BACKGROUND: The metabolite content of a seed and its ability to germinate are determined by genetic makeup and environmental effects during development. The interaction between genetics, environment and seed metabolism and germination was studied in 72 tomato homozygous introgression lines (IL) derived from Solanum pennelli and S. esculentum M82 cultivar. Plants were grown in the field under saline and fresh water irrigation during two consecutive seasons, and collected seeds were subjected to morphological analysis, gas chromatograph-mass spectrometry (GC-MS) metabolic profiling and germination tests. RESULTS: Seed weight was under tight genetic regulation, but it was not related to germination vigor. Salinity significantly reduced seed number but had little influence on seed metabolites, affecting only 1% of the statistical comparisons. The metabolites negatively correlated to germination were simple sugars and most amino acids, while positive correlations were found for several organic acids and the N metabolites urea and dopamine. Germination tests identified putative loci for improved germination as compared to M82 and in response to salinity, which were also characterized by defined metabolic changes in the seed. CONCLUSIONS: An integrative analysis of the metabolite and germination data revealed metabolite levels unambiguously associated with germination percentage and rate, mostly conserved in the different tested seed development environments. Such consistent relations suggest the potential for developing a method of germination vigor prediction by metabolic profiling, as well as add to our understanding of the importance of primary metabolic processes in germination.

Wild emmer wheat (Triticum turgidum ssp. dicoccoides) is considered a promising source for improving stress resistances in domesticated wheat. Here we explored the potential of selected quantitative trait loci (QTLs) from wild emmer wheat, introgressed via marker-assisted selection, to enhance drought resistance in elite durum (T. turgidum ssp. durum) and bread (T. aestivum) wheat cultivars. The resultant near-isogenic lines (BC3F3 and BC3F4) were genotyped using SNP array to confirm the introgressed genomic regions and evaluated in two consecutive years under well-watered (690-710 mm) and water-limited (290-320 mm) conditions. Three of the introgressed QTLs were successfully validated, two in the background of durum wheat cv. Uzan (on chromosomes 1BL and 2BS), and one in the background of bread wheat cvs. Bar Nir and Zahir (chromosome 7AS). In most cases, the QTL x environment interaction was validated in terms of improved grain yield and biomass-specifically under drought (7AS QTL in cv. Bar Nir background), under both treatments (2BS QTL), and a greater stability across treatments (1BL QTL). The results provide a first demonstration that introgression of wild emmer QTL alleles can enhance productivity and yield stability across environments in domesticated wheat, thereby enriching the modern gene pool with essential diversity for the improvement of drought resistance.

Background: Wheat domestication is considered as one of the most important events in the development of human civilization. Wheat spikelets have undergone significant changes during evolution under domestication, resulting in soft glumes and larger kernels that are released easily upon threshing. Our main goal was to explore changes in transcriptome expression in glumes that accompanied wheat evolution under domestication. Methods: A total of six tetraploid wheat accessions were selected for transcriptome profiling based on their rachis brittleness and glumes toughness. RNA pools from glumes of the central spikelet at heading time were used to construct cDNA libraries for sequencing. The trimmed reads from each library were separately aligned to the reference sub-genomes A and B, which were extracted from wheat survey sequence. Differentially expression analysis and functional annotation were performed between wild and domesticated wheat, to identity candidate genes associated with evolution under domestication. Selected candidate genes were validated using real time PCR. Results: Transcriptome profiles of wild emmer wheat, wheat landraces, and wheat cultivars were compared using next generation sequencing (RNA-seq). We have found a total of 194,893 transcripts, of which 73,150 were shared between wild, landraces, and cultivars. From 781 differentially expressed genes (DEGs), 336 were down-regulated and 445 were up-regulated in the domesticated compared to wild wheat genotypes. Gene Ontology (GO) annotation assigned 293 DEGs (37.5 %) to GO term groups, of which 134 (17.1 %) were down-regulated and 159 (20.4 %) up-regulated in the domesticated wheat. Some of the down-regulated DEGs in domesticated wheat are related to the biosynthetic pathways that eventually define the mechanical strength of the glumes, such as cell wall, lignin, pectin and wax biosynthesis. The reduction in gene expression of such genes, may explain the softness of the glumes in the domesticated forms. In addition, we have identified genes involved in nutrient remobilization that may affect grain size and other agronomic traits evolved under domestication. Conclusions: The comparison of RNA-seq profiles between glumes of wheat groups differing in glumes toughness and rachis brittleness revealed a few DEGs that may be involved in glumes toughness and nutrient remobilization. These genes may be involved in processes of wheat improvement under domestication. © 2015 Zou et al.

Wheat domestication and subsequent evolution under domestication occurred since the dawn of agriculture and caused significant genetic changes that affected plant morphology, physiology and phenology. The majority of these traits are quantitative traits controlled by many genes. Correspondingly, the main goal of the current study is genetic dissection of the key domestication trait (brittle rachis) and traits evolved under domestication, based on quantitative phenotyping. Genetic mapping of quantitative trait loci (QTL) affecting brittle rachis, threshability, threshing efficiency, spike harvest index and kernel weight was conducted using a recombinant inbred lines population derived from a cross between Triticum durum and wild emmer wheat. Using a new quantitative phenotyping approach, we discovered novel QTLs underlying rachis fragility, spike threshability and other domestication-related traits and confirmed some of the known putative locations for QTLs affecting these traits. Overall, the number of domestication-related QTLs mapped to the A genome was twofold higher than those found on the B genome, in accordance with the concept of ‘genome asymmetry’, implying that the A genome is dedicated to the control of morphological traits, house-keeping metabolic reactions and yield components. Our results add a new dimension to this important concept and contribute to a better understanding of the initial steps of domestication evolution of cereals. © 2014, Springer Science+Business Media Dordrecht.

'Domestication syndrome' (DS) denotes differences between domesticated plants and their wild progenitors. Crop plants are dynamic entities; hence, not all parameters distinguishing wild progenitors from cultigens resulted from domestication. In this opinion article, we refine the DS concept using agronomic, genetic, and archaeobotanical considerations by distinguishing crucial domestication traits from traits that probably evolved post-domestication in Near Eastern grain crops. We propose that only traits showing a clear domesticated-wild dimorphism represent the pristine domestication episode, whereas traits showing a phenotypic continuum between wild and domesticated gene pools mostly reflect post-domestication diversification. We propose that our approach may apply to other crop types and examine its implications for discussing the timeframe of plant domestication and for modern plant science and breeding. © 2013 Elsevier Ltd.