Raman developmental markers in root cell walls are associated with lodging tendency in tef.

MAIN CONCLUSION: Using Raman micro-spectroscopy on tef roots, we could monitor cell wall maturation in lines with varied genetic lodging tendency. We describe the developing cell wall composition in root endodermis and cylinder tissue. Tef [Eragrostis tef (Zucc.) Trotter] is an important staple crop in Ethiopia and Eritrea, producing gluten-free and protein-rich grains. However, this crop is not adapted to modern farming practices due to high lodging susceptibility, which prevents the application of mechanical harvest. Lodging describes the displacement of roots (root lodging) or fracture of culms (stem lodging), forcing plants to bend or fall from their vertical position, causing significant yield losses. In this study, we aimed to understand the microstructural properties of crown roots, underlining tef tolerance/susceptibility to lodging. We analyzed plants at 5 and 10 weeks after emergence and compared trellised to lodged plants. Root cross sections from different tef genotypes were characterized by scanning electron microscopy, micro-computed tomography, and Raman micro-spectroscopy. Lodging susceptible genotypes exhibited early tissue maturation, including developed aerenchyma, intensive lignification, and lignin with high levels of crosslinks. A comparison between trellised and lodged plants suggested that lodging itself does not affect the histology of root tissue. Furthermore, cell wall composition along plant maturation was typical to each of the tested genotypes independently of trellising. Our results suggest that it is possible to select lines that exhibit slow maturation of crown roots. Such lines are predicted to show reduction in lodging and facilitate mechanical harvest.

The Effects of Irrigation, Genotype and Additives on Tef Silage Making.

Tef is known as a multi-harvest crop with high production capacity and outstanding fodder quality. Hence, our overall goal is to develop tef as a new multi-harvest summer crop that can maintain high-quality feed and contribute to both field crops and the livestock industry in Israel. In this study, we aimed to evaluate the ability to preserve tef as silage. Four tef genotypes grown under well-watered (100%) and water-limited (75%) irrigation regimes were harvested at grain filling stage and ensiled with either no additives (control, CTL), or with heterofermentative inoculum (HI), molasses (MOL), and both MOL + HI. Our results showed for the first time that tef could be ensiled, although water-soluble carbohydrates (WSC) were lower than those in corn, "the perfect ensiling crop". Most of the tef silage qualitative parameters were better at water-limited irrigation. Additives HI or MOL or MOL + HI also improved silage parameters, e.g., lowered pH and ammonia nitrogen content, but increased in vitro dry matter digestibility, lactic acid and crude protein content, and lactic acid bacteria counts of tef silage. The current results imply increasing the diversity of local ruminant fodder crops, ensuring high-quality feed supply during the summer.

Dissection of a grain yield QTL from wild emmer wheat reveals sub-intervals associated with culm length and kernel number.

Genetic diversity in wheat has been depleted due to domestication and modern breeding. Wild relatives are a valuable source for improving drought tolerance in domesticated wheat. A QTL region on chromosome 2BS of wild emmer wheat (Triticum turgidum ssp. dicoccoides), conferring high grain yield under well-watered and water-limited conditions, was transferred to the elite durum wheat cultivar Uzan (T. turgidum ssp. durum) by a marker-assisted backcross breeding approach. The 2B introgression line turned out to be higher yielding but also exhibited negative traits that likely result from trans-, cis-, or linkage drag effects from the wild emmer parent. In this study, the respective 2BS QTL was subjected to fine-mapping, and a set of 17 homozygote recombinants were phenotyped at BC4F5 generation under water-limited and well-watered conditions at an experimental farm in Israel and at a high-throughput phenotyping platform (LemnaTec-129) in Germany. In general, both experimental setups allowed the identification of sub-QTL intervals related to culm length, kernel number, thousand kernel weight, and harvest index. Sub-QTLs for kernel number and harvest index were detected specifically under either drought stress or well-watered conditions, while QTLs for culm length and thousand-kernel weight were detected in both conditions. Although no direct QTL for grain yield was identified, plants with the sub-QTL for kernel number showed a higher grain yield than the recurrent durum cultivar Uzan under well-watered and mild drought stress conditions. We, therefore, suggest that this sub-QTL might be of interest for future breeding purposes.

Precision phenotyping across the life cycle to validate and decipher drought-adaptive QTLs of wild emmer wheat (Triticum turgidum ssp. dicoccoides) introduced into elite wheat varieties.

Drought events or the combination of drought and heat conditions are expected to become more frequent due to global warming, and wheat yields may fall below their long-term average. One way to increase climate-resilience of modern high-yielding varieties is by their genetic improvement with beneficial alleles from crop wild relatives. In the present study, the effect of two beneficial QTLs introgressed from wild emmer wheat and incorporated in the three wheat varieties BarNir, Zahir and Uzan was studied under well-watered conditions and under drought stress using non-destructive High-throughput Phenotyping (HTP) throughout the life cycle in a single pot-experiment. Plants were daily imaged with RGB top and side view cameras and watered automatically. Further, at two time points, the quantum yield of photosystem II was measured with a top view FluorCam. The QTL carrying near isogenic lines (NILs) were compared with their corresponding parents by t-test for all non-invasively obtained traits and for the manually determined agronomic and yield parameters. Data quality of phenotypic traits (repeatability) in the controlled HTP experiment was above 85% throughout the life cycle and at maturity. Drought stress had a strong effect on growth in all wheat genotypes causing biomass reduction from 2% up to 70% at early and late points in the drought period, respectively. At maturity, the drought caused 47-55% decreases in yield-related traits grain weight, straw weight and total biomass and reduced TKW by 10%, while water use efficiency (WUE) increased under drought by 29%. The yield-enhancing effect of the introgressed QTLs under drought conditions that were previously demonstrated under field/screenhouse conditions in Israel, could be mostly confirmed in a greenhouse pot experiment using HTP. Daily precision phenotyping enabled to decipher the mode of action of the QTLs in the different genetic backgrounds throughout the entire wheat life cycle. Daily phenotyping allowed a precise determination of the timing and size of the QTLs effect (s) and further yielded information about which image-derived traits are informative at which developmental stage of wheat during the entire life cycle. Maximum height and estimated biovolume were reached about a week after heading, so experiments that only aim at exploring these traits would not need a longer observation period. To obtain information on different onset and progress of senescence, the CVa curves represented best the ongoing senescence of plants. The QTL on 7A in the BarNir background was found to improve yield under drought by increased biomass growth, a higher photosynthetic performance, a higher WUE and a "stay green effect."

Genome-Wide Association Study in Bread Wheat Identifies Genomic Regions Associated with Grain Yield and Quality under Contrasting Water Availability.

The objectives of this study were to identify genetic loci in the bread wheat genome that would influence yield stability and quality under water stress, and to identify accessions that can be recommended for cultivation in dry and hot regions. We performed a genome-wide association study (GWAS) using a panel of 232 wheat accessions spanning diverse ecogeographic regions. Plants were evaluated in the Israeli Northern Negev, under two environments: water-limited (D; 250 mm) and well-watered (W; 450 mm) conditions; they were genotyped with ~71,500 SNPs derived from exome capture sequencing. Of the 14 phenotypic traits evaluated, 12 had significantly lower values under D compared to W conditions, while the values for two traits were higher under D. High heritability (H2 = 0.5-0.9) was observed for grain yield, spike weight, number of grains per spike, peduncle length, and plant height. Days to heading and grain yield could be partitioned based on accession origins. GWAS identified 154 marker-trait associations (MTAs) for yield and quality-related traits, 82 under D and 72 under W, and identified potential candidate genes. We identified 24 accessions showing high and/or stable yields under D conditions that can be recommended for cultivation in regions under the threat of global climate change.

Genomic Architecture of Phenotypic Plasticity in Response to Water Stress in Tetraploid Wheat.

Phenotypic plasticity is one of the main mechanisms of adaptation to abiotic stresses via changes in critical developmental stages. Altering flowering phenology is a key evolutionary strategy of plant adaptation to abiotic stresses, to achieve the maximum possible reproduction. The current study is the first to apply the linear regression residuals as drought plasticity scores while considering the variation in flowering phenology and traits under non-stress conditions. We characterized the genomic architecture of 17 complex traits and their drought plasticity scores for quantitative trait loci (QTL) mapping, using a mapping population derived from a cross between durum wheat (Triticum turgidum ssp. durum) and wild emmer wheat (T. turgidum ssp. dicoccoides). We identified 79 QTLs affected observed traits and their plasticity scores, of which 33 reflected plasticity in response to water stress and exhibited epistatic interactions and/or pleiotropy between the observed and plasticity traits. Vrn-B3 (TaTF1) residing within an interval of a major drought-escape QTL was proposed as a candidate gene. The favorable alleles for most of the plasticity QTLs were contributed by wild emmer wheat, demonstrating its high potential for wheat improvement. Our study presents a new approach for the quantification of plant adaptation to various stresses and provides new insights into the genetic basis of wheat complex traits under water-deficit stress.

Variation Between Three Eragrostis tef Accessions in Defense Responses to Rhopalosiphum padi Aphid Infestation.

Tef (Eragrostis tef), a staple crop that originated in the Horn of Africa, has been introduced to multiple countries over the last several decades. Crop cultivation in new geographic regions raises questions regarding the molecular basis for biotic stress responses. In this study, we aimed to classify the insect abundance on tef crop in Israel, and to elucidate its chemical and physical defense mechanisms in response to insect feeding. To discover the main pests of tef in the Mediterranean climate, we conducted an insect field survey on three selected accessions named RTC-144, RTC-405, and RTC-406, and discovered that the most abundant insect order is Hemiptera. We compared the differences in Rhopalosiphum padi (Hemiptera; Aphididae) aphid performance, preference, and feeding behavior between the three accessions. While the number of aphid progeny was lower on RTC-406 than on the other two, the aphid olfactory assay indicated that the aphids tended to be repelled from the RTC-144 accession. To highlight the variation in defense responses, we investigated the physical and chemical mechanisms. As a physical barrier, the density of non-granular trichomes was evaluated, in which a higher number of trichomes on the RTC-406 than on the other accessions was observed. This was negatively correlated with aphid performance. To determine chemical responses, the volatile and central metabolite profiles were measured upon aphid attack for 4 days. The volatile analysis exposed a rich and dynamic metabolic profile, and the central metabolism profile indicated that tef plants adjust their sugars and organic and amino acid levels. Overall, we found that the tef plants possess similar defense responses as other Poaceae family species, while the non-volatile deterrent compounds are yet to be characterized. A transcriptomic time-series analysis of a selected accession RTC-144 infested with aphids revealed a massive alteration of genes related to specialized metabolism that potentially synthesize non-volatile toxic compounds. This is the first report to reveal the variation in the defense mechanisms of tef plants. These findings can facilitate the discovery of insect-resistance genes leading to enhanced yield in tef and other cereal crops.

Limited divergent adaptation despite a substantial environmental cline in wild pea.

Isolation by environment (IBE) is a widespread phenomenon in nature. It is commonly expected that the degree of difference among environments is proportional to the level of divergence between populations in their respective environments. It is therefore assumed that a species' genetic diversity displays a pattern of IBE in the presence of a strong environmental cline if gene flow does not mitigate isolation. We tested this common assumption by analysing the genetic diversity and demographic history of Pisum fulvum, which inhabits contrasting habitats in the southern Levant and is expected to display only minor migration rates between populations, making it an ideal test case. Ecogeographical and subpopulation structure were analysed and compared. The correlation of genetic with environmental distances was calculated to test the effect of isolation by distance and IBE and detect the main drivers of these effects. Historical effective population size was estimated using stairway plot. Limited overlap of ecogeographical and genetic clustering was observed, and correlation between genetic and environmental distances was statistically significant but small. We detected a sharp decline of effective population size during the last glacial period. The low degree of IBE may be the result of genetic drift due to a past bottleneck. Our findings contradict the expectation that strong environmental clines cause IBE in the absence of extensive gene flow.

Nitrogen availability and genotype affect major nutritional quality parameters of tef grain grown under irrigation.

Worldwide demand for tef (Eragrostis tef) as a functional food for human consumption is increasing, thanks to its nutritional benefits and gluten-free properties. As a result, tef in now grown outside its native environment in Ethiopia and thus information is required regarding plant nutrition demands in these areas, as well as resulting grain health-related composition. In the current work, two tef genotypes were grown in Israel under irrigation in two platforms, plots in the field and pots in a greenhouse, with four and five nitrogen treatments, respectively. Nutritional and health-related quality traits were analyzed, including mineral content, fatty acid composition, hydrophilic and lipophilic antioxidative capacity, total phenolic content and basic polyphenolic profile. Our results show that tef genotypes differ in their nutritional composition, e.g. higher phenolic contents in the brown compared to the white genotype. Additionally, nitrogen availability positively affected grain fatty acid composition and iron levels in both experiments, while negatively affecting total phenolics in the field trials. To conclude, nitrogen fertilization is crucial for crop growth and productivity, however it also implicates nutritional value of the grains as food. These effects should be considered when fertilizing tef with nitrogen, to optimize both crop productivity and nutritional effects.

GenoTypeMapper: graphical genotyping on genetic and sequence-based maps.

BACKGROUND: The rising availability of assemblies of large genomes (e.g. bread and durum wheat, barley) and their annotations deliver the basis to graphically present genome organization of parents and progenies on a physical scale. Genetic maps are a very important tool for breeders but often represent distorted models of the actual chromosomes, e.g., in centromeric and telomeric regions. This biased picture might lead to imprecise assumptions and estimations about the size and complexity of genetic regions and the selection of suitable molecular markers for the incorporation of traits in breeding populations or near-isogenic lines (NILs). Some software packages allow the graphical illustration of genotypic data, but to the best of our knowledge, suitable software packages that allow the comparison of genotypic data on the physical and genetic scale are currently unavailable. RESULTS: We developed a simple Java-based-software called GenoTypeMapper (GTM) for comparing genotypic data on genetic and physical maps and tested it for effectiveness on data of two NILs that carry QTL-regions for drought stress tolerance from wild emmer on chromosome 2BS and 7AS. Both NILs were more tolerant to drought stress than their recurrent parents but exhibited additional undesirable traits such as delayed heading time. CONCLUSIONS: In this article, we illustrate that the software easily allows users to display and identify additional chromosomal introgressions in both NILs originating from the wild emmer parent. The ability to detect and diminish linkage drag can be of particular interest for pre-breeding purposes and the developed software is a well-suited tool in this respect. The software is based on a simple allele-matching algorithm between the offspring and parents of a crossing scheme. Despite this simple approach, GTM seems to be the only software that allows us to analyse, illustrate and compare genotypic data of offspring of different crossing schemes with up to four parents in two different maps. So far, up to 500 individuals with a maximum number of 50,000 markers can be examined with the software. The main limitation that hampers the performance of the software is the number of markers that are examined in parallel. Since each individual must be analysed separately, a maximum of ten individuals can currently be displayed in a single run. On a computer with an Intel five processor of the 8th generation, GTM can reliably either analyse a single individual with up to 12,000 markers or ten individuals with up to 3,600 markers in less than five seconds. Future work aims to improve the performance of the software so that more complex crossing schemes with more parents and more markers can be analysed.

Environmental and genetic determinants of amphicarpy in Pisum fulvum, a wild relative of domesticated pea.

Pisum fulvum is an annual legume native to Syria, Lebanon, Israel and Jordan. In certain locations, P. fulvum individuals were documented to display a reproductive dimorphism - amphicarpy, with both above and below ground flowers and pods. Herein we aimed to study the possible role of soil texture on amphicarpy in P. fulvum, to investigate the possible bio-climatic associations of P. fulvum amphicarpy and to identify genetic markers associated with this phenotype. A set of 127 germplasm accessions sampled across the Israeli distribution range of the species was phenotyped in two common garden nurseries. Land use and bioclimatic data were used to delineate the eco-geographic clustering of accession's sampling sites. Single nucleotide polymorphism (SNP) markers were employed in genome-wide association study to identify associated loci. Amphicarpy was subject to strong experimental site x genotype interaction with higher phenotypic expression in fine textured soil relative to sandy loam. Amphicarpy was more prevalent among accessions sampled in eastern Judea and Samaria and was weakly associated with early phenology and relatively modest above ground biomass production. Twelve SNP markers were significantly associated with amphicarpy, each explaining between 8 and 12 % of the phenotypic variation. In P. fulvum amphicarpy seems to be a polygenetic trait controlled by an array of genes that is likely to be affected by environmental stimuli. The probable selective advantage of the association between amphicarpy and early flowering is in line with its relative prevalence in drought prone territories subject to heavy grazing.

Variation in phosphorus and sulfur content shapes the genetic architecture and phenotypic associations within the wheat grain ionome.

Dissection of the genetic basis of wheat ionome is crucial for understanding the physiological and biochemical processes underlying mineral accumulation in seeds, as well as for efficient crop breeding. Most of the elements essential for plants are metals stored in seeds as chelate complexes with phytic acid or sulfur-containing compounds. We assume that the involvement of phosphorus and sulfur in metal chelation is the reason for strong phenotypic correlations within ionome. Adjustment of element concentrations for the effect of variation in phosphorus and sulfur seed content resulted in drastic change of phenotypic correlations between the elements. The genetic architecture of wheat grain ionome was characterized by quantitative trait loci (QTL) analysis using a cross between durum and wild emmer wheat. QTL analysis of the adjusted traits and two-trait analysis of the initial traits paired with either P or S considerably improved QTL detection power and accuracy, resulting in the identification of 105 QTLs and 617 QTL effects for 11 elements. Candidate gene search revealed some potential functional associations between QTLs and corresponding genes within their intervals. Thus, we have shown that accounting for variation in P and S is crucial for understanding of the physiological and genetic regulation of mineral composition of wheat grain ionome and can be implemented for other plants.

CoverageTool: A semi-automated graphic software: applications for plant phenotyping.

BACKGROUND: Characterization and quantification of visual plant traits is often limited to the use of tools and software that were developed to address a specific context, making them unsuitable for other applications. CoverageTool is flexible multi-purpose software capable of area calculation in cm2, as well as coverage area in percentages, suitable for a wide range of applications. RESULTS: Here we present a novel, semi-automated and robust tool for detailed characterization of visual plant traits. We demonstrate and discuss the application of this tool to quantify a broad spectrum of plant phenotypes/traits such as: tissue culture parameters, ground surface covered by annual plant canopy, root and leaf projected surface area, and leaf senescence area ratio. The CoverageTool software provides easy to use functions to analyze images. While use of CoverageTool involves subjective operator color selections, applying them uniformly to full sets of samples makes it possible to provide quantitative comparison between test subjects. CONCLUSION: The tool is simple and straightforward, yet suitable for the quantification of biological and environmental effects on a wide variety of visual plant traits. This tool has been very useful in quantifying different plant phenotypes in several recently published studies, and may be useful for many applications.

Ancestral QTL Alleles from Wild Emmer Wheat Enhance Root Development under Drought in Modern Wheat.

A near-isogenic line (NIL-7A-B-2), introgressed with a quantitative trait locus (QTL) on chromosome 7AS from wild emmer wheat (Triticum turgidum ssp. dicoccoides) into the background of bread wheat (T. aestivum L.) cv. BarNir, was recently developed and studied in our lab. NIL-7A-B-2 exhibited better productivity and photosynthetic capacity than its recurrent parent across a range of environments. Here we tested the hypothesis that root-system modifications play a major role in NIL-7A-B-2's agronomical superiority. Root-system architecture (dry matter and projected surface area) and shoot parameters of NIL-7A-B-2 and 'BarNir' were evaluated at 40, 62, and 82 days after planting (DAP) in a sand-tube experiment, and root tip number was assessed in a 'cigar-roll' seedling experiment, both under well-watered and water-limited (WL) treatments. At 82 DAP, under WL treatment, NIL-7A-B-2 presented greater investment in deep roots (depth 40-100 cm) than 'BarNir,' with the most pronounced effect recorded in the 60-80 cm soil depth (60 and 40% increase for root dry matter and surface area, respectively). NIL-7A-B-2 had significantly higher root-tip numbers (∼48%) per plant than 'BarNir' under both treatments. These results suggest that the introgression of 7AS QTL from wild emmer wheat induced a deeper root system under progressive water stress, which may enhance abiotic stress resistance and productivity of domesticated wheat.

Environmental and genetic effects on tomato seed metabolic balance and its association with germination vigor.

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.

Ancestral QTL alleles from wild emmer wheat improve grain yield, biomass and photosynthesis across enviroinments in modern wheat.

Wild emmer wheat (Triticum turgidum ssp. dicoccoides) is considered a promising source for improving drought resistance in domesticated wheat. Nevertheless, wild germplasm has not been widely used in wheat breeding for abiotic stress resilience. In the current study, a near isogenic line NIL-7A-B-2, introgressed with a drought-related QTL from wild emmer wheat on chromosome 7A, and its recurrent parent, bread wheat cv. BarNir, were investigated under four environments across 2 years-water-limited and well-watered conditions in a rain-protected screen-house (Year 1) and two commercial open field plots under ample precipitation (Year 2). NIL-7A-B-2 exhibited an advantage over BarNir in grain yield and biomass production under most environments. Further physiological analyses suggested that enhanced photosynthetic capacity and photochemistry combined with higher flag leaf area are among the factors underlying the improved productivity of NIL-7A-B-2. These were coupled with improved sink capacity in NIL-7A-B-2, manifested by greater yield components than its parental line. This study provides further support for our previous findings that introgression of wild emmer QTL alleles, using marker assisted selection, can enhance grain yield and biomass production across environments in domesticated wheat, thereby enriching the modern gene pool with essential diversity for the improvement of yield and drought resistance.

Ancestral QTL Alleles from Wild Emmer Wheat Improve Drought Resistance and Productivity in Modern Wheat Cultivars.

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.

Transcriptome profiling of wheat glumes in wild emmer, hulled landraces and modern cultivars.

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.

Plant domestication versus crop evolution: a conceptual framework for cereals and grain legumes.

'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.

Threshing efficiency as an incentive for rapid domestication of emmer wheat.

BACKGROUND AND AIMS: The harvesting method of wild and cultivated cereals has long been recognized as an important factor in the emergence of domesticated non-shattering ear genotypes. This study aimed to quantify the effects of spike brittleness and threshability on threshing time and efficiency in emmer wheat, and to evaluate the implications of post-harvest processes on domestication of cereals in the Near East. METHODS: A diverse collection of tetraploid wheat genotypes, consisting of Triticum turgidum ssp. dicoccoides - the wild progenitor of domesticated wheat - traditional landraces, modern cultivars (T. turgidum ssp. durum) and 150 recombinant (wild × modern) inbred lines, was used in replicated controlled threshing experiments to quantify the effects of spike brittleness and threshability on threshing time and efficiency. KEY RESULTS: The transition from a brittle hulled wild phenotype to non-brittle hulled phenotype (landraces) was associated with an approx. 30 % reduction in threshing time, whereas the transition from the latter to non-brittle free-threshing cultivars was associated with an approx. 85 % reduction in threshing time. Similar trends were obtained with groups of recombinant inbred lines showing extreme phenotypes of brittleness and threshability. CONCLUSIONS: In tetraploid wheat, both non-brittle spike and free-threshing are labour-saving traits that increase the efficiency of post-harvest processing, which could have been an incentive for rapid domestication of the Near Eastern cereals, thus refuting the recently proposed hypothesis regarding extra labour associated with the domesticated phenotype (non-brittle spike) and its presumed role in extending the domestication episode time frame.