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Arduini, I., Masoni, A., Ercole, L., Mariotti, M. 2006. Grain yield, and dry matter and nitrogen accumulation and remobilization in durum wheat as affected by variety and seeding rate. Eur. J. Agron. 25 :309

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Recently, four novel genes named Pinb-2, with 57–60% sequence similarity with wild-type allele Pinb-D1a coding for grain-hardness related puroindoline B have been shown to occur on homoeologous group 7 chromosomes in bread wheat (Triticum aestivum). In the present report, T. monococcum ssp. monococcum (Am genome) revealed a Pinb-2 gene with a poly-G tract and an in-frame TAG stop codon at the 5′ terminus of the coding DNA sequence. The stop codon was observed in 53 accessions of different geographic origins, suggesting that Pinb-2 in ‘monococcum’ wheat is unlikely to be expressed. By contrast, the coding DNA sequence of Pinb-2 in T. urartu (Au genome) was found to be 99% identical to its counterpart on chromosome 7AL in bread and durum (T. turgidum ssp. durum) wheat. Moreover, a sequence very similar to “urartu” Pinb-2 was found in tetraploid wheat T. timopheevii and hexaploid wheat T. zhukovskyi. This latter species exhibited an additional Pinb-2 pseudogene inherited from T. monococcum. The results are discussed in relation to the lineage of T. zhukovskyi and the potential role of Pin-b2 on kernel texture.

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Purple colour of wheat grain is determined by anthocyanin accumulation in the pericarp. This trait is controlled in hexaploid Triticum aestivum or tetraploid T. durum wheats by two complementary dominant genes Pp1 (chromosome 7B) and Pp3 (chromosome 2A). It remained unclear, whether functional alleles of one of the two complementary Pp genes occur in the diploid progenitors of allopolyploid wheat or in tetraploid T. timopheevii. In the current study, a purple-grained wheat line PC was obtained by crossing non-purple-grained T. aestivum Line 821 and Line 102/00i carrying introgressions from T. timopheevii and Aegilops speltoides, respectively. Crosses of lines 821 and 102/00i with a number of tester lines and cultivars did not result in purple-grained genotypes suggesting that expression of this trait in PC was controlled by complementary factors, one located in the T. timopheevii introgression and the other in the introgression inherited from Ae. speltoides. Genotyping of PC and other parental lines using microsatellite markers located on wheat chromosomes 7B and 2A showed that PC carries chromosome 7S of Ae. speltoides substituting for chromosome 7B, whereas chromosome 2A of PC contains an extended introgression from T. timopheevii.

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Abstract  

Twelve biological-matrix, agricultural/food reference materials, Corn Stalk (Zea Mays) (NIST RM 8412), Corn Kernel (Zea Mays) (NIST RM 8413), Bovine Musele Powder (NIST RM 8414), Whole Egg Powder (NIST RM 8415), Microcrystalline Cellulose (NIST RM 8416), Wheat Gluten (NIST RM 8418), Corn Starch (NIST RM 8432), Corn Bran (NIST RM 8433), Whole Milk Powder (NIST RM 8435), Durum Wheat Flour (NIST RM 8436), Hard Red Spring Wheat Flour (NIST RM 8437) and Soft Winter Wheat Flour (NIST RM 8438) were developed. They were characterized with respect to elemental composition via two extensive international interlaboratory characterization campaigns providing 303 reference and informational concentration values for 34 elements (Al, As, B, Ba, Br, Ca, Cd, Cl, Co, Cr, Cs, Cu, F, Fe, Hg, I, K, Mg, Mn, Mo, N, Na, Ni, P, Pb, Rb, S, Sb, Se, Sr, Ti, V, W, Zn) of nutritional, toxicological, and environmental significance. These products are available to the analytical community, for quality control of elemental composition analytical data, from the Standard Reference Materials Program, National Institute of Standards and Technology, Gaithersburg, MD, USA.

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The low seedling vigour of Russian wildrye grass ( Psathyrostachys juncea ) (RWR) limits its use. Shading from durum wheat ( Triticum turgidum ) reduced RWR leaf number, tiller number, leaf area and seedling dry weight in a growth room experiment. Treatments with similar shading differed in tiller number and dry weight, which suggested that light quality may have also contributed to these responses. In a second growth room experiment, light intensity (PAR) and red:far-red light ratio (670:730 nm) were altered by coloured plastic filters suspended above seedlings of Russian wildrye, crested wheatgrass ( Agropyron desertorum ) (CWG) and Dahurian wildrye grass ( Elymus dahuricus ) (DWR). Leaf area, tiller number and dry weight of RWR seedlings were reduced by declining red:far-red light ratio while light intensity differences at similar red:far-red ratio did not affect these variables. CWG exhibited similar responses to declining red:far-red light ratio as RWR, except that it exhibited a seedling weight response to light intensity. DWR tiller number was not responsive to low red:far-red light ratio but rather to low light intensity. However, DWR seedling weight, tiller weight and leaf area were responsive to declining red:far-red light ratio. These results indicate that RWR seedlings are sensitive to light quality changes caused by neighbouring plants.

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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.

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This study examines the occurrence of aflatoxins (AFS) and ochratoxin A (OTA) in bread and durum wheat samples. A total of 141 samples were collected from eleven different regions of Turkey. An analytical method based on liquid extraction, immunoaffinity column (IAC) clean-up followed by high performance liquid chromatography (HPLC) was used for the determination of AFs and OTA levels. As a result, AFs and OTA were detected in 2% and 9.2% of wheat samples at concentrations varying from 0.21 to 0.44 µg kg−1 and from 0.1 to 3.2 µg kg−1, respectively. Aflatoxin B1 (AFB1) and aflatoxin B2 (AFB2) were found positive in samples ranging between 0.21–0.35 µg kg−1 and 0.094 µg kg−1, respectively. However, none of the samples contained aflatoxin G1 (AFG1) and aflatoxin G2 (AFG2). The study also recommended that contamination levels in wheat and wheat-based products should be routinely monitored in greater sample numbers to insure food safety.

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Wild diploid goatgrass, Aegilops tauschii Coss., is the D-genome donor to hexaploid bread wheat. Goatgrass has been crossed with tetraploid durum wheat (Triticum turgidum var. durum L.) and hexaploid bread wheat (T. aestivum L. ssp. aestivum) to broaden the genetic base of bread wheat. We examined the contribution of main stem water-soluble carbohydrates (WSC) and current assimilates to grain yield in one goatgrass relative to those in one durum and four cultivars of bread wheat under well-watered and droughted field conditions across two years. Drought reduced grain yield and its components. Number of tillers per plant was higher in goatgrass, but 55% of tillers produced were sterile. Number of grains per spike was lower in goatgrass. Grain weight was the component severely limiting potential yield in goatgrass. Main stem WSC and concentration was lowest in goatgrass. Linear rate of grain growth in goatgrass was 20 and 17 mg spike−1 day−1 under well-watered and droughted conditions, whereas those in durum and bread wheats ranged from 55 to 73 and from 37 to 60 mg spike−1day−1, respectively. Current assimilates were the major source of carbon to fill the grains under both irrigation regimes. A large number of goatgrass accessions and adapted durum cultivars should be examined for grain yield and its components to identify promising accessions to be used in producing synthetics.

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Stone mulch offers potential benefits for water conservation in many rain-fed agricultural systems of the arid regions. The effects of stone mulch on transpiration and grain yield were examined for a durum wheat crop grown under soil water deficit stress. In a greenhouse trial, stone mulches with two levels of ground coverage significantly decreased soil-surface evaporation and increased crop transpiration. The transpiration increase contributed to increases both in biomass and grain yield. Field experiments over two cropping seasons confirmed yield increases of 12% in soil half-covered and 24% in soil fully-covered by stones. These significant yield increases indicate the potential usefulness of stone mulch technology in rain-fed cereal cropping. It is suggested that stones should not be removed from cereal fields unless their presence obstructs management severely. It remains to develop technologies for effectively managing soils containing large numbers of sizable stones in order to obtain the benefits of the potential yield increase associated with their presence on the soil surface.

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Crop simulation models use allometric relationships to predict plant height from vegetative characteristics. The objective of this study was to find relationships between plant height (PH) and number of leaves on main stem (NLMS), stem dry weight (SDW) (g plant−1) and total vegetative components (leaves and stems) dry weight (TVDW) (g plant−1) in wheat (Triticum aestivum L.). For this purpose, an experiment was conducted using seven wheat cultivars including two durum wheat cultivars (Arya and Taro) and five bread wheat cultivars (Darya, Kuhdasht, Shiroudi, Tajan and Zagros) under irrigated and rainfed conditions during 2008-2009 at Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran. The experimental design was a randomized complete block design with four replications. Sampling was started from beginning of tillering and continued until maturity. A segmented nonlinear regression model was used to describe allometric relationships between PH and the vegetative characteristics. The results showed that there was no significant difference between cultivars and the two conditions for allometric relationships, so one equation was usable for all cultivars under both irrigated and rainfed conditions. Significant relationships were found between PH and NLMS (R2 = 0.94), SDW (R2 = 0.95) and TVDW (R2 = 0.95). These equations can be used for estimation of PH in simulation models of wheat.

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