SDS-PAGE of the high-molecular-weight subunits of wheat glutenin and the characterization of 1R (1B) substitution and 1BL/1RS translocation lines

Summary The high-molecular-weight subunits of glutenin from wheat 1R(1B) substitution and 1BL/1RS translocation lines were fractionated by SDS-PAGE. Two new subunits denoted R₁ and R₂ were characterized in 1R(1B) substitution, but not in 1BL/1RS translocation lines. R₁ and R₂ were proved to be rye proteins by 2d electrophoresis (NEPHGE x SDS-PAGE).In contrast to literature citations it was demonstrated that the cultivar Winnetou is a 1R(1B) substitution line and the cultivars Clement and Mildress both are 1BL/1RS translocation lines.     

Genetical analysis of contribution of low-molecular-weight glutenin subunits to dough strength in common wheat (Triticum aestivum L.)

To evaluate the effect of low-molecular-weight glutenin subunit (LMW-GS) genes on dough strength, locus-specific primers of LMW-GS genes and gliadin bands tightly linked to LMW-GS genes were analyzed in common wheat. Segregation analysis of the F₂ progeny from a cross between Haruhikari, a good bread-making quality cultivar, and Asakaze-komugi, a poor bread-making quality cultivar, showed that dough strength significantly correlated with one amplified LMW-GS gene located at the Glu-B3 locus from Haruhikari. There was no specific reference to the gliadin bands identified as promising markers in the cross under study. The LMW-GS gene of Haruhikari had a seven amino-acid deletion in the repetitive domain relative to Asakaze-komugi, as well as six amino-acid substitutions, three of which would be expected to cause changes in hydrophilicity. The presence of the LMW-GS gene and other LMW-GS genes tightly linked to it may affect the dough strength of wheat.     

Variation in high molecular weight glutenin subunits in landraces of hexaploid wheat from Afghanistan

Summary Variation for high molecular weight (HMW) glutenin subunits is reported in Afghan hexaploid wheat landraces from different locations in the country ranging in altitude from 395 to 3170 metres. The variation appeared to be independent of the altitude and geographical location of the landraces. Studies of a number of samples from each of five sites revealed that at some sites there was allelic variation at theGlu-A1 andGlu-B1 loci coding from HMW glutenin subunits, but there was no variation at theGlu-D1 locus within and between sites.     

Additive and epistatic effects of allelic variation at the high molecular weight glutenin subunit loci in determining the bread-making quality of breeding lines of wheat

Summary The relation has been studied between the high molecular weight glutenin (HMWg) subunit alleles and the bread-making quality of 226 lines of winter wheat (T. aestivum L.), grown in The Netherlands. The lines represented a wide range of genetic backgrounds, and had not been selected for quality, in contrast to the established varieties used by other authors.The variation in HMWg subunit genotypes accounted for about 20% of the total variation in loaf volume among the lines. Most important was the allelic variation at the Glu-D1 locus. The Glu-D1 allele encoding the subunits 5+10 was superior to its allelic counterpart, encoding 2+12. The difference in average of loaf volume between groups of lines containing 5+10 or 2+12 was negatively related with protein content of the flours. When protein content was below 9.2%, no effect of allelic variation at the Glu-D1 locus was present. Epistatic effects between the Glu-I loci also contributed to the variation in loaf volume of the lines: i.e. the effect of allelic variation at Glu-A1 and Glu-B1 depended on the allele present at the Glu-D1. The contribution of the epistatic effects was about half the contribution of the additive effects, and should therefore be included in predictive models for bread-making quality.     

Influence of genotype and culture conditions on the production of embryos from anthers of tetraploid wheat (Triticum turgidum)

Summary Anther culture of 10 tetraploid wheat (Triticum turgidum) genotypes and two backcross lines representing a wide range of genetic variation was studied in a randomized block design with three replications. Each replication consisted of 2 pots with 3 plants. The day length was 16h and temperature 25° C/15°C for day/night in a controlled greenhouse where the anther donor plants were grown. Two different treatments were used for anther culture. The first one was potato 2 medium (Chuang et al., 1978) modified by adding 0.5 mg/l glutamine and solidified by gelrite (4g/l) (Henry & De Buyser, 1981). Cultures were incubated in light (15 E m^–2 S^–1) at 26°C at 16h day length. The second medium was described by Fadel & Wenzel (1990), differing from the first by the nature of the sugar (maltose) and consistency of the medium (semiliquid by ficoll). Anther cultures were incubated in the dark at 28°C. The study of about 1300 anthers per genotype and treatment showed that both genotype and treatment affected embryo formation of tetraploid wheat. The backcross lines exhibited significant differences for androgenic abilities when compared to their common parent. Most of the genotypes were medium dependent for androgenesis and revealed significant interactions with the two treatments. Five green plantlets were regenerated and fertile doubled haploid plants were obtained from three out of the 12 studied genotypes.     

The high-molecular-weight glutenin subunit composition of Soviet wheat varieties

Summary One hundred and twenty-eight wheat varieties bred in the Soviet Union were screened for the composition of high-molecular-weight (HMW) subunits of glutenin. In general, variability was low compared to that seen in varieties from other countries. However, varieties from different regions showed distinctive patterns, in some cases clearly due to the use of particular parents in certain breeding programmes, but in others possibly due to the adaptive value of particular alleles to the environmental conditions under which the varieties were bred. For example, among spring varieties, the Glu-D1 allele encoding subunits 2+12 was more common in varieties from areas with limited rainfall than was the allele encoding subunits 5+10.The pattern of HMW glutenin subunits amongst varieties with superior bread-making quality showed few differences from that amongst bread-making varieties of lower quality.Abbreviations BMQ bread-making quality - HMW high-molecular-weight - LMW low-molecular-weight - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis     

Genetics of morphological traits in wild wheat,Triticum turgidum var.dicoccoides

Summary The mode of inheritance, linkage groups, and chromosomal location of 23 morphological and 4 biochemical traits were characterized in the wild tetraploid emmer wheat,Triticum turgidum var.dicoccoides. These traits were described and their mode of inheritance was determined by their segregation in four F₂ populations derived from crosses between four var.dicoccoides accessions and a tetraploiddurum cultivar. Linkage groups among the genes encoding for these traits were determined or postulated, and their chromosomal location was deduced by linkage to previously located genes. The genetic control of the following traits was characterized and is first reported here: black keel; hairy leaf sheath; hairy auricles; hairy rachilla; hairy kernel brush; obtuse flag leaf; and curved neck/peduncle. The linkage data indicated that developmentally-related genes tended to occur in clusters.     

High molecular weight glutenin subunits of current bread wheats grown in Iran

Variation of high molecular weight gluteninsubunits (HMW-GS) at the Glu-1 lociwas studied using SDS-PAGE method in 43advanced lines or cultivars commonly grownin Iran. Fourteen alleles and 21 alleliccompositions were detected. Among the 43bread wheats analysed only five showed aunique HMW-GS composition. The mostfrequent HMW-GS patterns were 2^*, 7+8,2+12 and 2^*, 17+18, 2+12 which wereobserved in 13 and six cultivars,respectively. In the remainings, each twoto three lines or cultivars showed a commonHMW-GS pattern. Therefore, allelicvariation at Glu-1 loci is of limitedvalue for cultivar identification comparedwith loci controlling gliadins. Sevencultivars were observed to consist of twoto three biotypes with different alleles.In cultivar Mahdavi a biotype showedinactivity at the Glu-B1 locus. Analready reported rare subunit pair'2^***+12' at Glu-D1locus was found in cultivar Kavir. Theresults of scoring cultivars for theirquality based on the HMW-GS compositionswith an average score of eight, wasgenerally good. Cultivars Inia, Tajan, andadvanced lines N-75-11 and N-75-15 showedquality score equal to 10, whereas Alamootand C-75-5 showed quality scores equal tofive. The quality of former and latterlines and cultivars were considered highestand lowest, respectively. The resultsobtained in this study are useful inbreeding programs to improve bread makingquality, developing uniformity andimproving heterogeneous cultivars by meansof selection of the best genotypes.     

Molecular mapping and detection of the yellow rust resistance gene Yr26 in wheat transferred from Triticum turgidum L. using microsatellite markers

Yellow rust (stripe rust), caused by Puccinia striiformis Westend f. sp. tritici, is one of the most devastating diseases of wheat throughout the world. Wheat-Haynaldia villosa 6AL.6VS translocation lines R43, R55, R64 and R77, derived from the cross of three species, carry resistance to both yellow rust and powdery mildew. An F₂ population was established by crossing R55 with the susceptible cultivar Yumai 18. The yellow rust resistance in R55 was controlled by a single dominant gene, which segregated independently of the powdery mildew resistance gene Pm21 located in the chromosome 6VS segment, indicating that the yellow rust resistance gene and Pm21 are unlikely to be carried by the same alien segment. This yellow rust resistance gene was considered to beYr26, originally thought to be also located in chromosome arm 6VS. Bulked Segregation Analysis and microsatellite primer screens of the population F₂ of Yumai 18 × R55 identified three chromosome 1B microsatellite locus markers, Xgwm11, Xgwm18 and Xgwm413, closely linked to Yr26. Yr26 was placed 1.9 cM distal of Xgwm11/Xgwml8, which in turn were 3.2 cM from Xgwm413. The respective LOD values were 21 and 36.5. Therefore, Yr26 was located in the short arm of chromosome 1B. The origin and distribution of Yr26 was investigated by pedigree, inheritance of resistance and molecular marker analysis. The results indicated that Yr26 came from Triticum turgidum L. Three other 6AL.6VS translocation lines, R43, R64 and R77, also carried Yr26. These PCR-based microsatellite markers were shown to be very effective for the detection of the Yr26 gene in segregating populations and therefore can be applied in wheat breeding. This revised version was published online in July 2006 with corrections to the Cover Date.     

Location of genes for high grain protein percentage and other quantitative traits in wild wheat Triticum turgidum var. dicoccoides

Summary The genetic control of grain protein percentage (GPP) in the wild tetraploid wheat, Triticum turgidum var. dicoccoides, was determined by crossing four accessions of this taxonomic variety with durum cultivar Inbar, and analyzing the parents, F₁ and F₂ populations. Reciprocal crosses indicated no cytoplasmic effect on GPP. The F₂ variation was continuous in all crosses, showing no transgressive segregation. However, crosses between different accessions of var. dicoccoides showed transgressive segregation indicating the presence of different genes for high GPP in these accessions. Grain protein percentage was mostly codominant with high GPP, showing either no dominance, or a weak dominance. Heritability coefficients (broad sense) ranged from 0.30 to 0.53. Correlation coefficients between GPP and yield components were usually significantly negative, with the exception of the number of spikelets per spike, and in some crosses, grain weight.The number and chromosomal location of genes coding for high GPP were determined by the association between GPP and 27 markers (23 morphological and 4 biochemical markers). For this purpose, the genetic control of these markers, their linkage groups and chromosomal location were studied. At least four loci for high GPP that segregated in the F₂ populations are suggested: one on chromosome arm 1AS, marked by the black glume gene (Bg); one on 1BS, marked by the HMW gliadin locus Gli-B1; one on group 5, marked by the genes for beaked glume (Bkg) and toothed palea (Tp); and one on group 7, marked by the kinky neck gene (Kn). The relationship between GPP and several yield components was studied in a similar manner. In general, loci of markers that correlated positively with high GPP were not correlated with a decrease in yield components. Moreover, several loci of var. dicoccoides were associated with an increase in yield components.The utilization of markers for chromosomal location of genes coding for quantitative traits is compared to the technique of aneuploid analysis, commonly used in wheat. The significance of the above findings for breeding is discussed.     

Improvement of somatic embryogenesis and plant regeneration from durum wheat (Triticum turgidum var. durum Desf.) scutellum and inflorescence cultures

Scutellum and inflorescence explants of four genotypes of durum wheat(Triticum turgidum var. durum Desf.) were used to define culture conditions to obtain high frequencies of embryogenesis and plant regeneration in vitro. Under all conditions tested, scutellum cultures gave higher frequencies of embryogenesis and plant regeneration than inflorescence cultures. Two different auxins, 2,4-D(2,4-dichlorophenoxyacetic acid) and picloram(4-amino-3,5,6-trichloropicolinic acid), were compared for their effect on scutellum and inflorescence explant response in vitro. Picloram was found to significantly increase the frequency of plant regeneration from both explants. When cultures were grown on regeneration medium containing zeatin for two three-week passages, the frequency of plant regeneration increased by between 20–30% compared with cultures exposed to hormones for a single three-week passage. Finally, the addition of 1 mg/l 6-BAP (6-benzyl aminopurine) to the plantlet growth medium was found to enhance tiller production in regenerants. The optimized culture conditions were applicable to the four genotypes tested and frequencies of plant regeneration varied between 97% to 100% for scutellum cultures (2 mg/l picloram in induction medium) and between45% and 80% for inflorescence cultures (4 mg/l picloram in induction medium). The number of plants regenerated per explant was improved over previous procedures, with means of 34 plants per scutellum, and 16 plants per inflorescence explant. This revised version was published online in July 2006 with corrections to the Cover Date.     

High molecular weight glutenin subunit composition of Chinese bread wheats

Summary The endosperm storage proteins of 205 Chinese bread wheat cultivars and advanced lines were fractionated by SDS-PAGE to determine their high molecular weight (HMW) glutenin subunit composition. Seventeen alleles were identified: three at Glu-A1, eight at Glu-B1, and six at Glu-D1. The most common alleles were Null, 1, 7+8, 7+9, and 2+12. The results indicate that wheats from different regions differ in their frequencies of HMW glutenin subunits, however, none of the subunits could be related to specific environments. The glutenin quality scores of Chinese wheats ranged from 3 to 10, with an average of 6.7. Increasing quality scores have implications in improving steam-bread making quality for Chinese consumers. On the basis of HMW glutenin subunit composition, Chinese wheats are close to European wheats, especially Italian wheats because several Italian introductions are widely distributed in the pedigrees of Chinese wheat.     

Increased grain protein content and its association with agronomic and end-use quality in two hard red spring wheat populations derived from Triticum turgidum L. var. dicoccoides

Suitability of wheat (Triticum aestivum L.) for many food products depends on its unique protein. Elevated grain protein content (GPC) and its quality influences the bread making properties of wheat. The objective of this study was to examine the association of elevated GPC with agronomic and end-use quality in two hard red spring wheat recombinant inbred (RI) populations derived from wild emmer (Triticum turgidum L. var. dicoccoides). The two hard red spring populations (ND683/Bergen and Glupro/Bergen) were developed using a single-seed-descent method. ND683 and ‘Glupro’ are high in GPC (180 g kg^-1), presumably due to the introgression of gene(s) from Triticum turgidum L. var. dicoccoides and ‘Bergen’ is low in GPC (145 g kg^-1). From each of the two populations 12 high- and 12 low-GPC RI lines (F_5:7) were selected for replicated testing at two North Dakota (ND) locations in 1995. In both populations, the high-GPC lines had significantly (p < 0.05) higher values compared to the low-GPC lines for mean GPC and water absorption. Mean grain yield of the high-GPC lines was not significantly different from the low-GPC lines in both populations. In the ND683/Bergen population, the high-GPC lines had significantly (p < 0.05) higher values than the low-GPC lines for mean plant height, days to heading, and flour extraction. GPC was significantly (p < 0.05)and negatively associated with test weight and also significantly (p < 0.01) and positively associated with water absorption in the Glupro/Bergen population. In these populations, results suggested that it may be possible to select lines that combine higher GPC and acceptable yield level, but later in maturity and taller in plant height. This revised version was published online in July 2006 with corrections to the Cover Date.     

Variation in landraces of durum wheat (T. turgidum L. conv. durum (Desf.) M.K.) from Turkey

Summary Durum wheat is historically an important crop in Turkey. Diverse durum wheat germplasm has been recorded many times in Turkish collections. 812 single plant genotypes from 190 durum wheat populations of 23 provinces in Turkey have been studied for number of days to germination, tillering, shooting, heading, maturity, and yield per plant. Variation in samples for traits studied was large enough and subsamples with different characteristics were identified. Grouping samples into provinces and altitudes of origin have revealed that variation in samples existed for some traits depending on province and altitude of origin. Yield per plant were not correlated with any of the developmental stages: but developmental stages were correlated with each other in varying magnitudes. Variation in yield per plant was not explained as well by developmental stages studied under a dry-cold environment. Further studies on samples needed to explore genetic variation more for other traits of economic importance.     

The effect ofGlu-B1 high molecular weight glutenin subunits on biscuit-making quality of wheat

Summary The aim of this study was to assess the effect of specificGlu-B1 HMW-GS on biscuit-making quality. Three soft spring wheat cultivars with the sameGlu-A1 andGlu-D1 HMW-GS, but differentGlu-B1 HMW-GS were used in crosses. F₂₄ derived lines were developed from these crosses.Glu-B1 HMW-GS 6+8 and 17+18; and 7+9 and 17+18 were compared. Lines with HMW-GS 6+8 versus those with HMW-GS 17+18 had a higher flour protein- and alveograph P/L ratio, shorter mixograph mixing time, more vitreous kernels, and a lower alveograph distensibility and strength (all values significant at p=0.05). Lines with HMW-GS 7+9 compared to those with 17+18 showed significant differences for flour extraction and biscuit diameter. The presence of HMW-GS 17+18 was significantly correlated with several biscuit-making quality characteristics in the Dirkwin/Zaragosa F₂₄ lines but not in the Waverley/Zaragosa F₂₄ lines, therefore the effect of HMW-GS 17+18 was modified by the genetic background in which they were expressed.     

Effects of substituted D genome chromosomes on photosynthetic rate of durum wheat (Triticum turgidum L. var. durum)

Summary A durum wheat cultivar Langdon (LDN) and fourteen disomic D genome chromosome substitution lines of Langdon, where A or B genome chromosomes were replaced with homoeologous D genome chromosomes of Chinese Spring (CS), were used to assess the compensatory effect of the D genome chromosomes on photosynthetic rates at tetraploid level. The LDN 1D(1B) and LDN 3D(3B) lines showed significantly higher photosynthetic rates than Langdon, whereas LDN 1D(1A) and LDN 3D(3A) lines were not greatly different from Langdon. It appears that chromosomes 1B and 3B decrease photosynthesis. This suggests the differentiation of the effects on the photosynthesis within the first and third homoeologous groups. Substitution with the 2D chromosomes did not compensate the effects of either 2A or 2B chromosomes as it reduced photosynthetic rate compared to plant with either chromosomes 2A or 2B. Tetra CS had a higher photosynthetic rate than CS and Penta CS. The photosynthetic rate of CS was similar to that of Penta CS, which lacked one set of D genome. The results suggest that it may be possible to increase photosynthesis, if both sets of the D genome were entirely removed from hexaploid wheat. However, it is difficult to conclude that the lower rate of photosynthesis of the hexaploids was mainly attributable to D genome chromosome effects, because we did not find a dose dependent effect of D genome. Homoeologous differentiation of chromosomes may be involved in photosynthesis.     

Evaluation of fresh pasta-making properties of extra-strong common wheat (Triticum aestivum L.)

The relationship between characterictics of flour of common wheat varieties and fresh pasta-making qualitites was examined, and the fresh pasta-making properties of extra-strong varieties that have extra-strong dough were evaluated. There was a positive correlation between mixing time (PT) and hardness of boiled pasta, indicating that the hardness of boiled pasta was affected by dough properties. Boiled pasta made from extra-strong varieties, Yumechikara, Hokkai 262 and Hokkai 259, was harder than that from other varieties and commercial flour. There was a negative correlation between flour protein content and brightness of boiled pasta. The colors of boiled pasta made from Yumechikara and Hokkai 262 grown under the condition of standard manuring culture were superior to those of boiled pasta made from other varieties. Discoloration of boiled pasta made from Yumechikara grown under the condition of heavy manuring culture was caused by increase of flour protein content. On the other hand, discoloration of boiled pasta made from Hokkai 262 grown under the condition of heavy manuring culture was less than that of boiled pasta made from Yumechikara. These results indicate that pasta made from extra-strong wheat varieties has good hardness and that Hokkai 262 has extraordinary fresh pasta-making properties.     

Carbon isotope discrimination and indirect selection for transpiration efficiency at flowering in lentil (Lens culinaris Medikus), spring bread wheat (Triticum aestivum L.) durum wheat (T. turgidum L.), and canola (Brassica napus L.)

Summary Carbon isotope discrimination has been proposed to indirectly select for transpiration efficiency in several C₃ species. To determine the effectiveness of carbon isotope discrimination to indirectly select for transpiration efficiency at flowering we measured: (i) variability for carbon isotope discrimination, (ii) the magnitude of the genotype-by-water regime interaction for carbon isotope discrimination, and (iii) the magnitude of the correlation between carbon isotope discrimination and both transpiration efficiency and dry matter at flowering. Ten lentil (Lens culinaris Medikus) genotypes, ten wheat genotypes (eight spring wheat (Triticum aestivum L.) and two durum wheat (Triticum turgidum L.)), and ten canola (Brassica napus L.) genotypes were grown in a greenhouse at 80, 50 and 30% field capacity. Above ground dry matter was harvested at 80% flowering and dry matter at flowering, water used, and carbon isotope discrimination determined. Genotype variation for carbon isotope discrimination was observed in lentil, spring wheat and canola at each water regime, and when averaged over the three water regimes. The largest range in carbon isotope discrimination among lentil and spring wheat genotypes was observed using the wet regime; whereas, the dry regime provided the largest range for CID in canola genotypes. In all species the genotype-by-water regime interaction for carbon isotope discrimination was nonsignificant. The correlation between carbon isotope discrimination and dry matter at flowering was inconsistent across water regimes and years. In addition, in all three crops, no correlation was observed between carbon isotope discrimination and transpiration efficiency at any of the water regimes, and when averaged over water regimes and years. These results suggests that under the conditions reported here, carbon isotope discrimination cannot be used effectively to indirectly select for transpiration efficiency in lentil, spring wheat, and canola.Abbreviations CID carbon isotope discrimination - DMF dry matter at flowering     

Cloning and characterization of a novel low molecular weight glutenin subunit gene at the Glu-A3 locus from wild emmer wheat (Triticum turgidum L. var. dicoccoides)

Amplification of the coding region, and upstream and downstream sequences of a low-molecular-weight glutenin subunits (LMW-GS) gene from wild emmer wheat (Triticum turgidum L. var. dicoccoides, 2n = 4x = 28, AABB) accession TD22 was carried out using designed allele-specific PCR (AS-PCR) primers. The complete 1,176 bp sequence of a novel LMW-i type subunit gene at the Glu-A3 locus, named LMW-TD22, is described. Analysis of the nucleotide and deduced amino acid sequences showed that this gene possessed striking characteristics although its molecular structure was generally similar to those of previously reported i-type LMW-GS genes that were isolated from common wheat and related species. The deduced amino acid sequence of LMW-TD22 gene contained 390 amino acid residues with the predicted molecular weight being 43,009.3 Da, which appeared to be the longest gene among the cloned LMW-i type genes from bread wheat and related species. The distinct feature of LMW-TD22 was two long polyglutamine stretches of 12 and 17 glutamines occurring in the repetitive and C-terminal domains as well as a cysteine residue present in the seventh amino acid residue of the signal peptide. These polyglutamine repeats are believed to improve the structure of gluten polymer and increase the strength of dough formed from the polymer. In addition, the putative 44 k subunit encoded by LMW-TD22 was verified by N-terminal microsequencing, gel electrophoresis and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) analysis. Certain types of post-translational modifications, such as phosphorylation and glycosylation, may be associated with this LMW-i type subunit. A. Wang and Y. Xiao made equal contribution to the research as the first author.