D-genome Chromosomes Research Articles

Aegilops tauschii single nucleotide polymorphisms shed light on the origins of wheat D‐genome genetic diversity and pinpoint the geographic origin of hexaploid wheat

Hexaploid wheat (Triticum aestivum, genomes AABBDD) originated by hybridization of tetraploid Triticum turgidum (genomes AABB) with Aegilops tauschii (genomes DD). Genetic relationships between A.tauschii and the wheat D genome are of central importance for the understanding of wheat origin and subsequent evolution. Genetic relationships among 477 A.tauschii and wheat accessions were studied with the A.tauschii 10K Infinium single nucleotide polymorphism (SNP) array. Aegilops tauschii consists of two lineages (designated 1 and 2) having little genetic contact. Each lineage consists of two closely related sublineages. A population within lineage 2 in the southwestern and southern Caspian appears to be the main source of the wheat D genome. Lineage 1 contributed as little as 0.8% of the wheat D genome. Triticum aestivum is subdivided into the western and Far Eastern populations. The Far Eastern population conserved the genetic make-up of the nascent T.aestivum more than the western population. In wheat, diversity is high in chromosomes 1D and 2D and it correlates in all wheat D-genome and A.tauschii chromosomes with recombination rates. Gene flow from A.tauschii was an important source of wheat genetic diversity and shaped its distribution along the D-genome chromosomes.

Identification of quantitative trait loci for flowering-related traits in the D genome of synthetic hexaploid wheat lines

The gene pool of Aegilops tauschii, the D-genome donor of common wheat (Triticum aestivum L.), can be easily accessed in wheat breeding, but remains largely unexplored. In our previous studies, many synthetic hexaploid wheat lines were produced through interspecific crosses between the tetraploid wheat cultivar Langdon and various A. tauschii accessions. The synthetic hexaploid wheat lines showed wide variation in many characteristics. To elucidate the genetic basis of variation in flowering-related traits, we analyzed quantitative trait loci (QTL) affecting time to heading, flowering and maturity, and the grain-filling period using four different F2 populations of synthetic hexaploid wheat lines. In total, 10 QTLs located on six D-genome chromosomes (all except 4D) were detected for the analyzed traits. The QTL on 1DL controlling heading time appeared to correspond to a flowering time QTL, previously considered to be an ortholog of Eps-A m 1 which is related to the narrow-sense earliness in einkorn wheat. The 5D QTL for heading time might be a novel locus associated with wheat flowering, while the 2DS QTL appears to be an allelic variant of the photoperiod response locus Ppd-D1. Some of the identified QTLs seemed to be novel loci regulating wheat flowering and maturation, including a QTL controlling the grain filling period on chromosome 3D. The exercise demonstrates that synthetic wheat lines can be useful for the identification of new, agriculturally important loci that can be transferred to, and used for the modification of flowering and grain maturation in hexaploid wheat.

Identification of quantitative trait loci controlling grain size and shape in the D genome of synthetic hexaploid wheat lines

Synthetic hexaploid wheat is an effective genetic resource for transferring agronomically important genes from Aegilops tauschii to common wheat. Wide variation in grain size and shape, one of the main targets for wheat breeding, has been observed among Ae. tauschii accessions. To identify the quantitative trait loci (QTLs) responsible for grain size and shape variation in the wheat D genome under a hexaploid genetic background, six parameters related to grain size and shape were measured using SmartGrain digital image software and QTL analysis was conducted using four F2 mapping populations of wheat synthetic hexaploids. In total, 18 QTLs for the six parameters were found on five of the seven D-genome chromosomes. The identified QTLs significantly contributed to the variation in grain size and shape among the synthetic wheat lines, implying that the D-genome QTLs might be at least partly functional in hexaploid wheat. Thus, synthetic wheat lines with diverse D genomes from Ae. tauschii are useful resources for the identification of agronomically important loci that function in hexaploid wheat.

Endosperm Tolerance of Paternal Aneuploidy Allows Radiation Hybrid Mapping of the Wheat D-Genome and a Measure of γ Ray-Induced Chromosome Breaks

Physical mapping and genome sequencing are underway for the ≈17 Gb wheat genome. Physical mapping methods independent of meiotic recombination, such as radiation hybrid (RH) mapping, will aid precise anchoring of BAC contigs in the large regions of suppressed recombination in Triticeae genomes. Reports of endosperm development following pollination with irradiated pollen at dosages that cause embryo abortion prompted us to investigate endosperm as a potential source of RH mapping germplasm. Here, we report a novel approach to construct RH based physical maps of all seven D-genome chromosomes of the hexaploid wheat ‘Chinese Spring’, simultaneously. An 81-member subset of endosperm samples derived from 20-Gy irradiated pollen was genotyped for deletions, and 737 markers were mapped on seven D-genome chromosomes. Analysis of well-defined regions of six chromosomes suggested a map resolution of ∼830 kb could be achieved; this estimate was validated with assays of markers from a sequenced contig. We estimate that the panel contains ∼6,000 deletion bins for D-genome chromosomes and will require ∼18,000 markers for high resolution mapping. Map-based deletion estimates revealed a majority of 1–20 Mb interstitial deletions suggesting mutagenic repair of double-strand breaks in pollen provides a useful resource for RH mapping and map based cloning studies.

Physical mapping resources for large plant genomes: radiation hybrids for wheat D-genome progenitor Aegilops tauschii

BackgroundDevelopment of a high quality reference sequence is a daunting task in crops like wheat with large (~17Gb), highly repetitive (>80%) and polyploid genome. To achieve complete sequence assembly of such genomes, development of a high quality physical map is a necessary first step. However, due to the lack of recombination in certain regions of the chromosomes, genetic mapping, which uses recombination frequency to map marker loci, alone is not sufficient to develop high quality marker scaffolds for a sequence ready physical map. Radiation hybrid (RH) mapping, which uses radiation induced chromosomal breaks, has proven to be a successful approach for developing marker scaffolds for sequence assembly in animal systems. Here, the development and characterization of a RH panel for the mapping of D-genome of wheat progenitor Aegilops tauschii is reported.ResultsRadiation dosages of 350 and 450 Gy were optimized for seed irradiation of a synthetic hexaploid (AABBDD) wheat with the D-genome of Ae. tauschii accession AL8/78. The surviving plants after irradiation were crossed to durum wheat (AABB), to produce pentaploid RH1s (AABBD), which allows the simultaneous mapping of the whole D-genome. A panel of 1,510 RH1 plants was obtained, of which 592 plants were generated from the mature RH1 seeds, and 918 plants were rescued through embryo culture due to poor germination (<3%) of mature RH1 seeds. This panel showed a homogenous marker loss (2.1%) after screening with SSR markers uniformly covering all the D-genome chromosomes. Different marker systems mostly detected different lines with deletions. Using markers covering known distances, the mapping resolution of this RH panel was estimated to be <140kb. Analysis of only 16 RH lines carrying deletions on chromosome 2D resulted in a physical map with cM/cR ratio of 1:5.2 and 15 distinct bins. Additionally, with this small set of lines, almost all the tested ESTs could be mapped. A set of 399 most informative RH lines with an average deletion frequency of ~10% were identified for developing high density marker scaffolds of the D-genome.ConclusionsThe RH panel reported here is the first developed for any wild ancestor of a major cultivated plant species. The results provided insight into various aspects of RH mapping in plants, including the genetically effective cell number for wheat (for the first time) and the potential implementation of this technique in other plant species. This RH panel will be an invaluable resource for mapping gene based markers, developing a complete marker scaffold for the whole genome sequence assembly, fine mapping of markers and functional characterization of genes and gene networks present on the D-genome.

A Method to Produce Radiation Hybrids for the D-Genome Chromosomes of Wheat (Triticum aestivum L.)

Radiation hybrid (RH) mapping is based on radiation-induced chromosome breakage rather than meiotic recombination, as a means to induce marker segregation for mapping. To date, the implementation of this mapping approach in hexaploid (Triticum aestivum L.; 2n = 6x = 42; AABBDD) and tetraploid (T. turgidum L.; 2n = 4x = 28; AABB) wheat has concentrated on the production of mapping panels for individual chromosomes. In order to extend the usefulness of this approach, we have devised a method to produce panels for the simultaneous mapping of all chromosomes of the D subgenome of hexaploid wheat. In this approach, seeds of hexaploid wheat (AABBDD) are irradiated and the surviving plants are crossed to tetraploid wheat (AABB) to produce a mapping panel based on quasi-pentaploids (AABBD). Chromosome lesions in the A and B genomes are largely masked in the quasi-pentaploids due to the presence of A- and B-genome chromosomes from the tetraploid parent. On the other hand, the chromosomes from the D-genome are present in one copy (hemizygous) and allow radiation hybrid mapping of all D-genome chromosomes simultaneously. Our analyses showed that transmission of D-genome chromosomes was apparently normal and that radiation-induced chromosome breakage along D-genome chromosomes was homogeneous. Chromosome breakage levels between D-genome chromosomes were comparable except for chromosome 6D which suffered greater chromosome breakage. These results demonstrate the feasibility of constructing D-genome radiation hybrids (DGRHs) in wheat.

The effect of selection for phenotypical characters on the chromosome constitution in spring triticale

A set of spring triticale selection forms was studied with the use of microsatellite markers specific for D-genome chromosomes and genomic in situ hybridization. 2R/2D substitutions were found in six of twelve forms. Two lines displayed segregation for the substitution: plants with the substitution and without it, and plants heterozygous for the substitution were revealed. Segregation of the lines and the presence in them of telocentric chromosomes of wheat and rye in the monosomic state suggest that the process of formation is still in progress. The data obtained also demonstrate that triticale is under selection for the 2R/2D substitution as controlling the spectrum of adaptively and selectively valuable traits.

Characterization of a new synthetic wheat – Aegilops biuncialis partial amphiploid

The aim of the experiments was to identify the synthetic wheat – Aegilops biuncialis germplasm Line 15-3-2 with 42 chromosomes. Morphologically, the spike of line 15-3-2 is intermediate to those of its wheat and Aegilops parents. Line 15-3-2 displays stable fertility and immunity to wheat powdery mildew and stripe rust. The seed storage protein electrophoresis showed that Line 15-3-2 presented almost all gliadin bands and a majority of glutenin subunits of its parents. Fluorescence in situ hybridization (FISH) suggested that Line 15-3-2 contained all 14 D-genome chromosomes and chromosome 5U. Therefore, it could be concluded that Line 15-3-2 is a new synthetic wheat – A. biuncialis partial amphiploid, and could be used to transfer the disease resistance genes to wheat.

Characterization of a new synthetic wheat – Aegilops biuncialis partial amphiploid

The aim of the experiments was to identify the synthetic wheat – Aegilops biuncialis germplasm Line 15-3-2 with 42 chromosomes. Morphologically, the spike of line 15-3-2 is intermediate to those of its wheat and Aegilops parents. Line 15-3-2 displays stable fertility and immunity to wheat powdery mildew and stripe rust. The seed storage protein electrophoresis showed that Line 15-3-2 presented almost all gliadin bands and a majority of glutenin subunits of its parents. Fluorescence in situ hybridization (FISH) suggested that Line 15-3-2 contained all 14 D-genome chromosomes and chromosome 5U. Therefore, it could be concluded that Line 15-3-2 is a new synthetic wheat – A. biuncialis partial amphiploid, and could be used to transfer the disease resistance genes to wheat.

Chromosome composition of hexaploid triticale

The chromosome complements of approximately 50 lines of hexaploid triticale and triticale wheat intercross lines were investigated by means of a Giemsa technique which makes it possible to distinguish between rye and wheat chromosomes. The number of rye chromosome pairs present in different lines varies from one to seven. This shows that the third genome of triticales can represent a wide range of combinations of rye- and D-genome chromosomes. Most of the advanced lines with good agronomic characters have a mixed chromosome composition.

Genetic diversity of the D-genome in T. aestivum and Aegilops species using SSR markers

Simple sequence repeats (SSRs), highly dispersed nucleotide sequences in genomes, were used for germplasm analysis and estimation of the genetic relationship of the D-genome among 52 accessions of T. aestivum (AABBDD), Ae. tauschii (D t D t ), Ae. cylindrica (CCD c D c ) and Ae. crassa (MMD cr1 D cr1 ), collected from 13 different sites in Iran. A set of 21 microsatellite primers, from various locations on the seven D-genome chromosomes, revealed a high level of polymorphism. A total of 273 alleles were detected across all four species and the number of alleles per each microsatellite marker varied from 3 to 27. The highest genetic diversity occurred in Ae. tauschii followed by Ae. crassa, and the genetic distance was the smallest between Ae. tauschii and Ae. cylindrica. Data obtained in this study supports the view that genetic variability in the D-genome of hexaploid wheat is less than in Ae. tauschii. The highest number of unique alleles was observed within Ae. crassa accessions, indicating this species as a great potential source of novel genes for bread wheat improvement. Knowledge of genetic diversity in Aegilops species provides different levels of information which is important in the management of germplasm resources.

Chromosomal rearrangements in wheat: their types and distribution

Four hundred and sixty polyploid wheat accessions and 39 triticale forms from 37 countries of Europe, Asia, and USA were scored by C-banding for the presence of translocations. Chromosomal rearrangements were detected in 70 of 208 accessions of tetraploid wheat, 69 of 252 accessions of hexaploid wheat, and 3 of 39 triticale forms. Altogether, 58 types of major chromosomal rearrangements were identified in the studied material; they are discussed relative to 11 additional translocation types described by other authors. Six chromosome modifications of unknown origin were also observed. Among all chromosomal aberrations identified in wheat, single translocations were the most frequent type (39), followed by multiple rearrangements (9 types), pericentric inversions (9 types), and paracentric inversions (3 types). According to C-banding analyses, the breakpoints were located at or near the centromere in 60 rearranged chromosomes, while in 52 cases they were in interstitial chromosome regions. In the latter case, translocation breakpoints were often located at the border of C-bands and the euchromatin region or between two adjacent C-bands; some of these regions seem to be translocation "hotspots". Our results and data published by other authors indicate that the B-genome chromosomes are involved in translocations most frequently, followed by the A- and D-genome chromosomes; individual chromosomes also differ in the frequencies of translocations. Most translocations were detected in 1 or 2 accessions, and only 11 variants showed relatively high frequencies or were detected in wheat varieties of different origins or from different species. High frequencies of some translocations with a very restricted distribution could be due to a "bottleneck effect". Other types seem to occur independently and their broad distribution can result from selective advantages of rearranged genotypes in diverse environmental conditions. We found significant geographic variation in the spectra and frequencies of translocation in wheat: the highest proportions of rearranged genotypes were found in Central Asia, the Middle East, Northern Africa, and France. A low proportion of aberrant genotypes was characteristic of tetraploid wheat from Transcaucasia and hexaploid wheat from Middle Asia and Eastern Europe.

Molecular characterization and chromosome-specific TRAP-marker development for Langdon durum D-genome disomic substitution lines

The aneuploid stocks of durum wheat (Triticum turgidum L. subsp. durum (Desf.) Husnot) and common wheat (T. aestivum L.) have been developed mainly in 'Langdon' (LDN) and 'Chinese Spring' (CS) cultivars, respectively. The LDN-CS D-genome chromosome disomic substitution (LDN-DS) lines, where a pair of CS D-genome chromosomes substitute for a corresponding homoeologous A- or B-genome chromosome pair of LDN, have been widely used to determine the chromosomal locations of genes in tetraploid wheat. The LDN-DS lines were originally developed by crossing CS nulli-tetrasomics with LDN, followed by 6 backcrosses with LDN. They have subsequently been improved with 5 additional backcrosses with LDN. The objectives of this study were to characterize a set of the 14 most recent LDN-DS lines and to develop chromosome-specific markers, using the newly developed TRAP (target region amplification polymorphism)-marker technique. A total of 307 polymorphic DNA fragments were amplified from LDN and CS, and 302 of them were assigned to individual chromosomes. Most of the markers (95.5%) were present on a single chromosome as chromosome-specific markers, but 4.5% of the markers mapped to 2 or more chromosomes. The number of markers per chromosome varied, from a low of 10 (chromosomes 1A and 6D) to a high of 24 (chromosome 3A). There was an average of 16.6, 16.6, and 15.9 markers per chromosome assigned to the A-, B-, and D-genome chromosomes, respectively, suggesting that TRAP markers were detected at a nearly equal frequency on the 3 genomes. A comparison of the source of the expressed sequence tags (ESTs), used to derive the fixed primers, with the chromosomal location of markers revealed that 15.5% of the TRAP markers were located on the same chromosomes as the ESTs used to generate the fixed primers. A fixed primer designed from an EST mapped on a chromosome or a homoeologous group amplified at least 1 fragment specific to that chromosome or group, suggesting that the fixed primers might generate markers from target regions. TRAP-marker analysis verified the retention of at least 13 pairs of A- or B-genome chromosomes from LDN and 1 pair of D-genome chromosomes from CS in each of the LDN-DS lines. The chromosome-specific markers developed in this study provide an identity for each of the chromosomes, and they will facilitate molecular and genetic characterization of the individual chromosomes, including genetic mapping and gene identification.

Development and QTL assessment of Triticum aestivum–Aegilops tauschii introgression lines

A set of 84 bread wheat lines, each containing a single homozygous introgression of the Aegilops tauschii genome was produced in the 'Chinese Spring' background via backcrossing of the D-genome chromosome substitution lines 'Chinese Spring'/Sears's 'Synthetic 6x' with the recurrent parent and subsequent selfing. The development of the lines was accompanied by microsatellite marker assisted selection. With the exception of three telomeric regions at chromosomes 1DL, 4DL and 7DS, and a region of less than 24 cM on the chromosome arm 3DL, the genome of Ae. tauschii is fully represented in these lines. The newly developed lines were used for the discovery of morphological and agronomical quantitative trait loci (QTLs) from the wild species. Fifty-two introgression lines were grown in the field and evaluated for six traits including flowering time, plant height, ear length, spikelet number, fertility and grain weight per ear. Seventeen significant QTLs were detected, Ae. tauschii contributed favourable alleles at nine loci influencing five traits. The whole set of 84 homozygous lines provides a tool for further testing the effects and stability of the detected QTLs and for the evaluation of new traits.

Effect of genome, induction medium and temperature pretreatment on green plant production in durum (Triticum turgidum var. durum) x bread wheat (Triticum aestivum L. em Thell) crosses

The recalcitrancy of durum wheat (Triticum turgidum var. durum) to anther culture, was attempted to be overcome by transferring the responsible genes form bread wheat B-genome to the respective on durum wheat, determining an appropriate induction medium and clarifying the necessity of cold pretreatment. For this, three durum wheat cultivars were crossed to two bread wheat (Triticum aestivum L. em Thell) cultivars. The resulting F1 plants and their original cultivars were grown in the field and anthers at the appropriate microspore stage were cultured on potato-2 and W14 media with and without low temperature pretreatment. No green plants were produced from the parental durum wheat cultivars. In contrast, green plants were produced from the F1 plants. The best results in three of the four F1 hybrids were recorded when potato-2 was used as induction medium. A more variable response of the examined genotypes was noticed with respect to temperature pretreatment. Regarding green plant production, a negative effect of cold pretreatment was observed in two of the F1 hybrids when they were cultured on potato-2. Chromosome counts on root tips from the resulting green plants revealed that they all carried D-genome chromosomes. The last observation could suggest that D-genome chromosomes are necessary for anther culture response in wheat. Yet, the production of one green plant with 15 chromosomes may indicate that the development of extracted durum genotypes from bread wheat genotypes with good response to in vitro anther culture might be possible. Further work however, is needed for this to be verified.

Agropyron elongatum chromatin localization on the wheat chromosomes in an introgression line

The introgressed small-chromosome segment of Agropyron elongatum (Host.) Neviski (Thinopyrum ponticum Podp.) in F5 line II-1-3 of somatic hybrid between common wheat (Triticum aestivum L.) and A. elongatum was localized by sequential fluorescence in situ hybridization (FISH), genomic in situ hybridization (GISH) and karyotype data. Karyotype analysis offered basic data of arm ratios and relative lengths of 21 pairs of chromosomes in parent wheat Jinan177 and hybrid II-1-3. Using special high repetitive sequences pSc119.2 and pAs1 for FISH, the entire B- and D-genome chromosomes were detected. The FISH pattern of hybrid II-1-3 was the same as that of parent wheat. GISH using whole genomic DNA from A. elongatum as probe determined the alien chromatin. Sequential GISH and FISH, in combination with some of the karyotype data, localized the small chromosome segments of A. elongatum on the specific sites of wheat chromosomes 2AL, 1BL, 5BS, 1DL, 2DL and 6DS. FISH with probe OPF-03(1296) from randomly amplified polymorphic DNA (RAPD) detected E-genome chromatin of A. elongatum, which existed in all of the small chromosome segments introgressed. Microsatellite primers characteristic for the chromosome arms above were used to check the localization and reveal the genetic identity. These methods are complementary and provide comprehensive information about the genomic constitution of the hybrid. The relationship between hybrid traits and alien chromatin was discussed.

Simultaneous painting of three genomes in hexaploid wheat by BAC-FISH

Fluorescence in situ hybridization (FISH) is widely used in the physical mapping of genes and chromosome landmarks in plants and animals. Bacterial artificial chromosomes (BACs) contain large inserts, making them amenable for FISH mapping. In our BAC-FISH experiments, we selected 56 restriction fragment length polymorphism (RFLP)-locus-specific BAC clones from the libraries of Triticum monococcum and Aegilops tauschii, which are the A- and D-genome donors of wheat (Triticum aestivum, 2n = 6x = 42), respectively. The BAC clone 676D4 from the T. monococcum library contains a dispersed repeat that preferentially hybridizes to A-genome chromosomes, and two BAC clones, 9I10 and 9M13, from the Ae. tauschii library contain a dispersed repeat that preferentially hybridizes to the D-genome chromosomes. These repeats are useful in simultaneously discriminating the three different genomes in hexaploid wheat, and in identifying intergenomic translocations in wheat or between wheat and alien chromosomes. Sequencing results show that both of these repeats are transposable elements, indicating the importance of transposable elements, especially retrotransposons, in the genome evolution of wheat.

Construction of a subgenomic BAC library specific for chromosomes 1D, 4D and 6D of hexaploid wheat.

The analysis of the hexaploid wheat genome (Triticum aestivum L., 2 n=6 x=42) is hampered by its large size (16,974 Mb/1C) and presence of three homoeologous genomes (A, B and D). One of the possible strategies is a targeted approach based on subgenomic libraries of large DNA inserts. In this work, we purified by flow cytometry a total of 10(7) of three wheat D-genome chromosomes: 1D, 4D and 6D. Chromosomal DNA was partially digested with HindIII and used to prepare a specific bacterial artificial chromosome (BAC) library. The library (designated as TA-subD) consists of 87,168 clones, with an average insert size of 85 kb. Among these clones, 53% had inserts larger than 100 kb, only 29% of inserts being shorter than 75 kb. The coverage was estimated to be 3.4-fold, giving a 96.5% probability of identifying a clone corresponding to any sequence on the three chromosomes. Specificity for chromosomes 1D, 4D and 6D was confirmed after screening the library pools with single-locus microsatellite markers. The screening indicated that the library was not biased and gave an estimated coverage of sixfold. This is the second report on BAC library construction from flow-sorted plant chromosomes, which confirms that dissecting of the complex wheat genome and preparation of subgenomic BAC libraries is possible. Their availability should facilitate the analysis of wheat genome structure and evolution, development of cytogenetic maps, construction of local physical maps and map-based cloning of agronomically important genes.

A direct repeat sequence associated with the centromeric retrotransposons in wheat.

A high-density BAC filter of Triticum monococcum was screened for the presence of a centromeric retrotransposon using the integrase region as a probe. Southern hybridization to the BAC digests using total genomic DNA probes of Triticum monococcum, Triticum aestivum, and Hordeum vulgare detected differentially hybridizing restriction fragments between wheat and barley. The fragments that hybridized to genomic DNA of wheat but not to that of barley were subcloned. Fluorescence in situ hybridization (FISH) analysis indicated that the clone pHind258 hybridized strongly to centromeric regions in wheat and rye and weakly to those in barley. The sequence of pHind258 was homologous to integrase and long terminal repeats of centromeric Ty3-gypsy retrotransposons of cereal species. Additionally, pHind258 has a pair of 192-bp direct repeats. FISH analysis indicated that the 192-bp repeat probe hybridized to centromeres of wheat and rye but not to those of barley. We found differential FISH signal intensities among wheat chromosomes using the 192-bp probe. In general, the A-genome chromosomes possess strong FISH signals, the B-genome chromosomes possess moderate signals, and the D-genome chromosomes possess weak signals. This was consistent with the estimated copy numbers of the 192-bp repeats in the ancestral species of hexaploid wheat.

The effect of introgressions of wheat D-genome chromosomes into ‘Presto’ triticale

Hexaploid triticale (X Triticosecale Wittmack) (2n= 6x= 42, AABBRR) and wheat (Triticum aestivum L.) (2n= 6x= 42, AABBDD) differ in their R and D-genomes. This produces differences in both agronomic and end-use quality characteristics. Our objective was to determine how introgressions of individual chromosomes from the D-genome of wheat affect these characteristics of a winter triticale 'Presto'. We studied the effects of 18 D-genome chromosome substitution lines, 15 sib-lines as controls, and five check cultivars at Lincoln, NE in 1996, using a randomized complete block design with two replications. The experiment was repeated at Lincoln and Mead, NE in 1997 and 1998 with 15 substitution lines that survived the first winter in Lincoln, along with their 12 control sibs and five check cultivars. Few D-genome chromosomes had positive effects. Chromosomes 2D, 4D, and 6D significantly reduced plant height when substituted for 2R, 4B, and 6R, respectively. No grain yield increases were associated with any of the D-genome chromosomes tested, but three substitutions decreased the grain yield. Depending on the allele of the hardness gene present, chromosome 5D increased or decreased kernel hardness when substituted for 5R or 5A, respectively. Introgressions of chromosomes 1D and 6D improved end-use quality characteristics of Presto. These results suggest that apart from beneficial effects of individual loci located on the D-genome chromosomes, no major benefit can be expected from D-genome chromosome substitutions.