urum wheat (DW), Triticum turgidum L. ssp. durum (Desf.) Husn., genome BBAA, is a cereal grain mainly used for pasta production and evolved from domesticated emmer wheat (DEW), T. turgidum ssp. dicoccum (Schrank ex Schübl.) Thell. DEW itself derived from wild emmer wheat (WEW), T. turgidum ssp. dicoccoides (Körn. ex Asch. & Graebn.

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BackgroundIn plants carotenoids play an important role in the photosynthetic process and photo-oxidative protection, and are the substrate for the synthesis of abscisic acid and strigolactones. In addition to their protective role as antioxidants and precursors of vitamin A, in wheat carotenoids are important as they influence the colour (whiteness vs. yellowness) of the grain. Understanding the genetic basis of grain yellow pigments, and identifying associated markers provide the basis for improving wheat quality by molecular breeding.ResultsTwenty-four candidate genes involved in the biosynthesis and catabolism of carotenoid compounds have been identified in wheat by comparative genomics. Single nucleotide polymorphisms (SNPs) found in the coding sequences of 19 candidate genes allowed their chromosomal location and accurate map position on two reference consensus maps to be determined. The genome-wide association study based on genotyping a tetraploid wheat collection with 81,587 gene-associated SNPs validated quantitative trait loci (QTLs) previously detected in biparental populations and discovered new QTLs for grain colour-related traits. Ten carotenoid genes mapped in chromosome regions underlying pigment content QTLs indicating possible functional relationships between candidate genes and the trait.ConclusionsThe availability of linked, candidate gene-based markers can facilitate breeding wheat cultivars with desirable levels of carotenoids. Identifying QTLs linked to carotenoid pigmentation can contribute to understanding genes underlying carotenoid accumulation in the wheat kernels. Together these outputs can be combined to exploit the genetic variability of colour-related traits for the nutritional and commercial improvement of wheat products.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3395-6) contains supplementary material, which is available to authorized users.

Glutamine synthetase (GS2) is a key enzyme in plant nitrogen metabolism responsible of the first step of ammonium assimilation and transformation into glutamine (an essential compound in the amino acid-biosynthetic pathway). The goal of the present study was to isolate and characterize GS2 genes and to assess the linkage with grain protein content (GPC), an important quantitative trait controlled by multiple genes. Here, we report the isolation of the complete glutamine synthetase gene sequences and their localization on the two homeologous chromosome 2A and 2B in durum wheat cvs. Ciccio and Svevo characterized by a different grain protein content. GS2-A2 located on 2A chromosome is comprised of 13 exons separated by 12 introns, and the allele sequence in the two cultivars were different for an insertion of 5 bp located in the third exon in the cv. Ciccio. The GS2-B2 has the same intron/exon structure, but the two cultivars differ for the insertion of a 33-bp sequence located in the second intron of the cv. Svevo. Specific primers were designed in the polymorphic region and amplified in a recombinant inbred line mapping population. The study localized GS genes (GS2-A2, GS2-B2 GSe, GSr) on chromosomes 2A, 2B, 4A, and 4B, where four significant QTLs for GPC were also located.

BackgroundIn higher plants, inorganic nitrogen is assimilated via the glutamate synthase cycle or GS-GOGAT pathway. GOGAT enzyme occurs in two distinct forms that use NADH (NADH-GOGAT) or Fd (Fd-GOGAT) as electron carriers. The goal of the present study was to characterize wheat Fd-GOGAT genes and to assess the linkage with grain protein content (GPC), an important quantitative trait controlled by multiple genes.ResultsWe report the complete genomic sequences of the three homoeologous A, B and D Fd-GOGAT genes from hexaploid wheat (Triticum aestivum) and their localization and characterization. The gene is comprised of 33 exons and 32 introns for all the three homoeologues genes. The three genes show the same exon/intron number and size, with the only exception of a series of indels in intronic regions. The partial sequence of the Fd-GOGAT gene located on A genome was determined in two durum wheat (Triticum turgidum ssp. durum) cvs Ciccio and Svevo, characterized by different grain protein content. Genomic differences allowed the gene mapping in the centromeric region of chromosome 2A. QTL analysis was conducted in the Svevo×Ciccio RIL mapping population, previously evaluated in 5 different environments. The study co-localized the Fd-GOGAT-A gene with the marker GWM-339, identifying a significant major QTL for GPC.ConclusionsThe wheat Fd-GOGAT genes are highly conserved; both among the three homoeologous hexaploid wheat genes and in comparison with other plants. In durum wheat, an association was shown between the Fd-GOGAT allele of cv Svevo with increasing GPC - potentially useful in breeding programs.

Grain protein content (GPC), is one of the most important trait in wheat and its characterized by a very complex genetic control. The identification of wheat varieties with high GPC (HGPC), as well as the characterization of central enzymes involved in these processes, are important for more sustainable agricultural practices. In this study, we focused on Glutamine synthetase (GS) as a candidate to study GPC in wheat. We analyzed GS expression and its enzymatic activity in different tissues and phenological stages in 10 durum wheat genotypes with different GPC. Although each genotype performed quite differently from the others, both because their genetic variability and their adaptability to specific environmental conditions, the highest GS activity and expression were found in genotypes with HGPC and vice versa the lowest ones in genotypes with low GPC (LGPC). Moreover, in genotypes contrasting in GPC bred at different nitrogen regimes (0, 60, 140 N Unit/ha) GS behaved differently in diverse organs. Nitrogen supplement increased GS expression and activity in roots of all genotypes, highlighting the key role of this enzyme in nitrogen assimilation and ammonium detoxification in roots. Otherwise, nitrogen treatments decreased GS expression and activity in the leaves of HGPC genotypes and did not affect GS in the leaves of LGPC genotypes. Finally, no changes in GS and soluble protein content occurred at the filling stage in the caryopses of all analyzed genotypes.

Over the last years, great efforts have been devoted to develop effective gluten detoxification strategies with a consequent detrimental alteration of the technological properties as well. Obtaining low-gluten products without affecting the rheological properties of wheat could still be considered a new challenge to face. In this investigation, we presented a comprehensive characterization of durum wheat genotypes aimed at identifying low gluten ones, which combine the potential lower toxicity/immunogenicity with conserved yield and rheological properties to encompass the perspective usability for bread or pasta making. A preliminary profiling of gluten proteins was accomplished by immunoassay-based quantification and liquid chromatography coupled to UV detection, focusing on the gliadin fraction as main responsible for immunoreactivity in celiac disease patients. In addition, data on grain protein content, grain yield per spike, dry gluten and gluten index were collected in order to provide complementary information about productivity-related traits and quali-quantitative characteristics related to wheat nutritional value and its technological properties. The whole pool of data was statistically evaluated driving to the selection of a preferred list of candidate low-toxicity genotypes that were subjected to in-vitro simulated gastroduodenal digestion and untargeted HR-MS/MS peptide identification. Finally, an in-silico risk assessment of potential toxicity for celiac disease patients was performed according to the most recent guidance provided by EFSA.