Gamma Gliadins Research Articles

Comparative Characterization of Grain Protein Content and Composition by Chromatography-Based Separation Methods (SE-HPLC and RP-HPLC) of Ten Wheat Varieties Grown in Different Agro-Ecological Zones of Algeria

To characterize and compare the protein quality of ten durum wheat genotypes grown under three cropping modalities in Algeria (subhumid in Algiers, subhumid-semiarid in Constantine, and semiarid in Sétif), the protein profile of their kernels was performed by High-Performance Liquid Chromatography (SE-HPLC and RP-HPLC). The “variety” factor has a major impact, mainly on the insoluble fraction (Fi), on the gliadin/glutenin ratio, on the large and small glutenin aggregates (F1 and F2, respectively), and on ω-gliadins and high molecular weight albumins (F3). Conversely, the total protein content and the albumin-globulin fraction (F5) depend mainly on the environment. The α- β- and γ-gliadins (F4) are equally dependent on variety and environment. The subhumid-semiarid agroecological conditions of Constantine (SH-SA) favored an important accumulation of proteins (14.1%), particularly by an increased synthesis of omega gliadins and high-molecular-weight glutenin subunits (HMW-GS), compared to those of Algiers (SH) and Sétif (SA). For these latter environments, metabolic-type proteins are predominant, reflected in a higher F5 fraction (p < 0.05) (albumin and globulin), and significantly more alpha-beta and gamma gliadins. The use of chromatographic analyses to characterize wheat genotypes remains a reliable tool for breeding and variety promotion programs and can provide a better understanding of the ecophysiology of cereal crops.

Omega-5 and Gamma Gliadin are the Major Allergens in Adult-Onset IgE-Mediated Wheat Allergy: Results from Thai Cohort with Oral Food Challenge.

BackgroundVarious clinical patterns based on routes of sensitization and sensitized allergens are reported in adult-onset IgE-mediated wheat allergy. There is still a paucity of data on IgE-bound wheat allergen profiles in wheat challenge-proven adult-onset wheat allergic cases. Therefore, we aim to identify the major sensitized allergens in Thai adult-onset wheat allergic patients whose first symptom occurred after the age of 18 years despite previous tolerance.MethodsThis cross-sectional pilot study recruited patients from the Thai Adult-onset IgE-mediated Wheat Allergy Cohort (TAWAC). The sera of patients with mostly challenge-proven cases were selected for allergen study, including ImmunoCAP and IgE-bound gliadins along with glutenins profiles. The IgE-bound proteins were identified by liquid chromatography-tandem mass spectrophotometry (LC-MS/MS). Direct binding of IgE to recombinant gliadin and glutenin was performed to confirm the results of immunoblot and LC-MS/MS.ResultsEleven wheat-dependent exercise-induced anaphylaxis (WDEIA) and 4 typical wheat allergy (WA) patients were enrolled. Serum IgE from >50% of bound proteins had a molecular weight ranging from 35 to 55 kDa in both gliadin and glutenin extracts. Further, ELISA demonstrated that γ-gliadin and ω5-gliadin were the most important major allergens. Other major allergens include α/β-gliadin, HMW glutenin, and possibly α-amylase inhibitor or LWM glutenin. Gamma-gliadin sensitization was found in all WA patients (4/4), while ω-5 gliadin was found in all WDEIA patients (11/11) from ELISA.ConclusionWheat γ-gliadin and ω-5 gliadin are major wheat allergens among adult-onset wheat allergy patients in Thailand. Component-resolved diagnosis using γ-gliadin might be helpful in high suspicion of wheat allergy.

Evaluation of N-terminal labeling mass spectrometry for characterization of partially hydrolyzed gluten proteins

Gluten, a group of proteins found in wheat, barley, and rye, is the trigger of celiac disease, an immune disorder that affects about 1% of people worldwide. The toxicity of partially hydrolyzed gluten (PHG) in fermented products is less well understood due to the significant analytical challenges in PHG characterization. In this project, an N-terminal labeling mass spectrometry method, terminal amine isotopic labeling of substrates (TAILS), was optimized for the in-depth analysis of PHG and validated using a test protease (trypsin) with known cleavage specificity. Gluten N-termini in test and control groups were labeled with heavy and light formaldehyde, respectively. Trypsin-generated neo N-termini were identified by exhibiting an MS1 Log2 H:L peak area ratio with a significant difference (p < .01) from zero and native N-termini with no significant difference from zero (p > .01). Using this strategy, all abundant, theoretical, test protease-generated peptides in exemplar alpha/beta gliadins and gamma gliadins were identified. SignificanceThis study is the first study that modified and evaluated TAILS analysis for the analysis of partially hydrolyzed gluten proteins. The evaluation indicated that the TAILS analysis could be modified and expanded to the identification of multiple protease cleavage sites in gluten proteins and is worth further evaluation as a novel strategy for the analysis of natural hydrolysis of gluten in food processes. This strategy also may be further applied to characterize a broader range of partially hydrolyzed allergens in foods and provide reference for their safety assessment to both industry and regulatory authorities.

Exploiting the reference genome sequence of hexaploid wheat: a proteomic study of flour proteins from the cultivar Chinese Spring

Although the economic value of wheat flour is determined by the complement of gluten proteins, these proteins have been challenging to study because of the complexity of the major protein groups and the tremendous sequence diversity among wheat cultivars. The completion of a high-quality wheat genome sequence from the reference wheat Chinese Spring recently facilitated the assembly and annotation of a complete set of gluten protein genes from a single cultivar, making it possible to link individual proteins in the flour to specific gene sequences. In a proteomic analysis of total wheat flour protein from Chinese Spring using quantitative two-dimensional gel electrophoresis combined with tandem mass spectrometry, gliadins or low-molecular-weight glutenin subunits were identified as the predominant proteins in 72 protein spots. Individual spots were associated with 40 of 56 Chinese Spring gene sequences, including 16 of 26 alpha gliadins, 10 of 11 gamma gliadins, six of seven omega gliadins, one of two delta gliadins, and nine of ten LMW-GS. Most genes that were not associated with protein spots were either expressed at low levels in endosperm or encoded proteins with high similarity to other proteins. A wide range of protein accumulation levels were observed and discrepancies between transcript levels and protein levels were noted. This work together with similar studies using other commercial cultivars should provide new insight into the molecular basis of wheat flour quality and allergenic potential.

Towards reducing the immunogenic potential of wheat flour: omega gliadins encoded by the D genome of hexaploid wheat may also harbor epitopes for the serious food allergy WDEIA

BackgroundOmega-5 gliadins are a group of highly repetitive gluten proteins in wheat flour encoded on the 1B chromosome of hexaploid wheat. These proteins are the major sensitizing allergens in a severe form of food allergy called wheat-dependent exercise-induced anaphylaxis (WDEIA). The elimination of omega-5 gliadins from wheat flour through biotechnology or breeding approaches could reduce the immunogenic potential and adverse health effects of the flour.ResultsA mutant line missing low-molecular weight glutenin subunits encoded at the Glu-B3 locus was selected previously from a doubled haploid population generated from two Korean wheat cultivars. Analysis of flour from the mutant line by 2-dimensional gel electrophoresis coupled with tandem mass spectrometry revealed that the omega-5 gliadins and several gamma gliadins encoded by the closely linked Gli-B1 locus were also missing as a result of a deletion of at least 5.8 Mb of chromosome 1B. Two-dimensional immunoblot analysis of flour proteins using sera from WDEIA patients showed reduced IgE reactivity in the mutant relative to the parental lines due to the absence of the major omega-5 gliadins. However, two minor proteins showed strong reactivity to patient sera in both the parental and the mutant lines and also reacted with a monoclonal antibody against omega-5 gliadin. Analysis of the two minor reactive proteins by mass spectrometry revealed that both proteins correspond to omega-5 gliadin genes encoded on chromosome 1D that were thought previously to be pseudogenes.ConclusionsWhile breeding approaches can be used to reduce the levels of the highly immunogenic omega-5 gliadins in wheat flour, these approaches are complicated by the genetic linkage of different classes of gluten protein genes and the finding that omega-5 gliadins may be encoded on more than one chromosome. The work illustrates the importance of detailed knowledge about the genomic regions harboring the major gluten protein genes in individual wheat cultivars for future efforts aimed at reducing the immunogenic potential of wheat flour.

Nanocarrier-mediated foliar zinc fertilization influences expression of metal homeostasis related genes in flag leaves and enhances gluten content in durum wheat.

BackgroundWheat is the staple food for most of the world’s population; however, it is a poor source of zinc. Foliar fertilization of zinc via zinc loaded chitosan nanocarriers (Zn-CNP) post-anthesis has proved to be a promising approach for grain zinc enhancement in durum wheat as evidenced in our earlier study. However, the molecular mechanism of uptake of zinc via Zn-CNP remains unclear.Methods/Principle findingsFoliar application of Zn-CNP was performed at post anthesis stages in two durum wheat cultivars (MACS 3125 and UC1114, containing the Gpc-B1 gene), and expression levels of several metal-related genes were analyzed during early senescence. Zn-CNP application indeed caused changes in gene expression as revealed by qPCR data on representative genes involved in metal homeostasis, phloem transporters, and leaf senescence. Furthermore, zinc-regulated transporters and iron (Fe)-regulated transporter-like protein (ZIP) family [ZIP1, ZIP7, ZIP15], CA (carbonic anhydrase), and DMAS (2’-deoxymugineic acid synthase) in flag leaves exhibited significant correlation with zinc content in the seeds. The analysis of grain endosperm proteins showed enhancement of gamma gliadins while other gluten subunits decreased. Gene expression within ZIP family members varied with the type of cultivar mostly attributed to the Gpc-B1, concentration of external zinc ions as well as the type of tissue analyzed. Correlation analysis revealed the involvement of the selected genes in zinc enhancement.ConclusionAt the molecular level, uptake of zinc via Zn-CNP nanocarrier was comparable to the uptake of zinc via common zinc fertilizers i.e. ZnSO4.

Proteomic analysis of low-molecular-weight glutenin subunits and relationship with their genes in a common wheat variety.

Although many studies on low-molecular-weight glutenin subunit (LMW-GS) function have been reported, a comprehensive comparison between specific genes and their protein product is still lacking. This study aimed to link the 43 genes isolated from the Korean wheat variety "Jokyoung" in the authors' previous study to their protein products. Proteins were separated using two-dimensional gel electrophoresis (2-DGE) and identified by tandem mass spectrometry (MS/MS) at the gene haplotype level. Using MS/MS analysis of 17 protein spots, two spots wereidentifiedin the Glu-A3 locus and the corresponding haplotype wasGluA3-13(Glu-A3c). Six spots were identified in the Glu-B3 locus and the corresponding haplotypes were GluB3-33 and GluB3-43 (Glu-B3h). Eight spots were identified in the Glu-D3 locus and the corresponding haplotypes were GluD3-11, GluD3-21, GluD3-31, GluD3-5, and GluD3-6 (Glu-D3a), and one spot was contaminated with gamma gliadin. Phylogenetic analysis and alignment of nucleotide and amino acid sequences assigned 35 of the 43 genes to seven haplotypes: GluA3-13, GluB3-43, GluD3-11, GluD3-21, GluD3-31, GluD3-42, and GluD3-5. Taken together, except for GluB3-33 and GluD3-6, which were not isolated, linking of each gene to the corresponding protein products at the gene haplotype level was accomplished using proteomic tools and phylogenetic analysis.

Molecular and Immunological Characterization of Gamma Gliadins As Major Allergens in Wheat Food Allergy

Molecular and Immunological Characterization of Gamma Gliadins As Major Allergens in Wheat Food Allergy

RNA interference targeting rye secalins alters flour protein composition in a wheat variety carrying a 1BL.1RS translocation

Wheat varieties carrying chromosome translocations from rye are part of the international wheat breeding pool despite being associated with defects in dough processing quality. One cause proposed for the quality defects of wheat carrying 1BL.1RS translocations is the presence of the secalins encoded by the Sec1 locus on the short arm of rye chromosome 1. In this report, we decrease the levels of these and related wheat proteins by RNA interference (RNAi). A plasmid designed to down-regulate secalin was introduced by biolistics into ‘Bobwhite’, which carries a 1BL.1RS translocation. Flour proteins of two independent transformants were analyzed in detail by 2-dimensional gel electrophoresis and tandem mass spectrometry. Compared to the parent, the transformants exhibited up to 5.5-fold decreases in the levels of individual secalins, up to 7-fold decreases in the closely related omega gliadins, and lesser decreases in many gamma gliadins, low-molecular-weight (LMW)-glutenins, and farinins. Increased levels were found for nearly all identified alpha gliadins, triticins, and y-type high-molecular-weight (HMW)-glutenins. Flour from the transgenic lines exhibited changes in dough mixing behavior in the 2-g mixograph, including longer development times and greater tolerance to mixing. We conclude that changes in protein composition engineered by this RNAi construct improved dough handling characteristics.

Genome-wide transcriptome study in wheat identified candidate genes related to processing quality, majority of them showing interaction (quality x development) and having temporal and spatial distributions

BackgroundThe cultivated bread wheat (Triticum aestivum L.) possesses unique flour quality, which can be processed into many end-use food products such as bread, pasta, chapatti (unleavened flat bread), biscuit, etc. The present wheat varieties require improvement in processing quality to meet the increasing demand of better quality food products. However, processing quality is very complex and controlled by many genes, which have not been completely explored. To identify the candidate genes whose expressions changed due to variation in processing quality and interaction (quality x development), genome-wide transcriptome studies were performed in two sets of diverse Indian wheat varieties differing for chapatti quality. It is also important to understand the temporal and spatial distributions of their expressions for designing tissue and growth specific functional genomics experiments.ResultsGene-specific two-way ANOVA analysis of expression of about 55 K transcripts in two diverse sets of Indian wheat varieties for chapatti quality at three seed developmental stages identified 236 differentially expressed probe sets (10-fold). Out of 236, 110 probe sets were identified for chapatti quality. Many processing quality related key genes such as glutenin and gliadins, puroindolines, grain softness protein, alpha and beta amylases, proteases, were identified, and many other candidate genes related to cellular and molecular functions were also identified. The ANOVA analysis revealed that the expression of 56 of 110 probe sets was involved in interaction (quality x development). Majority of the probe sets showed differential expression at early stage of seed development i.e. temporal expression. Meta-analysis revealed that the majority of the genes expressed in one or a few growth stages indicating spatial distribution of their expressions. The differential expressions of a few candidate genes such as pre-alpha/beta-gliadin and gamma gliadin were validated by RT-PCR. Therefore, this study identified several quality related key genes including many other genes, their interactions (quality x development) and temporal and spatial distributions.ConclusionsThe candidate genes identified for processing quality and information on temporal and spatial distributions of their expressions would be useful for designing wheat improvement programs for processing quality either by changing their expression or development of single nucleotide polymorphisms (SNPs) markers.

Exploring T cell reactivity to gliadin in young children with newly diagnosed celiac disease.

Class II major histocompatibility molecules confer disease risk in Celiac disease (CD) by presenting gliadin peptides to CD4 T cells in the small intestine. Deamidation of gliadin peptides by tissue transglutaminase creates immunogenic peptides presented by HLA-DQ2 and DQ8 molecules to activate proinflammatory CD4 T cells. Detecting gliadin specific T cell responses from the peripheral blood has been challenging due to low circulating frequencies and heterogeneity in response to gliadin epitopes. We investigated the peripheral T cell responses to alpha and gamma gliadin epitopes in young children with newly diagnosed and untreated CD. Using peptide/MHC recombinant protein constructs, we are able to robustly stimulate CD4 T cell clones previously derived from intestinal biopsies of CD patients. These recombinant proteins and a panel of α- and γ-gliadin peptides were used to assess T cell responses from the peripheral blood. Proliferation assays using peripheral blood mononuclear cells revealed more CD4 T cell responses to α-gliadin than γ-gliadin peptides with a single deamidated α-gliadin peptide able to identify 60% of CD children. We conclude that it is possible to detect T cell responses without a gluten challenge or in vitro stimulus other than antigen, when measuring proliferative responses.

Identification of wheat proteins involved in active stage of celiac disease: are gamma gliadins the major disease-specific antigens?

Methods We developed a method wherein the alcohol extracted gliadins was fractionated in two steps of ion-exchange chromatography, Sulphopropyl (SP) was used for the first step and the flow through (FT) fraction obtained was further fractionated using DEAE. Each generated fraction’s reactivity to serum IgA, from clinically well defined CD (active/diet) patients and non-CD patients was analyzed. Identification of disease specific antigens in the fractions was attempted using mass spectrometry and N-terminal sequencing.

Analysis of expressed sequence tags from a single wheat cultivar facilitates interpretation of tandem mass spectrometry data and discrimination of gamma gliadin proteins that may play different functional roles in flour

BackgroundThe gamma gliadins are a complex group of proteins that together with other gluten proteins determine the functional properties of wheat flour. The proteins have unusually high levels of glutamine and proline and contain large regions of repetitive sequences. While most gamma gliadins are monomeric proteins containing eight conserved cysteine residues, some contain an additional cysteine residue that enables them to be linked with other gluten proteins into large polymers that are critical for flour quality. The ability to differentiate among the gamma gliadins is important for studies of wheat flour quality because proteins with similar sequences can have different effects on functional properties.ResultsThe complement of gamma gliadin genes expressed in the wheat cultivar Butte 86 was evaluated by analyzing publicly available expressed sequence tag (EST) data. Eleven contigs were assembled from 153 Butte 86 ESTs. Nine of the contigs encoded full-length proteins and four of the proteins contained nine cysteine residues. Only one of the encoded proteins was a perfect match with a sequence reported in NCBI. Contigs from four different publicly available EST assemblies encoded proteins that were perfect matches with some, but not all, of the Butte 86 gamma gliadins and the complement of identical proteins was different for each assembly. A specialized database that included the sequences of Butte 86 gamma gliadins was constructed for identification of flour proteins by tandem mass spectrometry (MS/MS). In a pilot experiment, proteins corresponding to six Butte 86 gamma gliadin contigs were distinguished by MS/MS, including one containing the extra cysteine residue. Two other proteins were identified as one of two closely related Butte 86 proteins but could not be distinguished unequivocally. Unique peptide tags specific for Butte 86 gamma gliadins are reported.ConclusionsInclusion of cultivar-specific gamma gliadin sequences in databases maximizes the number and quality of peptide identifications and increases sequence coverage of these gamma gliadins by MS/MS. This approach makes it possible to distinguish closely related proteins, to associate individual proteins with sequences of specific genes, and to evaluate proteomic data in a biological context to better address questions about wheat flour quality.

RFLP and PCR analyses at Gli-1, Gli-2, Glu-1 and Glu-3 loci in cultivated and wild wheats

RFLP and PCR analyses at the Gli-1, Gli-2, Glu-1 and Glu-3 loci have been carried out in Aegilops L. and Triticum L. species. High level of polymorphism was found by RFLP analyses both between Aegilops species and Triticum species, and between durum wheat cultivars, whereas PCR analyses of the coding region of the same genotypes showed a different degree of variation between the analyzed loci. Gamma gliadin amplified products revealed a moderate level of polymorphism between Aegilops and Triticum species, and showed the possibility of distinguishing durum wheat cultivars with good and poor technological properties. PCR products of alpha/beta gliadins and low (LMW) and high molecular weight (HMW) glutenins showed a low degree of variation between Aegilops and Triticum species. Finally, RFLP analysis at the Gli-2 locus of Aegilops species has shown that it is possible to differentiate the Ae. squarrosa subsp. strangulala from the Ae. squarrosa subsp. squarrosa, and suggests introgression from Ae. longissima or Ae. searsii into tetraploid and hexaploid Ae. crassa, Ae. juvenalis, and Ae. vavilovii.

RFLP and PCR analyses at Gli-1, Gli-2, Glu-1 and Glu-3 loci in cultivated and wild wheats

DOVIDIO, R., TANZARELLA, 0. A., MASCI, S., LAFIANDRA, D. and PORCEDDU, E. 1992. RFLP and PCR analyses at Gli-I, 01;-2, Glu-i and Glu-3loci in cultivated and wild wheats. - Hereditus 116: 79-85. Lund, Sweden. ISSN 0018-0661. Received August 2, 1991. Accepted October 20, 1991 RFLP and PCR analyses at the Gli-I, Gli-2, Glu-l and Gh-3 loci have been carried out in Aegilops L. and Triticum L. species. High level of polymorphism was found by RFLP analyses both between Aegilops species and Triticum species, and between durum wheat cultivars, whereas PCR analyses of the coding region of the same genotypes showed a different degree of variation between the analyzed loci. Gamma gliadin amplified products revealed a moderate level of polymorphism between Aegilaps and Triticurn species, and showed the possibility of distinguishing durum wheat cultivars with good and poor technological properties. PCR products of alpha/beta gliadins and low (LMW) and high molecular weight (HMW) glutenins showed a low degree of variation between Aegilop..r and Triticum species. Finally, RFLP analysis at the Gli-2 locus of Aegilops species has shown that it is possible to differentiate the Re. squarrosu subsp. strangulala from the Ae. squarrosa subsp. squarrosa, and suggests introgression from Ae. longissima or Ae. searsii into tetraploid and hexaploid Ae. crassa, Ae. juuenalis, and Ae. uavilauii.

Antibody responses to deamidated gliadin peptide show high specificity and parallel antibodies to tissue transglutaminase in developing coeliac disease

Coeliac disease (CD) is an enteropathy induced in genetically susceptible individuals by gluten components, gliadin, hordein and secalin, polypeptides present in cereals such as wheat, barley and rye, respectively. Although the disease starts as intolerance to gliadins, antibodies to tissue transglutaminase (tTG) in the gut epithelium are characteristic of the disease. Whereas serum autoantibodies against tTG (tTGA) are highly specific for CD, antibodies to gliadin are less informative as they can also be detected in other enteropathies, and even in healthy individuals. However, it was shown recently that antibodies to certain gliadin peptides occur with high specificity in CD patient sera. We developed a solid phase lanthanide-based immunofluorometric assay for simultaneous detection of serum IgA and IgG antibodies to a synthetic peptide derived from gamma gliadin of wheat comprising amino acids 86-103. Three glutamine residues of this native 18-mer peptide were replaced by glutamic acids and the peptide was biotinylated. Sera from 87 individuals who had undergone duodenal biopsy and were diagnosed with CD and from 81 healthy individuals were analysed for the presence of both IgA and IgG anti-gliadin peptide antibodies. The performance of the peptide AGA assay was excellent, showing a specificity and sensitivity of 90% and 92% for IgA, and 98% and 75% for IgG, respectively. The corresponding values for conventional anti-gliadin antibody (AGA) enzyme-linked immunosorbent assay (ELISA) tests were 72% specificity and 87% sensitivity for IgA, and 64% specificity and 78% sensitivity for IgG. In a prospective study, almost all the tTGA-positive sera drawn from children who later developed CD were also positive for gliadin peptide antibodies.

Omega gliadin genes expressed in Triticum aestivum cv. Butte 86: Effects of post-anthesis fertilizer on transcript accumulation during grain development

The partial coding sequences of omega gliadin genes expressed in developing wheat kernels Triticum aestivum cv. Butte 86 were identified in databases of expressed sequence tags (ESTs). Three gene assemblies encode proteins with PQQPFP as the predominant repetitive motif. Of these, two encode proteins with at least one cysteine and thus may be incorporated into the glutenin polymer. Another two gene assemblies encode proteins with FPQQQ and QQIPQQ repeats. Quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) was used to investigate the accumulation of omega gliadin transcripts in developing wheat grains produced with or without post-anthesis fertilizer supplied as 20–20–20 nitrogen–phosphorous–potassium (NPK). Omega gliadin transcripts were detected at 8 days post-anthesis (DPA). The levels of transcript changed little in the absence of NPK during grain development, but increased when plants were supplied with post-anthesis NPK. By 32 DPA, levels of omega gliadin transcripts were considerably higher in grains that received NPK than in those that did not receive NPK. Transcripts for a gamma gliadin showed a different profile, increasing from 8 to about 22 DPA, then decreasing at later time points. In contrast to omega gliadins, both the timing and levels of gamma gliadin transcripts were similar in grains produced with or without post-anthesis NPK.

An assessment of cultivated emmer germplasm for gluten proteins

The storage protein composition of 61 accessions of Triticum dicoccum was analyzed by SDS-PAGE (HMW- and LMW-glutenin subunits) and Acid-PAGE (gliadins). In the HMW-glutenin subunits, four allelic variants at the Glu-A1 and eight at the Glu-B1 locus were detected resulting in a total of 17 patterns. The Glu-B1 locus was found to be more polymorphic than the Glu-A1 locus. Interestingly, the presence of HMW subunits like 13+16, 2∗ and 1 associated with good quality was observed. Three accessions were null for both the Glu-A1 and Glu-B1 loci. There was less variation for gliadins. Three different gamma gliadin fractions coded by Gli-B1 locus were detected and there were eight different LMW-B glutenin patterns at the Glu-3 loci. The variability can be used to improve the utility of this crop.

EVALUATION OF GRAIN QUALITY PROPERTIES OF SOME IRAQI AND ICARDA SELECTED DURUM WHEAT CULTIVARS

Four samples of Iraqi durum wheat cultivars and six selected varieties of ICARDA were involved in this study, for their grain quality tests and flour rheological properties comparison. Their gliadin electrophoresis was also conducted. Results showed a significant variation among tested varieties for the grain characters, protein quantity and quality in term of SDS-sedimentation test. The highest levels of SDS-values and SDS-index were recorded for Haurani, Korifla, Gidara-2, and Om rabi-5, but Caronia is the best in pigments. Among the tested cultivars, Iraqi cultivar Caronia resemble the Syrian one (Haurani) in giving positive reaction with phenol test. Concerning with the gliadin subunits electrophoregrams patterns, cultivars can be classified into two groups, those possess the gamma gliadin components designated 45 and the linked omega gliadin 35, include cultivars (Caronia, Acsad-65, Simeto, Creso, Om rabi-5, Haurani, Korifla and Gidara-2, while those possess gamma gliadin 42, included cultivars (Waha, , and Cham-5).

Recombination within the Gli-B1 Locus in Durum Wheat

Recombination within the closely linked genes encoding for omega and gamma gliadins at the complex Gli-B1 locus present on the short arm of chromosome 1B was detected in a durum-wheat line (Triticum durum) from Iran. This recombinant differs from a previous one the authors detected in the durum-wheat cultivar ‘Berillo’ since it shows the gamma gliadin component 45 associated with a triplet of omega components usually found linked with the allelic gamma gliadin 42. Analysis of low-molecular-weight glutenin subunits, encoded by genes at the complex Glu-B3 locus associated with the Gli-B1 locus, showed the presence of the protein type designated LMW-1 which is peculiar to durum-wheat cultivars possessing the gamma gliadin 42.