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  • Author or Editor: M. Mardi x
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In this study, simple sequence repeat (SSR) markers were used to investigate the genetic diversity and evolutionary relationships among 74 barley accessions; 15 landraces (Hordeum vulgare) and 59 wild accessions (twenty-one Hordeum spontaneum, ten Hordeum bulbosum, thirteen Hordeum murinum and fifteen Hordeum marinum). A total of 66 alleles were detected at 12 SSR loci, with an average of 5.5 alleles per locus in the entire samples. The average number of alleles (4.2) per locus was higher in H. vulgare and H. spontaneum, reflecting more genetic diversity within these two species compared with the other species. All index values of genetic diversity revealed that there was higher genetic diversity within H. vulgare landraces than within the wild species, indicating that cultivation unlikely to have caused a loss of genetic diversity in cultivated barley compared with its wild relatives. Analysis of molecular variance (AMOVA) revealed that 31% of the total observed variation was accounted for among species. Based on neighbor-joining clustering, the five species were classified into three main groups: (i) all accessions of H. marinum and H. bulbosum plus two accessions of H. murinum; (ii) H. vulgare and H. spontaneum accessions, in small, separated groups; and (iii) the remaining accessions of H. murinum. Principal coordinates analysis (PCoA) for SSR data also supported the neighbor-joining clustering. These results have important implications for barley germplasm characterization, improvement, molecular systematics and conservation.

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High temperature is a major determinant of wheat development and growth and causes yield loss in many regions of the world. This study was conducted to assess heat stress effects on yield and yield related traits of wheat. The 144 recombinant inbred lines derived from the cross of Kauz (heat tolerant) and MTRWA116 (susceptible) together with some commercial cultivars were evaluated during 2006–2007, 2007–2008 under normal and heat stress (late sowing) conditions. Grain yield, head length, kernels per spike, spiklets per spike, plant height, grain filling duration, peduncle length and 1000 kernels weight were measured. The results showed a significant difference among RILs for all traits in stress and control conditions. High temperature significantly decreased all traits specially grain yield (46.63%), 1000-kernel weight (20.61%) and grain filling duration (20.42%). Grain yield was most affected and spikelets per spike was least affected (11.77%). Grain yield under heat stress was directly correlated (r = 0.49) with yield in normal condition. Head length and grain yield had the highest (93.18%) and the lowest (62.97%) heritability, respectively. Peduncle length and grain filling duration showed the highest correlation with yield under both normal and heat stress conditions suggesting that these two traits could be used as reliable screening tools for development of heat-tolerant genotypes.

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Twenty four SSR primer pairs were used to determine the genetic diversity in the subspecies of Aegilops tauschii . All microsatellite markers showed a high level of polymorphism. The average number of alleles observed was relatively similar in subsp. tauschii (9.00) to that in strangulata (8.30). The tauschii group had also similar average PIC value (0.80) with the strangulata group (0.77). The range of similarity was higher in subsp. tauschii than subsp. strangulata , reflecting a higher level of genetic variation in the first subspecies. Cluster and PCO analyses revealed a relative pattern of differentiation between two taxonomic classified subspecies, but there were some exceptional accessions in each group, reflecting possible intermediate forms between these two subspecies. Wide distribution of alleles found in both subspecies can be used for wheat improvement.

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Simple sequence repeat (SSR) DNA markers were used to characterize the genetic diversity in 70 accessions of Aegilops crassa from Iran as well as to determine relationships among these accessions with 9 accessions of Aegilops tauschii (subsp. tauschii and strangulata ) and 5 Triticum aestivum landraces. All twenty SSR primer pairs were polymorphic and identified a total number of 149 alleles corresponding to an average of 7.5 alleles per locus. The highest and lowest PIC values were obtained in subsp. strangulata and Ae. crassa accessions, respectively. Data obtained were used to estimate genetic similarity using the Dice coefficient, and dendrogram was constructed using the UPGMA method. The dendrogram separated the 84 accessions into two main groups. All species grouped according to their genomes. A good level of genetic diversity was observed in the accessions of Ae. crassa , even in geographically close regions, which can be used in the broadening of the genetic base of bread wheat. In addition, T. aestivum and subsp. tauschii were clustered further away from Ae. crassa , confirming probably chromosomal rearrangements in the Dgenome of Ae. crassa during the processes of evolution.

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Abstract  

The analytical potential of ICP-AES (ICP) and 3He+-activation for the determination of boron was examined. The paper compares ICP-levels of B, obtained from aqueous solutions containing digested plant material, with minimum detectable limits attained in solid matrices that were subjected to prompt gamma-ray analysis using 2 MeV 3He+ ions. The analytically useful gamma-rays originated mainly from (3He,p) and (3He,a) reactions on 11B and Coulomb excitation of 10B. The numerical capabilities of the two techniques for such measurements are discussed, and detailed methodologies and possible difficulties are presented.

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Abstract  

The analytical capabilities of ICP-AES (ICP) and deuteron activation (associated with prompt gamma-rays and delayed X-rays) for the determination of certain transition metals, were investigated. The sensitivities of the three methods are given, and the general applicability of each technique is evaluated. In the case of ICP, numerical data were obtained from aqueous solutions containing digested plant material. These experimental results were assessed against minimum detectable limits attained in relevant solid matrices that were subjected to prompt gamma-ray and delayed X-ray spectrometry using 5 MeV 2H+ ions. The analytically useful lines originated mainly from (d,p) and (d,n) reactions. The potential of the three techniques for routine analysis is discussed and detailed methodologies are presented.

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