Allelic diversity at gliadin-coding gene loci in cultivars of spring durum wheat (<Emphasis Type="Italic">Triticum durum</Emphasis> Desf.) Bred in Russia and former Soviet republics in the 20th century

Allelic diversity at five gliadin-coding gene loci has been studied in the most important spring durum wheat cultivars released in Russia and former Soviet republics in the 20th century (66 cultivars). Seven, 5, 8, 13, and 2 allelic variants of blocks of gliadin components controlled by the loci Gli-A1 ^d , Gli-B1 ^d , Gli-A2 ^d , Gli-B2 ^d , and Gli-B5 ^d , respectively, have been identified. The allelic diversity did not exhibit a consistent trend during the period studied. Nei’s diversity index (H) was 0.68 in the period from 1929 to 1950, increased to 0.70 in 1951–1980, and decreased to 0.58 after the year 1981. It has been found that the most frequent alleles in this collection are relatively rare in other regions of the world, which suggests unique ways of the formation of the diversity of durum wheat cultivars in the former Soviet Union. The efficiency of electrophoresis of storage proteins as a method for identification of durum wheat cultivars by the gliadin electrophoretic pattern has been estimated.     

Analysis of common wheat varieties and near-isogenic lines by PCR with allele-specific primers for Gli-1 and Glu-3 loci

The allelic characteristics of the Gli-A1, Gli-B1, Gli-D1 and Glu-A3 loci of 14 bread wheat varieties and 6 near-isogenic lines derived from Bezostaya 1 have been detected by PCR analysis. The conformity of molecular-genetic data and electrophoresis of storage proteins has been determined: the allelic variants of gliadins Gli-A1o and Gi-A1m correspond to the PCR-allele GliA1.2, the gliadin variants Gli-A1f, Gli-A1b, Gli-A1c correspond to the PCR-allele GliA 1.1, the allelic variants Gli-B1b, Gli-B1d--to the PCR-allele GliB1.1 and the variants Gli-B1e, Gli-B1g, Gli-B1c-to the PCR-allele GliB1.2. A new PCR-allele at the GliB) locus in the line Gli-B1-12 (with the gliadin block Gli-B1o from Levent) was identified.     

Polymorphism of omega-gliadins in durum wheat as revealed by the two-step APAGE/SDS-PAGE technique

Polymorphism of omega-gliadins was studied in 243 durum wheats from 27 countries using the two-step one-dimensional APAGE/SDS-PAGE technique. A total of 12 bands of different mobility were observed, and four of them were found to be different from those previously detected by Khelifi et al. (1992) in bread wheat. Fifteen alleles, six coded by the Gli-A1 locus and nine coded by the Gli-B1 locus, were identified, accounting for 19 different electrophoretic patterns. Seven new alleles were detected: two at the Gli-A1 locus and five at the Gli-B1 locus. The polymorphism found at the Gli-A1 and Gli-B1 loci was slightly greater than that found in bread wheat. Allelic differences between both species were higher at the Gli-B1 locus. A comparison of the frequencies of alleles in both species was carried out. The null allele, Gli-A1e, was more common in durum wheat than in bread wheat. The Gli-B1b allele, present in 60% of the bread wheats, was found in only 2% of the durum wheats and Gli-B1e, very common in durum wheat (45%), was rare in bread wheat (4%). The Gli-B1IV allele, common in durum wheat (28%), was not detected in bread wheat.     

PCR analysis of the wheat varieties and near-isogenic wheat lines with the use of allele-specific primers for the <Emphasis Type="Italic">Gli-1</Emphasis> and <Emphasis Type="Italic">Glu-3</Emphasis> loci

The allelic characteristics of Gli-A1, Gli-B1, Gli-D1 and Glu-A3 loci of 14 bread wheat varieties and 6 near-isogenic wheat lines derived from the Bezosta 1 variety were found by the use of PCR. The conformity between molecular-genetic and storage protein electrophoretic data was revealed: the GliA1.2 allele corresponds to the Gli-A1o and Gli-A1m allelic variants of gliadin blocks; the GliA1.1 PCR allele corresponds to the Gli-A1f, Gli-A1b and Gli-A1c variants of gliadin blocks; the GliB1.1 allele corresponds to the Gli-B1b and Gli-B1d allelic variants; and the GliB1.2 allele corresponds to the Gli-B1e, Gli-B1g and Gli-B1c variants. A new PCR allele with primers for marker GliB1.1 at the Gli-B1 locus in the GLI-B1-12 line (with the gliadin Gli-Blo block), which was generated from crossing of Bezosta 1 and the variety Levent, was detected.     

Variation at storage protein loci in winter common wheat cultivars of the central forest-steppe of Ukraine

Genotypes at the gliadin loci Gli-A1, Gli-B1, Gli-D1 and the high-molecular-weight glutenin subunit loci Glu-A1, Glu-B1, Glu-D1 were identified in 77 winter common wheat cultivars developed in the Central Forest Steppe of Ukraine in different periods of time. The highest level of variation was observed at the Gli-A1 locus. Predominant alleles (one or two per locus) were revealed. The comparison of allele frequencies in groups of cultivars developed in different periods of time (before 1996 and in 1996–2007) has demonstrated appearance of new alleles and change of frequencies of existing alleles at the storage protein loci. The high frequency of cultivars with the wheat-rye 1BL/1RS translocation was detected (about 40%). The wheat rye 1AL/1RS translocation was identified in six cultivars developed in the last decade. Four gliadin alleles, Gli-A1w (a marker for the 1AL/1RS translocation), Gli-A1x, Gli-A1y and Gli-B1x, were proposed for cataloging. The article is published in the original.     

Gliadin alleles in Canadian western red spring wheat cultivars: use of two different procedures of acid polyacrylamide gel electrophoresis for gliadin separation.

Gliadin allele compositions of 21 Canadian spring common wheat cultivars, most of which belong to the Canada western red spring (CWRS) class, were studied and great similarity in their genotypes was confirmed. It was found that alleles frequent in the set of Canadian wheats (such as Gli-B1d, Gli-D1j, Gli-A2m, and Gli-D2h) are very rare or absent in common wheat cultivars from other regions and countries studied earlier, indicating that germplasm of CWRS cultivars is rather unique. It may be suggested that alleles frequent in Canadian cultivars relate to important technological characteristics of these wheats and may possibly serve as marker genes during selection for quality traits. Similarity of gliadin electrophoregrams obtained by two different acid polyacryl-amide gel electrophoretic procedures for the same genotype was established, and the component composition of allelic variants of blocks of gliadin components found in the set of Canadian cultivars and in standard cultivars Chinese Spring and Bezostaya 1 are described.     

Comparison of alleles at the <Emphasis Type="Italic">Gli-1</Emphasis> loci of common wheat by means of two-dimensional electrophoresis of gliadin and RFLP analysis

Allelic variants of the Gli-1 locus is known to control groups (blocks) of gliadin polypeptides (gliadins). Some allelic variants of blocks that differ in the electrophoretic (acid gel) mobility (EM) of only one gliadin of the block were compared using two-dimensional electrophoresis (SDS-PAGE) and the RFLP procedure. It was found that, in these pairs of similar alleles (Gli-B1f, Gli-B1s, and Gli-D1a as compared with Gli-B1e, Gli-B1n, and Gli-D1c, respectively), faster γ-gliadin had smaller molecular weight (MW). Alleles at the Gli-A1 locus (Gli-A1j, Gli-A1i, Gli-A1a, Gli-A1k, and Gli-A1f) differ in the EM of the γ-gliadin so that Gli-A1j controls the slowest γ-gliadin and Gli-A1f controls the fastest one. We found that, in this order of alleles, faster γ-gliadin always had smaller MW. It was suggested that similar alleles might arise from one another by spontaneous mutations changing the number of repeating sequences or length of the polyglutamine domain present in the γ-gliadin gene thereby influencing MW and EM of encoding polypeptide. Other mechanisms of the mutational appearance of new alleles were found earlier by comparison of allele pairs: Gli-D1a and Gli-D1k (gene silencing) and Gli-D1b and Gli-D1d (gene amplification). We discovered contrasting families of alleles at the Gli-B1 and at the Gli-D1 loci and also two variants of apparently the same allele Gli-D1a that differed in the number of encoded ω-gliadins. Families of alleles at one locus of T. aestivum might inherit from different genotypes of corresponding diploid donor, as we suggested earlier.     

Genetic Diversity of Gli-1, Gli-2 and Glu-1 Alleles in Sichuan Wheat Landraces

Genetic diversity at Gli-1, Gli-2 and Glu-1 loci was investigated in 89 Sichuan wheat ( Triticum aestivum L.) landraces by using acid polyacrylamide gel electrophoresis (APAGE) and SDS-PAGE. In these landraces, a total of 32 gliadin and 3 high-molecular-weight (HMW) glutenin patterns were observed. In total, 14, 15 and 5 alleles were identified at Gli-1, Gli-2 and Glu-1, respectively. At each locus, the alleles in higher frequency were Gli-A1a (89%), Gli-B1 h (46%), Gli-D1a (65%), Gli-A2a (64%), Gli-B2j (45%), Gli-D2 a (48%), Glu-A1c (99%), Glu-B1b (99%) and Glu-D1a (100%). The Nei's genetic variation index (H) of Sichuan wheat landraces was 0.3706, varying from 0 to 0.7087. The highest genetic diversity was found at Gli-B2 locus, while the lowest was found at Glu-D1 . The genetic diversity at Gli loci was higher than that of Glu-1 loci among these landraces, but it was much lower than that of modern wheat cultivars. These results indicated a narrow genetic base of Sichuan wheat landraces. In this study, “Chengdu-guangtou” had the identical gliadin and HMW-glutenin patterns with “Chinese Spring”, further supporting the proposal that “Chinese Spring” is a strain of “Chengdu-guangtou”.     

Comparison of Alleles at <Emphasis Type="Italic">Gli-2</Emphasis> Loci of Common Wheat by Means of Two-Dimensional Electrophoresis of Gliadin

Electrophoretic mobility (EM) and molecular weight (MW) of some allelic variants of α- and β-gliadins contrlled by Gli-2 loci were compared by means of two-dimensional (APAGE × SDS) electrophoresis. Comparison of α-gliadins of the alleles Gli-A2b and Gli-A2p, of β-gliadins of the Gli-B2b and Gli-B2c, and of β-gliadins of the Gli-D2b, Gli-D2c, Gli-D2j, and Gli-D2r indicated that a gliadin with lower EM had, as a rule, bigger MW which is known to depend on the length of the polyglutamine domain of gliadin of α-type. However, allelic variants of the α-gliadin encoded by Gli-D2b and Gli-D2e differ in EM but not in apparent MW. It might be caused by a substitution of some charged/uncharged aminoacids in the polypeptide of gliadin. Allele Gli-B2o which is very frequent in up-to-date common wheat germplasm originated probably by means of unequal crossingover. Some alleles at Gli-A2 is found to control completely different blocks of gliadins and therefore might come to common wheat from different genotypes of the polymorphic diploid donor of the A genome. The results indicate that the reason of the known more vast polymorphism of gliadins controlled by Gli-2 loci as compared with Gli-1 loci is the considerable difference of the structure, first, of Gli-1 and Gli-2 loci (Gli-2 loci have more expressed genes per locus) and, second, of genes encoding gliadins of α- and γ-types (α-gliadins are shown to contain a long polyglutamine sequences highly variable in their length).     

Genetic diversity of French common wheat germplasm based on gliadin alleles

 Analysis of gliadin electrophoretic (APAGE) patterns made it possible to identify 79 alleles at six Gli-1 and Gli-2 loci (from 9 to 18 per locus) and 173 gliadin genotypes in the 187 French common wheat cultivars considered. Six new alleles were registered in the catalogue of gliadin alleles. The genetic diversity of French common wheats was found to be high (H=0.714) and had not changed much during the last 25–50 years. Analysis of genetic distances showed some gradual changes in French wheat germplasm over the course of time. Genetic distances between French and several European wheat germplasm were analysed; genotypes of European wheats were found to relate very distantly to Canadian genotypes. The considerable differentiation of wheat genotypes from different countries and cereal companies might be caused by breeders’ personal preferences and by hidden natural selection specific to each local environment. In French cultivars, genetic variation in earliness, and in the North/South habit of the cultivars studied, correlated significantly with allelic variation at Gli-B1, Gli-A2 and Gli-D2 for earliness, and at Gli-D2 for the North/ South habit. Early and late cultivars are grown mainly in Southern and Northern France, respectively (r ²=0.30). Cultivars having either the 1B/1R translocation or allele Gli-D2g are, on average, later and more resistant to cold; they hence are grown in the North of France. Alternatively, cultivars with the allele Gli-D2m are earlier and cold-sensitive, and are grown in the South of France. Received: 5 February 1997 / Accepted: 19 September 1997     

Null alleles for gliadin blocks in bread and durum wheat cultivars

Summary Wheat gliadin proteins are coded by clusters of genes (complex loci) located on the short arms of chromosomes of homoeologous groups 1 and 6 in bread (6x) and durum (4x) wheats. The proteins expressed by the various complex loci have been designated gliadin blocks. In a survey of accessions from the Germplasm Institute (C.N.R., Bari, Italy) collection, several different accessions have been found that lack particular blocks of proteins (null alleles). In some bread wheat accessions, seeds do not express gliadins that are coded by chromosomes 1D and 6A in normal cultivars. Similarly, some durum wheat accessions lack -gliadin components coded for by genes on chromosomes 1A and 1B. The missing proteins do not result from the absence of whole chromosomes, but may be the consequence of partial deletion of these genes at a complex locus or result from their silencing.     

On the Use of Alleles of Gliadin-Coding Loci as Possible Adaptability Markers in the Spring Wheat (Triticum aestivum L.) Cultivars during Seed Germination

Prolamine proteolysis is assumed to be among numerous adaptability factors in cereals. The patterns of gliadin proteolysis have been studied in 16 cultivars of spring wheat via analysis of electrophoretic spectra. Four proteolytic patterns have been identified. It is hypothesized that the cultivars characterized by early and rapid proteolysis (the first and third types) are the most adaptable. The gliadin genetic formulas of chromosomes of the first homeologous group have been determined. The alleles of gliadin loci (Gli-A1f, Gli-B1e, Gli-D1a, and Gli-D1b) have been found that can be used as markers of adaptability in spring wheat cultivars.     

Genealogical and statistical analyses of the inheritance of gliadin-coding alleles in a model set of common wheat <Emphasis Type="Italic">Triticum aestivum</Emphasis> L. cultivars

Allelic diversity of the gliadin-coding loci Gli-1 and Gli-2 was compared with the genealogical profiles of common wheat cultivars developed in Saratov. Allele tracking through their pedigrees and hierarchic cluster analysis associated 31 Gli alleles with groups of original ancestors. The cultivars Poltavka (12 alleles of six loci) and Selivanovskii Rusak (six alleles of six loci) were identified as sources of the majority of alleles. The results of the cluster analysis fully coincided with the results of allele tracking for alleles occurring at high frequencies. For rare alleles, the resolution of the cluster analysis was somewhat lower and depended on the similarity/distance measure. Thus, it proved possible to indirectly identify the donors of gene alleles by multidimensional statistics even when data on alleles identified in ancestors are unavailable. This approach to the analysis of inheritance has two limitations: detailed pedigree data should be known, and relatively high frequencies (no less than 15–20%) should be observed for the alleles in a sample under study. Cluster analysis was used to study the association of gliadin alleles with commercial quality classes. The most important gliadin-coding alleles, which mark strong cultivars, were identified. In the Saratov cultivars, such alleles include Gli-A1f, GliB1e, Gli-D1a, Gli-A2q, Gli-B2s, and Gli-D2e, which were inherited from the landrace Poltavka, and Gli-A1i, Gli-A2s, and Gli-B2q, which were inherited from the landrace Selivanovskii Rusak.     

Genetic characterization of storage proteins in a set of F1-derived haploid lines in bread wheat

Wheat storage proteins were evaluated by SDS-PAGE in a population of 206 doubled haploid (DH) lines, produced from a cross between bread wheat cvs Chinese Spring (CS) and Courtot (CT). The analysis of gliadins and high- and low-molecular-weight glutenins gave rise to 11 protein markers between parental varieties. Among these, one each was encoded at the Glu-A1, Gli-A1, Gli-A2, Gli-A5, Glu-B3, Gli-B1 and Gli-D1 loci and four were encoded at the Glu-D3 locus. Only the Gli-A2 marker showed a distorted segregation. A distance of 1.94 cM was evaluated between the Gli-A1 locus and the recently found Gli-A5 locus. Among the DH lines, only nine exhibited an unexpected pattern. The chromosome allocation was determined for almost all the LMW-GS and gliadin bands of CS using nullitetrasomic and ditelosomic lines. Two C LMW-GS were found to be coded by 6DS. Similarly, substitution lines into CT allowed the allelic determination of numerous LMW-GS and gliadin bands. A correspondence between gliadin markers separated in SDS-PAGE and in A-PAGE revealed that the common allele Gli-Aa between CS and CT determined in A-PAGE was able to be separated into two alleles when SDS-PAGE was used.     

Alleles at storage protein loci in Triticum spelta L. accessions and their occurrence in related wheats

The diversity at eight storage protein loci was analyzed in the collection of Triticum spelta accesssions from the National Center for Plant Genetic Resources of Ukraine (most of accessions were European spelts). Seven alleles at the Gli-B1 locus; five alleles at the Gli-A1 and Glu-B1 loci; three alleles at the Glu-B1 locus; and two alleles at the Gli-D1, Gli-B5, Glu-A1, and Glu-D1 loci were identified. Most alleles are found among common wheat cultivars; only five spelt-specific alleles were detected. The high frequency of the GliB1hs* and h alleles encoding the 45-type γ-gliadin among European spelt and durum wheat, as well as the occurrence of these alleles in T. dicoccum (particularly, in emmer accessions from Switzerland and Germany), are evidence in favor of von Büren’s hypothesis that the European spelt arose from the hybridization between tetraploid wheat with the 45-type γ-gliadin and hexaploid wheat. The analysis of genetic distances based on the genotypes at eight storage protein loci allowed differentiating the Asian spelt accession from European spelts.     

Polymorphism and inheritance of gliadin components controlled by chromosome 6A of spring durum wheat

The gliadin composition of 78 spring durum wheat varieties has been studied by one-dimensional (Al-lactate, pH 3.1) and two-dimensional (first dimension, Al-lactate, pH 3.1; second dimension, sodium dodecyl sulfate-polyacrylamide gel) electrophoresis. Analysis of hybrids has shown that all components of the alpha zone of gliadin spectra are inherited together as blocks and are, probably, coded for by a cluster of tightly linked genes located on chromosome 6A. Fourteen variants of gliadin blocks have been identified, which can be classified into five families on the basis of component composition. All families but one have analogues among chromosome 6A-controlled blocks of bread wheat. The results indicate that some of the genome A diploid genotypes that were ancestors of durum wheats were also ancestors of bread wheats and that polyploid wheats were produced by repeated allopolyploidization events, as has been suggested earlier.     

RFLP patterns of gliadin alleles in Triticum aestivum L.: implications for analysis of the organization and evolution of complex loci

A correspondence between RFLP patterns and gliadin alleles at the Gli-1 and Gli-2 loci was established in a set of 70 common wheat (T.aestivum L.) cultivars using -gliadin (K32) and -gliadin (pTU1) specific probes. All Gli-B1 and Gli-D1 alleles which differed in encoded -gliadins showed definite RFLP patterns after hybridization with the K32 probe. Two groups of Gli-B1 alleles, Gli-B1b-like and Gli-B1e-like, were identified, and these could originate from distinct genotypes of the presumptive donor of the B-genome. Intralocus recombination and/or gene conversion as well as small deletions, gene silencing and gene amplification were assumed to be responsible for the origin of new gliadin alleles. Silent -gliadin sequences were shown to exist in all of the genotypes studied. K32 also differentiated Gli-A1a from all other Gli-A1 alleles as well as the Gli-B11 allele in cultivars carrying the 1B/1R (wheat/rye) translocation. PTU1 was shown to recognize several Gli-A2 alleles, but not the Gli-B2 or Gli-D2 alleles. Moreover, this probe hybridized to chromosome 1R sequences suggesting the existence of rye gene(s), probably silent, for -gliadin-like proteins on chromosome 1R.     

The segregation characteristics at the alleles of the gliadin-coding Gli-B1 locus in hybrid soft winter wheat

Segregation at the Gli-B1 locus was studied in F2 seeds of common wheat from crosses between near-isogenic lines with respect to this locus. Segregations differed from the expected ratio in hybrids involving the lines with the allele Gli-B1l (Gli-B1-3), which is a marker for the 1BL/1RS translocation, as well as in the hybrid between the lines with the alleles Gli-B1b (1) and Gli-B1e (4). Reduced transmission of the chromosome with the 1BL/1RS translocation through pollen was observed in the hybrids involving the line with this translocation. In the cross GLI-B1-1 x GLI-B1-4, the significantly lower frequency of female gametes with the allele Gli-B1e (4) was detected. This is due to linkage of the Gli-B1 locus to a factor responsible for segregation distortion in female gametes. We proposed to designate this locus Sd3. The line with the gliadin block Gli-B1e differs in alleles at the Sd3 locus from the lines with the blocks Gli-B1b and Gli-B1o.     

Genetic diversity of local spring bread wheats (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) of West and East Siberia in gliadin genes

A considerable polymorphism in gliadin genes was detected in the wheat landraces of West Siberia (Altai krai, Omsk oblast, and Kurgan oblast) and the local cultivars characteristic of several East Siberian regions (Krasnoyarsk krai, Irkutsk oblast, Tuva, and Yakutia), and the genetic formulas were determined. The common alleles characteristic of the wheats of both regions were detected, namely, Gli-A1f, Gli-A1j, Gli-A1i, Gli-A1m, Gli-B1e, Gli-B1m, Gli-D1a, Gli-A2q, Gli-A2k, Gli-A2u, Gli-D2a, and Gli-D2q, as well as 14 novel alleles unknown earlier. It was demonstrated that several genotypes had formed in Siberia. Of them, the genotypes Gli-A1f_Gli-B1e_Gli-D1a and Gli-A1j_Gli-B1e_Gli-D1a occur both in West and East Siberia, whereas the genotypes Gli-A1i_Gli-B1m_Gli-D1a_Gli-A2new10, Gli-A1m_Gli-B1b_Gli-D1a_Gli-A2f, and Gli-A1m_Gli-B1m_Gli-D1a_Gli-A2u are found only in East Siberia.     

Recombination mapping of Gli-5, a new gliadin-coding locus on chromosomes 1A and 1B in common wheat

Inheritance studies of gliadin loci on chromosomes 1A and 1B were carried out in the progeny from crosses between cv Salmone and six other common wheat varieties. The map distance between the Rg-1 locus for glume colour and the gliadin locus Gli-B1 on the satellite of chromosome 1B was calculated as 2.0±0.6 cM. An additional gliadin locus, Gli-B5, was mapped between Gli-B1 and Rg-1, 1.4 cM from the former. A genetic distance of 1.8±0.4 cM was obtained between the Hg-1 locus for hairy glumes and a gliadin locus that seems to be remote from Gli-A1 and homoeologous to Gli-B5. Statistically significant differences in recombination values were found in the six crosses, indicating the influence of genotype on the frequency of recombination. The similarity in chromosomal location of seed storage protein genes in wheat, barley and rye is discussed.