Molecular characterization of a LMW-GS gene located on chromosome 1B and the development of primers specific for the Glu-B3 complex locus in durum wheat

 Low-molecular-weight glutenin subunits (LMW-GS) represent a specific class of wheat storage proteins encoded at the Glu-3 loci. Particularly interesting are the LMW-GS encoded at the Glu-B3 locus because they have been shown to play an important role in determining the pasta-making properties of durum wheat. Genes encoding LMW-GS have been characterized but only a few of them have been assigned to specific loci. Notably, no complete LMW-GS gene encoded at the Glu-B3 locus has yet been described. The present paper reports the isolation and characterization of a lmw-gs gene located at the Glu-B3 locus. The clone involved, designated pLDNLMW1B, contains the entire coding region and 524 bp of the 5′ upstream region. A nucleotide comparison between the pLDNLMW1B clone and other LMW-GS genes showed the presence of some peculiar structural characteristics, such as short insertions in the promoter region, the presence of a cysteine codon in the repetitive domain, and a more regular structure of this region, which could be important for its tissue-specific expression and for the functional properties of the encoded protein, respectively. Received : 30 May 1997 / Accepted : 29 July 1997     

Storage-protein variation in wild emmer wheat (Triticum turgidum ssp.dicoccoides) from Jordan and Turkey. I. Electrophoretic characterization of genotypes

Seed storage-protein variation at theGlu-A1,Glu-B1 andGli-B1/Glu-B3 loci in the tetraploid wild progenitor of wheat,T. dicoccoides, was studied electrophoretically in 315 individuals representing nine populations from Jordan and three from Turkey. A total of 44 different HMW-glutenin patterns were identified, resulting from the combination of 15 alleles in the A genome and 19 in the B genome. Twenty-seven new allelic variants, 12 at theGlu-A1 locus and 15 at theGlu-B1 locus, were identified by comparing the mobilities of their subunits to those previously found in bread and durum wheats. The novel variants include six alleles at theGlu-A1 locus showing both x and y subunits. The genes coding for the 1Bx and 1By subunits showed no or very little (3%) inactivity, the 1Ax gene showed a moderate degree (6.3%) of inactivity whereas the gene coding for lAy showed the highest degree of inactivity (84.8%). A high level of polymorphism was also present for the omega- and gamma-gliadins and LMW-glutenin subunits encoded by genes at the linkedGli-B1 andGlu-B3 loci (19 alleles). Some Jordanian accessions were found to contain omega-gliadin 35, gamma-gliadin 45, and LMW-2 also present in cultivated durum wheats and related to good gluten viscoelasticity. The newly-discovered alleles enhance the genetic variability available for improving the technological quality of wheats. Additionally some of them may facilitate basic research on the relationship between industrial properties and the number and functionality of HMW- and LMW-glutenin subunits.     

Variation and classification of B low-molecular-weight glutenin subunit alleles in durum wheat

 The B low-molecular-weight (LMW) glutenin subunit composition of a collection of 88 durum wheat cultivars was analyzed. Extensive variation has been found and 18 different patterns were detected. Each cultivar exhibited 4–8 subunits, and altogether 20 subunits of different mobility were identified. The genetic control of all these subunits was determined through the analysis of nine F₂ populations and one backcross. Five subunits were controlled at the Glu-A3 locus, 14 at Glu-B3 and 1 at Glu-B2. At the Glu-A3 locus each cultivar possessed from zero to three bands and eight alleles were identified. At the Glu-B3 locus each cultivar showed four or five bands and nine alleles were detected. Only one band was encoded by the Glu-B2 locus. A nomenclature for these alleles is proposed and the relationship between them and the commonly used LMW-model nomenclature is discussed. Received: 10 February 1997 / Accepted: 25 April 1997     

Allelic variations in <Emphasis Type="Italic">Glu-1</Emphasis> and <Emphasis Type="Italic">Glu-3</Emphasis> loci of historical and modern Iranian bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) cultivars

Proline and glutamine-rich wheat seed endosperm proteins are collectively referred to as prolamins. They are comprised of HMW-GSs, LMW-GSs and gliadins. HMW-GSs are major determinants of gluten elasticity and LMW-GSs considerably affect dough extensibility and maximum dough resistance. The inheritance of glutenin subunits follows Mendelian genetics with multiple alleles in each locus. Identification of the banding patterns of glutenin subunits could be used as an estimate for screening high quality wheat germplasm. Here, by means of a two-step 1D-SDS-PAGE procedure, we identified the allelic variations in high and low-molecular-weight glutenin subunits in 65 hexaploid wheat (Triticum aestivum L.) cultivars representing a historical trend in the cultivars introduced or released in Iran from the years 1940 to 1990. Distinct alleles 17 and 19 were detected for Glu-1 and Glu-3 loci, respectively. The allelic frequencies at the Glu-1 loci demonstrated unimodal distributions. At Glu-A1, Glu-B1 and Glu-D1, we found that the most frequent alleles were the null, 7 + 8, 2 + 12 alleles, respectively, in Iranian wheat cultivars. In contrast, Glu-3 loci showed bimodal or trimodal distributions. At Glu-A3, themost frequent alleles were c and e. At Glu-B3 the most frequent alleles were a, b and c. At Glu-D3 locus, the alleles b and a, were the most and the second most frequent alleles in Iranian wheat cultivars. This led to a significantly higher Nei coefficient of genetic variations in Glu-3 loci (0.756) as compared to Glu-1 loci (0.547). At Glu-3 loci, we observed relatively high quality alleles in Glu-A3 and Glu-D3 loci and low quality alleles at Glu-B3 locus.     

Molecular marker-assisted selection of HMW glutenin alleles related to wheat bread quality by PCR-generated DNA markers

While quality in hexaploid wheat (Triticum aestivum L. em Thell.) is a very complex trait, it is known that the water-insoluble gluten proteins are responsible for the elasticity and chohesiveness (strength) of dough and are therefore important determinants of breadmaking quality. High-molecular-weight (HMW) glutenin subunits encoded by genes on the long arm of group 1 chromosomes have been associated with gluten strength, and a portion of the variability between cultivars can be attributed to glutenin subunit composition. Good or poor wheat breadmaking quality is associated with two allelic pairs at the Glu-D1 complex locus, designated 1Dx5–1Dy10 and 1Dx2–1Dy12, respectively. Among the HMW glutenin subunits encoded at Glu-B1, Bx7 is quite common, being associated with either of two subunits, By8 or By9. Both allelic pairs contribute moderately well to good breadmaking quality by increasing dough elasticity. Glutenin subunit screening is accomplished using electrophoresis (SDS-PAGE). In this paper, I report the development of an alternative screening method based on glutenin genes themselves using the polymerase chain reaction (PCR). This easy, quick and non-destructive PCR-based approach is an efficient alternative to standard procedures for selecting bread-wheat genotypes with good breadmaking characteristics. Received: 14 August 1999 / Accepted: 21 March 2000     

Variation in the HMW and LMW glutenin subunits from Spanish accessions of emmer wheat (Triticum turgidum ssp. dicoccum Schrank)

Emmer wheat (Triticum turgidum ssp. dicoccum Schrank) is hulled wheat that survives in marginal areas of the Mediterranean Region. The HMW and LMW glutenin subunit composition of 97 accessions of emmer wheat from Spain have been analysed by SDS-PAGE. For the HMW glutenin subunits, four allelic variants were detected for the Glu-A1 locus; one of them has not been previously described. For the Glu-B1 locus, three of the nine alleles detected have not been found before. A high degree of variation was evident for the LMW glutenin subunits, and up to 23 different patterns were detected for the B-LMW glutenin subunits. Considering both types of proteins (HMW and LMW), 30 combinations were found between all the evaluated lines. This wide polymorphism can be used to transfer new quality genes to wheat, and to widen its genetic basis. Received: 13 June 2000 / Accepted: 3 July 2000     

Identification of new low-molecular-weight glutenin subunit genes in wheat

To clarify the composition of low-molecular-weight glutenin subunits (LMW-GSs) in a soft wheat cultivar, we cloned and characterized LMW-GS genes from a cDNA library and genomic DNA in Norin 61. Based on alignment of the conserved N- and C- terminal domains of the deduced amino-acid sequences, these genes are classified into 12 groups. One of these groups (group 5), the corresponding gene of which has not been reported previously, contains two additional hydrophobic amino-acid clusters interrupting the N-terminal repetitive domain. Other groups (groups 11 and 12), which were not identified in other cultivars as a protein product, showed all eight cysteines in the C-terminal conserved domain. With specific primer sets for these groups it was revealed that Glu-D3 and Glu-A3 encoded the former and the latter, respectively. Both groups of genes were expressed in immature seeds. The presence of these groups of LMW-GSs may affect the dough strength of soft wheat. Received: 26 March 2001 / Accepted: 16 July 2001     

The low-molecular-weight glutenin subunit proteins of primitive wheats. IV. Functional properties of products from individual genes

 Three genes encoding the low-molecular-weight glutenin subunits (LMW-GSs), LMWG-E2 and LMWG-E4, from A-genome diploid wheat species, and LMW-16/10 from a D-genome diploid wheat, were expressed in bacteria. The respective proteins were produced on a relatively large scale and compared with respect to their effects on flour-processing properties such as dough mixing, extensibility and maximum resistance; these are important features in the end-use of wheat for producing food products. The LMWG-E2 and LMWG-E4 proteins caused significant increases in peak resistance and mixing time, compared to the control, when incorporated into dough preparations. The LMWG-16/10 protein was qualitatively less effective in producing these changes. All three proteins also conferred varying degrees of decrease in dough breakdown. LMWG-E2 and LMWG-E4 caused significant increases in dough extensibility, and decreases in maximum resistance, relative to the control. LMW-16/10 did not show a significant effect on extensibility but showed a significant decrease in maximum resistance. The refinement of relating specific features of the structure of the LMW-GS genes to the functional properties of their respective proteins is discussed. Received: 24 November 1997 / Accepted: 18 August 1998     

Genetic diversity for morphological traits and seed storage proteins in Spanish rivet wheat

The objective of the current work was to analyse the variability of high and low molecular mass (HMM and LMM) glutenin subunits, along with some morphological characteristics in sixty Spanish accessions of rivet wheat (Triticum turgidum L. ssp. turgidum). The lines were grouped in sixteen botanical varieties and five additional types, according the morphological criteria. Up to 13 allelic variants (four alleles for the Glu-A1 locus and nine alleles for the Glu-B1 locus) and 34 B-LMMGs patterns were found in the evaluated lines. The current data indicated a clear reduction of morphological variability, along with an asymmetric distribution of the alleles and patterns for seed storage proteins. This polymorphism could be useful for enlarging the genetic background of modern durum wheat.     

PCR analysis of genes encoding allelic variants of high-molecular-weight glutenin subunits at the Glu-D1 locus

Genes encoding high-molecular-weight (HMW) glutenin subunits, present in bread-wheat lines and cultivars, were studied by RFLP (restriction fragment length polymorphism) and PCR (polymerase chain reaction) analyses. In particular, allelic subunits of the x-or y-type, encoded at the Glu-D1 locus present on the long arm of chromosome 1D, were investigated. The variation in size, observed in different allelic subunits, is mainly due to variation in the length of the central repetitive domain, typical of these proteins. Deletions or duplications, probably caused by unequal crossingover, have given rise to the size heterogeneity currently observed. The possibility of using the PCR technique for a detailed analysis of HMW glutenin genes in order to obtain a more accurate estimation of the molecular weight of their encoded subunits, and the detection of unexpressed genes, is also described.     

Development of haplotype-specific molecular markers for the low-molecular-weight glutenin subunits

Low-molecular-weight glutenin subunits (LMW-GSs) are one of the major components of gluten, and their allelic variation has been widely associated with different wheat end-use quality parameters. These proteins are encoded by multigene families located at the orthologous Glu-3 loci (Glu-A3, Glu-B3, and Glu-D3); the genes at each locus are divided by large intergenic and highly recombinogenic regions. Among the methods used for the LMW-GS allele identification, polymerase chain reaction (PCR)-based molecular markers have the advantages of being simple, accurate, and independent from the plant stage of development. However, the available LMW-GS molecular markers are either incapable of capturing the complexity of the LMW-GS gene family or difficult to interpret. In the present study, we report the development of a set of PCR-based molecular markers specific for the LMW-GS haplotypes present at each Glu-3 locus. Based on the LMW-GS gene sequences available in GenBank, single nucleotide polymorphisms (SNPs) specific for each Glu-3 haplotype were identified and the relevant PCR primers were designed. In total, we developed three molecular markers for the Glu-A3 and Glu-B3 loci, respectively, and five molecular markers for the Glu-D3 locus. The markers were tested on 44 bread wheat varieties previously characterized for their LMW-GS genic profile and found to be equally or more efficient than previously developed LMW-GS PCR-based markers. This set of markers allows an easier and less ambiguous identification of specific LMW-GS haplotypes associated with gluten strength and can facilitate marker-assisted breeding for wheat quality.     

Characterization of Low Molecular Weight Glutenin Subunit Gene Representing Glu-B3 Locus of Indian Wheat Variety NP4

Low molecular weight (LMW) glutenin subunits represent major part (30%) of storage proteins in wheat endosperm and determine the quality of dough. Despite their importance few LMW glutenin genes have been characterized so far and none from Indian wheat variety. In the present investigation PCR technique was employed to characterize LMW-GS gene representing Glu-B3 locus from Indian bread wheat cultivar NP4. The deduced protein sequence coded by Glu-B3 locus of LMW-GS gene from NP4 showed the presence of regular structure of the repetitive domain with varying numbers of glutamine (Q) residues and the presence of 1^st cysteine residue within the repetitive domain at 40^th position in mature polypeptide. Such structure might increase and stabilize the gluten polymer through intermolecular interactions of the large numbers of glutamine side chains and cysteine residues for intermolecular disulphide bond formation leading to stronger dough quality of NP4. Moreover, Glu-B3 specific primers could also be used for identifying 1BL/1RS translocation in addition to amplifying LMW glutenin genes. There was no amplification in 1B/1R translocation lines as short arm of wheat was replaced by short arm of rye chromosome in these lines. Such information can be useful in wheat improvement for dough properties for better chapati and bread quality.     

Allelic variation of high-molecular-weight glutenin genes in bread wheat

The composition and quantity of high-molecular-weight glutenin subunits plays an important role in determining the bread-making quality of wheat. Molecular-genetic analysis of allelic composition of high-molecular-weight glutenin genes in 102 bread wheat cultivars and lines from different geographical regions was conducted. Three alleles at the Glu-A1 locus, nine alleles at the Glu-B1 locus, and two alleles at the Glu-D1 locus were identified. Among the investigated cultivars and lines, 21 were characterized by intracultivar polymorphism. High allelic variation of high-molecular-weight glutenin subunit genes was shown for the collection: 21 and 9 combinations were defined in monomorphic and polymorphic cultivars and lines, respectively. However, the major part of the collection (66.7%) contained four allelic combinations: Glu-A1b Glu-B1c Glu-D1d, Glu-A1b Glu-B1c Glu-D1-2a, Glu-A1a Glu-B1c Glu-D1d, and Glu-A1b Glu-B1c Glu-D1d/Glu-D1-2a. Fourteen cultivars of bread wheat were selected, and they were characterized by a favorable allelic composition of Glu-1 loci.     

Evidence of intralocus recombination at the <Emphasis Type="Italic">Glu-3</Emphasis> loci in bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Key message

Recombination at the Glu-3 loci was identified, and strong genetic linkage was observed only between the amplicons representing i-type and s-type genes located, respectively, at the Glu-A3 and Glu-B3 loci.

Abstract

The low-molecular weight glutenin subunits (LMW-GSs) are one of the major components of wheat seed storage proteins and play a critical role in the determination of wheat end-use quality. The genes encoding this class of proteins are located at the orthologous Glu-3 loci (Glu-A3, Glu-B3, and Glu-D3). Due to the complexity of these chromosomal regions and the high sequence similarity between different LMW-GS genes, their organization and recombination characteristics are still incompletely understood. This study examined intralocus recombination at the Glu-3 loci in two recombinant inbred line (RIL) and one doubled haploid (DH) population, all segregating for the Glu-A3, Glu-B3, and Glu-D3 loci. The analysis was conducted using a gene marker system that consists of the amplification of the complete set of the LMW-GS genes and their visualization by capillary electrophoresis. Recombinant marker haplotypes were detected in all three populations with different recombination rates depending on the locus and the population. No recombination was observed between the amplicons representing i-type and s-type LMW-GS genes located, respectively, at the Glu-A3 and Glu-B3 loci, indicating tight linkage between these genes. Results of this study contribute to better understanding the genetic linkage and recombination between different LMW-GS genes, the structure of the Glu-3 loci, and the development of more specific molecular markers that better represent the genetic diversity of these loci. In this way, a more precise analysis of the contribution of various LMW-GSs to end-use quality of wheat may be achieved.

     

The low-molecular-weight glutenin subunit proteins of primitive wheats. III. The genes from D-genome species

 The isolation and characterisation by DNA sequencing of two different low molecular weight glutenin subunit (LMW-GS) genes from a genomic library derived from Triticum tauschii is described. These genes are similar (more than 90% similarity) but not identical to previously published LMW-GS gene sequences from cultivated wheats. A comparison of nucleotide sequence of the coding regions revealed the presence of insertions and deletions preferentially located in the region encoding the domains in the LMW-GS proteins rich in proline and glutamine and the middle part of the C-domain. The signal sequences, the amino-terminus and the remaining parts of the C-domain were conserved between all the LMW-GSs compared. The differences detected between the deduced amino-acid sequences in these three regions are only due to single nucleotide substitutions. The most important characteristic of all compared LMW-GS genes is the conservation of eight cysteine residues that could be involved in potential secondary or tertiary structure and disulphide-bond interactions. Comparisons between the 5′ and 3′ non-coding sequences of one of the isolated clones (LMW-16/10) with those of different prolamin genes from wheat, barley and rye led to the distinction of five different gene families, and confirmed the evolutionary relationships determined previously for these genes mainly on the basis of the coding region. In particular, the LMW-GS sequences are more closely related to the B-hordein sequences than to any other prolamin genes from wheat, barley and rye. Formal proof that the isolated genes coded for LMW-GSs, as defined by gel electrophoresis, was obtained by moving one of these genes (LMW-16/10) into a bacterial expression vector based on bacteriophage T7 RNA polymerase. The resulting plasmid directed the synthesis of large amounts of the mature form of the subunit in Escherichia coli. This protein exhibited solubility characteristics identical to those of the LMW-GSs and cross-reacted with antibodies reactive with these proteins. Received: 24 November 1997 / Accepted: 18 August 1998     

Characterization of low-molecular-weight glutenin subunit genes and their protein products in common wheats

To characterize the low-molecular-weight glutenin subunit (LMW-GS), we developed specific PCR primer sets to distinguish 12 groups of LMW-GS genes of Norin 61 and to decide their loci with nullisomic–tetrasomic lines of Chinese Spring. Three, two, and ten groups were assigned to Glu-A3, Glu-B3, and Glu-D3 loci, respectively. To identify the proteins containing the corresponding amino acid sequences, we determined the N-terminal amino acid sequence of 12 spots of LMW-GSs of Norin 61 separated by two-dimensional gel electrophoresis (2DE). The N-terminal sequences of the LMW-GS spots showed that 10 of 12 groups of LMW-GSs were expressed as protein products, which included LMW-i, LMW-m, and LMW-s types. Four spots were encoded by Glu-A3 (LMW-i). Three spots were encoded by Glu-B3 (LMW-m and LMW-s). Five spots were encoded by Glu-D3 (LMW-m and LMW-s). A minor spot of LMW-m seemed to be encoded by the same Glu-B3 gene as a major spot of LMW-s, but processed at a different site. Comparing among various cultivars, there were polymorphic and non-polymorphic LMW-GSs. Glu-A3 was highly polymorphic, i.e., the a, b, and c alleles showed one spot, the d allele showed four spots, and the e allele had no spot. Insignia used as one of the Glu-A3 null standard cultivars had a LMW-GS encoded by Glu-A3. We also found that Cheyenne had a new Glu-D3 allele. Classification of LMW-GS by a combination of PCR and 2DE will be useful to identify individual LMW-GSs and to study their contribution to flour quality.     

Identification and molecular characterization of a large insertion within the repetitive domain of a high-molecular-weight glutenin subunit gene from hexaploid wheat

High-molecular-weight (HMW) glutenin subunits are a particular class of wheat endosperm proteins containing a large repetitive domain flanked by two short N- and C-terminal non-repetitive regions. Deletions and insertions within the central repetitive domain has been suggested to be mainly responsible for the length variations observed for this class of proteins. Nucleotide sequence comparison of a number of HMW glutenin genes allowed the identification of small insertions or deletions within the repetitive domain. However, only indirect evidence has been produced which suggests the occurrence of substantial insertions or deletions within this region when a large variation in molecular size is present between different HMW glutenin subunits. This paper represents the first report on the molecular characterization of an unusually large insertion within the repetitive domain of a functional HMW glutenin gene. This gene is located at the Glu-D1 locus of a hexaploid wheat genotype and contains an insertion of 561 base pairs that codes for 187 amino acids corresponding to the repetitive domain of a HMW glutenin subunit encoded at the same locus. The precise location of the insertion has been identified and the molecular processes underlying such mutational events are discussed.     

High Molecular Weight Glutenin Subunit Composition of Indian Wheats and Their Relationships with Dough Strength

One hundred and seventy two wheat varieties including twenty-five durum wheat cultivars were evaluated for high molecular weight glutenin subunit (HMW-GS) composition using SDS-PAGE. The relationship between HMW-GS and sedimentation tests for dough strength was studied. Three alleles were present at the Glu-A1 locus, eight at Glu-B1 and two at Glu-D1 in bread wheat. The data indicated the prevalence of the Glu-A1b allele (63.5%) at the Glu-A1 and Glu-D1a (71.4%) at Glu-D1 loci. Three alleles, namely Glu-B1b (30.61%), Glu-B1c (25.85%) and Glu-B1i (34.00%) represented about 90% of the alleles at Glu-B1 locus. The combination of Glu-A1b, Glu-B1i and Glu-D1d alleles exhibited highest dough strength as measured by sedimentation value in comparison to other combinations (p<0.001). However, this combination was present only in 7% of the samples evaluated. In durum wheat, the null allele (Glu-A1c) was observed more frequently (76%) than the Glu-A1b allele (24%). Glu-B1f and Glu-B1e alleles represented equally (32% each). Protein subunits 13+16 and 6+8 were found correlated positively (p<0.05) with improved dough strength as compared to subunit 20 in durum wheat. This information can be a valuable reference for designing breeding programme for the improvement of bread and pasta making quality of bread and durum wheats, respectively in India.     

Molecular characterization and genomic organization of low molecular weight glutenin subunit genes at the Glu-3 loci in hexaploid wheat (Triticum aestivum L.)

In this study, we report on the molecular characterization and genomic organization of the low molecular weight glutenin subunit (LMW-GS) gene family in hexaploid wheat (Triticum aestivum L.). Eighty-two positive BAC clones were identified to contain LMW-GS genes from the hexaploid wheat ‘Glenlea’ BAC library via filter hybridization and PCR validation. Twelve unique LMW glutenin genes and seven pseudogenes were isolated from these positive BAC clones by primer-template mismatch PCR and subsequent primer walking using hemi-nested touchdown PCR. These genes were sequenced and each consisted of a single-open reading frame (ORF) and untranslated 5′ and 3′ flanking regions. All 12 LMW glutenin subunits contained eight cysteine residues. The LMW-m-type subunits are the most abundant in hexaploid wheat. Of the 12 LMW-GS, 1, 2 and 9 are i-type, s-type and m-type, respectively. The phylogenetic analysis suggested that the LMW-i type gene showed greater differences to LMW-s and LMW-m-type genes, which, in turn, were more closely related to one another. On the basis of their N-terminal sequences, they were classified into nine groups. Fingerprinting of the 82 BAC clones indicated 30 BAC clones assembled into eight contigs, while the remaining clones were singletons. BAC end sequencing of the 82 clones revealed that long terminal repeat (LTR) retrotransposons were abundant in the Glu-3 regions. The average physical distance between two adjacent LMW-GS genes was estimated to be 81 kb. Most of LMW-GS genes are located in the d-genome, suggesting that the Glu-D3 locus is much larger than the Glu-B3 locus and Glu-A3 locus. Alignments of sequences indicated that the same type (starting with the same N-terminal sequence) LMW-GS genes were highly conserved in the homologous genomes between hexaploid wheat and its donors such as durum wheat and T. tauschii. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Inheritance of B subunits of glutenin and ω-and γ-gliadins in tetraploid wheats

A double-1RS wheat-rye translocation line lacking all B subunits of glutenin was produced in durum wheat cv ‘Langdon’ for use in backcrosses and testcrosses in the study of the inheritance of low-molecular-weight (LMW) glutenin subunits in tetraploid wheats. The B subunits of glutenin and γ-and ω-gliadin bands present in parents derived from Triticum durum and T. dicoccoides, encoded by Glu-3 and Gli-1 loci, respectively, were found to be inherited mainly as units (blocks), as reported previously. Two rare recombination events between the Glu-A3 and Gli-A1 loci were detected in testcross progeny from ‘Edmore’ x T. dicoccoides landrace 19–27. Several rare recombinants were also detected within the 1BS-controlled B subunits of glutenin blocks, suggesting that there are two separate tightly linked loci (3.07±1.35 cM) within the Glu-B3 ‘locus’. Evidence was also obtained for the presence of an additional locus coding for a B subunit of glutenin in ‘Edmore’ that is loosely linked (20.9±3.18%) with the main Glu-B3 ‘locus’.