Description of durum wheat linkage map and comparative sequence analysis of wheat mapped DArT markers with rice and Brachypodium genomes

Diversity of chemical composition and nutritional value in grain from selected winter wheat cultivars grown in south-western Poland

Given the low protein coverage by legumes in Poland, alternatives (with high protein content and high nutritional value) are being sought (with high protein content and high nutritional value of protein) that could replace these plants. Cereal cultivation dominates in Poland; hence, the search for high-value plants will also consider this group of plants. The aim of the study was to compare the nutritional value of proteins from two wheat cultivars. A field experiment conducted in Zawidowice in south-western Poland in 2019 investigated the nutritional values of two winter wheat cultivars: Aurelius and Activus. These two cultivars were compared in terms of their chemical composition, the biological value of their proteins for animal nutrition, and the content of macro- and microelements. Significant differences in chemical composition were found between the tested wheat cultivars. In terms of the chemical composition, i.e. the content of protein, fiber and ash, the Activus cultivar was characterized by significantly better parameters. This cultivar also had significantly higher gross energy. In turn, a significantly higher content of essential amino acids, i.e. lysine, cysteine, tryptophan, histidine, leucine, ioleucine, and valine, was found in the Aurelius cultivar; therefore, the indicators determining the biological value of the protein are more favorable in the Aurelius cultivars. Meanwhile, in terms of selected macro- and microelements the Auerlius cultivar was more valuable. Varietal progress is necessary to obtain cultivars with the essential nutrients needed by animals to satisfy their dietary requirements.

Genetic Variation for Protein Content and Yield-Related Traits in a Durum Population Derived From an Inter-Specific Cross Between Hexaploid and Tetraploid Wheat Cultivars

Wheat grain protein content (GPC) and yield components are complex quantitative traits influenced by a multi-factorial system consisting of both genetic and environmental factors. Although seed storage proteins represent less than 15% of mature kernels, they are crucial in determining end-use properties of wheat, as well as the nutritional value of derived products. Yield and GPC are negatively correlated, and this hampers breeding programs of commercially valuable wheat varieties. The goal of this work was the evaluation of genetic variability for quantity and composition of seed storage proteins, together with yield components [grain yield per spike (GYS) and thousand-kernel weight (TKW)] in a durum wheat population obtained by an inter-specific cross between a common wheat accession and the durum cv. Saragolla. Quantitative trait loci (QTL) analysis was conducted and closely associated markers identified on a genetic map composed of 4,366 SNP markers previously obtained in the same durum population genotyped with the 90K iSelect SNP assay. A total of 22 QTL were detected for traits related to durum wheat quality. Six genomic regions responsible for GPC control were mapped on chromosomes 2B, 3A, 4A, 4B, 5B, and 7B, with major QTL on chromosomes 2B, 4A, and 5B. Nine loci were detected for GYS: two on chromosome 5B and 7A and one on chromosomes 2A, 2B, 4A, 4B, 7B, with the strongest QTL on 2B. Eight QTL were identified for TKW, three of which located on chromosome 3A, two on 1B and one on 4B, 5A, and 5B. Only small overlapping was found among QTL for GYS, TKW, and GPC, and increasing alleles coming from both parents on different chromosomes. Good candidate genes were identified in the QTL confidence intervals for GYS and TKW.

Analysis of agronomic and domestication traits in a durum × cultivated emmer wheat population using a high-density single nucleotide polymorphism-based linkage map

Development of a high-density SNP map and evaluation of QTL shed light on domestication events in tetraploid wheat and the potential utility of cultivated emmer wheat for durum wheat improvement. Cultivated emmer wheat (Triticum turgidum ssp. dicoccum) is tetraploid and considered as one of the eight founder crops that spawned the Agricultural Revolution about 10,000 years ago. Cultivated emmer has non-free-threshing seed and a somewhat fragile rachis, but mutations in genes governing these and other agronomic traits occurred that led to the formation of today's fully domesticated durum wheat (T. turgidum ssp. durum). Here, we evaluated a population of recombinant inbred lines (RILs) derived from a cross between a cultivated emmer accession and a durum wheat variety. A high-density single nucleotide polymorphism (SNP)-based genetic linkage map consisting of 2,593 markers was developed for the identification of quantitative trait loci. The major domestication gene Q had profound effects on spike length and compactness, rachis fragility, and threshability as expected. The cultivated emmer parent contributed increased spikelets per spike, and the durum parent contributed higher kernel weight, which led to the identification of some RILs that had significantly higher grain weight per spike than either parent. Threshability was governed not only by the Q locus, but other loci as well including Tg-B1 on chromosome 2B and a putative Tg-A1 locus on chromosome 2A indicating that mutations in the Tg loci occurred during the transition of cultivated emmer to the fully domesticated tetraploid. These results not only shed light on the events that shaped wheat domestication, but also demonstrate that cultivated emmer is a useful source of genetic variation for the enhancement of durum varieties.

Genome-wide association for grain morphology in synthetic hexaploid wheats using digital imaging analysis

BACKGROUND

Grain size and shape greatly influence grain weight which ultimately enhances grain yield in wheat. Digital imaging (DI) based phenomic characterization can capture the three dimensional variation in grain size and shape than has hitherto been possible. In this study, we report the results from using digital imaging of grain size and shape to understand the relationship among different components of this trait, their contribution to enhance grain weight, and to identify genomic regions (QTLs) controlling grain morphology using genome wide association mapping with high density diversity array technology (DArT) and allele-specific markers.

RESULTS

Significant positive correlations were observed between grain weight and grain size measurements such as grain length (r = 0.43), width, thickness (r = 0.64) and factor from density (FFD) (r = 0.69). A total of 231 synthetic hexaploid wheats (SHWs) were grouped into five different sub-clusters by Bayesian structure analysis using unlinked DArT markers. Linkage disequilibrium (LD) decay was observed among DArT loci > 10 cM distance and approximately 28% marker pairs were in significant LD. In total, 197 loci over 60 chromosomal regions and 79 loci over 31 chromosomal regions were associated with grain morphology by genome wide analysis using general linear model (GLM) and mixed linear model (MLM) approaches, respectively. They were mainly distributed on homoeologous group 2, 3, 6 and 7 chromosomes. Twenty eight marker-trait associations (MTAs) on the D genome chromosomes 2D, 3D and 6D may carry novel alleles with potential to enhance grain weight due to the use of untapped wild accessions of Aegilops tauschii. Statistical simulations showed that favorable alleles for thousand kernel weight (TKW), grain length, width and thickness have additive genetic effects. Allelic variations for known genes controlling grain size and weight, viz. TaCwi-2A, TaSus-2B, TaCKX6-3D and TaGw2-6A, were also associated with TKW, grain width and thickness. In silico functional analysis predicted a range of biological functions for 32 DArT loci and receptor like kinase, known to affect plant development, appeared to be common protein family encoded by several loci responsible for grain size and shape.

CONCLUSION

Conclusively, we demonstrated the application and integration of multiple approaches including high throughput phenotyping using DI, genome wide association studies (GWAS) and in silico functional analysis of candidate loci to analyze target traits, and identify candidate genomic regions underlying these traits. These approaches provided great opportunity to understand the breeding value of SHWs for improving grain weight and enhanced our deep understanding on molecular genetics of grain weight in wheat.