Wild Emmer Accession Research Articles

Characterizing Agronomic and Shoot Morphological Diversity across 263 Wild Emmer Wheat Accessions

Wild emmer, the direct progenitor of modern durum and bread wheat, has mostly been studied for grain quality, biotic, and abiotic stress-related traits. Accordingly, it should also have a certain amount of diversity for morphological and agronomic traits. Despite having a high chance of huge diversity, it has not been deeply explored. In the current study, 263 wild emmer accessions collected from different regions of Israel, Turkey, Lebanon, and Syria were characterized for a total of 19 agronomic and shoot morphological traits. Three trials were carried out in Western Australia, which demonstrated a large variation in these traits. The average phenotypic diversity (H’) was 0.91 as quantified by Shannon’s diversity index. A high heritability was recorded for most of the traits, where biomass/plant and yield/plant were identified as the most potential traits. Correlation analysis revealed several significant associations between traits, including significant positive correlation between yield and tiller number, first leaf area, spike length, and biomass/plant. The principal component analysis (PCA) demonstrated that most of the traits contributed to the overall observed variability. The cluster analysis categorized 263 accessions into five clusters on average. On the other hand, accessions were categorized into eight populations based on the collection region and a comparative analysis demonstrated considerable variations between populations for plant height, spike length, and flag leaf area. Despite the low yield, several wild emmer accessions demonstrated superior performance compared to modern bread wheat cultivars, when selection was based on combining yield with multiple traits. These observations indicate that wild emmer contains a broad gene pool for several agronomic and shoot morphological traits, which can be utilized for bread and durum wheat improvement.

Harnessing the diversity of wild emmer wheat for genetic improvement of durum wheat

Key messageThe multiple derivative lines (MDLs) characterized in this study offer a promising strategy for harnessing the diversity of wild emmer wheat for durum and bread wheat improvement.Crop domestication has diminished genetic diversity and reduced phenotypic plasticity and adaptation. Exploring the adaptive capacity of wild progenitors offer promising opportunities to improve crops. We developed a population of 178 BC1F6 durum wheat (Triticum turgidum ssp. durum) lines by crossing and backcrossing nine wild emmer wheat (T. turgidum ssp. dicoccoides) accessions with the common durum wheat cultivar ‘Miki 3’. Here, we describe the development of this population, which we named as multiple derivative lines (MDLs), and demonstrated its suitability for durum wheat breeding. We genotyped the MDL population, the parents, and 43 Sudanese durum wheat cultivars on a Diversity Array Technology sequencing platform. We evaluated days to heading and plant height in Dongola (Sudan) and in Tottori (Japan). The physical map length of the MDL population was 9 939 Mb with an average of 1.4 SNP/Mb. The MDL population had greater diversity than the Sudanese cultivars. We found high gene exchange between the nine wild emmer accessions and the MDL population, indicating that the MDL captured most of the diversity in the wild emmer accessions. Genome-wide association analysis identified three loci for days to heading on chromosomes 1A and 5A in Dongola and one on chromosome 3B in Tottori. For plant height, common genomic loci were found on chromosomes 4A and 4B in both locations, and one genomic locus on chromosome 7B was found only in Dongola. The results revealed that the MDLs are an effective strategy towards harnessing wild emmer wheat diversity for wheat genetic improvement.

Fine mapping of powdery mildew resistance gene MlWE74 derived from wild emmer wheat (Triticum turgidum ssp. dicoccoides) in an NBS-LRR gene cluster.

Powdery mildew resistance gene MlWE74, originated from wild emmer wheat accession G-748-M, was mapped in an NBS-LRR gene cluster of chromosome 2BS. Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a globally devastating disease. Wild emmer wheat (Triticum turgidum var. dicoccoides) is a valuable genetic resource for improving disease resistance in common wheat. A powdery mildew resistance gene was transferred to hexaploid wheat line WE74 from wild emmer accession G-748-M. Genetic analysis revealed that the powdery mildew resistance in WE74 is controlled by a single dominant gene, herein temporarily designated MlWE74. Bulked segregant analysis (BSA) and molecular mapping delimited MlWE74 to the terminal region of chromosome 2BS flanking by markers WGGBD412 and WGGBH346 within a genetic interval of 0.25cM and corresponding to 799.9kb genomic region in the Zavitan reference sequence. Sequence annotation revealed two phosphoglycerate mutase-like genes, an alpha/beta-hydrolases gene, and five NBS-LRR disease resistance genes that could serve as candidates for map-based cloning of MlWE74. The geographical location analysis indicated that MlWE74 is mainly distributed in Rosh Pinna and Amirim regions, in the northern part of Israel, where environmental conditions are favorable to the occurrence of powdery mildew. Moreover, the co-segregated marker WGGBD425 is helpful in marker-assisted transfer of MlWE74 into elite cultivars.

Genetic identification and characterization of chromosomal regions for kernel length and width increase from tetraploid wheat

BackgroundImprovement of wheat gercTriticum aestivum L.) yield could relieve global food shortages. Kernel size, as an important component of 1000-kernel weight (TKW), is always a significant consideration to improve yield for wheat breeders. Wheat related species possesses numerous elite genes that can be introduced into wheat breeding. It is thus vital to explore, identify, and introduce new genetic resources for kernel size from wheat wild relatives to increase wheat yield.ResultsIn the present study, quantitative trait loci (QTL) for kernel length (KL) and width (KW) were detected in a recombinant inbred line (RIL) population derived from a cross between a wild emmer accession ‘LM001’ and a Sichuan endemic tetraploid wheat ‘Ailanmai’ using the Wheat 55 K single nucleotide polymorphism (SNP) array-based constructed linkage map and phenotype from six different environments. We identified eleven QTL for KL and KW including two major ones QKL.sicau-AM-3B and QKW.sicau-AM-4B, the positive alleles of which were from LM001 and Ailanmai, respectively. They explained 17.57 to 44.28% and 13.91 to 39.01% of the phenotypic variance, respectively. For these two major QTL, Kompetitive allele-specific PCR (KASP) markers were developed and used to successfully validate their effects in three F3 populations and two natural populations containing a panel of 272 Chinese wheat landraces and that of 300 Chinese wheat cultivars, respectively. QKL.sicau-AM-3B was located at 675.6–695.4 Mb on chromosome arm 3BL. QKW.sicau-AM-4B was located at 444.2–474.0 Mb on chromosome arm 4BL. Comparison with previous studies suggested that these two major QTL were likely new loci. Further analysis indicated that the positive alleles of QKL.sicau-AM-3B and QKW.sicau-AM-4B had a great additive effect increasing TKW by 6.01%. Correlation analysis between KL and other agronomic traits showed that KL was significantly correlated to spike length, length of uppermost internode, TKW, and flag leaf length. KW was also significantly correlated with TKW. Four genes, TRIDC3BG062390, TRIDC3BG062400, TRIDC4BG037810, and TRIDC4BG037830, associated with kernel development were predicted in physical intervals harboring these two major QTL on wild emmer and Chinese Spring reference genomes.ConclusionsTwo stable and major QTL for KL and KW across six environments were detected and verified in three biparental populations and two natural populations. Significant relationships between kernel size and yield-related traits were identified. KASP markers tightly linked the two major QTL could contribute greatly to subsequent fine mapping. These results suggested the application potential of wheat related species in wheat genetic improvement.

Genetic identification of a major, novel and stably expressed QTL for effective tiller number from tetraploid wheat

Effective tiller number (ETN) is an important factor affecting plant architecture and wheat yield. The reduction of genetic diversity in common wheat breeding forces us to explore new genetic resources for ETN from wheat related species to increase wheat yield. Here, a tetraploid wheat recombinant inbred line (RIL) population developed from the cross between a durum and a wild emmer accession was used to construct a genetic map using the wheat 55 K single nucleotide polymorphism (SNP) array. The map contained 1154 SNP markers with a total length of 2452.79 cM and an average density of 2.13 cM/marker. Quantitative trait locus (QTL) analysis identified a major and stably expressed QTL, Qetn-DW-4B.1 for ENT, explaining 12.40–15.25% of the phenotypic variation. The favorable allele of this QTL was from wild emmer wheat and physically mapped in a 2.25 Mbp interval of 4BL containing 23 genes among which several were likely related to tiller development. Further comparison with previous studies showed that Qetn-DW-4B.1 is likely a novel QTL. Genetic associations between ETN and other agronomic traits were also analyzed. Collectively, this study reported a major QTL for ENT from related species and lays a foundation to fine mapping and further wheat molecular breeding. Supplemental data for this article is available online at https://doi.org/10.1080/13102818.2021.1996271 .

Wild emmer chromosome arm substitution lines: Useful resources for wheat genetic study and breeding

AbstractAs the progenitor of durum wheat (Triticum durum Desf.) and common wheat (T. aestivum L.), wild emmer wheat (T. turgidum L. subsp. dicoccoides, TTD) has many valuable alleles for enlarging the genetic pool of common wheat. Chromosome arm substitution lines (CASLs) are useful genetic resources producing genome‐wide variations in the background of certain cultivars, with each CASL containing a pair of an individual chromosome arms from the donor parent. Therefore, CASLs can be used to identify a broad range of phenotypes that are usually different from the parental lines, to map causal genes or quantitative trait loci and to broaden the genetic pools of existing cultivars as prebreeding materials. In this review we summarize recent progress in wheat genetic studies and breeding using two sets of CASLs of the wild emmer accession TTD140 in two common wheat backgrounds of ‘Chinese Spring’ and ‘Bethlehem’. We report the production of CASLs, confirmation of their chromosome structure using molecular markers, and their application in discovering and mapping agronomically important genes. We propose that, together with the release of high‐quality reference genomes of wild emmer and common wheat, wild emmer CASLs are useful resources for genetic study and breeding of wheat.

Distribution and Nucleotide Diversity of Yr15 in Wild Emmer Populations and Chinese Wheat Germplasm.

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating fungal disease of wheat. The wild emmer gene, Yr15 (Wtk1), which confers a strong broad-spectrum resistance to Pst isolates, is composed of kinase and pseudokinase domains. The analysis of 361 wild emmer accessions from a wide range of natural habitats confirms that functional Wtk1 is distributed mainly along a narrow axis from Mt. Carmel to Mt. Hermon regions, in the northern part of Israel, where environmental conditions are favorable to the onset of stripe rust. An analysis of full-length Wtk1 DNA sequences from 49 wild emmer accessions identified three haplotypes and extremely low nucleotide diversity (π = 0.00002). The sequence diversity of Wtk1 is 9.5 times lower than that of broad-spectrum partial resistance gene Yr36 (π = 0.00019), and both are in sharp contrast to the high level of nucleotide diversity previously reported for race-specific resistance genes (e.g., Lr10 and Pm3). However, the nonfunctional wtk1 sequences possess high level of nucleotide diversity (π = 0.07). These results may reflect the different resistance mechanisms and the different evolutionary processes that shaped these resistance genes. Yr15 was absent in 189 Chinese wheat landraces and was present in only 1.02% of the 583 tested modern Chinese wheat cultivars. These results corroborate our previous results showing that Yr15 was absent in 94% of a worldwide collection of 513 wheat cultivars, therefore indicating the importance of Yr15 in wheat stripe rust resistance breeding programs in China and elsewhere around the globe.

Identification of a major dominant gene for race-nonspecific tan spot resistance in wild emmer wheat.

A single dominant gene found in tetraploid and hexaploid wheat controls broad-spectrum race-nonspecific resistance to the foliar disease tan spot caused by Pyrenophora tritici-repentis. Tan spot is an important foliar disease of durum and common wheat caused by the necrotrophic fungal pathogen Pyrenophora tritici-repentis. Genetic studies in common wheat have shown that pathogen-produced necrotrophic effectors interact with host genes in an inverse gene-for-gene manner to cause disease, but quantitative trait loci (QTLs) with broad race-nonspecific resistance also exist. Less work has been done to understand the genetics of tan spot interactions in durum wheat. Here, we evaluated a set of Langdon durum-wild emmer (Triticum turgidum ssp. dicoccoides) disomic chromosome substitution lines for reaction to four P. tritici-repentis isolates representing races 1, 2, 3, and 5 to identify wild emmer chromosomes potentially containing tan spot resistance genes. Chromosome 3B from the wild emmer accession IsraelA rendered the tan spot-susceptible durum cultivar Langdon resistant to all four fungal isolates. Genetic analysis indicated that a single dominant gene, designated Tsr7, governed resistance. Detailed mapping experiments showed that the Tsr7 locus is likely the same as the race-nonspecific QTL previously identified in the hexaploid wheat cultivars BR34 and Penawawa. Four user-friendly SNP-based semi-thermal asymmetric reverse PCR (STARP) markers cosegregated with Tsr7 and should be useful for marker-assisted selection of resistance. In addition to 3B, other wild emmer chromosomes contributed moderate levels of tan spot resistance, and, as has been shown previously for tetraploid wheat, the Tsn1-Ptr ToxA interaction was not associated with susceptibility. This is the first report of a major dominant gene governing resistance to tan spot in tetraploid wheat.

The novel function of the Ph1 gene to differentiate homologs from homoeologs evolved in Triticum turgidum ssp. dicoccoides via a dramatic meiosis-specific increase in the expression of the 5B copy of the C-Ph1 gene.

The Ph1 gene is the principal regulator of homoeologous chromosome pairing control (HECP) that ensures the diploid-like meiotic chromosome pairing behavior of polyploid wheat. The HECP control was speculated to have evolved after the first event of polyploidization. With the objective to accurately understand the evolution of the HECP control, wild emmer wheat accessions previously known to differ for HECP control were characterized for the structure and expression of the candidatePh1 gene, C-Ph1. The C-TdPh1-5A and 5B gene copies of emmer wheat showed 98 and 99% DNA sequence similarity respectively with the corresponding hexaploid wheat copies. Further, the C-TdPh1-5B carried the C-Ph1-5B specific structural changes and transcribed three splice variants as observed in the hexaploid wheat. Further, single nucleotide changes differentiating accessions varying for HECP control were identified. Analyzed by quantitative expression analysis, the wild emmer accessions with HECP control showed ~ 10,000-fold higher transcript abundance of the C-TdPh1-5B copy during prophase-I compared to accessions lacking the control. Differential transcriptional regulation of C-TdPh1-5B splice variants further revealed that C-Ph1-5Balt1 variant is mainly responsible for differential accumulation of C-Ph1-5B copy in accessions with HECP control. Taken together, these results showed that the HECP control evolved via transcriptional regulation of splice variants during meiosis.

Wheat domestication in light of haplotype analyses of the Brittle rachis 1 genes (BTR1-A and BTR1-B)

Wheat domestication was a milestone in the rise of agrarian societies in the Fertile Crescent. As opposed to the freely dispersing seeds of its tetraploid progenitor wild emmer, the hallmark trait of domesticated wheat is intact, harvestable spikes. During domestication, wheat acquired recessive loss-of-function mutations in the Brittle Rachis 1 genes, both in the A genome (BTR1-A) and B genome (BTR1-B). In this study, we probe the geographical provenances of these mutations via haplotype analyses of a collection of wild and domesticated accessions. Our results show that the precursor of the domesticated haplotype of BTR1-A was detected in 32% of the wild accessions gathered throughout the Levant, from central Israel to central Turkey. In contrast, the precursor of the domesticated haplotype of BTR1-B, which carries a distinct 11 bp deletion in the promoter region, was found in only 10% of the tested wild accessions, all from the Southern Levant. Moreover, we identified of a single wild emmer accession in Southern Levant that carries the progenitor haplotypes for both BTR1-A and BTR1-B genes. These observations suggest that at least part of the emmer domestication process occurred in Southern Levant, contrary to the widely held view that the northern part of the Fertile Crescent was the center of wheat domestication.

GNI-A1 mediates trade-off between grain number and grain weight in tetraploid wheat.

Wild emmer allele of GNI-A1 ease competition among developing grains through the suppression of floret fertility and increase grain weight in tetraploid wheat. Grain yield is a highly polygenic trait determined by the number of grains per unit area, as well as by grain weight. In wheat, grain number and grain weight are usually negatively correlated. Yet, the genetic basis underlying trade-off between the two is mostly unknown. Here, we fine-mapped a grain weight QTL using wild emmer introgressions in a durum wheat background and showed that grain weight is associated with the GNI-A1 gene, a regulator of floret fertility. In-depth characterization of grain number and grain weight indicated that suppression of distal florets by the wild emmer GNI-A1 allele increases weight of proximal grains in basal and central spikelets due to alteration in assimilate distribution. Re-sequencing of GNI-A1 in tetraploid wheat demonstrated the rich allelic repertoire of the wild emmer gene pool, including a rare allele which was present in two gene copies and contained a nonsynonymous mutation in the C-terminus of the protein. Using an F2 population generated from a cross between wild emmer accessions Zavitan, which carries the rare allele, and TTD140, we demonstrated that this unique polymorphism is associated with grain weight, independent of grain number. Moreover, we showed, for the first time, that GNI-A1 proteins are transcriptional activators and that selection targeted compromised activity of the protein. Our findings expand the knowledge of the genetic basis underlying trade-off between key yield components and may contribute to breeding efforts for enhanced grain yield.

Durum wheat genome highlights past domestication signatures and future improvement targets

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.

Wheat powdery mildew resistance gene Pm64 derived from wild emmer (Triticum turgidum var. dicoccoides) is tightly linked in repulsion with stripe rust resistance gene Yr5

Stripe rust and powdery mildew are both devastating diseases for durum and common wheat. Pyramiding of genes conferring resistance to one or more diseases in a single cultivar is an important breeding approach to provide broader spectra of resistances in wheat improvement. A new powdery mildew resistance gene originating from wild emmer (Triticum turgidum var. dicoccoides) backcrossed into common wheat (T. aestivum) line WE35 was identified. It conferred an intermediate level of resistance to Blumeria graminis f. sp. tritici isolate E09 at the seedling stage and a high level of resistance at the adult plant stage. Genetic analysis showed that the powdery mildew resistance in WE35 was controlled by a dominant gene designated Pm64. Bulked segregant analysis (BSA) and molecular mapping indicated that Pm64 was located in chromosome bin 2BL4-0.50–0.89. Polymorphic markers were developed from the corresponding genomic regions of Chinese Spring wheat and wild emmer accession Zavitan to delimit Pm64 to a 0.55 cM genetic interval between markers WGGBH1364 and WGGBH612, corresponding to a 15 Mb genomic region on Chinese Spring and Zavitan 2BL, respectively. The genetic linkage map of Pm64 is critical for fine mapping and cloning. Pm64 was completely linked in repulsion with stripe rust resistance gene Yr5. Analysis of a larger segregating population might identify a recombinant line with both genes as a valuable resource in breeding for resistance to powdery mildew and stripe rust.

Variation in Stripe Rust Resistance and Morphological Traits in Wild Emmer Wheat Populations

Wild emmer wheat (Triticum dicoccoides), the tetraploid progenitor of cultivated wheats, is indigenous to the Near East Fertile Crescent. An important center of distribution is found today in and around the catchment area of the upper Jordan Valley in Israel and surrounding regions. In the current study, the field stripe rust resistance and morphological traits were analyzed using 98 sample accessions that represented the geographical distribution of wild emmer populations in Israel and its vicinity. The resistance tests at two field locations revealed that the majority of the wild emmer accessions possess quantitative resistance against stripe rust. This could be due to the high frequency of Yr36 in the wild emmer populations. The identification of potentially novel stripe rust resistance in this set of germplasm is highly significant. In total, 11 morphological traits were examined in this study. Wide range of natural variation was revealed in the tested morphological traits. Most of the morphological traits had significant correlations with climate variables, indicating that the local environmental conditions have a profound effect on shaping the genetic structure of wild emmer wheat. Our results suggest that wild emmer wheat has the enormous potential to improve stripe rust resistance and various important agronomical traits in wheat.

Genome Based Meta-QTL Analysis of Grain Weight in Tetraploid Wheat Identifies Rare Alleles of GRF4 Associated with Larger Grains.

The domestication and subsequent genetic improvement of wheat led to the development of large-seeded cultivated wheat species relative to their smaller-seeded wild progenitors. While increased grain weight (GW) continues to be an important goal of many wheat breeding programs, few genes underlying this trait have been identified despite an abundance of studies reporting quantitative trait loci (QTL) for GW. Here we perform a QTL analysis for GW using a population of recombinant inbred lines (RILs) derived from the cross between wild emmer wheat accession ‘Zavitan’ and durum wheat variety ‘Svevo’. Identified QTLs in this population were anchored to the recent Zavitan reference genome, along with previously published QTLs for GW in tetraploid wheat. This genome-based, meta-QTL analysis enabled the identification of a locus on chromosome 6A whose introgression from wild wheat positively affects GW. The locus was validated using an introgression line carrying the 6A GW QTL region from Zavitan in a Svevo background, resulting in >8% increase in GW compared to Svevo. Using the reference sequence for the 6A QTL region, we identified a wheat ortholog to OsGRF4, a rice gene previously associated with GW. The coding sequence of this gene (TtGRF4-A) contains four single nucleotide polymorphisms (SNPs) between Zavitan and Svevo, one of which reveals the Zavitan allele to be rare in a core collection of wild emmer and completely absent from the domesticated emmer genepool. Similarly, another wild emmer accession (G18-16) was found to carry a rare allele of TtGRF4-A that also positively affects GW and is characterized by a unique SNP absent from the entire core collection. These results exemplify the rich genetic diversity of wild wheat, posit TtGRF4-A as a candidate gene underlying the 6A GW QTL, and suggest that the natural Zavitan and G18-16 alleles of TtGRF4-A have potential to increase wheat yields in breeding programs.

Molecular mapping of YrTZ2, a stripe rust resistance gene in wild emmer accession TZ-2 and its comparative analyses with Aegilops tauschii

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating disease that can cause severe yield losses. Identification and utilization of stripe rust resistance genes are essential for effective breeding against the disease. Wild emmer accession TZ-2, originally collected from Mount Hermon, Israel, confers near-immunity resistance against several prevailing Pst races in China. A set of 200 F6:7 recombinant inbred lines (RILs) derived from a cross between susceptible durum wheat cultivar Langdon and TZ-2 was used for stripe rust evaluation. Genetic analysis indicated that the stripe rust resistance of TZ-2 to Pst race CYR34 was controlled by a single dominant gene, temporarily designated YrTZ2. Through bulked segregant analysis (BSA) with SSR markers, YrTZ2 was located on chromosome arm 1BS flanked by Xwmc230 and Xgwm413 with genetic distance of 0.8 cM (distal) and 0.3 cM (proximal), respectively. By applying wheat 90K iSelect SNP genotyping assay, 11 polymorphic loci (consisting of 250 SNP markers) closely linked to YrTZ2 were identified. YrTZ2 was further delimited into a 0.8-cM genetic interval between SNP marker IWB19368 and SSR marker Xgwm413, and co-segregated with SNP marker IWB28744 (co-segregated with 28 SNP). Comparative genomics analyses revealed high level of collinearity between the YrTZ2 genomic region and the orthologous region of Aegilops tauschii 1DS. The genomic region between loci IWB19368 and IWB31649 harboring YrTZ2 is orthologous to a 24.5-Mb genomic region between AT1D0112 and AT1D0150, spanning 15 contigs on chromosome 1DS. The genetic and comparative maps of YrTZ2 provide a framework for map-based cloning and marker-assisted selection of YrTZ2.

Comprehensive evaluating of wild and cultivated emmer wheat (Triticum turgidum L.) genotypes response to salt stress

Emmer wheat as the progenitor of common wheat, holds the genetic potentiality for improvement of wheat yield, quality and stress tolerance such as drought and salt. To comprehensively evaluate the salt tolerance of emmer wheat, a total of 30 traits including growth, physiology and photosynthesis related as well as K+ and Na+ content of 30 wild emmer and 14 durum wheat accessions were systematically investigated and compared between normal and saline conditions. Salt tolerance index (STI) based on multiple regression analysis of these traits was calculated and five wild emmer accessions showed high salt tolerance, which could be used as valuable resource for wheat salt tolerance improvement. Furthermore, wild emmer genotypes showed wider trait performance variation compared to durum wheat, indicating the higher genetic diversity in wild emmer wheat. Then, shoot Na+ content, shoot K+/Na+ ratio, root length and root surface area were identified as suitable indexes for salt tolerance evaluation. Na+ exclusion mechanism was found to be playing an important role in response to salt stress in emmer wheat. The salt tolerance in emmer wheat was systematically characterized here, which not only provided the elite germplasm for wheat improvement, but also provided the efficient method and some useful indexes for salt tolerance assessing.

A High-Density Genetic Map of Wild Emmer Wheat from the Karaca Dağ Region Provides New Evidence on the Structure and Evolution of Wheat Chromosomes.

Wild emmer (Triticum turgidum ssp. dicoccoides) is a progenitor of all cultivated wheat grown today. It has been hypothesized that emmer was domesticated in the Karaca Dağ region in southeastern Turkey. A total of 445 recombinant inbred lines of T. turgidum ssp. durum cv. ‘Langdon’ x wild emmer accession PI 428082 from this region was developed and genotyped with the Illumina 90K single nucleotide polymorphism Infinium assay. A genetic map comprising 2,650 segregating markers was constructed. The order of the segregating markers and an additional 8,264 co-segregating markers in the Aegilops tauschii reference genome sequence was used to compare synteny of the tetraploid wheat with the Brachypodium distachyon, rice, and sorghum. These comparisons revealed the presence of 15 structural chromosome rearrangements, in addition to the already known 4A-5A-7B rearrangements. The most common type was an intra-chromosomal translocation in which the translocated segment was short and was translocated only a short distance along the chromosome. A large reciprocal translocation, one small non-reciprocal translocation, and three large and one small paracentric inversions were also discovered. The use of inversions for a phylogeny reconstruction in the Triticum–Aegilops alliance was illustrated. The genetic map was inconsistent with the current model of evolution of the rearranged chromosomes 4A-5A-7B. Genetic diversity in the rearranged chromosome 4A showed that the rearrangements might have been contemporary with wild emmer speciation. A selective sweep was found in the centromeric region of chromosome 4A in Karaca Dağ wild emmer but not in 4A of T. aestivum. The absence of diversity from a large portion of chromosome 4A of wild emmer, believed to be ancestral to all domesticated wheat, is puzzling.

The allelic distribution and variation analysis of the NAM-B1 gene in Chinese wheat cultivars

The NAM-B1 gene is a member of the NAC (NAM, ATAF, and CUC) transcription factor family and plays an important role in regulating wheat grain protein content (GPC). The ancestral NAM-B1 allele has been discovered in many tetraploid wild emmer (Triticum turgidum ssp. dicoccoides) accessions and few domesticated emmer accessions (T. turgidum ssp. dicoccum), however, it is rarely found in hexaploid bread wheat (Triticum aestivum L.). There are no systematic reports on the distribution of NAM-B1 alleles in Chinese wheat cultivars. In this study, the NAM-B1 alleles in 218 Chinese cultivars were investigated. The cultivars were collected from five major wheat regions (12 provinces), covering most of the winter wheat growing regions in China. The results showed that the NAM-B1 gene is present in 53 (24.3%) cultivars and absent in the remaining 165 (75.7%) cultivars. Further analysis revealed that in contrast to the wild-type allele, the NAM-B1 gene in Chinese wheat cultivars contained a 1-bp insertion in the coding region. This caused a frame-shift mutation and introduced a stop codon in the middle of the gene, rendering it non-functional. Polymorphisms were detected in DNA sequences of 21 cultivars among these 53 cultivars. However, cDNA sequence analysis suggested that these variations in the exon region were not able to restore NAM-B1 gene (1-bp insertion) function. Thus, exploring the distribution of NAM-B1 gene variations (1-bp insertion and deletion) can provide some information for improving the quality of winter wheat in China and other countries.

Flour Quality and Related Molecular Characterization of High Molecular Weight Glutenin Subunit Genes from Wild Emmer Wheat Accession TD-256.

To clarify the effect of high molecular weight glutenin subunit (HMW-GS) from wild emmer wheat on flour quality, which has the same mobility as that from common wheat, the composition and molecular characterization of HMW-GS from wild emmer wheat accession TD-256, as well as its flour quality, were intensively analyzed. It is found that the mobilities of Glu-A1 and Glu-B1 subunits from TD-256 are consistent with those of bread wheat cv. 'XiaoYan 6'. Nevertheless, dough rheological properties of TD-256 reveal its poor flour quality. In the aspect of molecular structure from HMW-GS, only two conserved cysteine residues can be observed in the deduced protein sequence of 1Bx14* from TD-256, while most Glu-1Bx contain four conserved cysteine residues. In addition, as can be predicted from secondary structure, the quantity both of α-helixes and their amino acid residues of the subunits from TD-256 is fewer than those of common wheat. Though low molecular weight glutenin subunit (LMW-GS) and gliadin can also greatly influence flour quality, the protein structure of the HMW-GS revealed in this work can partly explain the poor flour quality of wild emmer accession TD-256.