Bánkúti 1201--an old Hungarian wheat variety with special storage protein composition

Exploring the legacy of Central European historical winter wheat landraces

Historical wheat landraces are rich sources of genetic diversity offering untapped reservoirs for broadening the genetic base of modern varieties. Using a 20K SNP array, we investigated the accessible genetic diversity in a Central European bread wheat landrace collection with great drought, heat stress tolerance and higher tillering capacity. We discovered distinct differences in the number of average polymorphisms between landraces and modern wheat cultivars, and identified a set of novel rare alleles present at low frequencies in the landrace collection. The detected polymorphisms were unevenly distributed along the wheat genome, and polymorphic markers co-localized with genes of great agronomic importance. The geographical distribution of the inferred Bayesian clustering revealed six genetically homogenous ancestral groups among the collection, where the Central European core bared an admixed background originating from four ancestral groups. We evaluated the effective population sizes (Ne) of the Central European collection and assessed changes in diversity over time, which revealed a dramatic ~ 97% genetic erosion between 1955 and 2015.

High-Molecular-Weight Glutenin Subunits: Genetics, Structures, and Relation to End Use Qualities

High-molecular-weight glutenin subunits (HMW-GSs) are storage proteins present in the starchy endosperm cells of wheat grain. Encoding the synthesis of HMW-GS, the Glu-1 loci located on the long arms of group 1 chromosomes of the hexaploid wheat (1A, 1B, and 1D) present multiple allelism. In hexaploid wheat cultivars, almost all of them express 3 to 5 HMW-GSs and the 1Ay gene is always silent. Though HMW-GSs are the minor components in gluten, they are crucial for dough properties, and certain HMW-GSs make more positive contributions than others. The HMW-GS acts as a "chain extender" and provides a disulfide-bonded backbone in gluten network. Hydrogen bonds mediated by glutamine side chains are also crucial for stabilizing the gluten structure. In most cases, HMW-GSs with additional or less cysteines are related to the formation of relatively more or less interchain disulfide bonds and HMW-GSs also affect the gluten secondary structures, which in turn impact the end use qualities of dough.

A Cross between Bread Wheat and a 2D(2R) Disomic Substitution Triticale Line Leads to the Formation of a Novel Disomic Addition Line and Provides Information of the Role of Rye Secalins on Breadmaking Characteristics

A bread wheat line (N11) and a disomic 2D(2R) substitution triticale line were crossed and backrossed four times. At each step electrophoretic selection for the seeds that possessed, simultaneously, the complete set of high molecular weight glutenin subunits of N11 and the two high molecular weight secalins of rye, present in the 2D(2R) line, was carried out. Molecular cytogenetic analyses of the BC₄F₈ generation revealed that the selection carried out produced a disomic addition line (2n = 44). The pair of additional chromosomes consisted of the long arm of chromosome 1R (1RL) from rye fused with the satellite body of the wheat chromosome 6B. Rheological analyses revealed that the dough obtained by the new addition line had higher quality characteristics when compared with the two parents. The role of the two additional high molecular weight secalins, present in the disomic addition line, in influencing improved dough characteristics is discussed.

A novel approach to the characterization of old wheat (Triticum aestivum L.) varieties by complex rheological analysis

BACKGROUND

Lines of the internationally recognized old Hungarian Bánkúti 1201 variety are important genetic resources for breeding programmes. Their protein composition and gluten dependent technological traits have been comprehensively studied, however, little information is available about their carbohydrate dependent viscous properties. The aim of this work was to obtain comprehensive rheological characterization of all sublines of Bánkúti 1201 maintained at Martonvásár and to investigate their variability if the carbohydrate dependent viscous behaviour was also included in the analyses.

RESULTS

The majority of the lines reflected the famously good mixing quality of Bánkúti, however, much higher diversity of pasting behaviour was detected. Cluster analysis of the Mixolab data was performed resulting in four sample groups. Since several lines of similar mixing properties had significantly different pasting characteristics, it was assumed that classification was mainly based on the viscous properties. From each cluster two to three representative samples were selected for wider examination using conventional testing methods. These results also supported the higher variability of pasting behaviour of the lines, which can be critical for end product quality. The members of the second cluster can be highlighted due to their waxy wheat like behaviour.

CONCLUSIONS

Possible reasons for the great variability of pasting behaviour could be the compositional and structural differences of starch and other carbohydrates (e.g. arabinoxylans). Complex rheological characterization and study of molecular background can provide information about important traits from the point of view of technology and product development, which are unknown in the case of old wheat varieties and landraces. © 2020 Society of Chemical Industry.

Exploring diverse wheat germplasm for novel alleles in HMW-GS for bread quality improvement

Wheat is one of the most important cereals used worldwide in the form of a range of products. Crop landraces have been an immense source of diversity for the breeders. In the present study, 517 Indian wheat landraces have been observed for the difference in bread making quality by assessing allelic behaviour of high molecular weight-glutenin subunits (HMW-GS). A total of 33 Glu-1 alleles (3 at Glu-A1, 15 at Glu-B1 and 15 at Glu-D1) were detected in wheat landraces. Allelic frequency of HMW-GS allelic band pattern null, 17 + 18, 2 + 12 (24.75%) was found to be the highest. Allelic frequency of HMW-GS allele null (68.27%) at Glu-A1, 17 + 18 (49.14%) at Glu-B1, and 2 + 12 (72.81%) at Glu-D1 was found to be the highest Five Novel alleles were identified at Glu-D1 locus, 12*, 12.1, 12.1*, 12.2 and 12.3. As Glu-D1 has highest quality contribution as compared to Glu-A1 and Glu-B1, reporting novel alleles at Glu-D1 represents that genetic variability available for selection is increased and it will provide tools for breeders to further improve dough properties and bread making quality.

Comprehensive Identification and Bread-Making Quality Evaluation of Common Wheat Somatic Variation Line AS208 on Glutenin Composition

High molecular weight glutenin subunits (HMW-GSs) are important seed storage proteins in wheat (Triticum aestivum) that determine wheat dough elasticity and processing quality. Clarification of the defined effectiveness of HMW-GSs is very important to breeding efforts aimed at improving wheat quality. To date, there have no report on the expression silencing and quality effects of 1Bx20 and 1By20 at the Glu-B1 locus in wheat. A wheat somatic variation line, AS208, in which both 1Bx20 and 1By20 at Glu-B1 locus were silenced, was developed recently in our laboratory. Evaluation of agronomic traits and seed storage proteins by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and reversed-phase high performance liquid chromatography (RP-HPLC) indicated that AS208 was highly similar to its parental cultivar Lunxuan987 (LX987), with the exception that the composition and expression of HMW-GSs was altered. The 1Bx20 and 1By20 in AS208 were further identified to be missing by polymerase chain reaction (PCR) and quantitative real-time RT-PCR (qRT-PCR) assays. Based on the PCR results for HMW-GS genes and their promoters in AS208 compared with LX987, 1Bx20 and 1By20 were speculated to be deleted in AS208 during in vitro culture. Quality analysis of this line with Mixograph, Farinograph, and Extensograph instruments, as well as analysis of bread-making quality traits, demonstrated that the lack of the genes encoding 1Bx20 and 1By20 caused various negative effects on dough processing and bread-making quality traits, including falling number, dough stability time, mixing tolerance index, crude protein values, wet gluten content, bread size, and internal cell structure. AS208 can potentially be used in the functional dissection of other HMW-GSs as a plant material with desirable genetic background, and in biscuit making industry as a high-quality weak gluten wheat source.

Characterization of a novel y-type HMW-GS with eight cysteine residues from Triticum monococcum ssp. monococcum

The composition and number of high-molecular-weight glutenin subunits (HMW-GSs) play important roles in determining the grain-processing quality of common wheat. The Glu-1Ay allele is silent in common wheat. In this study, an active y-type HMW-GS allele termed 1Ay8.2 (GenBank No. KP137569) was identified from Triticum monococcum L. ssp. monococcum (AmAm, 2n=2x=14), a species with a genome related to the A-genome of common wheat. Compared with previously reported active 1Ay subunits, this novel subunit contained an extra cysteine residue at position 103 of the amino acid sequence in the N-terminal region, in addition to the six cysteines in the N- and C-terminal regions found in most active 1Ay subunits and the one in the repetitive region that appears in only a few 1Ay alleles. This subunit was expressed in an amphiploid (AAAmAmBB, 2n=6x=42) between Triticum turgidum L. ssp. dicoccon and T. monococcum ssp. monococcum. This amphiploid could be used as a bridge to transfer 1Ay8.2 into common wheat cultivars. Replacing the silenced 1Ay in common wheat with the active 1Ay8.2 allele harboring an extra cysteine residue is expected to improve the quality by increasing the number of HMW-GSs and promoting the formation of covalent interactions through disulfide bonds with the extra cysteine residue.

Molecular characterization of two y-type high molecular weight glutenin subunit alleles 1Ay12 and 1Ay8 from cultivated einkorn wheat (Triticum monococcum ssp. monococcum)

Two y-type high molecular weight glutenin subunits (HMW-GSs) 1Ay12 and 1Ay8 from the two accessions PI560720 and PI345186 of cultivated einkorn wheat (Triticum monococcum ssp. monococcum, AA, 2n=2x=14), were identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The mobility of 1Ay12 and 1Ay8 was similar to that of 1Dy12 and 1By8 from common wheat Chinese Spring, respectively. Their ORFs respectively consisted of 1812bp and 1935bp, encoding 602 and 643 amino acid residues with the four typical structural domains of HMW-GS including signal peptide, conserved N-, and C-terminal and central repetitive domains. Compared with the most similar active 1Ay alleles previous published, there were a total of 15 SNPs and 2 InDels in them. Their encoding functions were confirmed by successful heterogeneous expression. The two novel 1Ay alleles were named as 1Ay12 and 1Ay8 with the accession No. JQ318694 and JQ318695 in GenBank, respectively. The two alleles were classed into the two distinct groups, Phe-type and Cys-type, which might be relevant to the differentiation of Glu-A1-2 alleles. Of which, 1Ay8 belonged to Cys-type group, and its protein possessed an additional conserved cysteine residue in central repetitive region besides the six common ones in N- and C-terminal regions of Phe-type group, and was the second longest in all the known active 1Ay alleles. These results suggested that the subunit 1Ay8 of cultivated einkorn wheat accession PI345186 might have a potential ability to strengthen the gluten polymer interactions and be a valuable genetic resource for wheat quality improvement.

Adequacy of different wheat cultivars for low-hydration bread making

BACKGROUND

There is considerable interest in recovering landraces as genetic resources and as raw materials in ecological production. Low-hydration bread, whose dough is submitted to a sheeting roll process, is commonly prepared in Spain and other countries. The aim of this study was to assess the adequacy of some landraces, compared with commercial cultivars and flours, for making this type of bread. Eight Spanish landraces, four wheat cultivars developed during the green revolution and three commercial flours were chosen, their alveographic and kneading behaviours were analysed and the characteristics of the resulting breads were determined.

RESULTS

The best correlations were obtained in breads with improver. Flours with extreme alveographic behaviour differed markedly from the rest. When these flours were excluded from the analysis, the parameters best correlated with bread quality (when using improver) were strength, tenacity and development time. A significant correlation between flour colour, a genetic factor, and crumb colour was found. This correlation was higher in breads without improver. CONCLUSION When flours with extreme characteristics were removed, the protein quality characteristics of flours defined the quality characteristics of low-hydration breads.

Molecular characterization of a HMW glutenin subunit allele providing evidence for silencing of x-type gene on Glu-B1

Understanding the molecular structure of high-molecular-weight glutenin subunit (HMW-GS) may provide useful evidence for the study on the improvement of quality of cultivated wheat and the evolution of Glu-1 alleles. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) shows that the subunits encoded by Glu-B1 were null, named 1Bxm, in a Triticum turgidum var. dicoccoides line PI94640. Primers based on the conserved regions in wheat HMW-GS gene promoter and coding sequences were used to amplify the genomic DNA of line PI94640. The PCR products were sequenced, and the total nucleotide sequence of 3,442 bp including upstream sequence of 1,070 bp was obtained. Compared with the reported gene sequences of Glu-1Bx alleles, the promoter region of the Glu-1Bxm showed close resemblance to 1Bx7. The Glu-1Bxm coding region differs from the other Glu-1Bx alleles for a deduced mature protein with only 212 residues, and a stop codon (TAA) at 637 bp downstream from the start codon was present, which was probably responsible for the silencing of x-type subunit genes at the Glu-B1 locus. Phylogenetic tree based on the nucleotide sequence alignment of HMW glutenin subunit genes showed that 1Bxm was the most ancient type of Glu-B1 alleles, suggesting that the evolution rates are different among Glu-1Bx genes. Further study on the contribution of the unique silenced Glu-B1 alleles to quality improvement was also discussed.

Evolutionary origin of the segmental duplication encompassing the wheat GLU-B1 locus encoding the overexpressed Bx7 (Bx7OE) high molecular weight glutenin subunit

Sequencing of a BAC clone encompassing the Glu-B1 locus in Glenlea, revealed a 10.3 Kb segmental duplication including the Bx7 gene and flanking an LTR retroelement. To better understand the evolution of this locus, two collections of wheat were surveyed. The first consisted of 96 diploid and tetraploid species accessions while the second consisted of 316 Triticum aestivum cultivars and landraces from 41 countries. The genotypes were first characterized by SDS-PAGE and a total of 40 of the 316 T. aestivum accessions were found to display the overexpressed Bx7 phenotype (Bx7OE). Three lines from the 96 diploid/tetraploid collection also displayed the stronger intensity staining characteristic of the Bx7(OE) subunit. The relative amounts of the Bx7 subunit to total HMW-GS were quantified by RP-HPLC for all Bx7OE accessions and a number of checks. The entire collection was assessed for the presence of four DNA markers namely an 18 bp indel of the coding region of Bx7 variant alleles, a 43 bp indel of the 5'-region and the left and right junctions of the LTR retrotransposon borders and the duplicated segment. All 43 accessions found to have the Bx7OE subunit by SDS-PAGE and RP-HPLC produced the four diagnostic PCR amplicons. None of the lines without the Bx7OE had the LTR retroelement/duplication genomic structure. However, the 18 and 43 bp indel were found in accessions other than Bx7OE. These results indicate that the overexpression of the Bx7 HMW-GS is likely the result of a single event, i.e., a gene duplication at the Glu-B1 locus mediated by the insertion of a retroelement. Also, the 18 and 43 bp indels pre-date the duplication event. Allelic variants Bx7*, Bx7 with and without 43 bp insert and Bx7OE were found in both tetraploid and hexaploid collections and shared the same genomic organization. Though the possibility of introgression from T. aestivum to T. turgidum cannot be ruled out, the three structural genomic changes of the B-genome taken together support the hypothesis of multiple polyploidization events involving different tetraploid progenitors.

Characterization of the HMW glutenin subunits from Aegilops searsii and identification of a novel variant HMW glutenin subunit

High molecular weight (HMW) glutenin subunits are conserved seed storage proteins in wheat and related species. Here we describe a more detailed characterization of the HMW glutenin subunits from Aegilops searsii, which is diploid and contains the S(s) genome related to the S genome of Aegilops speltoides and the A, B and D genomes of hexaploid wheat. SDS-PAGE experiments revealed two subunits (one x and one y) for each of the nine Ae. searsii accessions analyzed, indicating that the HMW glutenin subunit gene locus of Ae. searsii is similar to the Glu-1 locus found in wheat in containing both x and y genes. The primary structure of the four molecularly cloned subunits (from two Ae. searsii accessions) was highly similar to that of the previously reported x and y subunits. However, in one accession (IG49077), the last 159 residues of the x subunit (1S(s)x49077), which contained the sequence element GHCPTSPQQ, were identical to those of the y subunit (1S(s)y49077) from the same accession. Consequently, 1S(s)x49077 contains an extra cysteine residue located at the C-terminal part of its repetitive domain, which is novel compared to the x-type subunits reported so far. Based on this and previous studies, the structure and expression of the Glu-1 locus in Ae. searsii is discussed. A hypothesis on the genetic mechanism generating the coding sequence for the novel 1S(s)x49077 subunit is presented.

Dissemination of the highly expressed Bx7 glutenin subunit (Glu-B1al allele) in wheat as revealed by novel PCR markers and RP-HPLC

Increased expression of the high molecular weight glutenin subunit (HMW-GS) Bx7 is associated with improved dough strength of wheat (Triticum aestivum L.) flour. Several cultivars and landraces of widely different genetic backgrounds from around the world have now been found to contain this so-called 'over-expressing' allelic form of the Bx7 subunit encoded by Glu-B1al. Using three methods of identification, SDS-PAGE, RP-HPLC and PCR marker analysis, as well as pedigree information, we have traced the distribution and source of this allele from a Uruguayan landrace, Americano 44D, in the mid-nineteenth century. Results are supported by knowledge of the movement of wheat lines with migrants. All cultivars possessing the Glu-B1al allele can be identified by the following attributes: (1) the elution of the By sub-unit peak before the Dx sub-unit peak by RP-HPLC, (2) high expression levels of Bx7 (>39% Mol% Bx), (3) a 43 bp insertion in the matrix-attachment region (MAR) upstream of the gene promoter relative to Bx7 and an 18 bp nucleotide duplication in the coding region of the gene. Evidence is presented indicating that these 18 and 43 bp sequence insertions are not causal for the high expression levels of Bx7 as they were also found to be present in a small number of hexaploid species, including Chinese Spring, and species expressing Glu-B1ak and Glu-B1a alleles. In addition, these sequence inserts were found in different isolates of the tetraploid wheat, T. turgidum, indicating that these insertion/deletion events occurred prior to hexaploidization.

Over-expression of HMW glutenin subunit Glu-B1 7x in hexaploid wheat varieties (Triticum aestivum)

In Canada in 1993, a special market class of wheat, Canada Western Extra Strong (CWES), was established to segregate wheat varieties known to produce very strong and extensible doughs. These exceptional dough properties enable CWES cultivars to be blended with wheats of lesser quality as well as being suited to the manufacture of frozen dough products. The high molecular weight (HMW) glutenin allele (Glu-B1al) that confers these properties, particularly dough strength, has now been identified. Typically, the presence of the Glu-B1al (7+8*) allele is associated with the overexpression of HMW-GS 1Bx 7. RP-HPLC was used to quantify the proportion (% area) of individual HMW-GS relative to total HMW-GS in wheat varieties of different origin. The B genome contributed the highest percentage of HMW-GS, with the exception of Glu-B1d (6+8*) where the D genome contributed the most. Cultivars that possessed the Glu-B1al allele contained a significantly higher (P < 0.001) proportion of HMW-GS (56.80 ± 3.25%) encoded by the B genome. This suggests that the proportion of Glu-B1 subunits, relative to the total amount of HMW-GS expressed, has a major effect on dough strength. We also identified germplasm, of different origin, that contains the Glu-B1al allele and overexpresses subunit 7, including the most likely source of this allele in bread wheat cultivars. The Glu-B1al allele in the varieties identified in this paper could be traced, at least through one parent, to the Argentinean bread wheat cultivar Klein Universal II. RP-HPLC elution and expression profiles of various common HMW-GS are also discussed.