Durum Wheat Germplasm Research Articles

Evaluation of Seedling Resistance to Tan Spot and Stagonospora nodorum Blotch in Tetraploid Wheat

Tetraploid durum wheat (Triticum turgidum L. subsp. durum), an important cereal used for making pasta products, is more vulnerable to various wheat diseases than bread wheat (T. aestivum L.). To identify resistant sources useful for improving durum resistance to tan spot [caused by Pyrenophora tritici‐repentis (Died.) Drechs.] and Stagonospora nodorum blotch (SNB) [caused by Phaeosphaeria nodorum (E. Müller) Hedjaroude], we evaluated 688 accessions belonging to T. turgidum L. subspecies T. carthlicum, T. polonicum, T. turgidum, T. dicoccum, and T. turanicum for their seedling resistance to P. tritici‐repentis and P. nodorum Accessions were inoculated with a P. tritici‐repentis race 1 isolate (Pti2) and a mixture of three diverse isolates of P. nodorum (LDNSn4, BBCSn5, and Sn2000). Then 206 accessions with low and intermediate disease reaction to either of the inocula were further evaluated for reactions to P. tritici‐repentis and P. nodorum and for sensitivity to host‐selective toxins produced by the two pathogens. Data showed that 25 and 132 accessions had high levels of or partial resistance to tan spot and SNB, respectively, with 10 accessions, including T. dicoccum and T. turgidum, showing resistance to both diseases. The resistant accessions identified in this study would be particularly useful for developing durum wheat germplasm resistant to tan spot and SNB due to their semidomesticated characteristics and same genomic constitutions as durum wheat.

Pyramiding different alien chromosome segments in durum wheat: Feasibility and breeding potential

Wheat chromosome engineering, i.e., the transfer of alien chromosome segments from various Triticeae species into cultivated wheats, is greatly benefiting from the recent advancements in molecular genetics, cytogenetics, and genomics. Powerful tools are currently available that make selection of desired genotypes far more pre- cise and effective than in the past, thus giving this transfer strategy considerable po- tential for meaningful practical achievements. Such tools were successfully applied to engineer the durum wheat genome with small alien segments containing genes for disease resistance and quality traits, including Lr19 (leaf rust resistance) and Yp (yellow endosperm pigmentation) from Thinopyrumponticum, Pm13 (powdery mildew resistance) from Aegilops longissima, and the Glu-D3 and Glu-D1 glutenin subunit genes from Triticumaestivum. Targeted segments with such genes, all being of minimal size, were first separately incorporated into durum wheat by ph1-induced homoeologous recombination. The positive performance of selected recombinant lines from each transfer project encouraged attempts to develop multiple alien seg- ment combinations. The results obtained with double and also triple recombinants indicate a good tolerance of the durum wheat genome even toward such complex manipulations, which thus appear to offer good prospects for simultaneously enrich- ing durum wheat germplasm with several valuable traits from related Triticeae.

Genetic dissection of seminal root architecture in elite durum wheat germplasm

AbstractAlthough root architecture has been shown to play an important role in crop performance, particularly under drought conditions, no information is available on the genetic control of root traits in durum wheat, a crop largely grown in rainfed areas with low rainfall. In our study, a panel of 57 elite durum wheat accessions were evaluated under controlled conditions for root and shoot traits at the seedling stage. Significant genetic variability was detected for all the root and shoot traits that were investigated. Correlation analysis suggested that root and shoot features were only partially controlled by common sets of genes. The high linkage disequilibrium (up to 5 cM) present in the germplasm collection herein considered allowed us to use simple sequence repeat‐based association mapping to identify chromosome regions with significant effects on the investigated traits. In total, 15 chromosome regions showed significant effects on one or more root architectural features. A number of these regions also influenced shoot traits and, in some cases, plant height measured in field conditions. Major effects were detected on chromosome arms 2AL (atXgwm294), 7AL (atXcfa2257andXgwm332) and 7BL (atXgwm577andXcfa2040). The accessions with the most remarkable differences in root features will provide a valuable opportunity to assemble durum wheat mapping populations well suited for ascertaining the effects of root architecture on water use efficiency and grain yield.

Identification of a Novel Fusarium Head Blight Resistance Quantitative Trait Locus on Chromosome 7A in Tetraploid Wheat

ABSTRACT Fusarium head blight (FHB) caused by Fusarium graminearum is one of the most destructive diseases of durum (Triticum turgidum sp. durum) and common wheat (T. aestivum). Promising sources of FHB resistance have been identified among common (hexaploid) wheats, but the same is not true for durum (tetraploid) wheats. A previous study indicated that chromosome 7A from T. turgidum sp. dicoccoides accession PI478742 contributed significant levels of resistance to FHB. The objectives of this research were to develop a genetic linkage map of chromosome 7A in a population of 118 recombinant inbred lines derived from a cross between the durum cv. Langdon (LDN) and a disomic LDN-T. turgidum sp. dicoccoides PI478742 chromosome 7A substitution line [LDN-DIC 7A(742)], and identify a putative FHB resistance quantitative trait locus (QTL) on chromosome 7A derived from LDN-DIC 7A(742). The population was evaluated for type II FHB resistance in three greenhouse environments. Interval regression analysis indicated that a single QTL designated Qfhs.fcu-7AL explained 19% of the phenotypic variation and spanned an interval of 39.6 cM. Comparisons between the genetic map and a previously constructed physical map of chromosome 7A indicated that Qfhs.fcu-7AL is located in the proximal region of the long arm. This is only the second FHB QTL to be identified in a tetraploid source, and it may be useful to combine it with the QTL Qfhs.ndsu-3AS in order to develop durum wheat germ plasm and cultivars with higher levels of FHB resistance.

Genomic Constitution and Expression of Disease Resistance in Agropyron cristatum * Durum Wheat Derivatives

Septoria leaf blotch, powdery mildew and yellow and brown rusts are major wheat diseases characterized by a worldwide distribution. The level of genetic resistance against these diseases is low in durum wheat (Triticum turgidum) germplasm, while some wheat relatives, such as crested wheatgrass (Agropyron cristatum), are resistant. In an attempt to incorporate resistance genes into durum wheat, crosses were carried out between durum wheat and a fertile allotetraploid (2n = 4x = 28; DDPP) previously obtained from a cross between diploid wheat (T. tauschii) and crested wheatgrass (A. cristatum). The plants were backcrossed twice to durum wheat and studied for their reaction to the diseases. The genomic constitution of all the backcross derivatives from these crosses were analyzed by fluorescence in situ hybridization (FISH) using both total genomic DNA of A. cristatum and the pAs1 repetitive DNA sequence isolated from T. tauschii. All of them retained chromosomes or chromosome segments of A. cristatum. All the analyzed plants were immune to septoria leaf blotch and powdery mildew and showed a high level of resistance to yellow and brown rusts.

Temporal variation of diversity in Italian durum wheat germplasm

The aim of this work is to analyse the temporal change of genetic diversity in Italian durum wheat germplasm. The germplasm deployed in this study (158 accessions), belonging to 5 different historical classes, was characterised for its microsatellite and gliadin markers. The level of genetic diversity (He), based on gliadin and SSR markers results – on average – greater in indigenous landraces present in Italy before 1915, with the exception of pure line material which had been selected from landraces (showing highest level of heterozigosity for gliadin markers). Genotypes obtained from crosses or mutagenesis (referring to the 1950–1960 period) along with those resulting from crosses between CIMMYT lines and old materials (1970s and beyond) were also genetically more diverse. Forty-nine percent of indigenous landraces were genetically heterogeneous. Nine out of 53 landrace accessions were able to capture 4 different SSR private alleles. It is speculated that the reduction of allele richness is an indicator of the genetic erosion of the pre-breeding germplasm and it is pointed out that the implementation of appropriate methods of genetic conservation of this germplasm is a priority for breeding and food safety.

Effect of Leaf Rust on Grain Yield and Yield Traits of Durum Wheats with Race-Specific and Slow-Rusting Resistance to Leaf Rust.

Leaf rust, caused by Puccinia triticina, is an important disease of durum wheat (Triticum turgidum) in many countries. We compared the effectiveness of different types of resistance in International Maize and Wheat Improvement Center-derived durum wheat germ plasm for protecting grain yield and yield traits. In all, 10 durum wheat lines with race-specific resistance, 18 with slow-rusting resistance, and 2 susceptible were included in two yield loss trials sown on different planting dates in Mexico with and without fungicide protection under high disease pressure. Eight genotypes with race-specific resistance were immune to leaf rust. Durum wheat lines with slow-rusting resistance displayed a range of severity responses indicating phenotypic diversity. Mean yield losses for susceptible, race-specific, and slow-rusting genotypes were 51, 5, and 26%, respectively, in the normal sowing date trial and 71, 11, and 44% when sown late. Yield losses were associated mainly with a reduction in biomass, harvest index, and kernels per square meter. Slow-rusting durum wheat lines with low disease levels and low yield losses, as well as genotypes with low yield losses despite moderate disease levels, were identified. Such genotypes can be used for breeding durum wheat genotypes with higher levels of resistance and negligible yield losses by using strategies that previously have been shown to be successful in bread wheat.

Evaluation of Pre-harvest Sprouting Resistance in Durum Wheat Germplasm

Evaluation of Pre-harvest Sprouting Resistance in Durum Wheat Germplasm

Detection of QTLs for grain protein content in durum wheat

Grain protein content (GPC) of durum wheat (Triticum turgidum L. var. durum) is an important trait for the nutritional value of grain and for influencing the technological property of flour. Protein content is a quantitative trait negatively correlated with grain yield, thus increase in protein quantity usually results in yield reduction. This study was initiated to introgress alleles for high GPC from var. dicoccoides into durum wheat germplasm by the backcross inbred line (BIL) method and to identify molecular markers linked to high GPC alleles not associated with depressing effects on yield. The backcross line 3BIL-85 with high GPC and similar grain yield to the recurrent parent was backcrossed to Latino, and the generations F2, F3 and F4 were evaluated for GPC and yield per spike (GYS) in three field trials. Three QTLs with major effects on GPC were detected on chromosome arms 2AS, 6AS and 7BL, identified by the markers Xcfa2164, XP39M37 (250) and Xgwm577, respectively. Multiple regression analysis indicated that the three QTLs explained all the genetic variances of the trait. The high GPC parental line 3BIL-85 was not significantly different from the recurrent parent Latino for GYS, but the phenotypic correlation coefficient between GPC and GYS had negative values (from -0.02 to -0.28) in each trial, although it was statistically significant only in the F3 progeny trial. No co-located QTL for GYS was detected, excluding the hypothesis that the putative QTLs for GPC were indirect QTLs for low grain yield. The negative protein-yield response could be due to: (a) co-location of grain yield per spike QTLs with reduced phenotypic effects not detectable by the experimental design or statistical procedures, or to (b) opposite pleiotropic gene effects due to the major bio-energetic requirements for synthesis of protein then carbohydrates. Mapping loci by BILs should enable the production of near-isogenic lines in which the individual effects of each QTL can be examined in detail without confounding variations due to other putative QTLs.

Using AFLPs to determine phylogenetic relationships and genetic erosion in durum wheat cultivars released in Italy and Spain throughout the 20th century

Characterization of germplasm by DNA-markers provides a tool for precise germplasm identification and a quantitative assessment of genetic diversity. The genetic structure of the durum wheat germplasm grown in the Mediterranean basin varies largely from traditional landraces and cultivars characterized by a high versatility, to the modern varieties characterized by high yield potential, wide adaptation, and commercial end-use quality. The objective of this study was to assess the phylogenetic relationships among 24 durum wheat cultivars selected from relevant germplasm obtained at different periods in Italy and Spain, and to quantify the genetic erosion caused in durum wheat by breeding activities during the last century in these two countries. Genetic similarity between cultivars was studied by AFLP markers through the calculation of the Dice’s coefficient. The results showed a high degree of genetic similarity between the old Spanish cultivars and the collection of Italian cultivars, suggesting that wheat could have been introduced in the Iberian Peninsula via Italy. Genetic diversity estimates based on AFLP data confirmed the maintenance of genetic diversity with time since the values of Polymorphic Information Content were 0.27 for old cultivars (released before 1945), 0.28 for intermediate cultivars (released between 1950 and 1985) and 0.29 for modern cultivars (released between 1988 and 2000). These results indicate that genetic variability in Italian and Spanish durum wheat seems to have been maintained quite constant throughout the breeding process over the last century.

Occurrence and Impact of a New Leaf Rust Race on Durum Wheat in Northwestern Mexico from 2001 to 2003.

Durum wheat (Triticum turgidum var. durum) is the main irrigated winter crop in northwestern Mexico. Historically, leaf rust, caused by Puccinia triticina, had not induced significant losses to durum production in the area until 2001. That year, a new race, designated as BBG/BN, was detected that caused the most widely grown cultivar, Altar C84, which had remained resistant for 16 years, to become susceptible. Other recommended cultivars also became either moderately susceptible or susceptible. Detailed characterization of avirulence/virulence characteristics on Lr genes indicated that this race possibly did not evolve from the older races, but may have been introduced. Rust epidemics during the 2000-2001, 2001-2002, and 2002-2003 crop seasons have caused estimated losses of at least US$32 million. Although a majority of cultivars from 31 different countries, including the United States and Canada, and most of CIMMYT's durum wheat germ plasm were highly susceptible, diversity for both race-specific resistance and moderate levels of slow rusting resistance were identified. Jupare C2001, a resistant cultivar released in 2001, showed high levels of resistance and negligible losses in grain yield in a trial where Altar C84 suffered over 27% losses.

Increasing boron efficiency in international bread wheat, durum wheat, triticale and barley germplasm will boost production on soils low in boron

Boron deficiency causes grain set failure and yield loss in many of the world’s wheat growing countries. We suggest growing B efficient genotypes as a means to overcome the problem. This study evaluated international germplasm of bread wheat ( Triticum aestivum L.), durum wheat ( Triticum durum Dest.), triticale ( Triticosecale Wittmack) and barley ( Hordeum vulgare L.) for B efficiency. The first set of germplasm consisted of bread wheat, durum wheat and triticale from CIMMYT 1996/1997 nurseries and a B efficient check wheat cv. ‘Fang 60’. The lines were grown in the field on soil with 0.1 and 0.2, and 0.3 mg HWS B kg −1 for durum wheat and triticale. The grain set index (GSI, percentage grain set in the first two florets of 10 central spikelets) measured B efficiency in wheat, durum and triticale genotypes without the need for a B sufficiency control. Three-quarters of the lines tested were B inefficient, which included all of the durum wheat, 84% of the triticale and 60% of the bread wheat lines. Six of the bread wheat lines evaluated were in the same B efficient class as Fang 60. The response to low B was confirmed in a sand culture experiment without added B. Similarly high frequency of B inefficiency was found in a second set of germplasm which included bread and durum wheat, barley and triticale lines from CIMMYT and ICARDA 2000/2001 international nurseries. Incorporating the B efficiency trait in germplasm such as these, would ensure their adaptation to low B soils, and so enable their genetic potential to be fully realized in some of the world’s difficult production areas.

Microsatellite analysis reveals a progressive widening of the genetic basis in the elite durum wheat germplasm.

It has been argued that the level of genetic diversity in the modern durum wheat ( Triticum turgidum L. var. durum) elite germplasm may have declined due to the high selection pressure applied in breeding programs. In this study, 58 accessions covering a wide spectrum of genetic diversity of the cultivated durum wheat gene pool were characterized with 70 microsatellite loci (or simple sequence repeats, SSRs). On average, SSRs detected 5.6 different allelic variants per locus, with a mean diversity index (DI) equal to 0.56, thus revealing a diversity content comparable to those previously observed with SSRs in other small-grain cereal gene pools. The mean genetic similarity value was equal to 0.44. A highly diagnostic SSR set has been identified. A high variation in allele size was detected among SSR loci, suggesting a different suitability of these loci for estimating genetic diversity. The B genome was characterized by an overall polymorphism significantly higher than that of the A genome. Genetic diversity is organised in well-distinct sub-groups identified by the corresponding foundation-genotypes. A large portion (92.7%) of the molecular variation detected within the group of 45 modern cvs was accounted for by SSR alleles tracing back to ten foundation-genotypes; among those, the most recent CIMMYT-derived founders were genetically distant from the old Mediterranean ones. On the other hand, rare alleles were abundant, suggesting that a large number of genetic introgressions contributed to the foundation of the well-diversified germplasm herein considered. The profiles of recently released varieties indicate that the level of genetic diversity present in the modern durum wheat germplasm has actually increased over time.

Variation of morphological and agronomical traits, andprotein composition in durum wheat germplasm from easternEurope

Broadening the genetic base upon which the breeding of durumwheat relies is a growing concern in Italy. Exotic materials canrepresent valuable sources of adaptive features and they have beenrepeatedly exploited in the past for direct utilisation and/orintrogression by crossing into existing germplasm. An increase of theavailable genetic variation for the breeding also appearsenvisageable in terms of end-product quality. This studyassessed the variation in germplasm from eastern Europe countries,which could represent novel gene sources for durum wheat improvementin Italy, and verified the presence of variants of potential interestfor agronomical and quality characteristics to be possibly exploitedfor breeding. Fifty-nine landraces from the former USSR and 91from Bulgaria were grown in Sicily and evaluated for agronomicaltraits, spike morphological characteristics (possibly bearingsome taxonomic relevance), and protein composition at three lociencoding for glutenin subunits responsible of flour quality features.The results suggested a similar overall diversity in the two groupsconsidering either the variance of the agronomical characters, or thediversity index (H′) across morphological traits, orthe frequency distribution of electrophoretic patterns of gluteninsubunits encoded at three loci. Genotypes of potential usefulness asdonors of positive agronomical or quality attributes were found inboth germplasm groups, although the agronomical characteristics ofthe exotic genotypes rarely matched those required by the breeding inthe target area. Conversely, the genetic variation found at the threeloci involved in the composition of glutenin subunits appeared ofgreater relevance for the breeding in Italy.

Yielding ability, yield stability, and quality of exotic durum wheat germplasm in Sicily

AbstractA set of 20 accessions of durum wheat (Triticum turgidum L., durum group), which mostly included exotic landraces from various Mediterranean countries, and four Italian improved varieties were evaluated for grain yield in five environments and for quality traits in two environments of Sicily. Glutenin composition was also assessed electro‐phoretically on six seeds per entry. The cultivars differed (P ≤ 0.01) for yield, protein content and sodium dodecyl sulphate (SDS‐sed) sedimentation volume, in the presence of significant (P ≥ 0.001) genotype‐environment interaction effects. These effects were large for yield and moderately large for protein content relative to genotype main effects following estimation of variance components. Most exotic cultivars yielded comparably with, and some of them showed greater stability than, the best yielding Italian variety 'Simeto. Some exotic cultivars combined outstanding yield, protein content and SDS‐sedimentation values and represent therefore extremely valuable germplasm sources to broaden the local genetic base. The glutenin composition LMW‐2 and HMW 7 + 8 was positively associated with gluten quality. Six entries showed heterogeneous electrophoretic patterns, suggesting the presence of different genotypes within the cultivar.

Screening for low grain cadmium phenotypes in sunflower, durum wheat and flax

Cadmium (Cd) level in nonoilseed sunflower (Helianthus annuus L.), flax (Linum usitatissimum L.), and durum wheat (Triticum turgidum L. var. durum) grown on uncontaminated, alkaline soils has exceeded limits established in Northern Europe. Separate field experiments were conducted to investigate variability of grain Cd levels among sunflower, durum wheat and flax germplasm, and to seek an efficient screening method for future breeding. There were large variations in leaf Cd concentration among 200 sunflower lines. These lines performed more consistently for Cd uptake at the R5 stage than at the V8 stage across 4 locations with markedly differing soils. Cd concentration in V8 leaves was not related to Cd in grain. The positive correlation between R5 leaf Cd and kernel Cd level was obtained from nonoilseed hybrid (Sigco 954) (R2; = 0.74**), and 200 lines (R2 = 0.44**) tested over 4 locations in 2 field trials, respectively. This indicates that an efficient and low cost screening method can be developed for genotype selection, but plants must be grown to the R5 stage. A preliminary evaluation of 30 durum wheat and 74 flax lines indicated large variations in grain Cd level of durum wheat and flax. Grain Cd concentration ranged from 0.11 to 0.34 mg Cd kg-1 DW for durum wheat, and 0.14 to 1.37 mg Cd kg-1 DW for flax, respectively. This variability indicates that breeding for low grain Cd in durum wheat and flax should be feasible.

Tolerance of durum wheat lines to an acid, aluminum‐toxic subsoil

Abstract Durum wheat, Triticum durum Desf., is reportedly more sensitive to aluminum (Al) toxicity in acid soils than hexaploid wheat, Triticum aestivum L. em. Thell. Aluminum‐tolerant genotypes would permit more widespread use of this species where it is desired, but not grown, because of acid soil constraints. Durum wheat germplasm has not been adequately screened for acid soil (Al) tolerance. Fifteen lines of durum wheat were grown for 28 days in greenhouse pots of acid, Al‐toxic Tatum subsoil at pH 4.5, and non‐toxic soil at pH 6.0. Aluminum‐tolerant Atlas 66 and sensitive Scout 66 hexaploid wheats were also included as standards. Based on relative shoot and root dry weight (wt. at pH 4.5/wt. at pH 6.0 X 100), durum entries differed significantly in tolerance to the acid soil. Relative shoot dry weight alone was an acceptable indicator of acid soil tolerance. Relative dry weights ranged from 55.1 to 15.5% for shoots and from 107 to 15.8% for roots. Durum lines PI 195726 (Ethiopia) and PI 193922 (Brazi...

Variation in landraces of durum wheat (T. turgidum L. conv. durum (Desf.) M.K.) from Turkey

Durum wheat is historically an important crop in Turkey. Diverse durum wheat germplasm has been recorded many times in Turkish collections. 812 single plant genotypes from 190 durum wheat populations of 23 provinces in Turkey have been studied for number of days to germination, tillering, shooting, heading, maturity, and yield per plant. Variation in samples for traits studied was large enough and subsamples with different characteristics were identified. Grouping samples into provinces and altitudes of origin have revealed that variation in samples existed for some traits depending on province and altitude of origin. Yield per plant were not correlated with any of the developmental stages: but developmental stages were correlated with each other in varying magnitudes. Variation in yield per plant was not explained as well by developmental stages studied under a dry-cold environment. Further studies on samples needed to explore genetic variation more for other traits of economic importance.

Sources of Resistance to Common Bunt (Tilletia foetida and T. caries) in Durum Wheat

AbstractScreening of durum wheat germplasm for resistance to common bunt (Tilletia foetida and T. caries) resulted in the identification of 26 resistant genotypes. The screening was made using nine common bunt isolates from the West Asia and North Africa (WANA) region. In one isolate the two pathogens were represented in ratio of 1:1, whereas eight isolates contained only T. foetida. The correlation, principal components and clustering analyses grouped the genotypes into three clusters., Cluster one comparised genotypes close to Senatore (S.) Cappelli and Haurani, the latter is a landrace from Syria. Cluster three comprised advanced genotypes containing resistance genes from Mindum, a Turkish landrace. Results indicated that donor sources of resistance appear to be related to the three major sources mentioned. Cultivar S. Cappelli is considered resistant since it has been grown by farmers on a large scale for many years and remained resistant to common bunt throughout 7 years of testing. This resistance is assumed to be of a durable type. The isolates were also grouped into three clusters representing different ecological areas and the wheat types from which the isolates originated. We infer that the different clusters reflect the presence of three pathotype groups of the pathogens.

Morpho-physiological traits as descriptors for discrimination of durum wheat germplasm

Seventeen morpho-physiological characters usable as descriptors in durum wheat were evaluated in terms of relatedness of their information and their relative contribution to discrimination of accessions in a large germplasm collection. Similarity of information provided by different traits and trait combinations were assessed respectively by Spearman's rank correlation and by hierarchical cluster analysis. Increase of discriminating capability (percent of uniquely identified accessions) as a function of increasing number of descriptors was investigated using the cluster analysis information to progressively determine the descriptors to retain. The resemblance between information provided by different characters was generally very low, and a 96.0% level of discrimination could be attained by combination of 13 traits. Of the descriptors recommended by the International Board for Plant Genetic Resources for preliminary characterization and evaluation of wheat germplasm, those considered in the study all proved useful for entry description. The results strongly supported the use of plant waxiness as a further descriptor.