of U.S. modern wheat appeared to be lower than previously reported diversity levels in worldwide germplasm collections. As expected, this collection was highly structured according to geographic origin and market class with soft and hard wheat clearly separated from each other. Hard wheat accessions were further divided into three subpopulations. Linkage disequilibrium (LD) was primarily distributed around centromere regions. The mean genome‐wide LD decay estimate was 10 cM (r2 &gt; 0.1), although the extent of LD was highly variable throughout the genome. Our results on genetic diversity of different gene pools and the distribution of LD facilitates the effective use of genetic resources for wheat breeding and the choice of marker density in gene mapping and marker‐assisted breeding.

Molecular Mapping of Stem‐Rust‐Resistance Gene Sr40 in Wheat

ABSTRACTStem rust, caused by Puccinia graminis f. sp. tritici, was historically one of the most destructive diseases of wheat (Triticum aestivum L.) worldwide. Deployment of resistant cultivars successfully prevented rust epidemics over the past several decades. Unfortunately, race TTKS (termed Ug99) has emerged in Africa to render several stem‐rust‐resistance genes ineffective. Sr40, a stem‐rust‐resistance gene from Triticum timopheevii ssp. armeniacum, was transferred to wheat on translocation chromosome T2BL/2G#2S and provides effective levels of seedling and adult plant resistance against Ug99. Two mapping populations were developed using Ug99‐resistant line RL6088 and moderately susceptible to susceptible hard winter wheat cultivars Lakin and 2174. The parents were screened with 83 simple sequence repeats (SSR) from chromosome 2B and the polymorphic markers were analyzed on F2 populations. F2 and F2:3 populations were inoculated with North American stem rust race RKQQ at the seedling stage. Marker locus Xwmc344 was most closely linked to Sr40 (0.7 cM) in the RL6088/Lakin linkage map, followed by Xwmc474 and Xgwm374 Marker locus Xwmc474 was mapped ∼2.5 cM proximal to Sr40 in the RL6088/2174 population. Xwmc474 and Xwmc661 flanked Sr40 in both populations. Markers linked to Sr40 will be useful for marker‐assisted integration and pyramiding of Sr40 into elite wheat breeding lines, and reduction in the size of the T. timopheevii segment harboring this gene.

Identification of new sources of aluminum resistance in wheat

Aluminum (Al) toxicity is a major constraint for wheat production in acidic soils. An Al resistance gene on chromosome 4DL that traces to Brazilian wheat has been extensively studied, and can provide partial protection from Al damage. To identify potentially new sources of Al resistance, 590 wheat accessions, including elite wheat breeding lines from the United States and other American and European countries, landraces and commercial cultivars from East Asia, and synthetic wheat lines from CIMMYT, Mexico, were screened for Al resistance by measuring relative root elongation in culture with a nutrient solution containing Al, and by staining Al-stressed root tips with hematoxylin. Eighty-eight wheat accessions demonstrated at least moderate resistance to Al toxicity. Those selected lines were subjected to analysis of microsatellite markers linked to an Al resistance gene on 4DL and a gene marker for the Al-activated malate transporter (ALMT1) locus. Many of the selected Al-resistant accessions from East Asia did not have the Al-resistant marker alleles of ALMT1, although they showed Al resistance similar to the US Al-resistant cultivar, Atlas 66. Most of the cultivars derived from Jagger and Atlas 66 have the Al-resistant marker alleles of ALMT1. Cluster analysis separated the selected Al-resistant germplasm into two major clusters, labeled as Asian and American–European clusters. Potentially new germplasm of Al resistance different from those derived from Brazil were identified. Further investigation of Al resistance in those new germplasms may reveal alternative Al-resistance mechanisms in wheat.

Cellular basis of resistance to different formae speciales of Blumeria graminis in Hordeum chilense, wheat, and tritordeum and agroticum amphiloids

Tritordeum and agroticum amphiploids, derived from hybridization of Triticum species with Hordeum chilense or Agropyron cristatum, were assessed for resistance to Blumeria graminis. In glasshouse tests, all parental lines of H. chilense and A. cristatum showed complete resistance to wheat powdery mildew [Blumeria graminis f. sp. tritici] while all Triticum parents, except one, were highly susceptible. The amphiploids were all resistant to B. graminis f. sp. tritici, allowing the development of only a few sporulating colonies on leaves. Microscopic examination of host-cell responses to B. graminis revealed that resistance in H. chilense and amphiploids was attributable to two major factors: (i) a significant reduction in successful fungal penetration by rapid deposition of papillae in the host epidermal cell wall and (ii) a significant increase in frequency of death of penetrated epidermal cells. Papillae formation was associated with localized autofluorescence in host epidermal cells. Cell death prevented further fungal growth and differentiation for the establishment of biotrophy. Tritordeums showed both forms of resistance when tested with Blumeria graminis f. sp. hordei and Blumeria graminis f. sp. avenae. The tritordeum and agroticum amphiploids may offer novel sources of resistance to powdery mildew. They could be used either directly or as a bridge in genetic crosses to introgress resistance to powdery mildew into elite wheat breeding lines.

Potential for effective marker-assisted selection of three quantitative trait loci conferring adult plant resistance to powdery mildew in elite wheat breeding populations

Three quantitative trait loci (QTL) associated with adult plant resistance (APR) to powdery mildew (Blumeria graminis) in wheat (Triticum aestivum) cultivar 'Massey' were mapped in a previous study. The three QTL were located on chromosomes 2A, 2B and 1B, and explained 50% of the total phenotypic variation. A 293 recombinant inbred line (RIL) breeding population (UJ) derived from the cross of 'USG 3209', a derivative of 'Massey', and 'Jaypee' was used to evaluate the potential effectiveness of marker-assisted selection (MAS) for APR. Powdery mildew severities of the 293 UJ RILs were evaluated in 2002 (F 5: 6 ) and 2003 (F 6: 7 ) under natural disease pressure in the field. The 293 RILs were also evaluated for disease severity in a 2004 (F 7:8 ) greenhouse experiment using a composite of five different isolates of B. graminis. Selection of RILs possessing the QTL on chromosome 2A, and to a lesser extent, the one on chromosome 1B was effective in identifying powdery mildew resistance in both greenhouse and field experiments. Overall, selecting RILs with QTL on chromosomes 2A and 2B was most successful in identifying highly resistant RILs, which had mean mildew severities of 4.4% and 3.2% in 2002 and 2003 field experiments, respectively. Breeders implementing MAS programs for APR to powdery mildew via selection of RILs containing the two QTL on chromosomes 2A and 2B likely will obtain RILs having high levels of resistance in the field, however combining all three QTL may ensure greater durability.

Genetic analysis of resistance to yellow rust in hexaploid wheat using a mixture model for multiple crosses

DNA-based molecular markers have been used in numerous studies for tagging specific genes in wheat for subsequent use in marker-assisted selection. Usually in plant breeding, procedures for mapping genes are based on analysis of a single segregating population. However, breeding programmes routinely evaluate large numbers of progeny derived from multiple-related crosses with some parental lines shared. In most such related crosses, the number of progeny is quite small. Thus, statistical techniques for detecting quantitative trait loci (QTLs) using data from conventional multi-cross breeding programmes are interesting. The objective of this study is to present a mixture model for QTL mapping in crosses of multiple inbred varieties with non-normal phenotype distributions and to use this model to map QTLs for yellow rust resistance in elite wheat breeding material. Three doubled haploid populations consisting of 41, 42 and 55 lines, respectively, originating from four parental varieties were studied. Multi-cross QTL analysis with three specific pathogen isolates of Puccinia striiformis f. sp. tritici and a mixture of the isolates revealed QTLs for resistance at four different genomic locations. These QTLs were found on chromosome 2AL, 2AS, 2BL and 6BL and explained between 21 and 41% of the phenotypic variation. Two of these QTLs, one on the long arm of chromosome 2A and one on the short arm of chromosome 2A were identical to the known yellow rust resistance genes Yr32 and Yr17, respectively, whereas the QTLs located on the long arms of chromosomes 2B and 6B may reflect types of resistance to yellow rust, which have not previously been mapped.

Wheat genetic diversity trends during domestication and breeding

It has been claimed that plant breeding reduces genetic diversity in elite germplasm which could seriously jeopardize the continued ability to improve crops. The main objective of this study was to examine the loss of genetic diversity in spring bread wheat during (1) its domestication, (2) the change from traditional landrace cultivars (LCs) to modern breeding varieties, and (3) 50 years of international breeding. We studied 253 CIMMYT or CIMMYT-related modern wheat cultivars, LCs, and Triticum tauschii accessions, the D-genome donor of wheat, with 90 simple sequence repeat (SSR) markers dispersed across the wheat genome. A loss of genetic diversity was observed from T. tauschii to the LCs, and from the LCs to the elite breeding germplasm. Wheat's genetic diversity was narrowed from 1950 to 1989, but was enhanced from 1990 to 1997. Our results indicate that breeders averted the narrowing of the wheat germplasm base and subsequently increased the genetic diversity through the introgression of novel materials. The LCs and T. tauschii contain numerous unique alleles that were absent in modern spring bread wheat cultivars. Consequently, both the LCs and T. tauschii represent useful sources for broadening the genetic base of elite wheat breeding germplasm.

Quantifying novel sequence variation and selective advantage in synthetic hexaploid wheats and their backcross-derived lines using SSR markers

Synthetic hexaploid wheats (SHWs) and synthetic backcross-derived lines (SBLs) obtained from them are novel sources of useful traits for broadening the diversity in breeding germplasm of hexaploid bread wheat (Triticum aestivum). Fifty-one EST-derived and 39 genomic-derived microsatellite markers (SSRs) covering the A, B, and D genomes were used to assess the genetic diversity present in 11 SHWs, their backcross derived families, and their durum and bread wheat parents and to test for the selective advantage of SHW alleles in SBL families after several generations of selection. The 90 SSR markers amplified 91 loci with 474 alleles across all genotypes. In many of the SHWs, novel alleles were observed which were stably inherited in the SBL families. Gene diversity, the average number of alleles per locus, cluster analysis, and principal coordinate analysis revealed a high level of genetic diversity in the Aegilops tauschii and durum parents of the SHWs, and also in the SBLs. In the latter, alleles from the SHW parent had a selective advantage for six SSR markers. This indicates that SHWs and SBLs are a valuable resource for broadening the genetic base of elite wheat breeding germplasm. Fingerprinting of SBLs and their corresponding SHW and bread wheat parents, and testing for selective advantage of SHWs alleles promises to be a useful method for detecting chromosomal regions of interest for bread wheat improvement.