Allelic variation of HMW and LMW glutenin subunits, HMW secalin subunits and 75K gamma-secalins of hexaploid triticale

Although the endosperm storage protein of hexaploid triticale have alreadybeen analysed, the allelic diversity of glutenins and secalins remains to bedescribed. Analysis, by SDS-PAGE, of about one thousand F2 seeds fromten triticale crosses allowed the inheritance of these storage proteins to bestudied in order to determine their allelic forms and to assign them toparticular chromosomes. Two new alleles encoding HMW subunits ofglutenin and five new alleles encoding HMW subunits of secalin weredetermined at Glu-B1 and Glu-R1 loci respectively. In additionto the three allelic forms of 75K gamma-secalins encoded at Gli-R2and previously reported, a null form was found. A nomenclature for theseproteins and their corresponding alleles was suggested. The composition ofB-LMW glutenin subunits of hexaploid triticale was described and allelicforms were determined: Five alleles were encoded at Glu-A3 andseven at Glu-B3 including one and two new allelic formsrespectively.     

Influence of HMW and LMW glutenin subunits on gluten strength in hexaploid tritordeum

In hexaploid tritordeum, the storage proteins of advanced progenies from two crosses between three hexaploid tritordeum lines were analysed. The effects of allelic variation at the Glu-B1, Glu-H^ch1 and Glu-A3/Glu-B3 loci on gluten strength, as measured by the sodium dodecyl sulphate sedimentation test, were determined using seeds from both crosses. Neither of the two alleles found at the Glu-B1 locus in the crosses analysed had significant effects on gluten strength, but allelic variation at the Glu-H^ch1 and Glu-A3/Glu-B3 loci showed significant differences in effects on gluten strength.     

Allelic variation and genetic diversity of HMW glutenin subunits in Chinese wheat (Triticum aestivum L.) landraces and commercial cultivars

Wheat landraces have abundant genetic variation at the Glu-1 loci, which is desirable germplasms for genetic enhancement of modern wheat varieties, especially for quality improvement. In the current study, we analyzed the allelic variations of the Glu-1 loci of 597 landraces and 926 commercial wheat varieties from the four major wheat-growing regions in China using SDS-PAGE. As results, alleles Null, 7+8, and 2+12 were the dominant HMW-GSs in wheat landraces. Compared to landraces, the commercial varieties contain higher frequencies of high-quality alleles, including 1, 7+9, 14+15 and 5+10. The genetic diversity of the four commercial wheat populations (alleles per locus (A) = 7.33, percent polymorphic loci (P) = 1.00, effective number of alleles per locus (Ae) = 2.347 and expected heterozygosity (He) = 0.563) was significantly higher than that of the landraces population, with the highest genetic diversity found in the Southwestern Winter Wheat Region population. The genetic diversity of HMW-GS is mainly present within the landraces and commercial wheat populations instead of between populations. The landraces were rich in rare subunits or alleles may provide germplasm resources for improving the quality of modern wheat.     

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.     

The effect of indirect tests for grain quality on the grain yield and industrial quality of bread wheat

The objective of this study was to examine the effect of selection using three indirect tests for grain quality on grain yield and dough, and baking properties, measured as alveograph strength, alveograph tenacity/extensibility ratio and loaf volume. The three tests were flour protein content, flour sedimentation and high molecular weight glutenin subunits. Of the indirect tests used for grain quality, sodium dodecyl sulphate (SDS)‐sedimentation allowed the highest intensity of selection for a combined trait index of the target grain quality and grain yield characteristics. The top 48% of the material could be retained on the basis of SDS‐sedimentation, resulting in retention of atleast two‐thirds of the top 10% of genotypes for the combined trait index. Flour protein percentage, a weighted high molecular weight glutenin index and an index combining all the indirect tests—flour protein, SDS‐sedimentation and high molecular weight glutenins—gave selection intensities of 61%, 64% and 55%, respectively, for the combined trait index. If the objective of selection is dough strength alone, then a weighted index of all indirect traits (flour protein, SDS‐sedimentation and high molecular weight glutenins) provided the highest selection intensity (26%). Other selection intensities for individual target traits were 24% for the prediction of loaf volume from flour protein, 40% for the prediction of tenacity/ extensibility ratio using SDS‐sedimentation and 68% for the prediction of grain yield using SDS‐sedimentation.     

Genetic variation of wheat glutenin subunits between landraces and varieties and their contributions to wheat quality improvement in China

Glutenin, one of major factors effecting bread-making quality, is comprised of a mixture of polymers, viz. high-molecular-weight glutenin subunits (HMW-GSs) and low-molecular-weight glutenin subunits (LMW-GSs). Understanding variation among these glutenin subunits can help breeders determine allelic effects on specific quality traits and to use them as genetic markers. The HMW-GS and LMW-GS compositions of 390 landraces and 225 released varieties were analyzed by SDS–PAGE, and some quality traits, including Zeleny sedimentation volume, dough development time, stability time and strengths, were evaluated. The results indicated that 17 and 13 HMW-GSs were present in landraces and released varieties, respectively. For LMW-GS (Glu-A3 and Glu-B3 loci), 12 alleles were found in both landraces and released varieties. Total allelic richness at glutenin loci in landraces was higher, but the genetic dispersion index was lower than in released varieties. Two new subunit combinations 6 + 16 and 7 + 22, and some rare subunits 6 + 9*, 23 + 22, 6* + 8, 7 and 8, were identified in landraces and released varieties. The Glu-D1 and Glu-B3 loci had significantly positive effects. Based on the comparison of the effect of each subunit on quality, it was concluded that subunits 1 at Glu-A1, 13 + 16, 17 + 18 and 6 + 16 at Glu-B1, 5 + 10 at Glu-D1, Glu-A3b at Glu-A3 and Glu-B3d at Glu-B3 contributed larger positive effects on bread-making quality than alternative alleles. From this study, genetic materials with strong gluten and good quality were identified in landraces that did not carry the 1BL.1RS translocation.     

The use of low molecular weight glutenin subunits to distinguish between wheat cultivars with and without resistance to the Russian wheat aphid, Diuraphis noxia

A number of resistance sources for the Russian wheat aphid have been reported in the last few years and were used to develop resistant cultivars from current commercial cultivars in various breeding programmes. It can be diffcult to distinguish between the cultivars with and without resistance without actual infestation and so in this study we looked at low molecular weight glutenin subunits (LMW-GS) of the two groups. Distinctly different banding patterns were found for the cultivars tested and their isogenic counterparts. Although the LMW-GS and DN1 and DN5 are coded on different chromosomes, the LMW-GS are highly repeatable and banding profiles of each cultivar can be used for the identification of unknown seed.     

Influence of allelic variations in glutenin on the quality of pan bread and white salted noodles made from Korean wheat cultivars

Dough rheological properties and end-use quality were evaluated to determine the effects of Glu-1 and Glu-3 alleles on those characteristics in Korean wheat cultivars. SDS-sedimentation volume based on protein weight was positively correlated with mixograph parameters and maximum height of dough and also positively correlated with bread volume, crumb firmness and springiness of cooked noodles. Protein content was negatively correlated with optimum water absorption of noodle dough, lightness of noodle dough sheet and hardness and cohesiveness of cooked noodles. Within Glu-1 loci, 1 or 2* subunit and 5 + 10 subunits showed longer mixing time, higher maximum dough height and larger bread volume than other alleles. Cultivars with 13 + 16 subunits at Glu-B1 locus showed higher protein content and optimum water absorption of mixograph than cultivars with 7 + 8 subunits. At Glu-3 loci, Glu-A3d showed longer mixing time than Glu-A3e, and Glu-B3d and Glu-B3h had stronger mixing properties than Glu-B3i. Glu-B3h had higher bread volume and hardness of cooked noodles than Glu-B3d. Glu-D3a had lower protein content than Glu-D3c, and Glu-D3b showed stronger mixing properties than Glu-D3a. Glu-D3c showed lower hardness of cooked noodles than others.     

Strategic use of Iranian bread wheat landrace accessions for genetic improvement: Core set formulation and validation

Iranian wheat landrace accessions (IWAs) were collected from country‐wide farm fields and market places in 1935 by a professor at the University of Tehran and shared with University of California at Davis, California. IWAs were further submitted to the genebank of International Maize and Wheat Improvement Center (CIMMYT), Mexico. 2,403 IWAs from CIMMYT’s genebank were assayed by DArT‐seq technology to assess genetic diversity. No apparent ecogeographic patterns related to genetic diversity were detected, probably due to long‐term transport and frequent interchange of landraces among farmers. A multivariate clustering procedure combining genotypic and phenotypic information was used in selecting a core‐set, which represented 15% of the hexaploid wheat accessions included in this study. This subset captured an estimated 93% of rare (frequency <0.05) alleles. Multisite phenotypic data (India, Mexico) validated the ability of the core‐set in detecting useful variants. Potential donor accessions for multiple traits (disease resistance, zinc concentration) were identified from the core‐set for wheat‐breeding. This report illustrates a breeder friendly robust core‐set formulation strategy for harnessing the useful genetic variation stored in the genebanks.     

The development and use of microsatellite markers for genetic analysis and plant breeding with emphasis on bread wheat

In recent years, a variety of molecular markers, based on microsatellites or simple sequence repeats (SSRs) have become the markers of choice, thus necessitating their development and use in a variety of plant systems. In this review, the basic principles underlying different hybridization-based (oligonucleotide fingerprinting) and PCR based approaches (STMS, MP-PCR, AMP-PCR/ ISSR/ ASSR, RAMPs/ dRAMPs, SAMPL), making use of microsatellites, have been outlined. Different methods for enrichment of genomic libraries for microsatellites have also been outlined. Relevant literature on the subject, giving a summary of results obtained using each approach, has been reviewed and critically discussed. The review also includes a discussion on literature, which deals with the use of microsatellites in genome mapping, gene tagging, DNA fingerprinting, characterization of germplasm and cytogenetics research. Special emphasis has been laid on the genome of bread wheat, where the work done in the authors' own laboratory has also been briefly reviewed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Introduction to bread wheat (Triticum aestivum L.) and assessment for bread-making quality of alleles from T. boeoticum Boiss. ssp. thaoudar at Glu-A1 encoding two high-molecular-weight subunits of glutenin

Two alleles, Glu-A1r encoding high-molecular-weight (HMW) glutenin subunits 39+40 and Glu-A1s encoding HMW glutenin subunits 41+42, were introgressed to bread wheat (Triticum aestivum L.) cv. Sicco from two accessions of T. boeoticum Boiss. ssp. thaoudar (A genome species, 2n=2x=14). Alleles at Glu-A1 in current commercial bread wheats encode zero or one subunit, and alleles at the homoeoloci Glu-B1 and Glu-D1 encode a maximum of two subunits; hence the maximum number of subunits found in commercial wheats is five, whereas the lines incorporating Glu-A1r and Glu-A1s carry six. Using near-isogenic lines, the current results demonstrated that the introduction of Glu-A1r resulted in diminished dough stickiness and improved stability during mixing compared with Glu-A1a encoding subunit 1, and a small improvement in gluten strength as shown by the SDS- sedimentation test. The introduction of Glu-A1a also resulted in a small improvement in gluten strength predicted by the SDS-sedimentation test. Thus the alleles are of potential value in breeding programmes designed to improve bread-making quality.     

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.     

Allelic variation of the HMW glutenin subunits in Aegilops tauschii accessions detected by sodium dodecyl sulphate (SDS-PAGE), acid polyacrylamide gel (A-PAGE) and capillary electrophoresis

Variability of high molecular weight glutenin subunits (HMW-GS) was studied in198 accessions of Ae. Tauschii (2n=2x=14, DD) by sodium dodecyl sulphate(SDS-PAGE) and acid polyacrylamide gel electrophoresis (A-PAGE) and capillary electrophoresis (CE). A high allelic variation of HMW-GS, including some novel x- and y-type subunits and variable subunit combinations were observed. One accession(TD159) showed a x-type null form. The results by A-PAGE analysis revealed that the subunits Dx5 ^t and Dy10 ^t encoded by Glu-D ^t 1 locus in Ae. tauschii were different in relative mobilities in comparison with the subunits Dx5 and Dy10 found in bread wheats, whereas they had the same mobilities, respectively, when separated by SDS-PAGE. The higher resolution of Ae. tauschii HMW-GS separated by CE method showed two clear peaks in accordance with x- and y-type subunits, respectively,except the accession TD151 which possessed only subunit Dy12.1^*t. The electro elution time of the x-type and y-type subunits were about 13–14 and 7–8minutes, respectively. Characterization of wheat HMW-GS was facilitated by using CE which provides high resolution and increases the speed of analysis in conjunction with the traditional gel electrophoretic methods. A total of 42HMW-GS alleles were identified, among which were several alleles not presently detected in bread wheats. Hence Ae. tauschii is potentially a valuable genetic resource for quality improvement of bread wheat. This revised version was published online in August 2006 with corrections to the Cover Date.     

Combination of resistance tests and molecular tests to postulate the yellow rust resistance gene Yr17 in bread wheat lines

Yellow rust caused by Puccinia striiformis is a wheat disease of worldwide importance. The Yr17 resistance gene introgressed from Aegilops ventricosa was effective, in France, against all yellow rust isolates until 1998. The SC‐Y15 marker is one of three molecular markers closely linked to Yr17. In this paper, results obtained are compared with the molecular marker SC‐Y15 and with resistance tests performed at the seedling and adult plant stages on 31 lines from five populations derived from recurrent selection programmes. The resistance tests showed that Yr17 controlled the resistance in seven lines, but that others had additional resistance at the adult stage (18 lines). The molecular test corresponded well with the resistance test in most lines (98% of 156 plants tested), including individual plants that were resistant or susceptible in heterogeneous lines. It also indicated the presence of Yr17 in lines in which it could not be identified by the resistance test because of the presence of other genes. Three of the 156 plants tested appeared to have the gene Yr17 according to the resistance tests, but lacked the molecular marker. These could have resulted from breakage of the linkage, the number being consistent with the estimate of linkage already published. This indicated the need for a resistance test, at least in later stages of breeding programmes, if it is considered essential to have the Yr17 gene present. The use of the selected lines in breeding programmes is also discussed.     

The development of precise genetic stocks in two wheat cultivars and their use in genetic analysis

Summary The results of genetic studies of common wheat that have been conducted in Novosibirsk, Russia, over the past 20 years by a research team are summarized. The research strategy was to develop a collection of aneuploids and substitution lines to be further used for chromosomal localization of genes and in the study of the genetic variability of wheat. On the basis of two cultivars, namely Saratovskaya 29 and Diamant, we have developed 6 sets of aneuploids with a complete set of monosomic lines for each, plus sets of lines ditelosomic and monotelosomic for standard arms. Exploiting the monotelosomics, 108 single chromosome intervarietal substitutions, 13 lines with alien substitutions (mono- and disomics) and 11 addition lines have been developed. A collection of lines isogenic for dominant marker genes of morphological characters has also been developed. The genetic collection was used in chromosomal localization of 15 genes, for many of which chromosome arms have been determined. Positively or negatively, the question of allelism within some loci has been answered.     

The use of microsatellite markers to determine the relative proportions of grain produced by cultivars and the frequency of hybridization in bread wheat mixtures

Two polymorphic microsatellite markers were selected to identify 24 bread wheat cultivars commonly grown in France and to estimate the proportions of cultivar and hybrid grains in the harvests of four 4‐cultivar mixtures (CM 1‐4) planted in equal proportions in farmers’ fields. This technology was used not only to determine whether a mixture comprises the declared cultivars, but also whether there is any contamination with other cultivars, to identify the contaminants and to estimate their proportions. At harvest, the cultivar proportions ranged from 15 to 37%. Only in the mixture CM2 (‘Malacca’, ‘Somme’, ‘Renan’ and ‘Soissons’), did the cultivars contribute equally to the harvest. The other cultivar mixtures CM1 (‘Malacca’, ‘Somme’, ‘Renan’ and ‘Camp Remy’), CM3 (‘Malacca’, ‘Texel’, ‘Apache’ and ‘Aligre’) and CM4 (‘Malacca’, ‘Somme’, ‘Apache’ and ‘Virtuose’) showed significantly unequal cultivar proportions with ‘Somme’ dominating ‘Renan’ and ‘Camp Remy’ in CM1, and ‘Apache’ dominating ‘Malacca’ and ‘Aligre’ in CM3 and ‘Malacca’ in CM4. Similar cultivar proportions were measured with gliadin and glutenin markers in the mixtures CM3 and CM4, confirming the results with microsatellites. No contamination was found. Hybrids accounted for between 1.3 and 6.3% of the grains produced in the four cultivar mixtures.     

The use of wheat-alien and Aegilops-rye amphiploids for introgression of genetic material to wheat

An introduction of genetic material from rye, Aegilops and Elymus into durum and common wheat by crossing the wheat species with different amphiploids, has been attempted. Meiotic studies of the hybrids demonstrated that the wheat Elymus sibiricus amphiploid contained several (two or three) genes suppressing the activity of the wheat homoeologous pairing control system. Somatic chromosome studies of the hybrids revealed that the distributions of the alien chromosomes transferred to the second hybrid generation did not correspond to random (0.5 + 0.5)^2k and binomial (p + q)^2k distributions. An essential amendment for gamete and zygote viability, allowing the approximation of distributions by binomial equation, is discussed. The preferential E. sibiricus chromosome transmission was observed. The first backcross was found to be a critical stage while using the Aegilops-rye amphiploids for production of wheat introgressive forms. Stabilisation of the somatic karyotype and improvement of the meiotic regularity was observed in a number of generations. The isolation of stable cytological lines in BC₃ was found to be possible. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparison of molecular markers and coefficients of parentage for the analysis of genetic diversity among spring bread wheat accessions

The comparison of different methods of estimating genetic diversity could define their usefulness in plant breeding and genetic improvement programs. This study evaluates and compares the genetic diversity of 70 spring wheat accessions representing a broad genetic pool based on molecular markers and parentage relationships. The sample was composed of 32 accessions from the International Maize and Wheat Improvement Center (CIMMYT) and 38 from other breeding programs worldwide. Eight AFLP-primer combinations and 37 pairs of SSR primers were used to characterize the accessions and the Coefficients of Parentage (COP) were calculated from registered pedigrees. The average genealogical (COP) similarity (0.09 with a range of 0.0–1.0) was low in comparison to similarity calculated using SSR markers (0.41 with a range of 0.15–0.88) and AFLP markers (0.70 with a range of 0.33–0.98). Correlation between the genealogical similarity matrix (excluding accessions with COPs = 0) and the matrices of genetic similarity based on molecular markers was 0.34≤r≤0.46 (p <0.05). It is concluded that AFLP and SSR markers are generally in agreement with estimates of diversity measured using COPs, especially when complete pedigree data are available. However, markers may provide a more correct estimate due to some unrealistic assumptions made when calculating COPs, such as absence of selection. Furthermore, both COP and marker distances indicate that CIMMYT accessions are different from the worldwide group of accessions. This revised version was published online in July 2006 with corrections to the Cover Date.