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Triticum boeoticum (2n = 2x = 14, AbAb) contains beneficial traits for common wheat improvement. The discrimination of Ab-genome chromosomes from A-genome chromosomes is an important step in gene transfer from T. boeoticum to common wheat. In this study, fluorescence in situ hybridization (FISH) analysis using nine oligonucleotide probes revealed high divergence between chromosomes of the common wheat germplasm Crocus and T. boeoticum accession G52. The combination of Oligo-pTa535-HM and Oligo-pSc119.2-HM can differentiate Ab and A chromosomes within homologous groups 2, 4, 5, and 6; chromosomes 2Ab and 6Ab can be identified by using (ACT)7, (CTT)7, and (GAA)7. The probes Oligo-pTa713 and (ACT)7 can be utilized for the identification of chromosomes 1Ab and 3Ab, respectively. Probes (CAG)7 and (CAC)7 can be applied in the identification of 7Ab. Moreover, probe combinations consisting of Oligo-pTa535-HM and (AAC)7 with (ACT)7 or (CTT)7 and of Oligo-pTa535-HM and Oligo-pTa713 with (CAC)7 or (CTT)7 will help discriminate the Ab-genome chromosomes of T. boeoticum. These probes are being used as potential markers to select common wheat Crocus-T. boeoticum G52 alien chromosome lines. Moreover, FISH patterns are highly divergent between Ab- and A-genome chromosomes, indicating that obvious chromosome structural variations arose during wheat evolution.

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a destructive fungal disease with a significant economic impact. Aegilops tauschii, the D-genome progenitor of wheat (Triticum aestivum, AABBDD), offers valuable gene pool for Pst resistance. The Ae. tauschii gene YrAS2388 confers resistance to a wide range of Pst races and encodes a typical nucleotide oligomerization domain-like receptor (NLR). The functional YrAS2388R has duplicated 3′ untranslated regions (3′UTRs). In the present study, we have developed two gene-specific kompetitive allele specific PCR (KASP) markers for YrAS2388R by comparing multiple homoeologous and paralogous genomic sequences of YrAS2388 alleles from allopolyploid wheat genomes. KASP-E5 was developed based on SNP in the exon5 sequences of YrAS2388, which behaves as a co-dominant marker. KASP-E6′ was developed based on the 3′UTR sequences of YrAS2388, which behaves as a dominant marker. These markers were validated in different types of wheat populations and showed clear functional differentiation that was completely agreement with the gel based gene-specific marker for YrAS2388R. Our results indicate that KASP-E5 and KASP-E6′ are perfect diagnostic markers for YrAS2388R and would be useful for marker assisted selection in wheat resistance breeding.

Introgressing one-eighth of synthetic hexaploid wheat genome through a double top-cross plus a two-phase selection is an effective strategy to develop high-yielding wheat varieties. The continued expansion of the world population and the likely onset of climate change combine to form a major crop breeding challenge. Genetic advances in most crop species to date have largely relied on recombination and reassortment within a relatively narrow gene pool. Here, we demonstrate an efficient wheat breeding strategy for improving yield potentials by introgression of multiple genomic regions of de novo synthesized wheat. The method relies on an initial double top-cross (DTC), in which one parent is synthetic hexaploid wheat (SHW), followed by a two-phase selection procedure. A genotypic analysis of three varieties (Shumai 580, Shumai 969 and Shumai 830) released from this program showed that each harbors a unique set of genomic regions inherited from the SHW parent. The first two varieties were generated from very small populations, whereas the third used a more conventional scale of selection since one of bread wheat parents was a pre-breeding material. The three varieties had remarkably enhanced yield potential compared to those developed by conventional breeding. A widely accepted consensus among crop breeders holds that introducing unadapted germplasm, such as landraces, as parents into a breeding program is a risky proposition, since the size of the breeding population required to overcome linkage drag becomes too daunting. However, the success of the proposed DTC strategy has demonstrated that novel variation harbored by SHWs can be accessed in a straightforward, effective manner. The strategy is in principle generalizable to any allopolyploid crop species where the identity of the progenitor species is known.

Wild relatives represent an important genetic pool for crop improvement. In wheat, a popular strategy for the introduction of alien genes is by manipulation of the Ph1 gene, to induce recombination between homoeologous chromosomes. However, the frequency of such homoeologous recombination is low and requires screening of large progeny samples. Consequently, the efficiency of selection of homoeologous recombinants is important. In this study, we developed two kompetitive allele-specific PCR (KASP) markers specific for chromosome arms 6VS of Haynaldia villosa L. and 6AS of wheat, Triticum aestivum L., one close to the terminal regions and the other near the centromeres. Of the 121 progeny from plants heterozygous for the 6VS·6AL translocation and homozygous for ph1b screened by the two KASP markers, three (2.5%) have shown an exchange of markers, and their recombinant nature was confirmed by in situ DNA hybridization. A recombinants chromosome with a small 6VS fragment carrying the powdery mildew resistance gene (Pm21) would be useful in wheat breeding. The two KASP markers tested here can be used for efficient detection of recombinants between 6AS and 6VS.

Six new amphiploids, Triticum kiharae Dorof. et Migusch. (2n = 6x = 42, AtAtGGDD), are described in this study. They were developed by the chromosome doubling of F1 hybrid crosses between Triticum timopheevii Zhuk. (AtAtGG) with high resistance to stripe rust and Aegilops tauschii Cosson (DD) by colchicine treatment. These amphiploids showed a high level of fertility of 68–80% and exhibited relatively normal chromosome pairing in meiotic metaphase I. Individual chromosomes of T. kiharae could be identified by multicolor fluorescence in situ hybridization using the combination of oligonucleotides probes Oligo-pSc119.2-1, Oligo-pTa535-1, and Oligo-pTa71-2. T. kiharae exhibited high resistance to predominant stripe rust races CYR34, CYR31, CYR32, CYR33, and SY11-4 both during the seedling and adult stages. However, high molecular weight glutenin subunits from Ae. tauschii parents were only partially expressed in the T. kiharae background. These T. kiharae lines provide novel materials to widen the genetic diversity of the common wheat gene pool.

Premature termination codons (PTCs) are an important reason for the silence of high-molecular-weight glutenin subunits in Triticum species. Although the Glu-A1y gene is generally silent in common wheat, we here isolated an expressed Glu-A1y gene containing a PTC, named 1Ay8.3, from Triticum monococcum ssp. monococcum (AmAm, 2n = 2x = 14). Despite the presence of a PTC (TAG) at base pair positions 1879–1881 in the C-terminal coding region, this did not obviously affect 1Ay8.3 expression in seeds. This was demonstrated by the fact that when the PTC TAG of 1Ay8.3 was mutated to the CAG codon, the mutant in Escherichia coli bacterial cells expressed the same subunit as in the seeds. However, in E. coli, 1Ay8.3 containing the PTC expressed a truncated protein with faster electrophoretic mobility than that in seeds, suggesting that PTC translation termination suppression probably occurs in vivo (seeds) but not in vitro (E. coli). This may represent one of only a few reports on the PTC termination suppression phenomenon in genes.

Seven Glu-A1m allelic variants of the Glu-A1mx genes in Triticum monococcum ssp. monococcum, designated as 1Ax2.1a, 1Ax2.1b, 1Ax2.1c, 1Ax2.1d, 1Ax2.1e, 1Ax2.1f, and 1Ax2.1g were characterized. Their authenticity was confirmed by successful expression of the coding regions in E. coli, and except for the 1Ax2.1a with the presence of internal stop codons at position of 313 aa, all correspond to the subunit in seeds. However, all the active six genes had a same DNA size although their encoding subunits showed different molecular weight. Our study indicated that amino acid residue substitutions rather than previously frequently reported insertions/deletions played an important role on the subunit evolution of these Glu-A1mx alleles. Since variation in the Glu-A1x locus in common wheat is rare, these novel genes at the Glu-A1mx can be used as candidate genes for further wheat quality improvement.

High-molecular-weight glutenin subunits (HMW-GSs) are important seed storage proteins associated with bread-making quality in common wheat (Triticum aestivum L., 2n = 6x = 42, AABBDD). Variation in the Glu-A1x locus in common wheat is scare. Diploid Triticum monococcum ssp. monococcum (2n = 2x = 14, AmAm) is the first cultivated wheat. In the present study, allelic variations at the Glu-A1mx locus were systematically investigated in 197 T. monococcum ssp. monococcum accessions. Out of the 8 detected Glu-A1mx alleles, 5 were novel, including Glu-A1m-b, Glu-A1m-c, Glu-A1m-d, Glu-A1m-g, and Glu-A1m-h. This diversity is higher than that of common wheat. Compared with 1Ax1 and 1Ax2*, which are present in common wheat, these alleles contained three deletions/insertions as well as some single nucleotide polymorphism variations that might affect the elastic properties of wheat flour. New variations in T. monococcum probably occurred after the divergence between A and Am and are excluded in common wheat population...

Gliadin is a main component of gluten proteins that affect functional properties of bread making and contributes to the viscous nature of doughs. In this study, thirteen novel ω-gliadin genes were identified in several Triticum species, which encode the ARH-, ATDand ATN-type proteins. Two novel types of ω-gliadins: ATD- and ATN- have not yet been reported. The lengths of 13 sequences were ranged from 927 to 1269 bp and the deduced mature proteins were varied from 309 to 414 residues. All 13 genes were pseudogenes because of the presence of internal stop codons. The primary structure of these ω-gliadin genes included a signal peptide, a conserved N-terminal domain, a repetitive domain and a conserved C-terminus. In this paper, we first characterize ω-gliadin genes from T. timopheevi ssp. timopheevi and T. timopheevi ssp. araraticum. The ω-gliadin gene variation and the evolutionary relationship of ω-gliadin family genes were also discussed.

Gene identification in cross-pollinating plants such as rye can be arduous and time consuming because of the difficulties involved with genetic population construction. Here, we provide an alternative approach for the construction of mapping populations to rapidly map genes in cross-pollinated cereal rye. The aim of the present experiments was to genetically analyze the dwarf stature expressed by a germplasm accession of rye. The dwarf phenotype was reversible when the seedlings were exposed to gibberellic acid; the reductions in plant height occurred via reductions in cell size. A mapping population was constructed by generating a set of wheat-rye amphihaploids bred from a single rye plant heterozygous for the dwarfing gene(s). The dwarfness phenotype was expressed in the amphihaploid background, and segregation in the mapping population was consistent with the presence of a single gene. Using rye SSR markers, the gene responsible was located on chromosome arm 1RL, which is also the location of the known rye dwarfing gene Ddw3. This gene is valuable for dwarf breeding of wheat as well as rye.

Background Aegilops tauschii is the donor of the bread wheat D genome. Based on spike morphology, the taxon has conventionally been subdivided into ssp. tauschii and ssp. strangulata. The present study was intended to address the poor match between this whole plant morphology-based subdivision and genetic relationships inferred from genotyping by fluorescence in situ hybridization karyotyping a set of 31 Ae. tauschii accessions. Results The distribution of sites hybridizing to the two probes oligo-pTa-535 and (CTT)10 split the Ae. tauschii accessions into two clades, designated Dt and Ds, which corresponded perfectly with a previously assembled phylogeny based on marker genotype. The Dt cluster was populated exclusively by ssp. tauschii accessions, while the Ds cluster harbored both ssp. strangulata and morphologically intermediate accessions. As a result, it is proposed that Ae. tauschii ssp. tauschii is restricted to carriers of the Dt karyotype: their spikelets are regularly spaced along the rachis, at least in the central portion of their spike. Accessions classified as Ae. tauschii ssp. strangulata carry the Ds karyotype; their spikelets are irregularly spaced. Based on this criterion, forms formerly classified as ssp. tauschii var. meyeri have been re-designated ssp. strangulata var. meyeri. Conclusions According to the reworking of the taxon, the bread wheat D genome was most probably donated by ssp. strangulata var. meyeri. Chromosomal differentiation reveals intra-species taxon of Ae. tauschii. Ae. tauschii ssp. tauschii has more distant relationship with breed wheat than ssp. strangulata and can be used for breeding improving effectively.

Univalent-dependent meiotic nonreduction, which leads to the production of unreduced gametes, is thought to be the predominant mechanism underlying allopolyploid plant formation. However, little is known about the underlying cytological mechanism. In the present study, we observed male sporogenesis in F1 amphihaploid hybrids of wheat–rye by FISH with the help of diagnostic PrCEN-1 specific for the rye centromere. Our observations indicated that at meiotic metaphase I, the chromosomes were accumulated on the equatorial plate. At this stage, the elongated centromeres were amphitelically oriented perpendicular to the equatorial plate, indicating tension from opposite poles. At late metaphase, the centromeres and sister chromatids started separating. Subsequently, the sister chromatids and centromeres split finally resulting in dyads. Our observations indicate that bipolar orientation of the sister kinetochores of univalents at the equatorial plate in metaphase I is important for the subsequent bipolar separation of sister chromatids in the first meiotic division. Allopolyploids are common in plants. Wide hybridization, the first step for the origination of allopolyploids, brings divergent genomes from different species together into an amphihaploid hybrid. Because only one set of homologous chromosomes is present, amphihaploids (analogous to haploid plants) are usually sterile due to reduced meiosis. Meiotic nonreduction (meiotic restitution), however, can lead to production of functionally unreduced gametes, and their union immediately generates an amphidiploid (allopolyploid). Meiotic nonreduction is thought to be the