Stefania L. Giove

Cell wall traits as potential resources to improve resistance of durum wheat against Fusarium graminearum

BackgroundFusarium graminearum, one of the causal agents of Fusarium Head Blight (FHB, scab), leads to severe losses in grain yield and quality due to the production of mycotoxins which are harmful to human and livestock. Different traits for FHB resistance in wheat were identified for common wheat (Triticum aestivum L.) while the sources of FHB resistance in durum wheat (Triticum turgidum ssp. Durum), one of the cereals most susceptible to F. graminearum infection, have not been found. New lines of evidence indicate that content and composition of cell wall polymers affect the susceptibility of the wall to degrading enzymes produced by pathogens during infection and can play a role in the outcome of host-pathogen interactions. The objective of our research is to identify potential cell wall biochemical traits linked to Fusariosis resistance to be transferred from a resistant common wheat to a susceptible durum wheat line.ResultsA detailed analysis of cell wall composition in spikes isolated from a highly resistant common wheat accession “02-5B-318”, a breeding line derived from the FHB-resistant Chinese cv. Sumai-3 and a high susceptible durum wheat cv. Saragolla was performed. Significant differences in lignin monolignols composition, arabinoxylan (AX) substitutions and pectin methylesterification were found between resistant and susceptible plants. We isolated and characterized a pectin methylesterase gene WheatPME1, which we found being down regulated in the FHB-resistant line and induced by fungal infection in the susceptible wheat.ConclusionsOur results indicate cell wall traits differing between the FHB sensitive and resistant wheat genotypes, possibly related to FHB-resistance, and identify the line 02-5B-318R as a potential resource of such traits. Evidence suggests that WheatPME1 is involved in wheat response to F. graminearum.

Comparison of genomic and EST-derived SSR markers in phylogenetic analysis of wheat

Microsatellite markers (simple sequence repeats, SSRs) are used for a wide range of crop genetic and breeding applications, including genetic diversity assessment, phylogenetic analysis, genotypic profiling and marker-assisted selection. Genomic SSR (gSSR) have attracted more attention because of abundance in plant genome, reproducibility, high level of polymorphism and codominant inheritance. Recently, the availability of data for expressed sequence tags (EST), has given more emphasis to EST-derived SSRs, which belong to the transcribed regions of DNA, and are expected to be more conserved and have a higher transferability rate across species than gSSR markers. In the present study, several gSSR and EST-SSR markers were investigated for their transferability and level of DNA polymorphism in different ancestral tetraploid and diploid Triticum and Aegilops species. The same gSSR and EST-SSR markers were also evaluated for their applicability in the phylogenetic analysis of wheat. Both gSSR and EST-SSR markers showed differences for the average transferability rate and the number of alleles/ locus. Phylogenetic trees based on gSSR and EST-SSR markers were in accordance with phylogenetic relations based on cytogenetic and molecular analyses.

Mapping QTLs for Fusarium Head Blight Resistance in an Interspecific Wheat Population

Fusarium head blight (scab) is one of the most widespread and damaging diseases of wheat, causing grain yield and quality losses and production of harmful mycotoxins. Development of resistant varieties is hampered by lack of effective resistance sources in the tetraploid wheat primary gene pool. Here we dissected the genetic basis of resistance in a new durum wheat (Triticum turgidum ssp. durum) Recombinant inbred lines (RILs) population obtained by crossing an hexaploid resistant line and a durum susceptible cultivar. A total of 135 RILs were used for constituting a genetic linkage map and mapping loci for head blight incidence, severity, and disease-related plant morphological traits (plant height, spike compactness, and awn length). The new genetic map accounted for 4,366 single nucleotide polymorphism markers assembled in 52 linkage groups covering a total length of 4,227.37 cM. Major quantitative trait loci (QTL) for scab incidence and severity were mapped on chromosomes 2AS, 3AL, and 2AS, 2BS, 4BL, respectively. Plant height loci were identified on 3A, 3B, and 4B, while major QTL for ear compactness were found on 4A, 5A, 5B, 6A, and 7A. In this work, resistance to Fusarium was transferred from hexaploid to durum wheat, and correlations between the disease and morphological traits were assessed.

Isolation and characterisation of cytosolic glutamine synthetase (GSe) genes and association with grain protein content in durum wheat

Abstract. 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.

Glutamine synthetase in Durum Wheat: Genotypic Variation and Relationship with Grain Protein Content.

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.

Cell wall features transferred from common into durum wheat to improve Fusarium Head Blight resistance

Durum wheat is naturally more susceptible to Fusarium graminerum infection in comparison to common wheat. The improvement of durum wheat resistance against F. graminearum is a challenge due to the lack of resistance sources in its gene pool. FHB-resistance factors were introduced in durum wheat by generating recombinant inbred lines (RILs), obtained by crossing the hexaploid resistant accession 02-5B-318 with the susceptible durum wheat cv. Saragolla. In this work we explored the possible contribution of cell wall (CW) in RILs with improved FHB resistance. We thoroughly studied CW components, mycotoxins content and the expression of related genes in different RILs selected for their extremely high and low resistance to FHB. Differences were found in resistant and susceptible lines in the degree of pectin methylesterification and in deoxynivalenol (DON) accumulation after fungal infection. Genes involved in biochemical modification of CW structure (WheatPme-1, Glu-1) and mycotoxins accumulation (ns-LTP-1) were analyzed as putative candidates for FHB resistance. Our results indicate that durum wheat plants with cell wall structure and gene response acquired from common wheat displayed an increased resistance to FHB.