The high and low molecular weight glutenin subunits and ω-gliadin composition of bread and durum wheats commonly grown in Portugal

A collection of 63 bread wheats (Triticum aestivum L.) and 21 durum wheats (Triticum durum Desf.) commonly grown in Portugal since 1982 were characterized for the composition of wheat storage proteins (WSP), high molecular weight glutenin subunits (HMW-GS), low molecular weight glutenin subunits (LMW-GS) and ω-gliadins. The composition of HMW-GS, LMW-GS and &-gliadins, encoded at loci Glu-1, Glu-3 and Gli-1, respectively, was revealed by sodium dodecyl sulphate polyacrylamide gel electrophoresis. WSP allelic compositions of bread and durum wheat patterns were given. In the bread wheats, a total of 24, 24 and 18 patterns were observed for HMW-GS, LMW-GS and ω-gliadins, respectively. Forty-two different alleles were identified for the nine loci studied, Glu-A1 (3), Glu-B1 (7), Glu-D1 (4), Glu-A3 (5), Glu-B1 (7), Glu-D3 (2), Gli-A1 (2), Gli-B1 (8) and Gli-D1 (4). In the case of durum wheats, 19 alleles were identified: one allele at Glu-A1, two at Glu-B3, Glu-B2 and Gli-A1, three at Glu-B1, four at Glu-A3 and five at Gli-B1. For HMW-GS, LMW-GS and ω-gliadins, three, six and six different patterns were revealed, respectively. This study represents the first attempt to discriminate the bread and durum wheat varieties commonly grown in Portugal by the allelic variation of storage proteins. The database is useful for varietal identification and for plant breeders who seek to devise effective programmes aimed at improving wheat quality.     

Relationship between common wheat (Triticum aestivum L.) gluten proteins and dough rheological properties

This paper reports the correlation between the rheological properties of bread wheat dough and the types and quantities of endosperm proteins in 28 common wheat cultivars. Different methods were used to analyse the allelic composition of these cultivars and the relative quantities of the different proteins contributing to the gluten structure. Neither dough strength (W) nor tenacity/extensibility (P/L) correlated with allelic composition. Different wheats with the same allelic composition (i.e., with respect to glutenins) showed different rheological properties. The glutenins were the most influential components of W and P/L, especially the high molecular weight (HMW) glutenin subunits and in particular the type x form. These proteins seem to increase W and are the main constituents of the gluten network. The gliadins and low molecular weight (LMW) glutenin subunits appear to act as a “solvent”, and thus modify the rheological properties of the dough by either interfering with the polymerisation of the HMW glutenin subunits, or by altering the relative amounts of the different types of glutenin available. Thus, the protein subunits coded for by the alleles Glu-B1x7 and Glu-D1x5 stabilised the gluten network, whereas those coded for by Glu-B1x17 and Glu-D1x2 had the opposite effect. Dough properties therefore appear to depend on the glutenin/gliadins balance, and on the ratio of the type x and type y HMW proteins. The influence of external factors seems to depend on the allelic composition of each cultivar.     

Diversity of seven glutenin and secalin loci within triticale cultivars grown in Europe

Analysis by SDS-PAGE of the majority of hexapoid triticales (× Triticosecale) (134 cultivars) grown in Europe allowed to identify 40 alleles at seven loci: Glu-A1, Glu-B1, Glu-R1, Gli-R2, Glu-B2, Glu-A3 and Glu-B3. Glu-B1 and Glu-B3 loci were the most polymorphic with 9 alleles at each locus. 95 allelic combinations were observed including 71 specific for one cultivar each. On the basis of allelic frequencies at the seven loci, genetic distances between hexapoid triticales grouped according to their origins revealed two clusters: winter triticales mostly originating from European germplasm and spring triticales essentially of CIMMYT origin. Comparison of allele frequencies between hexaploid triticale cultivars and a world collection of bread (Triticum aestivum) and durum (Triticum durum) wheat was investigated at Glu-A1 and Glu-B1: only a significant association was found for Glu-A1 alleles (γ²=2.26, p=0.36) between triticale and bread wheat. This revised version was published online in July 2006 with corrections to the Cover Date.     

Detection and genotyping of SNPs tightly linked to two disease resistance loci, Rsv1 and Rsv3, of soybean

Allele‐specific polymerase chain reaction (AS‐PCR) for assaying single nucleotide polymorphisms (SNPs) would be more widely used with increased availability of AS primers sufficient to distinguish between SNP alleles. AS‐PCR could be a means unambiguously to detect the presence or absence of PCR products. Examples are given here of the detection and genotyping of SNPs in the genomic DNA fragments tightly linked to two soybean mosaic virus resistance genes, Rsv1 and Rsv3, with a modified AS‐PCR procedure in soybean. The modified AS‐PCR that introduces an additional base mismatch closest to the 3′‐end of the AS primers and uses publicly available microsatellite markers as positive controls directly determined SNP alleles from primary PCR of genomic DNAs. It was demonstrated that a set of AS primers designed from two adjacent SNP loci could simultaneously detect the two SNP loci. Using the modified procedure, many SNP loci in eight soybean parental lines and F₂ individuals of three mapping populations could be genotyped. The modified AS‐PCR procedure could greatly facilitate small‐to‐medium scale marker‐assisted selection programmes for agronomically important genes.     

Genetic diversity of European spelt wheat (Triticum aestivum ssp. spelta L. em. Thell.) revealed by glutenin subunit variations at the Glu-1 and Glu-3 loci

Summary High and low molecular weight glutenin subunit (HMW-GS and LMW-GS) compositions of 270 European spelts, 15 Iranian spelts and 25 bread wheat cultivars were analyzed by one- and two-dimensional gel electrophoresis. The results revealed a total of 22 HMW-GS alleles (4 at Glu-A1, 11 at Glu-B1 and 7 at Glu-D1) and 32 allele combinations among the three Glu-1 loci. Two major genotypes of HMW-GS: 1, 13+16, 2+12 and 1, 6.1+22.1, 2+12 were found to occur in Central European spelt wheat cultivars and landraces at higher frequencies of 35 and 28%, respectively. The Glu-B1 locus displayed the greatest variation and genetic diversity index (H) was 0.69 whereas Glu-A1 and Glu-D1 showed H index values of 0.26 and 0.19, respectively. The dendrogram constructed by HMW and LMW glutenin subunit bands revealed that European spelts form a separated cluster from common wheat suggesting that spelt and common wheat form distinct groups. In addition, all 15 Iranian spelt land variety accessions differed from European spelts and possessed similar HMW-GS alleles to common wheat. Because of a wider polymorphism Central European spelt wheats are an important genetic reserviour for improving common wheat quality. Both authors contributed equally to this work     

Biochemical and molecular characterisation of Glu-1 loci in Argentinean wheat cultivars

The high molecular weight glutenin subunit (HMW-GS) composition of acollection of 107 Argentinean bread wheat cultivars was analysed bysodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE).Allelic variation at the Glu-1 loci was identified and its frequencycalculated. Eleven alleles were detected, three encoded at the Glu-A1locus, six at the Glu-B1 locus and two at the Glu-D1 locus. Alow frequency of the null allele at the Glu-A1 locus and a highfrequency of subunits 5+10 at the Glu-D1 locus were observed.Reversed phase-high performance liquid chromatography (RP-HPLC)analysis was used to further characterise HMW-GS. Two different types ofBx subunit 8 (named subunits 8 and 8) were detected, the latterhaving shorter elution time. Subunit 8 was not identifiable bySDS-PAGE. According to quantification by RP-HPLC analysis, two groupsof subunit 7 were observed. One group, with a relatively high proportionof subunit 7 (approximately 39% of the total amount of HMW-GS)appeared in cultivars with allele 7+8 at the Glu-B1 locus; asecond group of subunit 7 (around 24% of the total amount ofHMW-GS), was found in alleles 7+8, 7+8 and 7+9. Restrictionfragment length polymorphisms (RFLP) analyses of HMW-GS genes werealso carried out after digestion of genomic DNA with HindIII andTaqI restriction enzymes. The relationship between DNA fragment sizeand glutenin subunits, as estimated by electrophoretic mobility inSDS-PAGE, was also examined. The restriction enzyme TaqIdemonstrated to be a useful tool to detect homozygous plants in selectionprograms against the Glu-A1 null allele.     

Breeding for salinity resistance in mulberry (<Emphasis Type="Italic">Morus</Emphasis> spp.)

Late maturity α-amylase (LMA) is a genetic defect that is fairly widely spread in bread wheat (Triticum aestivum L.) germplasm, and recently detected in durum cultivars, which can result in unacceptably high α-amylase activity (low falling number) in ripe grain. LMA has also been observed at unexpectedly high frequency and severity in synthetic hexaploid wheats derived from the interspecific hybridisation of Triticum durum (AABB) and Aegilops tauschii (DD). Since synthetic hexaploids represent an important new source of resistances/tolerances to a range of biotic and abiotic stresses for wheat breeders, there is a pressing need to understand the mechanisms involved in LMA in synthetics and develop strategies for avoiding its adverse effects on grain quality. The objectives of this study were to firstly, compare the LMA phenotype of synthetics that varied for plant height, secondly, to characterise the LMA phenotype in groups of synthetics derived from the same durum parents and finally to determine whether LMA in primary synthetics is associated with the QTL previously reported in conventional bread wheat. More than 250 synthetic hexaploids, a range of durum cultivars and a doubled haploid population derived from Worrakatta (non-LMA) × AUS29663 (high LMA synthetic) were phenotyped and genotyped with markers reported to be linked to LMA in conventional bread wheat and markers diagnostic for the semi-dwarfing gene, Rht1. More than 85% of synthetics were prone to LMA, approximately 60% ranked as very high. Genetic control of LMA in synthetic hexaploids appeared to involve QTL located on 7B, and to a lesser extent 3B, similar to bread wheats. However, the LMA phenotype of many synthetic hexaploids appeared to be more extreme than could be explained by comparisons with bread wheat even taking into account the apparent absence of Rht1 in most genotypes. Other mechanisms, possibly triggered by the interaction between the AABB and DD genomes cannot be excluded. The presence of wild type rht1 in most synthetic hexaploids and their extreme height is difficult to reconcile with the semi-dwarf, Rht1, stature of many of the durums used in the interspecific hybridisation process. Mechanisms that could explain this observation remain unclear.     

Allelic variation at the <Emphasis Type="Italic">Glu-1</Emphasis> and <Emphasis Type="Italic">Glu-3</Emphasis> loci,presence of the 1B.1R translocation,and their effects on mixographic properties in Chinese bread wheats

Allelic variations at the Glu-1 and Glu-3 loci play an important role in determining dough properties and bread-making quality. Two hundred and fifty-one cultivars and advanced lines from four major Chinese wheat-producing zones in the autumn-sown wheat regions were used to investigate the high-molecular-weight glutenin subunits (HMW GS) and low-molecular-weight glutenin subunit (LMW GS) composition controlled by the Glu-1 and Glu-3 loci, respectively, as well as the presence of the 1B.1R translocation, and to determine the association of storage protein composition with protein content, SDS sedimentation value, and dough-mixing properties measured by mixograph. Three, nine, and four allelic variations were present at Glu-A1, Glu-B1, and Glu-D1, respectively. Subunits 1, N, 7+8, 7+9, and 2+12 are the dominant HMW GS, with frequencies of 51.3, 39.4, 38.2, 45.0, and 59.8%, respectively. Five and eight allelic variations were present at the Glu-A3 and Glu-B3 loci (data of Glu-D3 were not available), Glu-A3a, Glu-A3d, Glu-B3j (presence of the 1B.1R translocation), and Glu-B3d are the dominant LMW GS, with frequencies of 37.1, 31.7, 44.6, and 20.3%, respectively. The frequencies of allelic variation at Glu-1 and Glu-3 differ greatly in different regions. The effects of HMW GS and LMW GS on SDS sedimentation value, mixing time, and mixing tolerance were significant at P = 0.01, with Glu-D1 and Glu-B3 showing the largest contributions to mixing time and mixing tolerance. Averaged data from two locations showed that the quality effects of glutenin loci could be ranked as Glu-B3 > Glu-B1 > Glu-A1 > Glu-D1 > Glu-A3 for SDS sedimentation value, Glu-D1 > Glu-B3 > Glu-A1 = Glu-B1 = Glu-A3 for mixing time, and Glu-D1 > Glu-B3 = Glu-B1 > Glu-A3 > Glu-A1 for mixing tolerance, respectively. The significant and negative effect of the 1B.1R translocation on dough properties was confirmed. It was concluded that the high frequency of undesirable HMW GS and LMW GS and the presence of the 1B.1R translocation are responsible for the weak gluten property of Chinese germplasm; hence, reducing the frequency of the 1B.1R translocation and integration of desirable subunits at Glu-1 and Glu-3 such as 1, 7+8, 14+15, 5+10, Glu-A3d, and Glu-B3d, could lead to the improvement of gluten quality in Chinese wheats.     

Multiplex-PCR typing of high molecular weight glutenin alleles in wheat

In Australian commercial cultivars, each high molecular weight glutenin (Glu-1) homoeologous locus consists of one of two predominant alleles: Glu-A1a (subunit Ax1) or Glu-A1b (subunit Ax2*) at the GluA1 locus, Glu-B1b (Bx7 and By8 subunits) or Glu-B1i (Bx17 and By18 subunits) at the Glu-B1 locus, and Glu-D1d (Dx5 and Dy10 subunits) or Glu-D1a (Dx2 and Dy12 subunits) at the Glu-D1 locus. PCR-based assays have been developed in this study to discriminate between these common alleles at each locus. Primers specific for the Glu-A1 Ax2* gene give a single fragment of 1319 bp only in the presence of this gene. Primers targeting the Glu-B1 locus resulted in a co-dominant marker for which the Bx7 genotype produced two fragments (630 bp and 766 bp) and the Bx17 genotype a single fragment (669 bp). The third pair of primers was specific for the Dx5 gene and resulted in a single band of 478 bp. A multiplexed PCR assay was established which permitted the discrimination of the major HMW glutenins in a single PCR reaction and agarose gel assay. As the HMW glutenin composition of a wheat line is extremely important in determining the functional properties of wheat gluten, these markers are useful for the purposes of marker-assisted breeding. These markers may also be useful for the purpose of DNA-based identification of wheat varieties. This revised version was published online in July 2006 with corrections to the Cover Date.     

低分子量谷蛋白亚基GlU-A3和GlU-B3位点对小麦面筋强度和烘焙特性影响

低分子量谷蛋白亚基是小麦谷蛋白亚基的重要组成部分,黄淮麦区小麦低分子量谷蛋白亚基组成对品质的效应尚缺乏系统的研究。本研究采用SDS-PAGE方法,鉴定了黄淮麦区42个小麦品种的Glu-A3位点和Glu-B3位点低分子量谷蛋白亚基组成,分析了低分子量谷蛋白亚基对小麦面筋强度和烘烤品质的影响。结果表明,在Glu-A3位点,对面筋强度和面包烘焙品质正向效应为:d,b>a,e;在Glu-B3位点,对面筋强度正效应为:h,d>f>g,b,j,对面包烘焙品质正向效应为:h>f,d>g,b,j。Glu-A3d/Glu-B3h亚基组合具有较好的面筋强度和烘焙品质。就低分子量谷蛋白亚基单个变异位点对品质综合效应而言,Glu-B3位点对品质作用比较大,与Glu-B1位点相近,同时,高低分子量谷蛋白亚基之间存在着互作效应,以Glu-B1/Glu-A3和Glu-D1/Glu-B3位点的互作效应比较显著。Glu-A3和Glu-B3位点及其所编码的不同亚基种类对品质的效应差异显著,并且与高分子量谷蛋白亚基位点存在互作,对不同位点优质亚基的聚合将有助于小麦品质的遗传改良。     

利用SSR和SNP标记分析鲁麦14对青农2号的遗传贡献

鲁麦14既是大面积推广品种, 又是育种骨干亲本, 衍生了40多个品种, 其中青农2号(鲁麦14/烟农15//矮秆麦)是近年审定的小麦品种。本研究利用350个SSR标记和小麦90k芯片检测的26 026个SNP标记, 解析了鲁麦14对青农2号的遗传贡献。鲁麦14和烟农15分别含有1/4和1/2蚰包麦血统, 基因组分子标记分析结果显示, 这两个品种有55.42%的SSR位点一致, 而SNP位点一致性高达71.53%。选择亲本间差异位点, 分析鲁麦14和烟农15对青农2号的遗传贡献, 结果表明鲁麦14对青农2号的贡献大于烟农15, 青农2号与亲本鲁麦14、烟农15分子标记的一致性, SSR标记分别为54.11%和36.30%, SNP标记分别为72.55%和26.98%。依据高通量SNP标记结果, 从染色体水平看, 烟农15贡献率超过50%的染色体有2B、3B和6A; 而鲁麦14在除此之外的18条染色体的遗传贡献率大于50%。青农2号遗传组成图谱揭示了遗传物质多以较大染色体片段形式从亲本传递至子代。对亲本和子代进行多年多点的农艺性状调查, 发现青农2号的旗叶长、旗叶宽、穗下节间长、穗叶距、抽穗度等株型相关性状及千粒重、粒长等产量相关性状与鲁麦14相近, 株高、生育期等性状与烟农15相近。本文从分子层面解析育种亲本对子代的遗传贡献, 为分子标记辅助育种提供了依据和理论基础。     

Variation at Glu-1 Loci in Club Wheats

Hexaploid club wheats (Triticum aestivum L.) possess unique end-use quality characteristics and are grouped as a U.S. market subclass of soft white common wheat. Although there have been many reports on associations among high-molecular-weight glutenin storage protein (HMW-Glu) sub-units with end-use quality in hard wheats; there has been very limited work done on surveying the club wheats for these subunits. The HMW-Glu subunits, spike types and grain color were determined for 41 U.S. club wheat cultivars and 79 club accessions obtained from the National Small Grains Collection (NSGC), USDA-ARS. Accession ‘Harlan JR 35’ (PI 420948), which appears morphologically to be a hexaploid club wheat, was determined to be tetraploid. Egyptian line ‘Maya II-Tel's’ (PI 422288) was shown to have previously undescribed HMW-Glu subunits. In the U.S. club wheats the most common HMW-Glu subunits were: null, 49 % (Glu-A1); 6, 37 % (Glu-B1); and 2 + 12, 94 % (Glu-D1). In the NSGC group the most common HMW-Glu sub-units were: 2*, 52 % (Glu-A1); 7 + 8, 31 % (Glu-B1); and 2 + 12, 92 % (Glu-D1). The high frequency of subunits 2 + 12 in the club wheat groups has not been observed previously in numerous surveys of diverse wheat cultivars. The Glu-B1 subunits 6 (without subunit 8) and 20 which have not been reported in US red wheats, were shown to be common in both club wheat groups. A comparison of diversity indices, including previous studies on HMW-Glu subunit frequencies on all market classes of wheat, showed that the club groups are as diverse for the Glu-A1 and Glu-B1 loci and less diverse for the Glu-D1 locus.     

Single nucleotide polymorphism discovery and linkage mapping of lipoxygenase-2 gene (Lx 2) in soybean

Lipoxygenase-2 (Lx ₂) in soybean seed is mainly responsible for generation of grassy-beany and bitter flavors. Genetic elimination of this flavor can be accelerated by the development of single nucleotide polymorphism (SNP) markers linked to Lx ₂. A frame map based on simple sequence repeat (SSR) markers was constructed first using a recombinant inbred line (RIL) population of Pureunkong × Jinpumkong 2. Sixty-five SSR markers were incorporated into 13 linkage groups (LGs) spanning a total of 737 cM. Among five primer pairs designed from the Lx ₂ gene sequence, one produced an amplicon with sequence variations between Pureunkong and Jinpumkong 2. Three SNPs, T/C, G/A and C/A, were identified at 251,367 and 420 bp, respectively, in the intron region of the 804 bp amplified product. Using single base chain extension based on the capture probe sequence in the 5' region of the T/C SNP, the 90 RILs were genotyped for each allele of Lx ₂. The allelic segregation for the SNP linked toLx ₂ was in accordance with the expected ratio of 1:1 in the RIL population. Based on the results of linkage analysis between Lx ₂ and the SSR markers, Lx ₂ was found to be positioned on one end of LG F in the frame map, flanked by the SSR markers Satt522 and Sat074. This study demonstrates that SNP markers closely linked to Lx ₂can be developed to facilitate marker-assisted selection and fine mapping of the region around this locus. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molecular mapping of powdery mildew resistance genes in wheat: A review

Powdery mildew, caused by Blumeria graminis f. sp. tritici (syn. Erysiphe graminis f. sp. tritici), is one of the most important diseases of common wheat (Triticum aestivum L.) worldwide. Molecular mapping and cloning of genes for resistance to powdery mildew in hexaploid wheat will facilitate the study of molecular mechanisms underlying resistance to powdery mildew diseases and help understand the structure and function of powdery mildew resistance genes, and permit marker-assisted selection in breeding programs. So far, 48 genes/alleles for resistance to powdery mildew at 32 loci have been identified and located on 16 different chromosomes, of which 21 resistance genes/alleles have been tagged by restriction fragment length polymorphisms (RFLPs), random-amplified polymorphic DNAs (RAPDs), amplified fragment length polymorphisms (AFLPs), sequence characterized amplified regions (SCARs), sequence-tagged sites (STS) or simple sequence repeats (SSRs). Several quantitative trait loci (QTLs) for adult plant resistance (APR) to powdery mildew have been associated with molecular markers. The detailed information on chromosomal location and molecular mapping of these genes has been reviewed. Isolation of powdery mildew resistance genes and development of valid molecular markers for pyramiding resistance genes in breeding programs is also discussed.     

Allelic variation and composition of HMW-GS in advanced lines derived from d-genome synthetic hexaploid / bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

The objective of this study was to identify allelic variations at Glu-1 loci of wheat (Triticum aestivum L.) advanced lines derived from hybridization of bread wheat and synthetic hexaploid wheats (2n = 6x = 42; AABBDD). Locally adapted wheat genotypes were crossed with synthetic hexaploid wheats. From the 134 different cross combinations made, 202 F₈ advanced lines were selected and their HMW-GS composition was studied using SDS-PAGE. In total, 24 allelic variants and 68 HMW-GS combinations were observed at Glu-A1, Glu-B1, and Glu-D1 loci. In bread wheat, the Glu-D1 locus is usually characterized by subunits 1Dx2+1Dy12 and 1Dx5+1Dy10 with the latter having a stronger effect on bread-making quality. The subunit 1Dx5+1Dy10 was predominantly observed in these advanced lines. The inferior subunit 1Dx2+1Dy12, predominant in adapted wheat germplasm showed a comparative low frequency in the derived advanced breeding lines. Its successful replacement is due to the other better allelic variants at the Glu-D1 locus inherited in these synthetic hexaploid wheats from Aegilops tauschii (2n = 2x = 14; DD).     

Gli-B3/Glu-B2 encoded prolamins do not affect selected quality properties in the durum wheat cross 'Abadía'×'Mexicali 75'

A study was made of the effects of the Gli-B3/Glu-B2 encoded prolamins on durum-wheat quality. Twenty-six F₃ lines from the durum wheat cross ‘Abadia’בMexicali 75’ were analysed electrophoretically for prolamin composition and for the following quality parameters: SDS sedimentation value, mixing properties, and percentage grain protein and percentage vitreous kernels. The results showed that the presence or absence of the Gli-B3/Glu-B2 encoded prolamins did not result in any significant difference in the quality characteristics of the F₃ lines; however, as expected, the LMW glutenins encoded at Glu-B3 showed large differences and are therefore the major prolamins influencing durum wheat gluten quality.     

Molecular genetic analysis of flour color using a doubled haploid population in bread wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Flour color is an important trait in the assessment of flour quality for the production of many end products. In this study, quantitative trait loci (QTLs) with additive effects, epistatic effects, and QTL × environment (QE) interactions for flour color in bread wheat (Triticum aestivum L.) were studied, using a set of 168 doubled haploid (DH) lines derived from a Huapei 3 × Yumai 57 cross. A genetic map was constructed using 283 simple sequence repeats (SSR) and 22 expressed sequence tags (EST)-SSR markers. The DH and parents were evaluated for flour color in three environments. QTL analyses were performed using QTLNetwork 2.0 software based on a mixed linear model approach. A total of 18 additive QTLs and 24 pairs of epistatic QTLs were detected for flour color, which were distributed on 19 of the 21 chromosomes. One major QTL, qa1B, closely linked to barc372 0.1 cM, could account for 25.64% of the phenotypic variation of a* without any influence from the environments. So qa1B could be used in the molecular marker-assisted selection (MAS) in wheat breeding programs. The results showed that both additive and epistatic effects were important genetic basis for flour color, and were also sometimes subject to environmental modifications. The information obtained in this study should be useful for manipulating the QTLs for flour color by MAS in wheat breeding programs. Kun-Pu Zhang and Guang-Feng Chen contributed equally to this study.     

Allelic variation at the storage protein loci of 55 US-grown white wheats

Fifty soft white and hard white wheat cultivars (Triticum aestivum L.), and five club wheat cultivars (T. compactum L.) were partially characterized in terms of their storage protein compositions, i.e. gliadins, and high molecular weight and low molecular weight glutenin subunits (HMW-GS and LMW-GS, respectively). At the Glu-1 loci, HMW-GS composition 1,7 + 9,2+ 12 was found to be predominant, being expressed in 11 cultivars out of 55. The most common alleles at the loci coding for gliadins and LMW-GS were found to be Gli-A1/Glu-A3a (43.6%), Gli-B1/Glu-B3b (36.4%), Gli-D1a/Glu-D3a (38.1%) and Gli-Dli/Glu-D3a (21.8%). Two-dimensional fractionation (acid-poly-acrylamide gel electrophoresis (A-PAGE) × sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE)) of reduced and alkylated glutenins revealed that the number and the relative mobility of LMW-GS polypeptides were different from those reported for the corresponding Glu-3 alleles of hard-bread wheat cultivars. This result could account for the different technological properties of soft white wheats compared with hard-bread wheat cultivars, owing to the major impact of LMW-GS on dough quality.     

Seed Storage Proteins of Triticum turgidum ssp. dicoccoides and Their Effect on the Technological Quality in Durum Wheat

F₄ progenies of a cross between durum wheat cultivar ‘Creso’ and an accession of Triticum turgidum ssp. dicoccoides with high protein content were analysed by two different electrophoretic procedures (A-PAGE and SDS-PAGE). Variation of storage proteins at the Glu-A1, Glu-B1, Glu-B3 and Gli-B1 loci was studied. Electrophoretic analyses have shown that parents contain different alleles at each of the four loci considered and that protein components of T. dicoccoides are uncommon among cultivated wheats. Recombination between the Glu-B3 and Gli-B1 loci was observed. To determine the effects of the allelic variants on gluten properties, F₅ grains from every F₄ line were analysed for protein content and SDS-sedimentation value. Gluten quality was strongly associated with the allelic type of proteins coded by the Glu-B3 locus and, to a lesser extent, to those coded by Glu-A1. Mean sedimentation value of progenies possessing the ‘Creso’Glu-B3 allele was significantly greater than that showing the T. dicoccoides allele. High molecular weight glutenin sub-units coded by the T. dicoccoides Glu-A1 locus were also associated with larger sedimentation values than null form of ‘Creso’. Results of SDS-test, obtained for recombinants between Glu-B3 and Gli-B1, confirmd that specific omega- and gamma-gliadins are only genetic markers of quality, whereas variation for LMW glutenin subunits coded at Glu-B3 is responsible for differences in gluten properties.