Wheat Genetic Diversity Research Articles

Applicability of CAAT Box-derived Polymorphism (CBDP) Markers for Analysis of Genetic Diversity in Durum Wheat

Progress in plant molecular tools has been resulted in the development of gene-targeted and functional marker systems. CAAT box region is a different pattern of nucleotides with a consensus sequence, GGCCAATCT, which situated upstream of the start codon of eukaryote genes and plays an important role during transcription. In the present study, several CAAT box-derived polymorphism (CBDP) primers were used for fingerprinting in mini-core collection of durum wheat (including internationally developed breeding lines and Iranian landraces). Twelve selected primers amplified 98 loci, of which all were polymorphic. The average values of the polymorphism information content (PIC) and resolving power (Rp) were 0.31 and 9.16, respectively, indicating a high level of variability among studied genotypes. Analysis of molecular variance (AMOVA) indicated that 92% of the total variation resided among populations. The values of the percentage polymorphic bands (PPL), the observed (Na) and effective (Ne) number of alleles, Nei’s gene diversity (He) and Shannon’s information index (I) for Iranian landraces were higher than the breeding lines. The Fandendrogram obtained by cluster analysis grouped all individuals into three main clusters. Our results showed a remarkable level of genetic diversity among studied durum wheat, especially among Iranian landraces, which can be interest for future breeding programs. More importantly, the present study also revealed that CBDP technique was efficient and powerful tool to assess genetic diversity in wheat germplasm. Hence, this technique could be employed individually or in combination with other molecular markers to evaluate genetic diversity and relations among different species.

Variation across a wheat genetic diversity panel for saccharification of hydrothermally pretreated straw

BackgroundWheat straw forms an important, reliable source of lignocellulosic biomass for use in second-generation ethanol production. However, there is limited understanding of the variation in quality of straw from current breeding cultivars, and studies on such variation have generally employed suboptimal pretreatments. There is also a degree of confusion regarding phenotypic characteristics relevant to optimising the enzymatic saccharification of cellulose after suitable pretreatments for biorefining compared with those which determine good ruminant digestibility. The aim of this study has been to (a) evaluate and compare the levels of glucose enzymatically released from straw obtained from 89 cultivars of winter wheat after optimised hydrothermal pretreatments and (b) identify the underlying phenotypic characteristics relevant to enhanced glucose production with special reference to the ratios of constituent tissue types.ResultsOptimised pretreatment involved hydrothermal extraction at 210 °C for 10 min. Using excess cellulases, quantitative saccharification was achieved within 24 h. The amount of glucose released ranged from 192 to 275 mg/g. The extent of glucose release was correlated with (a) the level of internode tissue (R = 0.498; p = 6.84 × 10−7), (b) stem height (R = 0.491; p = 1.03 × 10−6), and (c) chemical characteristics particular to stem tissues including higher levels of cellulose (R = 0.552; p = 2.06 × 10−8) and higher levels of lignin R = 0.494; p = 8.67 × 10−7.ConclusionsIn order to achieve maximum yields of cellulosic glucose for second-generation ethanol production, a predisposition for wheat to produce cellulose-enriched internode stem tissue, particularly of longer length, would be beneficial. This contrasts with the ideotype for ruminant nutrition, in which an increased proportion of leaf tissue is preferable.

Keragaman Genetik Gandum (Triticum aestivum L) Hasil Persilangan Konvergen

Wheat is a subtropical crop with a limited genetic resources in indonesia since it belong to tropical country. Convergent breeding is an effort to expand genetic diversity in wheat and to get the plant genotipes that have spesific characters. The aim of this reserch was to determine genetic diversity of wheat segregants resulted from convergent breeding using Simple Sequence Repeats (SSRs). Fifty seven wheat genotipes were tested using 39 SSR markers to determine their diversity. The results showed grouping by upgma of similarity matrix with genetic similarity coefficient ranged from 0.30 to 0.95. The similarity coefficient at 0.3 separated the 57 genotipes into two groups: the first group consisted of segregants, Oasis and Guri1 and Guri2 and the second group consisted of Dewata, Alibey, Rabe/M088, Selayar, HP 1744 and Tepoca/Rabe. Alleles which are formed from the entire genotipes using 39 primers were 137 alleles with a range of base pairs formed between 85.6-553 bp. PIC value and the average number of alleles were 0.35 and 3.51, respectively. The genetic variability being increased in wheat germplasm population and obtained 22 candidates of genotipe recombination having a high value of genetic distance (≥0.75) with a chance of many recombination.

Genetic Diversity under Soil Compaction in Wheat: Root Number as a Promising Trait for Early Plant Vigor.

Soil compaction of arable land, caused by heavy machinery constitutes a major threat to agricultural soils in industrialized countries. The degradation of soil structure due to compaction leads to decreased (macro-) porosity resulting in increased mechanical impedance, which adversely affects root growth and crop productivity. New crop cultivars, with root systems that are adapted to conditions of increased soil strength, are needed to overcome the limiting effects of soil compaction on plant growth. This study aimed (i) to quantify the genetic diversity of early root system development in wheat and to relate this to shoot development under different soil bulk densities and (ii) to test whether root numbers are suitable traits to assess the genotypic tolerance to soil compaction. Fourteen wheat genotypes were grown for 3 weeks in a growth chamber under low (1.3 g cm-3), moderate (1.45 g cm-3), and high soil bulk density (1.6 g cm-3). Using X-ray computed tomography root system development was quantified in weekly intervals, which was complemented by weekly measurements of plant height. The development of the root system, quantified via the number of axial and lateral roots was strongly correlated (0.78 < r < 0.88, p < 0.01) to the development of plant height. Furthermore, significant effects (p < 0.01) of the genotype on root system development and plant vigor traits were observed. Under moderate soil strength final axial and lateral root numbers were significantly correlated (0.57 < r < 0.84, p < 0.05) to shoot dry weight. Furthermore, broad-sense heritability of axial and lateral root number was higher than 50% and comparable to values calculated for shoot traits. Our results showed that there is genetic diversity in wheat with respect to root system responses to increased soil strength and that root numbers are suitable indicators to explain the responses and the tolerance to such conditions. Since root numbers are heritable and can be assessed at high throughput rates under laboratory and field conditions, root number is considered a promising trait for screening toward compaction tolerant varieties.

Enhancement of dwarf wheat germplasm with high-yield potential derived from induced mutagenesis

AbstractThe dwarfing wheat (Triticum aestivum L.) breeding has promoted a dramatic increase in yields. Since the utilized dwarfing genes in wheat are very limited, identification of novel dwarfing genes is necessary for improving the genetic diversity of wheat. In this study, more than 300 dwarfing wheat lines from induced mutation were screened by kompetitive allele-specific PCR and gibberellin (GA) treatment. The 17.49% of Rht-D1b and 1.37% of Rht-B1b dwarfing mutants were identified in this mutant group. Additionally, Rht-D1b mutants showed more effective in reduction of plant height and higher 1000-grain weight comparing with that of Rht-B1b mutants. By combing with comparison of yield components and expression profile of GA biosynthetic genes with wild-type, the GA-responsive mutant dm15 without directly involvement in GA metabolism, significantly increased 1000-grain weight but no change of other yield components in two locations of field experiments. Meanwhile, another elite mutant dm11 with change of GA biosynthetic genes expression was also identified. These mutants will be promising candidates for dwarfing wheat breeding.

Temporal evolution of varietal, spatial and genetic diversity of bread wheat between 1980 and 2006 strongly depends upon agricultural regions in France

An in-depth analysis of the spatio-temporal evolution of crop diversity in agricultural landscapes is necessary to provide insights on how to improve the resilience of agroecosystems to climate instability and new pest pressures by increasing in situ crop diversity, while promoting a greater sustainability of agriculture. However, most of the indicators of crop diversity used in previous studies were based on ex situ genetic diversity, or on official lists of varieties or breeding programs, without taking acreage of the varieties actually grown in farmers’ fields into account. Acreage of varieties represent however a relevant information to assess the actual genetic vulnerability of a crop (genetic uniformity at landscape scale) cultivated in the considered regions over the period studied. To bridge this gap, we analyzed spatial varietal and genetic diversity of bread wheat in France – an important production area – over the 1980–2006 period at a yearly time step and a district scale, i.e. ‘département’. We used HT*, an indicator integrating both the spatial evenness of variety distribution and molecular genetic data, to finely examine the spatio-temporal evolution of spatially weighted bread wheat genetic diversity. We also computed several simpler and complementary indicators accounting for the number of varieties, the spatial varietal diversity and the genetic diversity, and we estimated the individual contribution of these simpler indicators to the spatio-temporal structure of the spatial genetic diversity HT*. HT* values showed significant but non linear temporal evolutions between 1980 and 2006, these evolutions being besides spatially structured. Moreover, both spatial varietal diversity and genetic diversity partly explained these temporal changes of HT* values while the number of varieties appeared non-explanatory. Similarly to HT*, all indicators studied also showed substantial differences of temporal changes among major French agricultural regions, furthermore sometimes opposite for varietal and genetic diversity. As an example, in the north of France, varietal richness and spatial varietal diversity showed a substantial increase, suggesting the adoption of an increasing number of bread wheat varieties by farmers in this region. However, considering that genetic diversity showed a slight but continuous decrease over the recent period, this could suggest an increase in genetic similarity among bread wheat varieties chosen by farmers. Taken as a whole, our results suggest that several determinants of crop diversity, such as the shortening of crop sequences or the recurrence of epidemics of some pathogens, could differentially affect varietal choices of farmers and thus the spatial structuration of the temporal changes of crop diversity. Finally, our results question the dominant use of ex situ nationwide datasets to characterize the evolution of spatial genetic diversity as a proxy of genetic vulnerability of a crop to face with future changes.

Harnessing Diversity in Wheat to Enhance Grain Yield, Climate Resilience, Disease and Insect Pest Resistance and Nutrition Through Conventional and Modern Breeding Approaches.

Current trends in population growth and consumption patterns continue to increase the demand for wheat, a key cereal for global food security. Further, multiple abiotic challenges due to climate change and evolving pathogen and pests pose a major concern for increasing wheat production globally. Triticeae species comprising of primary, secondary, and tertiary gene pools represent a rich source of genetic diversity in wheat. The conventional breeding strategies of direct hybridization, backcrossing and selection have successfully introgressed a number of desirable traits associated with grain yield, adaptation to abiotic stresses, disease resistance, and bio-fortification of wheat varieties. However, it is time consuming to incorporate genes conferring tolerance/resistance to multiple stresses in a single wheat variety by conventional approaches due to limitations in screening methods and the lower probabilities of combining desirable alleles. Efforts on developing innovative breeding strategies, novel tools and utilizing genetic diversity for new genes/alleles are essential to improve productivity, reduce vulnerability to diseases and pests and enhance nutritional quality. New technologies of high-throughput phenotyping, genome sequencing and genomic selection are promising approaches to maximize progeny screening and selection to accelerate the genetic gains in breeding more productive varieties. Use of cisgenic techniques to transfer beneficial alleles and their combinations within related species also offer great promise especially to achieve durable rust resistance.

Assessing genetic diversity in bread wheat using inter simple sequence repeat (ISSR) markers

A major effort of a plant breeder is the constant improvement of the best available genotypes for further enhancement in their yield potential either directly or through improvement of various factors which contribute indirectly to high yield. Genetic diversity of wheat cultivars is very important in reducing genetic vulnerability during plant breeding efforts. In order to estimate the genetic diversity, molecular markers provide excellent tools. The aim of this study was to molecularly characterize the fifty wheat accessions to assess phylogenetic relationship and mutual genetic distances through the use of 10 ISSR markers and 50 accessions of wheat. The dendrogram separated genotypes into two clusters I and II comprising of 49 and 1 accessions, respectively. The allelic polymorphism information content (PIC) value ranged from 0.147 to 0.467 with an average of 0.287. The similarity co-efficient ranged from .41 to .89. Significant correlation of microsatellite genetic distance was tested by mantel test (r= 0.77557). Results shows that high level of polymorphism among the wheat accessions. Cluster analysis suggested that ISSR markers were efficient tools for estimating intra-specific genetic diversity in wheat and this molecular marker could differentiate the accessions obtained from different locations. ISSRs have been successfully used to estimate the extent of genetic diversity at interand intra-specific level in a wide range of crops. The genetic relationships estimated by the polymorphism of ISSR markers revealed greater level of genetic variability in wheat accessions of wide adaptability and applicability.

A unified framework for hybrid breeding and the establishment of heterotic groups in wheat.

Global wheat genetic diversity can be used in a unified framework to support and accelerate hybrid breeding and the development of heterotic groups in wheat. Hybrid wheat breeding has great potential to increase the global wheat grain yield level particularly in view of the increasing abiotic and biotic stress challenges as well as variable climatic conditions. For the long-term success of hybrid wheat breeding and the maximum exploitation of heterosis, high-yielding heterotic patterns must be established. Here, we propose a unified framework for hybrid breeding and the establishment of heterotic groups in autogamous crops and exemplify it for hybrid wheat breeding in Germany. A key component is the establishment of genetic distance between heterotic groups and in this context, we assessed genetic diversity in a global collection of 1110 winter wheat varieties released during the past decades in 35 countries but with a focus on European origin. Our analyses revealed the absence of major population structure but nevertheless suggest genetically distinct subgroups with potential for hybrid wheat breeding. Taking our molecular results and additional phenotypic data together, we propose how global genetic diversity can be used to accelerate and support reciprocal recurrent selection for the development of genetically distinct heterotic groups in hybrid wheat breeding.

Characterizing Croatian Wheat Germplasm Diversity and Structure in a European Context by DArT Markers.

Narrowing the genetic base available for future genetic progress is a major concern to plant breeders. In order to avoid this, strategies to characterize and protect genetic diversity in regional breeding pools are required. In this study, 89 winter wheat cultivars released in Croatia between 1936 and 2006 were genotyped using 1,229 DArT (diversity array technology) markers to assess the diversity and population structure. In order to place Croatian breeding pool (CBP) in a European context, Croatian wheat cultivars were compared to 523 European cultivars from seven countries using a total of 166 common DArT markers. The results show higher genetic diversity in the wheat breeding pool from Central Europe (CE) as compared to that from Northern and Western European (NWE) countries. The most of the genetic diversity was attributable to the differences among cultivars within countries. When the geographical criterion (CE vs. NWE) was applied, highly significant difference between regions was obtained that accounted for 16.19% of the total variance, revealing that the CBP represents genetic variation not currently captured in elite European wheat. The current study emphasizes the important contribution made by plant breeders to maintaining wheat genetic diversity and suggests that regional breeding is essential to the maintenance of this diversity. The usefulness of open-access wheat datasets is also highlighted.

Mechanisms of waterlogging tolerance in wheat--a review of root and shoot physiology.

We review the detrimental effects of waterlogging on physiology, growth and yield of wheat. We highlight traits contributing to waterlogging tolerance and genetic diversity in wheat. Death of seminal roots and restriction of adventitious root length due to O2 deficiency result in low root:shoot ratio. Genotypes differ in seminal root anoxia tolerance, but mechanisms remain to be established; ethanol production rates do not explain anoxia tolerance. Root tip survival is short-term, and thereafter, seminal root re-growth upon re-aeration is limited. Genotypes differ in adventitious root numbers and in aerenchyma formation within these roots, resulting in varying waterlogging tolerances. Root extension is restricted by capacity for internal O2 movement to the apex. Sub-optimal O2 restricts root N uptake and translocation to the shoots, with N deficiency causing reduced shoot growth and grain yield. Although photosynthesis declines, sugars typically accumulate in shoots of waterlogged plants. Mn or Fe toxicity might occur in shoots of wheat on strongly acidic soils, but probably not more widely. Future breeding for waterlogging tolerance should focus on root internal aeration and better N-use efficiency; exploiting the genetic diversity in wheat for these and other traits should enable improvement of waterlogging tolerance.

Polymorphism of microsatellite loci in bread wheat (Triticum aestivum L.) and related species

This study analysed polymorphism of 15 microsatellite loci in the col?lection comprising of 40 genotypes of bread wheat (Triticum aestivum L.), 32 genotypes belonging to other species within Triticum genus and 3 genotypes from Aegilops genus. The results showed significant differences in the variability of the tested loci in bread wheat and related species. In the collection of bread wheat genotypes, 119 alleles were detected with the average number of 7.9 alleles per locus. In wild and cultivated related species 157 alleles were identified, with the average of 10.5 alleles per locus. All analysed parameters of micro?satellite loci variability (PIC value, gene diversity, heterozygosity, etc.) indicated higher level of polymorphism in wild relatives than in the cultivated bread wheat. Analyses of individual genomes indicated that in the bread wheat genetic diversity of the B and D genomes was significantly reduced in relation to the A genome, while the differences in polymorphism between genomes in the wild relatives were significantly lower. The results showed that wild related species can be used as sources for new variability in wheat breeding.

The study of agronomical traits determining productivity of Triticum aestivum/Triticum timopheevii introgression lines with resistance to fungal diseases

Development of resistant cultivars is one of the effective ways for protection of common wheat T. aestivum L. from fungal pathogens. The gene pool of wild and cultivated wheat relatives is often used for widening the wheat genetic diversity of resistance genes. However, alien genetic material introgressed into the wheat genome can contain genetic factors negatively affecting agronomically important traits. T. aestivum/ T. timopheevii introgression lines derived from different common wheat cultivars have characteristically good resistance to leaf rust and powdery mildew. A comparative assessment of these lines and initial wheat varieties during four field seasons revealed a significant effect of environmental factors on the phenotypic differences between traits that have relevance to productivity. Averaged data obtained for individual introgression lines and for cross combinations revealed both positive and negative tendencies in variations of agronomical traits. The positive effects include a significant increase in the numbers of tillers and spikelets per spike of the lines derived from cv. Skala. Reduction in spike productivity was found in groups of the lines derived from cv. Tselinnaya 20 and cv. Novosibirskaya 67. However, no significant differences in 1000-grain weight were found between most lines and original wheat cultivars. Analysis of the data obtained showed no apparent correlation between the reduction of agronomic traits and the amount of alien genetic material introgressed into the common wheat genome. T. aestivum/T. timopheevii introgression lines can be used as a source of resistance genes without reducing the yield of wheat cultivars.

Phylogenetic analysis of wheat cultivars in Kazakhstan based on the wheat 90 K single nucleotide polymorphism array

The recent introduction of Illumina single nucleotide polymorphism (SNP) arrays is an important step towards comprehensive genome-wide studies of genetic diversity in wheat. In this study, 90 cultivars of hexaploid spring wheat growing in Kazakhstan were genotyped using the high-density wheat 90 K Illumina SNP array. The analysis allowed the identification of 30,288 polymorphic SNPs. A subset of 3541 high-quality SNPs were used for a comparison of 690 wheat accessions representing landraces and varieties, including those from Asia, Australia, Canada, Europe, Kazakhstan, USA and other parts of the world. Phylogenetic analysis showed a clear separation of wheat cultivars according to their geographic origin. In the phylogenetic tree, accessions from Kazakhstan and the USA formed two neighbouring clusters with a common node, and they were distinct from accessions from other regions of the world, including Europe. The results provide important new insights into the genetic relationships between diverse wheat accessions.

Attempts to Create Wheat (Triticum aestivum L.) Superior High-Yielded Variety through Mutation Breeding

Experiments to determine radiation dose effective for increasing wheat genetic diversity has been conducted from March to May 2015. Wheat seeds radiation was carried out at Research Center and PATIR BATAN, South Jakarta, followed by wheat growth screening at greenhouse of PATPKP UNAND at Alahan Panjang, Municipality of Solok, the Province of West Sumatra. Wheat genotypes of IS-Jarissa dan GURI 6 UNAND were subjected to gamma radiation as follow: 0 . 1; 0 . 2; 0 . 3; 0.4; 0.5; 0.6; 0.7; 0.8; 0.9; 1. 0 kGy ; and 0 kGy as control treatment. The wheat seeds were then grown in a mixture of soil and cow manure (3:1) w/w in a greenhouse. Data demonstrated that increasing the radiation doses resulted in decreasing in wheat growth. The effective doses of gamma radiation were 0.2 and 0.3 kGy. No wheat grown observed from the treatment groups of 0.5kGy gamma radiation and higher.

Explaining the decrease in the genetic diversity of wheat in France over the 20th century

Changing and more volatile climate conditions are leading to higher vulnerability and lower resilience for crop production. Recent studies indicate that crop diversity in agricultural fields may ensure pest control and yield stability in the face of environmental changes. However, few studies have evaluated crop diversity in the field, especially at the within-species level. Applying a new indicator, HT*, which integrates both the spatial evenness of different varieties and molecular genetic data (within and between variety genetic diversity), we followed the evolution of bread wheat genetic diversity on French agricultural landscapes during the 20th century. To our knowledge, the monitoring of crop genetic diversity at such a large but detailed spatial and temporal scale has never before been conducted. In comparison to two frequently used but less integrative indicators (the number of varieties grown in the field and their allelic diversity as measured by the Nei index), the HT* indicator revealed increasing genetic homogenization overall. This trend was due to the disappearance of diversity within varieties (initial replacement of landraces by more homogeneous old lines and later by modern pure lines), to the spatial homogenization occurring in the last period of the 20th century with the different ‘départements’ (French administrative territories) progressively cultivating the same varieties and to their increasing genetic similarities. This result calls into question the effects of plant breeding, seed system organization and seed regulation on wheat genetic diversity, especially in the context of current environmental changes.

Wheat gene pool and its conservation in Nepal

Aim This paper explores diversity of wheat gene pool present in the Nepalese bread wheat cultivars and landraces, and discusses their conservation initiatives. Location Nepal. Material and Methods This study is carried out using an extensive literature survey on distribution of landraces and wild relatives of wheat in Nepal. Key findings The results showed that there were 35 improved wheat cultivars, 540 landraces and 10 wild relatives of wheat in Nepal. Mexico, India and Nepal were the countries of origin for 35 cultivars. A total of 89 ancestors of wheat originated from 22 countries were used to develop 35 cultivars. The highest number of ancestors was from India. Ancestors of both aestivum and durum species having winter, spring and intermediate growth habit indicated that these species were of wide gene pool. The genetic erosion in wheat gene pool is the main conservation challenge of landraces due to introduction of improved varieties. Conservation implications Genetic diversity of wheat is indispensible for sustainable wheat production. Therefore, on-farm and ex-situ conservations of cultivars, landraces and wild varieties of wheat and their use in breeding programs are necessary for maintaining existing genetic diversity. DOI: http://dx.doi.org/10.3126/cs.v1i1.9584 Conservation Science 2013 1(1), 39-46

Wheat in the Mediterranean revisited--tetraploid wheat landraces assessed with elite bread wheat Single Nucleotide Polymorphism markers.

BackgroundSingle Nucleotide Polymorphism (SNP) panels recently developed for the assessment of genetic diversity in wheat are primarily based on elite varieties, mostly those of bread wheat. The usefulness of such SNP panels for studying wheat evolution and domestication has not yet been fully explored and ascertainment bias issues can potentially affect their applicability when studying landraces and tetraploid ancestors of bread wheat. We here evaluate whether population structure and evolutionary history can be assessed in tetraploid landrace wheats using SNP markers previously developed for the analysis of elite cultivars of hexaploid wheat.ResultsWe genotyped more than 100 tetraploid wheat landraces and wild emmer wheat accessions, some of which had previously been screened with SSR markers, for an existing SNP panel and obtained publically available genotypes for the same SNPs for hexaploid wheat varieties and landraces. Results showed that quantification of genetic diversity can be affected by ascertainment bias but that the effects of ascertainment bias can at least partly be alleviated by merging SNPs to haplotypes. Analyses of population structure and genetic differentiation show strong subdivision between the tetraploid wheat subspecies, except for durum and rivet that are not separable. A more detailed population structure of durum landraces could be obtained than with SSR markers. The results also suggest an emmer, rather than durum, ancestry of bread wheat and with gene flow from wild emmer.ConclusionsSNP markers developed for elite cultivars show great potential for inferring population structure and can address evolutionary questions in landrace wheat. Issues of marker genome specificity and mapping need, however, to be addressed. Ascertainment bias does not seem to interfere with the ability of a SNP marker system developed for elite bread wheat accessions to detect population structure in other types of wheat.

Microsatellites in the analysis of wheat genetic diversity

Microsatellite markers (SSR) were used to study wheat genetic diversity. A set of 87 wheat genotypes was analysed with four SSR markers. Primers used for the amplification of adequate microsatellite loci (Xgwm) are according to R?DER et al. (2002). Results were obtained using Applied Biosystems 3130 genetic analyser. Total of 28 alleles were determined, i.e. average of 7 alleles per marker. Number of alleles for individual markers ranged from six (Xgwm3) to eight (Xgwm18). The presence of two null alleles for Xgwm18 and Xgwm155 was found. There were five rare alleles (frequency &lt;2%). Polymorphism information content (PIC) values ranged from 0.52 for Xgwm408 to 0.80 for Xgwm18. Mean PIC value was 0.69 for all markers, which signifies a high level of the detected polymorphism. According to the data collected through the analysis of four markers, most genotypes can be grouped in clusters. The results show usefulness of microsatellite markers in detecting polymorphism, identifying genotypes and assessing genetic diversity.

Preliminary screening for water stress tolerance and genetic diversity in wheat (Triticum aestivum L.) cultivars from Sudan

The present study was carried out to screen 12 Sudanese wheat (Triticum aestivum L.) cultivars for their response to water stress at early germination stages and to characterize sources that could be used in breeding programs to develop wheat cultivars with better adaptation to water stress. The effect of osmotic stress on the early growing stages was evaluated, in vitro, using five con- centrations of Polyethylene glycol. Genetic diversity was studied using 24 allele specific simple sequence repeats (SSR) markers associated with drought tolerance in wheat. The presence of the drought genes and their chromosomal location was also investigated by isolating and sequencing the dehydration responsive element binding protein (dreb1). Results of the in vitro screening among the cultivars showed significant differences in the root length, shoot length and root/shoot ratio. The 24 drought specific SSR markers used revealed 50 alleles, with an average of 2.0 alleles per locus. Of these, 60% were polymorphic with polymorphism information content (PIC) ranging from 0.16 to 0.89. A dendrogram based on the similarity values generated from the SSR data revealed three major clusters. Of the five specific primers for dreb1 genes, only primer P25F/PR pro- duced amplification products with the expected fragment sizes. Sequencing and BLAST results of the cloned fragments excised from the gels showed 99% homology to the dreb1 gene on chromo- some 3A. a 2013 Production and hosting by Elsevier B.V. on behalf of Academy of Scientific Research & Technology.