Chromosome 1U Research Articles

Grain quality indices in common wheat lines with introgressions of chromosome 1U from Aegilops biuncialis Vis.

Aim. The aim of this study was to analyze grain quality indices in winter common wheat lines with introgressions of chromosome 1U from Aegilops biuncialis Vis. marked by storage protein loci. Methods. Acid polyacrylamide gel electrophoresis and SDS-electrophoresis of storage proteins were performed to identify introgressions. Grain quality indices (SDS sedimentation volume and grain protein content) were analyzed in lines with introgressed chromosome 1U or its arm 1UL, as well as in the cultivars Panna and Bezostaya 1. Results. SDS-sedimentation volume in the cultivars and lines depended on year’s conditions. The studying of the lines during two years has demonstrated that the presence of the allele at the high molecular weight glutenin subunit locus Glu-U1 from Ae. biuncialis was associated with a high volume of SDS-sedimentation SDS30 (higher than that in the cultivar Bezostaya 1). The introgressive lines show high grain protein content. Conclusions. The effect of the allele at the high molecular weight glutenin subunit locus Glu-U1 from Ae. biuncialis on SDS-sedimentation value is similar to that of the high-quality allele Glu-B1al. The lines with the introgressed allele at Glu-U1 from Ae. biuncialis are valuable initial material for breeding for quality.Keywords: Triticum aestivum, Aegilops biuncialis, high molecular weight glutenin subunits, SDS-sedimentation, protein content.

Special features of transmission of markers for Aegilops biuncialis Vis. Chromosome 1U in common wheat hybrids

Aim. The wild wheat relative Aegilops biuncialis Vis. is a potential source of new storage protein alleles for enriching the common wheat gene pool. We have produced the wheat material from direct crossing of common wheat with Crimean samples of Ae. biuncialis followed by backcrossing with wheat. Using storage proteins as genetic markers, lines with introgressions of chromosome 1U have been selected. The objective of the investigation was to study the transmission of markers for chromosome 1U in the hybrid from crossing the common wheat cultivar Bezostaya 1 with a line carrying chromosome 1U. Methods. F2 seeds from the cross of the common wheat cultivar Besostaya 1 and the line NVG41 carrying Ae. biuncialis chromosome 1U were analyzed. Storage proteins encoded by Gli-U1 and Glu-U1 served as markers for chromosome 1U. Gliadins were analyzed by acid polyacrylamide gel electrophoresis by the procedure of Kozub et al. (2009). Electrophoresis of total seed proteins, including high-molecular-weight glutenin subunits, was carried out by the procedure of Laemmli (1970).Results. Among the F2 seeds analyzed, we identified four classes of genotypes with respect to the markers Gli-U1 and Glu-U1: 1) with complete chromosome 1U, 2) with the 1UL arm only, 3) with the 1US arm only, 4) without chromosome 1U. In the F1 hybrid NVG41 × Bezostaya 1, Ae. biuncialis chromosome 1U was transmitted with an increased frequency (with respect to the marker Glu-U1 and the simultaneous presence of the markers Gli-U1 and Glu-U1). The frequency of centric misdivision of chromosome 1U (univalent) in the F1 hybrid amounted about 9 %. This resulted in a significantly lower number of seeds with the 1US arm only (2 %) than that with the 1UL arm (6 %).Conclusions. In the progeny of F1 hybrids with Ae. biuncialis univalent 1U, a lower frequency of genotypes with the 1US arm only as compared with the 1UL arm only can be observed at the grain stage. This could be due to the loss of telocentrics with the 1US arm at gamete formation or reduced viability of genotypes with 1US only at the gamete stage or after zygote formation.Manuscript received 02.04.2020

Studying common wheat material from crosses with Aegilops biuncialis vis. using markers for chromosome 1U

Aim. The aim of the research was to study common wheat material developed from crosses with Aegilops biuncialis Vis. using storage protein loci as markers for chromosome 1U. Methods. SDS and APAG electrophoreses of seed storage proteins were employed to identify alleles at the Glu-1 and Gli-1 loci. The following markers of chromosome 1U of Ae. biuncialis were used: the Glu-U1 locus encoding high-molecular-weight glutenin subunits located on the long arm (1UL) and the gliadin locus Gli-U1 on the short arm (1US). Results. In F6–F7, elimination of chromosome 1U material with a frequency of about 0.222 proceeded. This indicates selection against unbalanced genotypes, which could be tracked using markers for chromosome 1U. In wheat F4–F6 hybrids from crosses with Ae. biuncialis, we revealed a high frequency of formation of genotypes possessing the 1UL arm and lacking 1US. Conclusions. Since the Glu-U1 locus on the arm 1UL encodes high-molecular-weight subunits which directly determine bread-making quality, the developed wheat material is a source of a new allele of this locus introgressed from Ae. biuncialis for enriching the common wheat gene pool. Keywords: Triticum aestivum, Aegilops biuncialis, storage proteins, introgression.

Development and studying of Triticum aestivum L. material with introgressions from Aegilops biuncialis Vis.

Aim. The aim of the study was to develop and study T. aestivum material with introgressions from Ae. biuncialis. Methods. Quantitative traits of F4 lines from crossing wheat with Crimean accessions of Ae. biuncialis were studied. SDS and APAG electrophoreses of storage proteins were used to identify alleles at the Glu-1 and Gli-1 loci, including introgressed ones. Results. F4 lines from crosses of wheat with Ae. biuncialis showed a wide range of yield traits. Some lines had a clavate spike and a hairy leaf blade. Using storage proteins as genetic markers the presence of chromosome 1U was identified among the progeny of plants analyzed; some of them had translocation of arm 1UL. Lines with introgressions of chromosome 1M were not revealed. Conclusions. T. aestivum lines with introgressions from Ae. biuncialis were developed without amphidiploid production. Lines with chromosome 1U were selected, including lines with translocations of arm 1UL.
 Keywords: Triticum aestivum L., Aegilops biuncialis Vis., introgression.

Genotyping-by-Sequencing Facilitates a High-Density Consensus Linkage Map for Aegilops umbellulata, a Wild Relative of Cultivated Wheat.

High-density genetic maps are useful to precisely localize QTL or genes that might be used to improve traits of nutritional and/or economical importance in crops. However, high-density genetic maps are lacking for most wild relatives of crop species, including wheat. Aegilops umbellulata is a wild relative of wheat known for its potential as a source of biotic and abiotic stress resistance genes. In this work, we have developed a framework consensus genetic map using two biparental populations derived from accessions PI 298905, PI 542369, PI 5422375, and PI 554395. The framework map comprised 3009 genotype-by-sequence SNPs with a total map size of 948.72 cM. On average, there were three SNPs per centimorgan for each chromosome. Chromosome 1U was the shortest (66.5 cM), with only 81 SNPs, whereas the remaining chromosomes had between 391 and 591 SNP markers. A total of 2395 unmapped SNPs were added to the linkage maps through a recombination frequency approach, and increased the number of SNPs placed on the consensus map to a total of 5404 markers. Segregation distortion was disproportionally high for chromosome 1U for both populations used to construct component linkage maps, and thus segregation distortion could be one of the probable reasons for the exceptionally reduced linkage size for chromosome 1U. From comparative analysis, Ae. umbellulata chromosomes except 4U showed moderate to strong collinearity with corresponding homeologous chromosomes of hexaploid wheat and barley. The present consensus map may serve as a reference map in QTL mapping and validation projects, and also in genome assembly to develop a reference genome sequence for Ae. umbellulata.

Characterization of a new wheat-Aegilops biuncialis addition line conferring quality-associated HMW glutenin subunits

In this study, a new disomic addition line, 12-5-2, with 44 chromosomes that was derived from BC3F2 descendants of the hybridization between Triticum aestivum cv. CN19 and Aegilops biuncialis was created and reported. 12-5-2 was immune to both powdery mildew and stripe rust and has stable fertility. Fluorescence in situ hybridization and C-banding revealed that 12-5-2 was a 1U(b) disomic addition line (ADL1U(b)). The seed storage protein electrophoresis showed that 12-5-2 presented all high molecular weight glutenin subunits (7 + 8 and 2 + 12) of CN19 and 2 new subunits that were designated Ux and Uy. Additionally, the flour quality parameters showed that the protein content, Zeleny sedimentation value, wet gluten content, and grain hardness of 12-5-2 were significantly higher than those of its parent CN19. Moreover, 5 pairs of the chromosome 1U(b)-specific polymerase chain reaction-based landmark unique gene markers, TNAC1021, TNAC1041, TNAC1071, TNAC1-01, and TNAC1-04, were also obtained. The new ADL1U(b) 12-5-2 could be a valuable source for wheat improvement, especially for wheat end-product quality and resistance to disease.

Chromosome isolation by flow sorting in Aegilops umbellulata and Ae. comosa and their allotetraploid hybrids Ae. biuncialis and Ae. geniculata.

This study evaluates the potential of flow cytometry for chromosome sorting in two wild diploid wheats Aegilops umbellulata and Ae. comosa and their natural allotetraploid hybrids Ae. biuncialis and Ae. geniculata. Flow karyotypes obtained after the analysis of DAPI-stained chromosomes were characterized and content of chromosome peaks was determined. Peaks of chromosome 1U could be discriminated in flow karyotypes of Ae. umbellulata and Ae. biuncialis and the chromosome could be sorted with purities exceeding 95%. The remaining chromosomes formed composite peaks and could be sorted in groups of two to four. Twenty four wheat SSR markers were tested for their position on chromosomes of Ae. umbellulata and Ae. comosa using PCR on DNA amplified from flow-sorted chromosomes and genomic DNA of wheat-Ae. geniculata addition lines, respectively. Six SSR markers were located on particular Aegilops chromosomes using sorted chromosomes, thus confirming the usefulness of this approach for physical mapping. The SSR markers are suitable for marker assisted selection of wheat-Aegilops introgression lines. The results obtained in this work provide new opportunities for dissecting genomes of wild relatives of wheat with the aim to assist in alien gene transfer and discovery of novel genes for wheat improvement.

Development of commercially valuable traits in hexaploid triticale lines with Aegilops introgressions as dependent on the genome composition

Introgressive hybridization is an efficient means to improve the genetic diversity of cultivated cereals, including triticale. To identify the triticale lines with Aegilops introgressions, genotyping was carried out with ten lines obtained by crossing hexaploid triticale with genome-substitution forms of the common wheat cultivar Avrora: Avrolata (AABBUU), Avrodes (AABBSS), and Avrotika (AABBTT). The genome composition of the triticale lines was studied by in situ hybridization, and recombination events involving Aegilops and/or common wheat chromosomes were assumed for nine out of the ten lines. Translocations involving rye chromosomes were not observed. Substitutions for rye chromosomes were detected in two lines resulting from crosses with Avrolata. Genomic in situ hybridization (GISH) with Ae. umbellulata DNA and molecular genetic analysis showed that chromosome 1R was substituted with Ae. umbellulata chromosome 1U in one of the lines and that 2R(2U) substitution took place in the other line. Fluorescence in situ hybridization (FISH) with the Spelt 1 and pSc119.2 probes revealed a translocation from Ae. speltoides to the long arm of chromosome 1B in one of the two lines resulting from crosses with Avrodes and a translocation in the long arm of chromosome 7B in the other line. In addition, the pSc119.2 probe revealed chromosome 1B rearrangements in four lines resulting from crosses with Avrolata and in a line resulting from crosses with Avrotika. The lines were tested for main productivity parameters. A negative effect on all productivity parameters was demonstrated for Ae. umbellulata chromosome 2U. The overwinter survival in all of the lines was similar to or even higher than in the original triticale cultivars. A substantial increase in winter resistance as compared with the parental cultivar was observed for the line carrying the T7BS-7SL translocation. The line with the 1R(1U) chromosome substitution seemed promising for the baking properties of triticale.

Demonstration ofAegilops biuncialischromosomes in a wheat background by genomicin situhybridization (GISH) and identification of U chromosomes by FISH using GAA sequences

The aims of the study were the optimisation of genomic in situ hybridization (GISH) and the use of a GAA satellite sequences as a fluorescence in situ hybridization (FISH) probe to discriminate Aegilops biuncialis and wheat chromosomes. The application of genomic DNA from the diploid progenitors, Ae. umbellulata and Ae. comosa , as a probe with a blocking ratio of 1:200 resulted in the clear visualization of Ae. biuncialis chromosomes. Based on the strong hybridization signals of the PCR-amplified GAA satellite sequences it was possible to identify chromosomes 1U, 2U, 4U and 5U of Ae. umbellulata . The improved GISH and GAA idiogram presented here allow the Ae. biuncialis chromatin to be traced in more detail during chromosome-mediated gene transfer to wheat.

Analysis of a set of homoeologous group 1 wheat-Aegilops umbellulata recombinant chromosome lines using genetic markers

Eleven wheat-Ae. umbellulata recombinant lines involving chromosome 1U, including an important high-molecular-weight glutenin locus, were characterized by protein and RFLP markers. Four 1U-1A recombinants, one 1U-1B recombinant, two 1U deletions with either nullisomy for chromosome 1A or 1B and a 1U ditelosomic addition line were detected, while 3 recombinant lines involved 1U and non-homoeologous wheat chromosomes. Similar recombination events were found in independent lines, and no small segmental translocations of Ae. umbellulata chromatin were detected. Correlation of the markers with physical maps of the wheat-Ae. umbellulata breakpoints obtained using in situ hybridization enabled the marker order to be established on chromosomes 1A, 1B and 1U. The short arm of chromosome 1A probably differs from both 1U and 1B by one inversion. As now being found to be universal in the Triticeae, clustering of the genetical map in the distal physical regions of the group 1 chromosomes was found.

Physical mapping of 5S and 18S–25S rDNA and repetitive DNA sequences in Aegilops umbellulata

An accurate physical map of the location of the 5S and the 18S-5.8S-25S rRNA genes and a repetitive DNA sequence has been produced on Aegilops umbellulata Zhuk., (2n = 2x = 14) chromosomes by in situ hybridization. Chromosome morphology together with the hybridization pattern of pSc119.2, a DNA sequence from rye, allowed identification and discrimination of different chromosomes; pSc119.2 hybridizes with all Ae. umbellulata chromosomes at the telomeres, except for the short arm of chromosome 6U, and shows intercalary sites on the long arms of chromosomes 6U and 7U. The 5S and 18S-25S rDNA have been mapped physically only on the short arms of chromosomes 1U and 5U. On chromosome 1U the order of the genes is 5S rDNA subterminal and 18S-25S rDNA more proximal, while on chromosome 5U the position of the genes is reversed. The relative order of the genes, together with the hybridization pattern of the pSc119.2, is useful in identifying whole chromosomes or chromosome segments from Ae. umbellulata in recombinant or addition lines with wheat. The data help link the physical organization of chromosomes to the genetic map. Other members of the Triticeae vary in the presence and order of the 5S and 18S-25S rDNA sequences on groups 1 and 5, indicating multiple and complex evolutionary rearrangements of the chromosome arms.

Exploitation of chromosome 4S1, from Aegilops sharonensis, for the production of stable 44-chromosome wheat lines

A number of chromosomes from species related to wheat carry genes of potentially high agronomic value. However, wheat lines carrying an additional pair of such chromosomes have never been exploited commercially because they are unstable and the extra chromosomes are frequently lost during gametogenesis. In order to overcome this problem translocations involving the long arm of the Aegilops sharonensis chromosome 4S1, which carries the gene(s) determining preferential transmission, and the long and short arms of chromosome 1U from Aegilops umbellulata, which carry respectively the genes Glu-U1 and Gli-U1, which affect bread making quality, have been isolated. These translocations are stable and preferentially transmitted.

DNase I sensitivity of ribosomal RNA Genes in chromatin and nucleolar dominance in wheat

Ribosomal RNA genes at different nucleolar organizer (NOR) loci in hexaploid wheat are expressed at different levels. The degree of expression of a particular organizer depends on the genetic background, especially on the presence of other NOR loci. For example, when chromosome 1U of Aegilops umbellulata is introduced into the hexaploid wheat cultivar “Chinese Spring” the A. umbellulata NOR accounts for most of the nucleolar activity and seems to suppress the activity of the wheat NOR loci. Even in wild-type “Chinese Spring”, the NOR on chromosome 1B is partially dominant to that on chromosome 6B, since the 1B locus is more active in spite of having fewer genes. We have previously shown that these and other examples of nucleolar dominance in wheat are associated with undermethylation of cytosine residues in certain regions of the dominant rDNA. Here, we show that rRNA genes at dominant loci are organized in a chromatin conformation that renders them more sensitive to DNase I digestion than other rRNA genes. In addition, we have mapped several DNase I-hypersensitive sites in the intergenic spacer region of the rDNA repeating unit. Some of these sites are located near the initiation region for the 45 S rRNA precursor, while others are associated with a series of short direct repeats 5′ to the 45 S rRNA initiation site. The results are discussed in terms of a model in which repeated sequences in the wheat intergenic DNA are presumed to function as upstream promoters and transcriptional enhancers similar to those in Xenopus.

Allosyndetic recombination between a chromosome of Aegilops umbellulata and wheat chromosomes

Allosyndetic recombination was induced between chromosome 1U of Aegilops umbellulata and wheat chromosomes by producing plants monosomic for this alien chromosome and homozygous for the mutant ph1b allele, which permits homoeologous chromosome pairing. Recombinants were selected among the progeny of such plants by observing the disruption of the Glu-1-Gpi-1-Gli-1 linkage on both the alien chromosome as well as along wheat chromosomes 1B and 1D. A frequency of 8·0 per cent recombination between the Gpi-U1 and the Gli-U1 loci was estimated when chromosomes 1U and 1B were simultaneously monosomic, whereas the rate of recombination was only 4·6 per cent when 1B was present as a disome. Some double homoeologous recombinants between the three loci Glu-1, Gpi-1 and Gli-1 were also isolated. Control populations, where homoeologous pairing was suppressed by the presence of Ph1, did not produce any allosyndetic recombinants between Gpi-1 and Gli-1.

Nucleolus organizer competition in Triticum aestivum — Aegilops umbellulata chromosome addition lines

The nucleolar organizer activity of wheat (Triticum aestivum, AABBDD) and Aegilops umbellulata (UU) chromosomes have been analyzed in the complete set of the chromosome addition lines by using a highly reproducible silver-staining procedure. Chromosomes 1U and 5U produce the partial inactivation of wheat nucleolar organizer chromosomes 6B, 1B and 5D. The chromosomes D and G from Ae. umbellulata, which are not SAT-chromosomes, seem to specifically influence the activity of wheat NORs. The predominant status of the U genome with respect to nucleolar competition in the Triticeae is confirmed.

Control of lectins in Triticum aestivum and Aegilops umbellulata by homoeologous group 1 chromosomes

Each of the three genomes in hexaploid wheat controls the expression of a specific lectin in the embryo. The chromosomes which control their synthesis were determined using nullisomic-tetrasomic and inter-varietal chromosome substitution lines of 'Chinese Spring'. All three wheat lectins were shown to be controlled by the homoeologous group 1 chromosomes. Using ditelosomic lines of 'Chinese Spring' the lectin genes could be localized on the long arms of chromosomes 1A and 1D. Inter-specific addition and substitution lines of Aegilops umbellulata chromosomes to 'Chinese Spring' indicated that chromosome 1U, which is homoeologous to the group 1 chromosomes of wheat, controls lectin synthesis.

Partial inactivation of wheat nucleolus organisers by the nucleolus organiser chromosomes from Aegilops umbellulata

Two pairs of chromosomes (1U and 5U) in Aegilops umbellulata possess ribosomal RNA genes. This has been proven by studying wheat plants into which 1U and 5U chromosomes have been introduced separately. These plants have more ribosomal RNA genes than the recipient wheat plants and additional clusters of rDNA when examined by in situ hybridisation. The repeating rDNA unit in Aegilops umbellulata is longer than most of the units in the wheat variety Chinese Spring, the additional DNA probably being in the non-transcribed spacer. This was determined from restriction endonuclease maps of rDNA. In Chinese Spring plants possessing 1U or 5U chromosomes, the largest nucleoli are formed on 1U or 5U chromosomes and the wheat nucleolus organisers form micronucleoli. This is not because the nucleolus organisers on chromosomes 1U and 5U have many more rRNA genes than wheat nucleolus organisers. It is suggested that the Aegilops umbellulata nucleolus organisers are dominant over those of wheat because they compete more effectively for some limiting factor. — The partial inactivation of the wheat nucleolus organisers by chromosomes 1U or 5U does not result in a reduced total nucleolus volume in root tip or pollen mother cells, because of the compensation by the nucleolus organisers of chromosomes 1U or 5U. The amount of RNA in seedlings is not markedly affected by the partial inactivation of the wheat nucleolus organisers.