Modern Wheat Breeding Research Articles

Mapping QTLs of yield-related traits using RIL population derived from common wheat and Tibetan semi-wild wheat.

QTLs controlling yield-related traits were mapped using a population derived from common wheat and Tibetan semi-wild wheat and they provided valuable information for using Tibetan semi-wild wheat in future wheat molecular breeding. Tibetan semi-wild wheat (Triticum aestivum ssp tibetanum Shao) is a kind of primitive hexaploid wheat and harbors several beneficial traits, such as tolerance to biotic and abiotic stresses. And as a wild relative of common wheat, heterosis of yield of the progeny between them was significant. This study focused on mapping QTLs controlling yield-related traits using a recombined inbred lines (RILs) population derived from a hybrid between a common wheat line NongDa3331 (ND3331) and the Tibetan semi-wild wheat accession Zang 1817. In nine location-year environments, a total of 148 putative QTLs controlling nine traits were detected, distributed on 19 chromosomes except for 1A and 2D. Single QTL explained the phenotypic variation ranging from 3.12 to 49.95%. Of these QTLs, 56 were contributed by Zang 1817. Some stable QTLs contributed by Zang 1817 were also detected in more than four environments, such as QPh-3A1, QPh-4B1 and QPh-4D for plant height, QSl-7A1 for spike length, QEp-4B2 for ears per plant, QGws-4D for grain weight per spike, and QTgw-4D for thousand grain weight. Several QTL-rich Regions were also identified, especially on the homoeologous group 4. The TaANT gene involved in floral organ development was mapped on chromosome 4A between Xksm71 and Xcfd6 with 0.8 cM interval, and co-segregated with the QTLs controlling floret number per spikelet, explaining 4.96-11.84% of the phenotypic variation. The current study broadens our understanding of the genetic characterization of Tibetan semi-wild wheat, which will enlarge the genetic diversity of yield-related traits in modern wheat breeding program.

Spanish Ancient Wheats: A Genetic Resource for Wheat Quality Breeding

Wheat (Triticum sp.) is one of the most important food crops worldwide. Di-, tetra- and hexaploid species are available, which along with the different subspecies of this genus have been used for food and feed. However, the genetic diversity of this crop has been seriously compromised, and only two main species; the durum and bread wheat, currently exist. The germplasm materials that were used in the past in Spain, have been regarded as ancient wheats, thus forming a group of neglected or underutilized crops that could be an interesting reservoir of variation for modern wheat breeding. In the last decade, our group has been evaluating and characterizing for the morphological and quality traits some of these Spanish ancient wheats. In these materials, using the SDS-PAGE technique and DNA sequencing, we detected an important variability for seed storage proteins, starch synthases and puroindolines, which are related with three important quality characteristics of wheat: gluten levels, starch levels and hardness, respectively. These novel variants could be used with the dual goal of genetic improvement and enriching the gene pool of these components in modern wheat.

Waxy genes from spelt wheat: new alleles for modern wheat breeding and new phylogenetic inferences about the origin of this species

Waxy proteins are responsible for amylose synthesis in wheat seeds, being encoded by three waxy genes (Wx-A1, Wx-B1 and Wx-D1) in hexaploid wheat. In addition to their role in starch quality, waxy loci have been used to study the phylogeny of wheat. The origin of European spelt (Triticum aestivum ssp. spelta) is not clear. This study compared waxy gene sequences of a Spanish spelt collection with their homologous genes in emmer (T. turgidum ssp. dicoccum), durum (T. turgidum ssp. durum) and common wheat (T. aestivum ssp. aestivum), together with other Asian and European spelt that could be used to determine the origin of European spelt. waxy genes were amplified and sequenced. Geneious Pro software, DNAsp and MEGA5 were used for sequence, nucleotide diversity and phylogenetic analysis, respectively. Three, four and three new alleles were described for the Wx-A1, Wx-B1 and Wx-D1 loci, respectively. Spelt accessions were classified into two groups based on the variation in Wx-B1, which suggests that there were two different origins for the emmer wheat that has been found to be part of the spelt genetic make-up. One of these groups was only detected in Iberian material. No differences were found between the rest of the European spelt and the Asiatic spelt, which suggested that the Iberian material had a different origin from the other spelt sources. The results suggested that the waxy gene variability present in wheat is undervalued. The evaluation of this variability has permitted the detection of ten new waxy alleles that could affect starch quality and thus could be used in modern wheat breeding. In addition, two different classes of Wx-B1 were detected that could be used for evaluating the phylogenetic relationships and the origins of different types of wheat.

Assessing genetic diversity and its changes of bread wheat in Qinghai Province, China, using agronomic traits and microsatellite markers

Little is known about the diversity of wheat in Qinghai Province, China. Agronomic traits and microsatellite markers were used to survey genetic diversity and its change with time in 66 wheat cultivars registered from 1957 to 2009 in Qinghai Province. The average values of plant height, ear length, spikelets per ear, effective spikelets per ear, effective tillers per plant, internode length under spike, kernels per spike, grain weight per ear, 1,000-grain weight, and distance of spike base to auricle of flag leaf were studied. The mean Shannon-Weaver diversity index (H’) was 1.67 and increased with time. One hundred and eighty nine microsatellite markers also were used to examine genetic diversity at a molecular level which showed that the average number of alleles (Na), genetic diversity index (He), and allelic richness (Rs) were 3.69, 0.5, and 3.45, respectively, and also increased with time but did not lead to a significant differentiation among the decades. These results suggest that the modern wheat breeding practice did not cause a genetic reduction in Qinghai Province.

Microsatellite genetic diversity analysis and allelic variation comparison of obsolete and modern Bulgarian bread wheat (Triticum aestivumL.) varieties

A set of 24 microsatellite markers was used for assessing the genetic diversity of 40 obsolete and modern Bulgarian winter wheat (Triticum aestivum L.) varieties. The total number of alleles detected was 215 with the average per locus 8.96 and varying from 4 (Xgwm480, Xgwm333) to 15 (Xgwm291). The obsolete varieties of interest were created in the period between 1911 and 1938 through selection of local populations, originating from three Bulgarian regions. The number of alleles detected in those old varieties was 182 with an average of 7.58, out of which 2.67 were rare. Regional differences in the allelic richness and diversity were also observed. Greater number of alleles was found in the old varieties, originating from South Bulgarian and Northeast landraces. Modern wheat breeding in Bulgaria has led to a decrease in the alleles per locus ratio and an increase in the allelic frequency. The same process has invalidated 44.2% of the old wheat alleles, preserved 40.9% and made possible an inflow of 14.9% new alleles. The artificial selection tolerated the preservation of a big number of the alleles of some loci found in old varieties (Xgwm205 and Xgwm160), while others experienced loss of alleles (Xgwm291, Xgwm312, Xgwm219 and Xgwm261). The genealogical analysis of 94 Bulgarian varieties, created in the period 1940–2000, showed that 27.7% of those varieties were based on Bulgarian landraces.

Presence of celiac disease epitopes in modern and old hexaploid wheat varieties: wheat breeding may have contributed to increased prevalence of celiac disease

Gluten proteins from wheat can induce celiac disease (CD) in genetically susceptible individuals. Specific gluten peptides can be presented by antigen presenting cells to gluten-sensitive T-cell lymphocytes leading to CD. During the last decades, a significant increase has been observed in the prevalence of CD. This may partly be attributed to an increase in awareness and to improved diagnostic techniques, but increased wheat and gluten consumption is also considered a major cause. To analyze whether wheat breeding contributed to the increase of the prevalence of CD, we have compared the genetic diversity of gluten proteins for the presence of two CD epitopes (Glia-α9 and Glia-α20) in 36 modern European wheat varieties and in 50 landraces representing the wheat varieties grown up to around a century ago. Glia-α9 is a major (immunodominant) epitope that is recognized by the majority of CD patients. The minor Glia-α20 was included as a technical reference. Overall, the presence of the Glia-α9 epitope was higher in the modern varieties, whereas the presence of the Glia-α20 epitope was lower, as compared to the landraces. This suggests that modern wheat breeding practices may have led to an increased exposure to CD epitopes. On the other hand, some modern varieties and landraces have been identified that have relatively low contents of both epitopes. Such selected lines may serve as a start to breed wheat for the introduction of ‘low CD toxic’ as a new breeding trait. Large-scale culture and consumption of such varieties would considerably aid in decreasing the prevalence of CD.

New DNA markers for high molecular weight glutenin subunits in wheat

End-use quality is one of the priorities of modern wheat (Triticum aestivum L.) breeding. Even though quality is a complex trait, high molecular weight (HMW) glutenins play a major role in determining the bread making quality of wheat. DNA markers developed from the sequences of HMW glutenin genes were reported in several previous studies to facilitate marker-assisted selection (MAS). However, most of the previously available markers are dominant and amplify large DNA fragments, and thus are not ideal for high throughput genotyping using modern equipment. The objective of this study was to develop and validate co-dominant markers suitable for high throughput MAS for HMW glutenin subunits encoded at the Glu-A1 and Glu-D1 loci. Indels were identified by sequence alignment of allelic HMW glutenin genes, and were targeted to develop locus-specific co-dominant markers. Marker UMN19 was developed by targeting an 18-bp deletion in the coding sequence of subunit Ax2* of Glu-A1. A single DNA fragment was amplified by marker UMN19, and was placed onto chromosome 1AL. Sixteen wheat cultivars with known HMW glutenin subunits were used to validate marker UMN19. The cultivars with subunit Ax2* amplified the 362-bp fragment as expected, and a 344-bp fragment was observed for cultivars with subunit Ax1 or the Ax-null allele. Two co-dominant markers, UMN25 and UMN26, were developed for Glu-D1 by targeting the fragment size polymorphic sites between subunits Dx2 and Dx5, and between Dy10 and Dy12, respectively. The 16 wheat cultivars with known HMW glutenin subunit composition were genotyped with markers UMN25 and UMN26, and the genotypes perfectly matched their subunit types. Using an Applied Biosystems 3130xl Genetic Analyzer, four F(2) populations segregating for the Glu-A1 or Glu-D1 locus were successfully genotyped with primers UMN19, UMN25 and UMN26 labeled with fluorescent dyes.

Using a gel‐free PCR‐ELISA for the molecular identification of wheat genotypes carrying wheat–rye translocations

AbstractCurrent techniques to identify wheat lines possessing the 1RS chromosome are generally unsuitable in relation to the speed and cost needs in modern wheat breeding programmes. A gel‐free, direct amplicon capture PCR‐ELISA assay was developed and evaluated, aiming at speeding the identification of wheat genotypes possessing the 1RS chromosome arm in breeding programmes. The chosen target sequence was the repetitive, interspersed rye‐specific element RIS‐1. Primers were end‐labelled with digoxigenin and biotin, and amplicons captured on to straptavidine‐coated microplates. Subsequent immunodetection of the digoxigenin moiety readily distinguished 1RS from non‐1RS control genotypes tested. When a nursery consisting of 120 winter and spring wheat lines was screened by PCR‐gel electrophoresis and the PCR‐ELISA, a perfect agreement between both techniques was observed. Test robustness, as measured by the tolerance to variations in DNA input, was better for PCR‐ELISA than PCR‐gel electrophoresis. In conclusion, a simple, robust, fast and scalable technique for the detection of 1RS chromosome carriers in wheat breeding programmes is now available.

Use of Detached Seedling Leaf Test to Evaluate Wheat Resistance to Septoria Tritici Blotch

Two experimental sets of selected winter wheat cultivars, breeding lines, old Czech and Slovak landraces and wheat wild relatives were infected with three isolates (R-116, UH-105, BR-331) of Mycosphaerella graminicola (anamorph Septoria tritici) isolated in the Czech Republic. Groups of cultivars with different disease severity to all three isolates of the pathogen were found. Differences between old Czech and Slovak landraces and wild wheat relatives were larger than between modern wheat cultivars and breeding materials. In experiment one the isolate BR-331 differed significantly from the other two isolates in virulence to the tested modern wheat cultivars and breeding lines. The method is considered as suitable for preliminary screening in wheat resistance breeding or phytopathological testing and as a complement to field tests.    

The genetic diversity of old and modern Siberian varieties of common spring wheat as determined by microsatellite markers

AbstractThe objective of this study was to assess genetic diversity within old and modern common spring wheat (Triticum aestivumL.) varieties cultivated in Siberia and to find out whether old Siberian varieties could be a potential source for genetic diversity in modern wheat breeding in Siberia. A set of 54 varieties was analysed using 22 wheat microsatellite markers (WMS), determining 23 loci located on 19 different chromosomes. In total, 151 alleles were detected with an average of 6.6, ranging from three to 11 alleles per locus. The average genetic diversity value (polymorphic information content) was 0.70. WMS located in the B genome produced more alleles per locus (7.6) compared with WMS located in the A (6.0) and D (6.0) genomes. Genetic similarity values between varieties ranged from 0.19 to 0.96 and were used to produce a dendrogram. With a few exceptions the varieties studied were clustered in two nearly equal groups consisting of predominantly old (released before 1960) and modern (released in 1960‐90s) varieties, respectively. Genetic diversity values within these two groups were similar with 0.60 and 0.58, respectively. The numbers of group‐specific alleles were 34 and 29, respectively. A significant variation in frequencies of 79 shared alleles was observed. The results obtained by using genomic microsatellite sequences demonstrated that breeding has not resulted in a decrease in the genetic diversity in Siberian spring wheat. However, significant quantitative and qualitative changes in allelic frequencies of different loci were detected. It may be suggested, that old Siberian common spring wheat varieties are a potential basis for genetic diversity in modern wheat breeding in Siberia.

Characterisation of wheat-rye recombinants with RFLP and PCR probes

The introgression of genetic material from alien species into wheat has become an important tool in modern wheat breeding. Ideally, only the trait of interest and no flanking material should be transferred. Random recombination between the genetic material is therefore of paramount importance. In a model system, we examined 17 recombinants putatively between chromosome 1D of wheat and 1R of rye with 60 random RFLP and three PCR markers. The recombinants had been generated by removing the normal effect of the Ph1 gene in the wheat background. Amongst the nine short-arm recombinants, three breakpoints were identified but no differentiation could be made between the five proximal recombinants. For the eight long-arm recombinants analysed only two breakpoints were identified with 36 markers. However, only a single RFLP marker was able to differentiate between the recombinants. Indeed the long-arm results are consistent with the possibility that only the rye telomeric region had been transferred. These results indicate either a strong clustering of the RFLP markers near the centromere or else imply that recombination induced between wheat and rye in the absence of the normal effect of the Ph1 gene occurs at only restricted sites. The results allow new primary recombinants to be selected for intercrossing to generate secondary recombinants which are expected to have a smaller interstitial rye segment than that present in DR-A1.

Biomass Yield — A Topical Issue in Modern Wheat Breeding Programmes

AbstractPlot experiments were made involving seven winter wheat varieties to study growth rate and biomass yield in relation to grain yield and yield stability. The results obtained with ‘Apollo’ show that it is possible to boost grain yield and obtain simultaneously an adequate yield stability by increasing the biomass potential until anthesis and maintaining high growth rates in the grain‐filling period. Higher grain yields were likewise reached by merely increasing the growth rate after anthesis at an equal or lower biomass potential at anthesis, but yield stability was lower then.

The Grain Quality of Landraces of Wheat as Compared with Modern Cultivars

AbstractLandraces of tetraploid and hexaploid wheat from the Northern Negev in Israel were evaluated over two years for their grain quality attributes. Twenty‐one populations of tetraploid wheat (Triticum durum, represented by 56 accessions) and 8 populations of hexaploid wheat (T. aestivum and T. compactum, represented by 13 accessions) were compared with 3 and 4 modern improved Israeli cultivars of tetraploid and hexaploid reheat, respectively. This comparison allowed to estimate the progress made in the improvement of gram quality m present‐day cultivars.Except for grain protein content in the hexaploids, significant variation was revealed among landraces in kernel weight, protein content (tetraploids), sedimentation, mixograph score and carotin content. The best modern cultivars were comparable to the best landraces in kernel weight and carotin content (tetraploids), indicating that modern wheat breeding maximized kernel weight and carotin content, as compared with the tested landraces. Gram protein content and/or quality was not maximized in modern cultivars and its improvement was deemed possible by introgression from the best landraces in this respect.