Powdery mildew is one of the devastating wheat diseases and is caused by the biotrophic fungus Blumeria graminis f.sp. tritici. The identification of natural sources of resistance and breeding for resistant varieties is the most effective way to control this disease, as chemical control is expensive. To date, more than 40 Pm resistance genes have been characterized, while only one of these genes, Pm3, has been cloned. Pm3 is localized on the short arm of wheat chromosome 1A and is present in 17 functional allelic forms (Pm3a to Pm3g, Pm3k to Pm3t). The Pm3 alleles confer race-specific resistance to different wheat powdery mildew races. The objectives of this work were to study the behaviour of powdery mildew resistance Pm3 gene in a collection of tetraploid wheats and to isolate the complete genomic sequence of Pm3 gene in susceptible and resistant genotypes in order to identify new functional alleles. The search for new Pm3 alleles was carried out on a collection of 233 tetraploid wheat genotypes (Triticum turgidum L.). The collection comprises 128 cultivars of durum wheat (ssp. durum), as well as 19 accessions of ssp. turgidum, 20 of ssp. turanicum, 20 of ssp. polonicum, 12 of ssp. carthlicum, 20 of ssp. dicoccum, and 14 of ssp. dicoccoides. The entire set of these accessions was phenotypically characterized for resistance against wheat powdery mildew by screening with one powdery mildew isolate (O2). This screening led to the identification of 34 resistant accessions (14,6% of the total set). The tetraploid wheat collection was analysed for the Pm3 haplotype by screening for the presence of a Pm3-like gene with a STS marker. This STS marker amplifies a 946 bp fragment from the 5' non- coding region of Pm3b and is diagnostic for the presence of a Pm3-like gene. A total of 129 accessions, both resistant and susceptible, out of 233 (55.4%) tested were identified with a likely presence of a Pm3 gene. Subsequently a set of 21 resistant and susceptible lines showing the presence of a Pm3-like gene was screened for the presence of Pm3a to Pm3g alleles. A positive PCR reaction was observed for the Pm3b allele. Five of these lines, either resistant and susceptible, were further analysed with 11 PCR primer combination covering all the Pm3b sequence. Pm3b allele from tetraploid wheat had a size of 4,442 bp, comprising two exons of 4,156 and 86 bp respectively, and an intron of 200 bp. Sequences alignment compared with the Pm3b sequence, used as reference, indicated that the Pm3 genes from the five tetraploid wheat lines contain several “indels” and SNPs in the form of highly polymorphic sequence blocks. The present study demonstrates that allelic variation occurs in functional genes and represents the first step for the identification and sequencing of new functional Pm3 alleles in tetraploid wheat genotypes.

Durum wheat (Triticum turgidum L. var. durum) is a very important crop in the Mediterranean basin. Intense breeding activities are carried out to improve its productivity, quality, and resistance, and new genomic tools are essential to speed up the breeding progress. A segregating population of 136 recombinant inbred lines derived from a cross between the durum wheat cv. Simeto and the T. dicoccum accession Molise Colli was genotyped with the wheat 90k iSelect Infinium SNP assay. A linkage map was developed with 9,040 markers. Forty-five linkage groups were obtained, which covered all of the chromosomes. The map covered 2,879.3 cM, with a mean length of 205.6 cM per chromosome. The number of markers for each chromosome was from 418 (4B) to 978 (2B), with an average of 645.7. The parents of the genetic map differ according to several features, from traits linked to spike and kernel morphology to grain yield. Quantitative trait loci (QTL) analysis was performed for traits related to kernel morphology and thousand-kernel weight: six QTL were identified on chromosomes 1B, 2B, 3A, 3B, 4B and 7A, and 2 QTL on chromosomes 3B and 4B. Bioinformatic and synteny analyses with rice and Brachypodium genomes were performed based on the SNP sequences, with the identification of a candidate gene corresponding to a kinesin under the QTL located on chromosome 1B. The SNP-based Simeto × Molise Colli linkage map represents a useful tool to dissect out the genetic basis of traits of agronomic relevance for the genetic improvement of durum wheat.

A durum wheat consensus linkage map was developed by combining segregation data from six mapping populations. All of the crosses were derived from durum wheat cultivars, except for one accession of T. ssp. dicoccoides. The consensus map was composed of 1,898 loci arranged into 27 linkage groups covering all 14 chromosomes. The length of the integrated map and the average marker distance were 3,058.6 and 1.6 cM, respectively. The order of the loci was generally in agreement with respect to the individual maps and with previously published maps. When the consensus map was aligned to the deletion bin map, 493 markers were assigned to specific bins. Segregation distortion was found across many durum wheat chromosomes, with a higher frequency for the B genome. This high-density consensus map allowed the scanning of the genome for chromosomal rearrangements occurring during the wheat evolution. Translocations and inversions that were already known in literature were confirmed, and new putative rearrangements are proposed. The consensus map herein described provides a more complete coverage of the durum wheat genome compared with previously developed maps. It also represents a step forward in durum wheat genomics and an essential tool for further research and studies on evolution of the wheat genome.

In the present study, a detailed deletion map for wheat chromosomes 5A and 5B is reported, as well as an integrated genetic linkage map of chromosome 5A enriched with single nucleotide polymorphism (SNP) markers, useful both for comparison studies with other existing maps and for mapping major genes and quantitative trait loci (QTLs). Physical mapping of 5,011 SNP markers was obtained using Chinese Spring bin deletion lines for the homoeologous chromosomes of group 5; 509 SNPs were also genetically mapped in a recombinant inbred line population segregating for chromosome 5A only, obtained by crossing the cultivar Chinese Spring and the disomic substitution line Chinese Spring-5A dicoccoides. The whole 5A genetic map, containing 572 markers, covered a total length of 248.7 cM distributed among three linkage groups of 83.5, 117.8 and 47.4, respectively. The majority of SNP markers physically mapped on 5A were mapped to a unique bin, while a small percentage was assigned a double location, suggesting the presence of a segment of 5A short arm which may have undergone a duplication followed by an insertion into the long arm of the same chromosome. A QTL analysis for yield components was performed, identifying a major QTL in the subtelomeric region of chromosome 5A, corresponding to the 5AL15-0.67-0.78 bin; the chromosome segment was 23.5 cM long and included 111 markers. Candidate genes for yield components on chromosome 5A were identified through a syntenic genomic approach by comparison with genomes of model species. Putative function analysis revealed genes involved in basic metabolism and in stress condition responses, including heat shock proteins, chaperones, serine/ threonine protein kinases and membrane transporters, located in the region of the QTL. This information represents an important step for map-based and candidate gene-based cloning of yield QTLs.

Wheat is the most widely grown crop in the world and provides 20% of the daily protein and food calories for 4.5 billion people. Together with rice, it is the most important food crop in the developing world. In the last decades, various symptoms have been recorded across the population due to the consumption of wheat products, also summarized as “wheat allergy.” Wheat allergy is usually reported as a food allergy but can also be a contact allergy as a result of exposure to wheat. Several important wheat allergens have been characterized in the last years through biochemical, immunological, and molecular biological techniques. In the present work, the identification of allelic variation of genes involved in wheat allergy was reported. A collection of wheat genotypes was screened in order to identify new alleles. A total of 14 new alleles were identified for profilin, triosephosphateisomerase, dehydrin, glyceraldehyde-3-phosphate-dehydrogenase, / gliadin, GluB3-23, and Glutathione transferase allergen genes (located on chromosomes 1B, 3B, 6A, and homoelogous groups 5 and 7), potentially related to a minor allergenicity and useful in breeding program

Powdery mildew caused by the pathogen Blumeria graminis f. sp. tritici, is a destructive foliar disease in many regions of the world. The tetraploid wheat Triticum turgidum ssp. dicoccum (2n = 4x = 28, genome AABB) shows particular promises as a donor of useful genetic variation for several traits including disease resistances to introgress in cultivated wheats. The accession MG5323, resistant to powdery mildew, was crossed to the susceptible durum wheat cultivar Latino and a set of 122 recombinant inbred lines (RILs) was produced. Segregation analysis of F2 plants combined with the resistance of F1 progeny to the isolate O2, tested under controlled greenhouse conditions, indicated that resistance is controlled by a single dominant allele. Among the 122 RILs, tested under controlled greenhouse conditions with the same isolate, 67 lines were susceptible and 55 were resistant. The segregation in the RILs fitted the 1:1 segregation ratio expected for a single resistance locus (χ 2 =1.18, 0.50 > P > 0.10). Molecular markers (gSSRs, EST-SSRs and RFLP-derived STS) were used to locate and map the resistance gene. Bulked segregant analysis (BSA), indicated that chromosome arm 2BS could be involved in the control of the resistance. Twelve genomic SSR (gSSRs), three ESTderived SSR markers (EST-SSRs) and one RFLP-derived STS, polymorphic between Latino and MG5323 and located on 2BS, were tested in the set of 122 RILs. Two gSSRs and one EST-SSR, physically mapped on bin 2BS3- 0.84-1.00, were found to be tightly linked to the resistance gene. Among the molecular markers observed in the linkage map of 2BS, few gSSRs showed Mendelian segregation (1:1), whereas most markers, showed significant deviation from the expected ratio. The marker EST-SSR, closely linked to the resistance gene, has potential use in marker-assisted selection and pyramiding of genes for resistance to powdery mildew in wheat.

Background: In 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. Results: We 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 Svevo6Ciccio 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. Conclusions: The 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.

Background: The importance of wheat to the world economy, together with progresses in high-throughput next-generation DNA sequencing, have accelerated initiatives of genetic research for wheat improvement. The availability of high density linkage maps is crucial to identify genotype-phenotype associations, but also for anchoring BAC contigs to genetic maps, a strategy followed for sequencing the wheat genome.Results: Here we report a genetic linkage map in a durum wheat segregating population and the study of mapped DArT markers. The linkage map consists of 126 gSSR, 31 EST-SSR and 351 DArT markers distributed in 24 linkage groups for a total length of 1,272 cM. Through bioinformatic approaches we have analysed 327 DArT clones to reveal their redundancy, syntenic and functional aspects. The DNA sequences of 174 DArT markers were assembled into a non-redundant set of 60 marker clusters. This explained the generation of clusters in very small chromosome regions across genomes. Of these DArT markers, 61 showed highly significant (Expectation < E-10) BLAST similarity to gene sequences in public databases of model species such as Brachypodium and rice. Based on sequence alignments, the analysis revealed a mosaic gene conservation, with 54 and 72 genes present in rice and Brachypodium species, respectively.Conclusions: In the present manuscript we provide a detailed DArT markers characterization and the basis for future efforts in durum wheat map comparing. © 2013 Colasuonno et al.; licensee BioMed Central Ltd

High-density genetic linkage maps of crop species are particularly useful in detecting qualitative and quantitative trait loci (QTLs) for agronomically important traits and in improving the power of classical approaches to identify candidate genes. The aim of this study was to develop a high-density genetic linkage map in a durum wheat recombinant inbred lines population derived from two elite wheat cultivars and to identify and characterize QTLs for yellow pigment content (YPC). A dense map was constructed by genotyping with the wheat 90K iSelect array and consisted of 5,670 loci, comprising 5,019 single nucleotide polymorphism (SNP), 467 DArT, 182 SSR markers and eight genes distributed in 35 linkage groups. Data for yellow pigment content were obtained from four replicated trials conducted at two locations in southern Italy for 2 years. A total of seven QTLs on different chromosome regions (1B, 2A, 2B, 5A, 5B, 7A and 7B) were identified, three of which were consistent in three or four environments and across environments. The genome scan for QTLs and the SNP homology prediction against annotated proteins in wheat and Brachypodium genomes identified two candidate genes of the carotenoid biosynthesis pathway (aldehyde oxidase, AO1, and diphosphomevalonate decarboxylase, DMAPD) significantly associated with YPC. This study provides a basis for further genetic QTL dissection and tools for marker-assisted breeding programs, because SNP markers and some carotenoid candidate genes were found to be tightly linked to major QTLs for YPC.

Totipotent cDNA libraries representative of all the potentially expressed sequences in a genome would be of great benefit to gene expression studies. Here, we report on an innovative method for creating such a library for durum wheat (Triticum turgidum L. var. durum) and its application for gene discovery. The use of suitable quantities of 5-azacytidine during the germination phase induced the demethylation of total DNA, and the resulting seedlings potentially express all of the genes present in the genome. A new wheat microarray consisting of 4925 unigenes was developed from the totipotent cDNA library and used to screen for genes that may contribute to differences in the disease resistance of two near-isogenic lines, the durum wheat cultivar Latino and the line 5BIL-42, which are respectively susceptible and resistant to powdery mildew. Fluorescently labeled cDNA was prepared from the RNA of seedlings of the two near-isogenic wheat lines after infection with a single powdery mildew isolate under controlled conditions in the greenhouse. Hybridization to the microarray identified six genes that were differently expressed in the two lines. Four of the sequences could be assigned putative functions based on their similarity to known genes in public databases. Physical mapping of the six genes localized them to two regions of the genome: the centromeric region of chromosome 5B, where the Pm36 resistance gene was previously localized, and chromosome 6B

The accession MG5323 of T. turgidun ssp. dicoccum, resistant to powdery mildew, was crossed to the susceptible durum wheat cultivar Latino and a set of 122 Recombinant Inbred Lines (RILs) was produced. Genetic analysis of F1 and F2 progenies and RIL population, tested with a powdery mildew isolate O2 in controlled greenhouse conditions, indicated that a single dominant gene, temporarily designed Ml5323, controls the powdery mildew resistance at the seedling stage. Molecular markers and bulk segregant analysis were used to characterize and map the powdery mildew resistance gene. Twelve microsatellite markers were found to be linked to the resistance gene and, among them, two gSSRs (Xwmc25, Xwmc243) and one EST-SSR (CA695634), were found to be tightly linked to the resistance gene. By means of Chinese Spring nullisomic-tetrasomic and ditelosomics lines the polymorphic markers and the resistance gene were assigned to chromosome arm 2BS and were physically mapped on bin 2BS3-0.84-1.00 by Chinese Spring deletion lines. The physical mapping of the microsatellite markers linked to the Ml5323 gene confirmed the presence of this locus in the short arm of 2B on bin 2BS3-0.84-1.00 where was also located the Pm26 gene. A test of allelism between Ml5323and Pm26 was carried out in order to estabilish the relationship between these two genes located in the same bin on chromosome 2BS. The mildew resistant accessions TTD140 of ssp. dicoccoides, that carries the recessive gene Pm26 and MG5323 of ssp. dicoccum with the dominant gene Ml5323 were crossed to obtain the F1 progeny (TTD140 x MG5323). Seedlings of TTD140, MG5323 and ten F1(TTD140 x MG5323) were highly resistant to the isolate O2. Two hundred and twelve F2 families from the TTD140 x MG5323 population were evaluated for their powdery mildew reaction under greenhouse conditions following the same procedures used for the Latino x MG5323 cross. The F2 population segregated for resistance and susceptibility to isolate O2 of powdery mildew and showed a significant deviation from the theoretical 15 resistant : 1 susceptible ratio expected for two dominant genes segregating independently. The results obtained indicated that the two genes Pm26 and Ml5323 are different and linked on the bin 2BS3-0.84-1.00.

Abstract Background: Powdery mildew (Blumeria graminis f. sp. tritici) is one of the most damaging diseases of wheat. The objective of this study was to identify the wheat genomic regions that are involved in the control of powdery mildew resistance through a quantitative trait loci (QTL) meta-analysis approach. This meta-analysis allows the use of collected QTL data from different published studies to obtain consensus QTL across different genetic backgrounds, thus providing a better definition of the regions responsible for the trait, and the possibility to obtain molecular markers that will be suitable for marker-assisted selection. Results: Five QTL for resistance to powdery mildew were identified under field conditions in the durum-wheat segregating population Creso × Pedroso. An integrated map was developed for the projection of resistance genes/ alleles and the QTL from the present study and the literature, and to investigate their distribution in the wheat genome. Molecular markers that correspond to candidate genes for plant responses to pathogens were also projected onto the map, particularly considering NBS-LRR and receptor-like protein kinases. More than 80 independent QTL and 51 resistance genes from 62 different mapping populations were projected onto the consensus map using the Biomercator statistical software. Twenty-four MQTL that comprised 2–6 initial QTL that had widely varying confidence intervals were found on 15 chromosomes. The co-location of the resistance QTL and genes was investigated. Moreover, from analysis of the sequences of DArT markers, 28 DArT clones mapped on wheat chromosomes have been shown to be associated with the NBS-LRR genes and positioned in the same regions as the MQTL for powdery mildew resistance. Conclusions: The results from the present study provide a detailed analysis of the genetic basis of resistance to powdery mildew in wheat. The study of the Creso × Pedroso durum-wheat population has revealed some QTL that had not been previously identified. Furthermore, the analysis of the co-localization of resistance loci and functional markers provides a large list of candidate genes and opens up a new perspective for the fine mapping and isolation of resistance genes, and for the marker-assisted improvement of resistance in wheat.

Levels of genetic diversity and population genetic structure of a collection of 230 accessions of seven tetraploid Triticum turgidum L. subspecies were investigated using six morphological, nine seed storage protein loci, 26 SSRs and 970 DArT markers. The genetic diversity of the morphological traits and seed storage proteins was always lower in the durum wheat compared to the wild and domesticated emmer. Using Bayesian clustering (K = 2), both of the sets of molecular markers distinguished the durum wheat cultivars from the other tetraploid subspecies, and two distinct subgroups were detected within the durum wheat subspecies, which is in agreement with their origin and year of release. The genetic diversity of morphological traits and seed storage proteins was always lower in the improved durum cultivars registered after 1990, than in the intermediate and older ones. This marked effect on diversity was not observed for molecular markers, where there was only a weak reduction. At K &gt;2, the SSR markers showed a greater degree of resolution than for DArT, with their identification of a greater number of groups within each subspecies. Analysis of DArT marker differentiation between the wheat subspecies indicated outlier loci that are potentially linked to genes controlling some important agronomic traits. Among the 211 loci identified under selection, 109 markers were recently mapped, and some of these markers were clustered into specific regions on chromosome arms 2BL, 3BS and 4AL, where several genes/quantitative trait loci (QTLs) are involved in the domestication of tetraploid wheats, such as the tenacious glumes (Tg) and brittle rachis (Br) characteristics. On the basis of these results, it can be assumed that the population structure of the tetraploid wheat collection partially reflects the evolutionary history of Triticum turgidum L. subspecies and the genetic potential of landraces and wild accessions for the detection of unexplored alleles.

The tetraploid wheat Triticum turgidum ssp. dicoccum shows particular promises as a donor of useful genetic variation for several traits including disease resistances to introgress in cultivated wheats. The accession MG5323 of ssp. dicoccum, resistant to powdery mildew and leaf rust, was crossed to susceptible durum wheat cultivar Latino and a set of 113 recombinant inbred lines (RILs) was produced. The objective of this work was to identify and map leaf rust and powdery mildew resistance loci from dicoccum accession. The parents and RIL population were phenotyped, under controlled greenhouse conditions, with two Puccinia triticina (VMC03 and 12766) and one Blumeria graminis (O2) isolates. Marker analysis of the RILs was performed using a large set of different molecular markers (SSR, EST-SSR,COS and SNP) leading to the construction of a linkage map containing 7,808 polymorphic loci covering 6,228 cM of genetic distance on the fourteen chromosomes of durum wheat, with an average distance of 0.80 cM between adjacent markers. Linkage analysis allowed the identification of different regions significantly associated with leaf rust and powdery mildew resistances. One major gene conferring resistance to leaf rust was detected on the short arm of chromosome 1B, explaining a total phenotypic variation ranging from 41.89 to 52.56% and an additional minor gene was located on chromosome 7B, explaining 12.16-31.24% of total phenotypic variation. About the powdery mildew resistance a single dominant gene was located on the short arm of chromosome 2B explaining 67.90% of total phenotypic variation. These results allowed the identification of new resistance genes to leaf rust and powdery mildew in a tetrapoid wheat genetic background and the closest linked markers identified can be used for marker-assisted selection (MAS) making feasible the development of resistant durum wheat cultivars using the discovered resistance genes.

Glutamine synthetase (GS) enzyme (EC 6.3.1.2) plays a central role in assimilating ammonia produced in the leaf from metabolic processes, spanning from assimilation to transamination reactions and catabolic processes. GS is located in both cytoplasm (GS1, GSe and GSr) and plastids (GS2) of plant cells. Glutamine and glutamate, produced by the concerted action of GS and glutamate synthase, are then transported from the leaf to the developing sinks or grain in wheat. The goal of the present study was to characterise GSe genes and to assess the linkage with grain protein content, an important quantitative trait controlled by multiple genes. Here, we report the isolation of the complete cytosolic GS gene sequences of the durum wheat cvv. 'Ciccio' and 'Svevo' (characterised by low and high protein content, respectively). GSe-A4 located on 4A chromosome comprises 12 exons separated by 11 introns, while the GSe-B4 gene on 4B chromosome comprises 11 exons separated by 10 introns. Quantitative real-time PCR indicated different expression levels of GSe-A4 and GSe-B4 genes in the two wheat cvv. 'Ciccio' and 'Svevo'. The two GSe genes were significantly associated to quantitative trait loci for grain protein content.

Powdery mildew caused by the fungal pathogen Blumeria graminis f. sp. tritici (Bgt), is a destructive foliar disease on wheat in many regions of the world. Triticum turgidum ssp. dicoccum (2n = 4x = 28) shows particular promises as a donor source of useful genetic variation for several traits, including disease resistances that could be introgressed to cultivated wheats. Accession MG5323, resistant to powdery mildew, was crossed to the susceptible durum cultivar Latino and a set of 122 recombinant inbred lines (RILs) was produced. F1 and F2 progenies and the RIL population were tested with one isolate of Blumeria graminis and data obtained indicated that a single dominant gene, temporarily designated Ml5323, controlled resistance at the seedling stage. Molecular markers were used to characterize and map the powdery mildew resistance gene. Twelve microsatellite markers were linked to the resistance gene, and among them, EST-SSR CA695634 was tightly linked to the resistance gene, which was assigned to chromosome arm 2BS and physically mapped to the gene rich region of fragment length (FL) 0.84–1.00. An allelism test showed that the Ml5323 gene and the resistant gene Pm26 of ssp. dicoccoides localized in the same bin, are not allelic and tightly linked.

Background: Nitrogen uptake and the efficient absorption and metabolism of nitrogen are essential elements in attempts to breed improved cereal cultivars for grain or silage production. One of the enzymes related to nitrogen metabolism is glutamine-2-oxoglutarate amidotransferase (GOGAT). Together with glutamine synthetase (GS), GOGAT maintains the flow of nitrogen from NH4 + into glutamine and glutamate, which are then used for several aminotransferase reactions during amino acid synthesis. Results: The aim of the present work was to identify and analyse the structure of wheat NADH-GOGAT genomic sequences, and study the expression in two durum wheat cultivars characterized by low and high kernel protein content. The genomic sequences of the three homoeologous A, B and D NADH-GOGAT genes were obtained for hexaploid Triticum aestivum and the tetraploid A and B genes of Triticum turgidum ssp. durum. Analysis of the gene sequences indicates that all wheat NADHGOGAT genes are composed of 22 exons and 21 introns. The three hexaploid wheat homoeologous genes have high conservation of sequence except intron 13 which shows differences in both length and sequence. A comparative analysis of sequences among di- and mono-cotyledonous plants shows both regions of high conservation and of divergence. qRT-PCR performed with the two durum wheat cvs Svevo and Ciccio (characterized by high and low protein content, respectively) indicates different expression levels of the two NADH-GOGAT-3A and NADH-GOGAT-3B genes. Conclusion: The three hexaploid wheat homoeologous NADH-GOGAT gene sequences are highly conserved – consistent with the key metabolic role of this gene. However, the dicot and monocot amino acid sequences show distinctive patterns, particularly in the transit peptide, the exon 16–17 junction, and the C-terminus. The lack of conservation in the transit peptide may indicate subcellular differences between the two plant divisions - while the sequence conservation within enzyme functional domains remains high. Higher expression levels of NADH-GOGAT are associated with higher grain protein content in two durum wheats.

arget region amplification polymorphism (TRAP) is a relatively new PCR-based technique that detects large numbers of loci in a single reaction without extensive pre-PCR processing of samples. The aim of this study was to integrate TRAP markers in an EST-derived SSR linkage map of a RIL mapping population from the cross of the durum wheat cultivars Ciccio and Svevo, for a more general purpose of establishing a high-throughput system for genetic map saturation. Primer combinations producing PCR products with at least 4-5 polymorphic bands were selected and analyzed across the mapping population. The PCR reactions produced a total of 2,881 fragments with an average of 52 peaks per reaction. A total of 142 new TRAP markers were mapped and found to be randomly distributed in the genome. The total length of the map was 2,043.0 cM, with an average chromosome length of 145.9 cM. Homoeologous group one had the highest number of TRAP markers (38 loci) and the longest map length (407.9 cM) for a total of 87 markers, while the homoeologous group five had the lowest TRAP marker number (5 loci) and the shortest map length (232.5 cM). The distribution of markers among the seven homoeologous groups was random. The results indicate that TRAP is highly efficient in genetic mapping, generating a large number of markers scattered across the genome. This closes many existing gaps in marker coverage and may join otherwise separate linkage groups