Durum Landraces Research Articles

Genome scans capture key adaptation and historical hybridization signatures in tetraploid wheat.

Tetraploid wheats (Triticum turgidum L.), including durum wheat (T. turgidum ssp. durum (Desf.) Husn.), are important crops with high nutritional and cultural values. However, their production is constrained by sensitivity to environmental conditions. In search of adaptive genetic signatures tracing historical selection and hybridization events, we performed genome scans on two datasets: (1) Durum Global Diversity Panel comprising a total of 442 tetraploid wheat and wild progenitor accessions including durum landraces (n=286), domesticated emmer (T. turgidum ssp. dicoccum (Schrank) Thell.; n=103) and wild emmer (T. turgidum ssp. dicoccoides (Korn. ex Asch. & Graebn.) Thell.; n=53) wheats genotyped using the 90K single nucleotide polymorphism (SNP) array, and (2) a second dataset comprising a total 121 accessions of nine T. turgidum subspecies including wild emmer genotyped with>100M SNPs from whole-genome resequencing. The genome scan on the first dataset detected six outlier loci on chromosomes 1A, 1B, 3A (n=2), 6A, and 7A. These loci harbored important genes for adaptation to abiotic stresses, phenological responses, such as seed dormancy, circadian clock, flowering time, and key yield-related traits, including pleiotropic genes, such as HAT1, KUODA1, CBL1, and ZFN1. The scan on the second dataset captured a highly differentiated region on chromosome 2B that shows significant differentiation between two groups: one group consists of Georgian (T. turgidum ssp.paleocolchicum A. Love & D. Love) and Persian (T. turgidum ssp. carthlicum (Nevski) A. Love & D. Love) wheat accessions, while the other group comprises all the remaining tetraploids including wild emmer. This is consistent with a previously reported introgression in this genomic region from T. timopheevii Zhuk. which naturally cohabit in the Georgian and neighboring areas. This region harbored several adaptive genes, including the thermomorphogenesis gene PIF4, which confers temperature-resilient disease resistance and regulates other biological processes. Genome scans can be used to fast-track germplasm housed in gene banks and in situ; which helps to identify environmentally resilient accessions for breeding and/or to prioritize them for conservation.

Evaluating agromorphological traits of Greek wheat landraces and exploring their potential for bread and pasta making based on seed physical properties

Physical and morphological characteristics of Greek wheat landrace and cultivar seeds were evaluated, aiming to assess their bread- and pasta-making quality. Furthermore, the plant agromorphological traits of wheat landraces and cultivars were measured and correlated with seed physical properties. Fifteen Triticum spp. accessions, out of which four cultivars (two Triticum aestivum and two T. durum), nine landraces (two T. durum, five T. aestivum, one T. dicoccum and one T. polonicum) and two T. durum of unknown status were studied. Seventeen morphological plant and seed traits were measured based on UPOV descriptors. Ear emergence was earlier in cultivars than in landraces. The plant weight of the landraces was, in some cases, almost twice the cultivars’. Seed firmness (62.96–194.85N) was positively correlated with thousand kernel weight and volume (0.840 and 0.791, P < 0.05, respectively). Based on the agromorphological traits, cluster analysis clearly separated the species and the cultivars from the landraces, and the unknown status accessions were grouped with the cultivars. Cluster analysis with all measured traits set the wheat accessions in the following distinct groups: (1) T. durum cultivars including the unknown status accessions, (2) T. aestivum cultivars, and (3) T. aestivum and T. durum landraces. T. polonicum and T. dicoccum each formed a separate group. Seed physical properties of the analyzed Greek landraces indicated their suitability for bread and/or pasta making.

Estimating genetic diversity among durum wheat (Triticum durum desf.) landraces using morphological and SRAP markers

The durum wheat (Triticum turgidum L. ssp. durum Desf.) Landraces are a valuable source of natural germplasm for enhancing the genetic diversity of existing durum wheat cultivars. The study analyzed the genetic diversity of twenty-two durum wheat landraces including eight local Saudi landraces and fourteen introduced landraces using sixteen morphological descriptors and sequence-related amplified polymorphism (SRAP) markers. The results showed significant differences between the analyzed agro-morphological parameters and a large degree of genetic variation across the tested landraces. Principle components analysis (PCA) was used to determine agro-morphological relationships among different traits. The first six principal components (PCs) accounted for 78.47 % of the cumulative variability among 22 landraces. The PC1demonstrated variability in coleoptile anthocyanin coloration, straw pith, culm neck glaucosity, flag leaf glaucosity, ear glaucosity, and length of awn at tip relative to length of ear. Wheat landraces (L8, L14, L497, L569, L590, L594, L600, L601, and L602) showed increased diversity in dry region and contributed to PC1. A couple landraces had higher plant height (L12, L598, and L654), heading days (650, 656), and ear length (L12, L594, and L650) respectively. The dendrogram generated from the standardized morphological data separated the twenty-two durum wheat genotypes mainly into two clusters. The landraces 14, 600 and 602 grouped into separate cluster with strong correlation to ear glaucosity. Genetic diversity of these landraces was also evaluated using eight SRAP markers, with 482 amplified fragments and an average polymorphic information content (PIC) of 0.27. The dendrogram based on SRAP markers separated into two clusters with some diversified landraces (L8, 594, 602, 977, and L650). The Mantel test found no significant correlation (phenotypic or genetic) between 22 wheat durum landraces (r = 0.013, p = 0.84, =0.05). The results demonstrated the power of morphological and SRAP markers for detecting diversity among durum wheat landraces in the semi-arid region of Saudi Arabia. Thus, study provides insights into wheat diversity for better in-situ and ex-situ conservation and paves the road for their use in a Saudi durum wheat breeding program.

SNP Diversity and Genetic Structure of "Rogosija", an Old Western Balkan Durum Wheat Collection.

Durum wheat landraces represent a genetic resource for the identification and isolation of new valuable genes and alleles, useful to increase the crop adaptability to climate change. Several durum wheat landraces, all denominated "Rogosija", were extensively cultivated in the Western Balkan Peninsula until the first half of the 20th century. Within the conservation program of the Montenegro Plant Gene Bank, these landraces were collected, but without being characterized. The main goal of this study was to estimate the genetic diversity of the "Rogosija collection" consisting of 89 durum accessions, using 17 morphological descriptors and the 25K Illumina single nucleotide polymorphism (SNP) array. The genetic structure analysis of the Rogosija collection showed two distinguished clusters localized in two different Montenegro eco-geographic micro-areas, characterized by continental Mediterranean climate and maritime Mediterranean climate. Data suggest that these clusters could be composed of two different Balkan durum landrace collections evolved in two different eco-geographic micro-areas. Moreover, the origin of Balkan durum landraces is discussed.

Comparative Genetic Analysis of Durum Wheat Landraces and Cultivars Widespread in Tunisia.

The durum wheat (Triticum turgidum L. ssp. durum Desf.) landraces constitute a useful natural germplasm to increase the genetic diversity in the modern durum cultivars. The Tunisian durum germplasm constitutes 28 accessions conserved in Genebank of Tunisia, which are still unexplored. In this study, a comparative genetic analysis was performed to investigate the relationships between the Tunisian durum lines and the modern cultivars and detect divergent loci involved in breeding history. The genetic diversity analyses carried out using nine morphological descriptors and the 25K single-nucleotide polymorphism (SNP) array allowed us to distinguish two groups of Tunisian landraces and one of durum cultivars. The analysis of molecular variance and diversity indices confirmed the genetic variability among the groups. A total of 529 SNP loci were divergent between Tunisian durum landraces and modern cultivars. Candidate genes related to plant and spike architecture, including FLOWERING LOCUS T (FT-B1), zinc finger CONSTANS, and AP2/EREBPs transcription factors, were identified. In addition, divergent genes involved in grain composition and biotic stress nucleotide-binding site and leucine-reach repeats proteins and disease resistance proteins (NBS-LRR and RPM) were found, suggesting that the Tunisian durum germplasm may represent an important source of favorable alleles to be used in future durum breeding programs for developing well-adapted and resilient cultivars.

Changes in "natural antibiotic" metabolite composition during tetraploid wheat domestication

Gramineous plants protect their seeds from a variety of biotic stresses by producing toxic and deterrent secondary metabolites such as benzoxazinoids. It is unclear how the composition and abundance of these natural toxins has changed over the course of crop-plant domestication. To address this uncertainty, we characterized differences in metabolic levels of benzoxazinoids and their derivatives, between four lines of tetraploid wheat: wild emmer wheat (WEW), the direct progenitor of modern wheat; non-fragile domesticated emmer wheat (DEW), which was first domesticated about 11,000 years ago; the subsequently developed non-fragile and free-threshing durum landraces (LD); and modern durum (MD) varieties. Three-dimensional principal component analysis of mass spectrometry data of wheat metabolites showed with high resolution clear differences between metabolic profiles of WEW, DEW, and durum (LD + MD) and similarity in the metabolic profiles of the two durum lines (LD and MD) that is coherent with the phylogenetic relationship between the corresponding wheat lines. Moreover, our results indicated that some secondary metabolites involved in plant defense mechanisms became significantly more abundant during wheat domestication, while other defensive metabolites decreased or were lost. These metabolic changes reflect the beneficial or detrimental roles the corresponding metabolites might play during the domestication of three taxonomic subspecies of tetraploid wheat (Triticum turgidum).

Genetic diversity of Ethiopian durum wheat landraces.

Genetic diversity and population structure assessment in crops is essential for marker trait association, marker assisted breeding and crop germplasm conservation. We analyzed a set of 285 durum wheat accessions comprising 215 Ethiopian durum wheat landraces, 10 released durum wheat varieties, 10 advanced durum wheat lines from Ethiopia, and 50 durum wheat lines from CIMMYT. We investigated the genetic diversity and population structure for the complete panel as well as for the 215 landraces, separately based on 11,919 SNP markers with known physical positions. The whole panel was clustered into two populations representing on the one hand mainly the landraces, and on the other hand mainly released, advanced and CIMMYT lines. Further population structure analysis of the landraces uncovered 4 subgroups emphasizing the high degree of genetic diversity within Ethiopian durum landraces. Population structure based AMOVA for both sets unveiled significant (P < 0.001) variation between populations and within populations. Total variation within population accessions (81%, 76%) was higher than total variation between populations (19%, 24%) for both sets. Population structure analysis based genetic differentiation (FST) and gene flow (Nm) for the whole set and the Ethiopian landraces were 0.19 and 0.24, 1.04, and 0.81, respectively indicating high genetic differentiation and limited gene flow. Diversity indices verify that the landrace panel was more diverse with (I = 0.7, He = 0.46, uHe = 0.46) than the advanced lines (I = 0.6, He = 0.42, uHe = 0.42). Similarly, differences within the landrace clusters were observed. In summary a high genetic diversity within Ethiopian durum wheat landraces was detected, which may be a target for national and international wheat improvement programs to exploit valuable traits for biotic and abiotic stresses.

Assessment of genetic diversity and agronomic traits of durum wheat germplasm under drought environment of the northern Great Plains

AbstractDurum wheat (Triticum turgidum L. ssp. durum) is an important food crop worldwide. Modern breeding has yielded elite durum wheat cultivars with improved grain yield, end‐use quality, and disease resistance. In this study, we compared 150 breeding lines from the North Dakota State University (NDSU) durum wheat breeding program to 163 durum landraces using a large set of single nucleotide polymorphism (SNP) markers. We found that the genetic diversity of the NDSU durum breeding population was decreased by ∼60% relative to collection of 163 landraces. Selective sweep analysis identified several candidate regions that might have undergone breeding selection. Also in this study, over 260 worldwide durum wheat accessions were evaluated in drought environments of the northern Great Plains for 3 yr, a major growing area of durum wheat in the United States. One line showed significantly higher grain yield than the local elite cultivars. A number of lines showed significantly higher grain yield component traits like seeds per spike and thousand‐kernel weight. Those desirable lines may contain complementary favorable alleles and can possibly be used to improve grain yield under drought stress. Genome‐wide association mapping found no major quantitative trait loci (QTL) but a number of QTL with minor effect for grain yield, which could be explained by grain yield's complex genetic nature, the rare frequency of the novel complementary alleles, and the limited number of environments and replications for phenotypic evaluation in the study. Further QTL mapping using biparental populations derived from the identified desirable lines and elite cultivars may be able to identify the QTL related to grain yield, which can facilitate introgression of the complementary favorable alleles through marker‐assisted selection.

Durum Wheat (Triticum turgidum ssp. durum) and its Comparison to Bread Wheat in Some Aspects

Durum wheat is an important cereal produced mainly in Middle East, North Africa, South Europe and North America. Under Mediterranean conditions, water deficiency and high temperature during reproduction period limit durum crop production severely. Water deficit is the major limiting factor in Mediterranean basin and durum yield is greatly reduced by drought in this zone. Origin, grain quality, diseases tolerance, adaptation to environmental conditions and changes and consumption areas of this species are different than common wheat. Old durum landraces are now replaced with modern cultivars due to demand of higher technological quality requirements from food industry. Wild emmer wheat gene pool is a major source for durum wheat genetic and breeding improvements. Breeders increased productivity and resilience of durum wheat by strong selection of genes managing important agronomical traits. Cropping system, tillage management and weather conditions can greatly affect durum wheat and common wheat grain yield and quality. Here in this review, knowledge extracted and selected from latest articles published in high quality articles in the last decade on durum wheat are mentioned and some of them are compared to bread wheat. Different than a systematic presentation of well known informations related to wheat and durum, as it will require hundred of pages, here in this mini review, it was targeted to present some interesting aspects of relation of durum wheat to common wheat.

Deep soil exploration vs. topsoil exploitation: distinctive rooting strategies between wheat landraces and wild relatives

AimsDiversity of root systems among genetic resources can contribute to optimize water and nutrient uptake. Topsoil exploitation vs. deep soil exploration represent two contrasting ideotypes in relation to resource use. Our study reveals how rooting patterns changed between wheat wild progenitors and landraces in regard to these ideotypes.MethodsRoot (partitioning, morphology, distribution, elongation, anatomy) and shoot traits (dry-matter, leaf area, assimilation) of durum landraces, wild emmer and wild einkorn from Iran, Syria, Turkey and Lebanon were phenotyped using the GrowScreen-Rhizo platform. Distinctive rooting patterns were identified via principal component analysis and relations with collection site characteristics analyzed.ResultsShoot trait differentiation was strongly driven by seed weight, leading to superior early vigor of landraces. Wild progenitors formed superficial root systems with a higher contribution of lateral and early-emerging nodal axes to total root length. Durum landraces had a root system dominated by seminal axes allocated evenly over depth. Xylem anatomy was the trait most affected by the environmental influence of the collection site.ConclusionsThe durum landrace root system approximated a deep soil exploration ideotype which would optimize subsoil water uptake, while monococcum-type wild einkorn was most similar to a topsoil exploiting strategy with potential competitive advantages for subsistence in natural vegetation.

Heat shock proteins gene expression and physiological responses in durum wheat (Triticum durum) under salt stress.

Salt stress is a major abiotic stress causing adverse effects on plant growth and development. The aim of this study was to investigate the effect of NaCl stress on growth, stress indicator parameters (lipid peroxidation, chlorophyll content and proline content), yield, and the expression of heat shock proteins genes (Hsp17.8, Hsp26.3, Hsp70 and Hsp101) of five Jordanian durum wheat (Triticum durum) landraces. Plants were irrigated with tap water as control or 200mM NaCl. Significant differences among the 5 Triticum durum landraces in terms of growth parameters,stress indicator parameters, and expression of heat shock proteins genes were observed. Salt stressed landraces demonstrated decreased growth, increased levels of stress indicator parameters, and upregulation in Hsp17.8, Hsp26.3, Hsp70 and Hsp101 expression. Landraces T11 and M23 showed the highest growth, lowest levels of stress indicator parameters, and high expression of heat shock protein genes under NaCl stress. Whereas, J2 and A8 landraces showed the lowest growth, highest levels of stress indicator parameters and low expression of heat shock protein genes under NaCl stress. In conclusion, NaCl stress caused significant reduction in growth parameters, increased level of lipid peroxidation and proline content and upregulation in heat shock proteins gene expression levels. Growth, stress indicator parameters and gene expression results suggest that T11 and M23 landraces are the most NaCl stress tolerant landraces and could be used to enhance the gene pool in wheat breeding programs.

Abscisic Acid, Stress, and Ripening (TtASR1) Gene as a Functional Marker for Salt Tolerance in Durum Wheat.

In semiarid Mediterranean agroecosystems, drought and salinity are the main abiotic stresses hampering wheat productivity and yield instability. Abscisic acid, stress, and ripening (ASR) are small plant proteins and play important roles in different biological processes. In the present study, the TtASR1 gene was isolated and characterized for the first time from durum wheat (Tritucum turgidum L. subsp. durum). TtASR1 is a small gene, about 684 bp long, located on chromosome 4AL, encoding a protein of 136 amino acid residues consisting of a histidine-rich N terminus and C-terminal conserved ABA-WDS domain (Pfam PF02496). Our results showed that TtASR1 protein could function as a chaperone-like protein and improve the viability of E. coli under heat and cold stress and increase the Saccharomyces cerevisiae tolerance under salt and osmotic stress. Transcript expression patterns of TtASR1 revealed that ASRs play important roles in abiotic stress responses in diverse organs. Indeed, TtASR1 was upregulated in leaves by different developmental (ABA) and environmental signals (PEG, salt). In cv. Mahmoudi (salt-tolerant Tunisian durum landraces) roots, TtASR1 was upregulated by salt stress, while it was downregulated in cv. Azizi (salt-sensitive Tunisian durum landraces), supporting the implication of this gene in the salt tolerance mechanism. Taken together and after validation in the plant system, the TtASR1 gene may provide a potential functional marker for marker-assisted selection in a durum wheat breeding program for salt tolerance.

Mapping of Novel Leaf Rust and Stem Rust Resistance Genes in the Portuguese Durum Wheat Landrace PI 192051

Leaf rust caused by Puccinia triticina Erikss. (Pt) and stem rust caused by Puccinia graminis f. sp. tritici Erikss. & E. Henn (Pgt) are serious constraints to production of durum wheat (Triticum turgidum L). The objective of this study was to identify leaf rust resistance (Lr) and stem rust resistance (Sr) genes/QTL in Portuguese durum landrace PI 192051. Four Pt-isolates, representing three virulence phenotypes (BBBQJ, BBBSJ & EEEEE) and six Pgt-races TTKSK, JRCQC, TKTTF, QFCFC, TPMKC and TMLKC were used to evaluate 180 recombinant inbred lines (RILs) derived from the cross Rusty (rust susceptible) × PI 192051-1 (rust resistant) at the seedling stage. The RILs were also phenotyped at the adult-plant stage in a stem rust nursery in Ethiopia in 2017. The RILs were genotyped using the Illumina iSelect 9K wheat SNP array. PI 192051-1 carries a previously unidentified major Sr gene designated as QSr.ace-7A on chromosome arm 7AS and Lr gene Lr.ace-4A in the pericentromeric region of chromosome 4A. In addition, three minor Sr QTL QSr.ace-1A, QSr.ace-2B and QSr.ace-4A were mapped in PI 192051-1 on chromosomes 1AL, 2BL, and 4A, respectively Lr.ace-4A could be co-located or tightly linked to QSr.ace-4A. Markers linked to the identified QTL/genes can be used for marker assisted selection. These findings enrich the genetic basis of rust resistance in both durum and common wheat.

Diverse responses of old, modern and landraces of Syrian wheat genotypes to common root rot under field conditions

Abstract The yield response of widely grown cultivars and landraces of Syrian wheat challenged with common root rot (CRR: Cochliobolus sativus) was measured by comparing plots with and without artificial inoculation under experimental conditions in two consecutive seasons. The results showed that response to CRR differed depending on the susceptibility levels of the wheat cultivars, and that the disease significantly (P&lt;0.05) reduced grain yield, number of tillers and kernel weight. The diseased plants had fewer tillers which consequently reduced grain yield per plant. Yield losses of Triticum durum cultivars were higher than those of Triticum aestivum. In addition, the T. durum landrace Horani exhibited the best level of resistance to the disease, which indicates that this landrace might be a candidate donor for resistance in future breeding programmes. As CRR can dramatically reduce wheat grain yields under favorable conditions, management practices that reduce disease severity are highly recommended.

Genomic Regions From an Iranian Landrace Increase Kernel Size in Durum Wheat.

Kernel size and shape are important parameters determining the wheat profitability, being main determinants of yield and its technological quality. In this study, a segregating population of 118 recombinant inbred lines, derived from a cross between the Iranian durum landrace accession “Iran_249” and the Iranian durum cultivar “Zardak”, was used to investigate durum wheat kernel morphology factors and their relationships with kernel weight, and to map the corresponding QTLs. A high density genetic map, based on wheat 90k iSelect Infinium SNP assay, comprising 6,195 markers, was developed and used to perform the QTL analysis for kernel length and width, traits related to kernel shape and weight, and heading date, using phenotypic data from three environments. Overall, a total of 31 different QTLs and 9 QTL interactions for kernel size, and 21 different QTLs and 5 QTL interactions for kernel shape were identified. The landrace Iran_249 contributed the allele with positive effect for most of the QTLs related to kernel length and kernel weight suggesting that the landrace might have considerable potential toward enhancing the existing gene pool for grain shape and size traits and for further yield improvement in wheat. The correlation among traits and co-localization of corresponding QTLs permitted to define 11 clusters suggesting causal relationships between simplest kernel size trait, like kernel length and width, and more complex secondary trait, like kernel shape and weight related traits. Lastly, the recent release of the T. durum reference genome sequence allowed to define the physical interval of our QTL/clusters and to hypothesize novel candidate genes inspecting the gene content of the genomic regions associated to target traits.

Exploring SNP Diversity in Wheat Landraces Germplasm and Setting of a Molecular Barcode for Fingerprinting

During the last century wheat landraces were replaced by modern wheat cultivars leading to a gradual process of genetic erosion. Landraces genotyping and phenotyping are strategically useful, as they could broaden the genetic base of modern cultivars. In this research, we explored Single Nucleotide Polymorphism (SNP) markers diversity in a collection of common and durum wheats, including both landraces and Italian elite cultivars. A panel of 6,872 SNP markers was used to analyze the genetic variability among the accessions, using both the Principal Components Analysis (PCA) and the Neighbour Joining clustering method. PCA analysis separated common wheat accessions from durum ones, and allowed to group separately durum landraces from durum elite cultivars. The Neighbour joining clustering validated PCA results, and moreover, separated common wheat landraces from common elite cultivars. The clustering results demonstrated that Italian durum landraces were poorly exploited in modern breeding programs. Combining cluster results with heterozygosity levels observed, it was possible to clarify synonymy and homonymy cases identified for Bianchetta, Risciola, Saragolla, Timilia and Dauno III accessions. The SNP panel was also used to detect the minimum number of markers to discriminate the studied accessions. A set of 33 SNPs were found to be highly informative and used for a molecular barcode, which could be useful for cultivar identification and for the traceability of wheat end-products.

Genetic Diversity and Molecular Characterization of Iranian Durum Wheat Landraces (Triticum turgidum durum (Desf.) Husn.) Using DArT Markers.

Durum wheat is grown mainly in rain-fed regions of Iran and the Mediterranean district under stressful conditions. Different environmental conditions and agricultural practices among ancient communities have led to the development of locally adapted genotypes known as landraces. Landraces are a valued source of genetic variety and show definite adaptation to local environmental conditions according to their home of origin. This study aimed to explore linkage disequilibrium (LD) analysis and the population structure and genetic diversity of Iranian durum wheat landraces. In this study, population structure and genome-wide LD were investigated in 129 durum landrace accessions using 1500 DArT markers. Both structure and discriminant analysis of principal components obviously subdivided the sample collection into seven distinct groups centered on key ancestors and regions of origin of the germplasm. Genetic diversity among the populations was primarily within population (68 vs. 32%). Mean LD values across the entire population sample decayed below r2 of 0.11 after 1cM. LD decay of genomes A and B of Iranian durum wheat landrace is approximately 2-3cM (r2 = 0.11) and approximately 0.5cM (r2 = 0.12), respectively. Altogether, low LD decay, a high number of subpopulations, and the high existence of genetic diversity among and within populations were characteristics of the Iranian durum landrace collection. Hence, the existing genetic diversity within the population can be associated with the very long evolutionary history of plants in Iran. The populations we studied are hence presented as a valuable resource that can be used in basic and applied research in durum wheat breeding.

Phenotypic and molecular variation in drought tolerance of Jordanian durum wheat (Triticum durum Desf.) landraces.

Drought is considered one of the major constraints of plant growth and productivity worldwide. Plants respond to drought through different mechanisms including physiological, biochemical, and gene expression modulation. Studying these mechanisms will provide better understanding of drought response mechanisms and will help breeders in developing new cultivars. In this study, growth, biochemical, and molecular responses of four wheat (Triticum durum Desf.) landraces to drought stress (300mM mannitol) were investigated at the seedling stage. Reverse transcription-polymerase chain reaction was used to assess gene expression level for a drought stress responsive gene (DHN15.1). Germination percentage, shoot length, root length, and root number for all T. durum landraces were decreased significantly under drought stress. However, drought stress caused an increase in proline content, lipid peroxidation level, and DHN15.1 transcript level. According to the studied traits, the Karak landrace showed long shoots (48% relative to its control), the longest roots (45% relative to its control) and the highest proline content (483% relative to its control). The results indicate that from the landraces studied, Karak may be selected as the most tolerant wheat landrace and may help in wheat breeding programs for adaptation to drought-prone environments.

Genetic diversity and phenetic analysis in wheat (Triticum turgidum subsp. durum and Triticum aestivum subsp. aestivum) landraces based on SNP markers

Durum (Triticum turgidum L. subsp. durum (Desf.) Husn.) and common (Triticum aestivum L. subsp. aestivum) wheat landraces are mixtures of mostly homozygous genotypes characterized by broad adaptations to local environmental conditions. In this study, we estimated the genetic diversity in three old durum landraces (“San Pasquale”, “Grano Ricco” and “Dauno III”) and a common wheat landrace (“Bianchetta”) by using phenotypic traits and Single Nucleotide Polymorphism (SNP) markers. Large phenotypic variation was found for yield components and grain-quality traits. The landraces “Grano Ricco” and “Dauno III” showed high grain yield per spike, kernel weight and grain protein content, suggesting that they could be a source of favorable alleles. SNP analysis showed a higher diversity within landraces in “Bianchetta” (9.5 %) and “Grano Ricco” (9.4 %) than in “Dauno III” (3.2 %) and “San Pasquale” (1.5 %). Comparing marker profiles, different haplotypes were found within each landrace indicating a genetic structure based on a mixture of genotypes. The phenetic analysis underlined four distinct clusters corresponding to the four wheat landraces examined. The phenetic tree showed that “Dauno III” and “San Pasquale” were strongly related with cultivars derived from Mediterranean durum landraces and genetically distant from “Grano Ricco” which clustered with ‘Russello’ and ‘Timilia’, two durum cultivars originated from southern Italy durum landraces.

Identification of Water Use Strategies at Early Growth Stages in Durum Wheat from Shoot Phenotyping and Physiological Measurements.

Modern imaging technology provides new approaches to plant phenotyping for traits relevant to crop yield and resource efficiency. Our objective was to investigate water use strategies at early growth stages in durum wheat genetic resources using shoot imaging at the ScreenHouse phenotyping facility combined with physiological measurements. Twelve durum landraces from different pedoclimatic backgrounds were compared to three modern check cultivars in a greenhouse pot experiment under well-watered (75% plant available water, PAW) and drought (25% PAW) conditions. Transpiration rate was analyzed for the underlying main morphological (leaf area duration) and physiological (stomata conductance) factors. Combining both morphological and physiological regulation of transpiration, four distinct water use types were identified. Most landraces had high transpiration rates either due to extensive leaf area (area types) or both large leaf areas together with high stomata conductance (spender types). All modern cultivars were distinguished by high stomata conductance with comparatively compact canopies (conductance types). Only few landraces were water saver types with both small canopy and low stomata conductance. During early growth, genotypes with large leaf area had high dry-matter accumulation under both well-watered and drought conditions compared to genotypes with compact stature. However, high stomata conductance was the basis to achieve high dry matter per unit leaf area, indicating high assimilation capacity as a key for productivity in modern cultivars. We conclude that the identified water use strategies based on early growth shoot phenotyping combined with stomata conductance provide an appropriate framework for targeted selection of distinct pre-breeding material adapted to different types of water limited environments.