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Hunt H.V.,University of Cambridge | Badakshi F.,University of Leicester | Romanova O.,Ni Vavilov Research Institute Of Plant Industry | Howe C.J.,University of Cambridge | And 2 more authors.
Journal of Experimental Botany | Year: 2014

Panicum miliaceum (broomcorn millet) is a tetraploid cereal, which was among the first domesticated crops, but is now a minor crop despite its high water use efficiency. The ancestors of this species have not been determined; we aimed to identify likely candidates within the genus, where phylogenies are poorly resolved. Nuclear and chloroplast DNA sequences from P. miliaceum and a range of diploid and tetraploid relatives were used to develop phylogenies of the diploid and tetraploid species. Chromosomal in situ hybridization with genomic DNA as a probe was used to characterize the genomes in the tetraploid P. miliaceum and a tetraploid accession of P. repens. In situ hybridization showed that half the chromosomes of P. miliaceum hybridized more strongly with labelled genomic DNA from P. capillare, and half with labelled DNA from P. repens. Genomic DNA probes differentiated two sets of 18 chromosomes in the tetraploid P. repens. Our phylogenetic data support the allotetraploid origin of P. miliaceum, with the maternal ancestor being P. capillare (or a close relative) and the other genome being shared with P. repens. Our P. repens accession was also an allotetraploid with two dissimilar but closely related genomes, the maternal genome being similar to P. sumatrense. Further collection of Panicum species, particularly from the Old World, is required. It is important to identify why the water-efficient P. miliaceum is now of minimal importance in agriculture, and it may be valuable to exploit the diversity in this species and its ancestors. © The Author 2014. Source

Hunt H.V.,University of Cambridge | Moots H.M.,University of Cambridge | Graybosch R.A.,University of Nebraska - Lincoln | Jones H.,John Bingham Laboratory | And 6 more authors.
Molecular Biology and Evolution | Year: 2013

Waxy mutants, in which endosperm starch contains ∼100% amylopectin rather than the wild-type composition of ∼70% amylopectin and ∼30% amylose, occur in many domesticated cereals. The cultivation of waxy varieties is concentrated in east Asia, where there is a culinary preference for glutinous-textured foods that may have developed from ancient food processing traditions. The waxy phenotype results from mutations in the GBSSI gene, which catalyzes amylose synthesis. Broomcorn or proso millet (Panicum miliaceum L.) is one of the world's oldest cultivated cereals, which spread across Eurasia early in prehistory. Recent phylogeographic analysis has shown strong genetic structuring that likely reflects ancient expansion patterns. Broomcorn millet is highly unusual in being an allotetraploid cereal with fully waxy varieties. Previous work characterized two homeologous GBSSI loci, with multiple alleles at each, but could not determine whether both loci contributed to GBSSI function. We first tested the relative contribution of the two GBSSI loci to amylose synthesis and second tested the association between GBSSI alleles and phylogeographic structure inferred from simple sequence repeats (SSRs). We evaluated the phenotype of all known GBSSI genotypes in broomcorn millet by assaying starch composition and protein function. The results showed that the GBSSI-S locus is the major locus controlling endosperm amylose content, and the GBSSI-L locus has strongly reduced synthesis capacity. We genotyped 178 individuals from landraces from across Eurasia for the 2 GBSSI and 16 SSR loci and analyzed phylogeographic structuring and the geographic and phylogenetic distribution of GBSSI alleles. We found that GBSSI alleles have distinct spatial distributions and strong associations with particular genetic clusters defined by SSRs. The combination of alleles that results in a partially waxy phenotype does not exist in landrace populations. Our data suggest that broomcorn millet is a system in the process of becoming diploidized for the GBSSI locus responsible for grain amylose. Mutant alleles show some exchange between genetic groups, which was favored by selection for the waxy phenotype in particular regions. Partially waxy phenotypes were probably selected against-this unexpected finding shows that better understanding is needed of the human biology of this phenomenon that distinguishes cereal use in eastern and western cultures. © 2012 The Author. Source

Plotnikova L.Ya.,Omsk State University | Pozherukova V.E.,Omsk State University | Meshkova L.V.,Siberian Agricultural Research Institute | Mitrofanova O.P.,Ni Vavilov Research Institute Of Plant Industry | And 2 more authors.
Mikologiya I Fitopatologiya | Year: 2015

Timopheevi wheat (Triticum timopheevii) is a valuable source of genes for resistance to rust diseases. In 20th century the T. timopheevii non-host resistance to leaf rust was determined in the European part of Russia and other regions of the world. West Siberian population of leaf rust fungus Puccinia triticina differs from the European one. Intensive microevolution occurred in population and virulent clones overcoming the common wheat resistance genes appeared regularly. The set of samples with known Lr1-Lr47 and Lr50 genes was estimated for the resistance to leaf rust in the field under high infection pressure in 2011 and 2013. Only juvenile genes Lr19, Lr39, Lr45 and Lr47 determined high resistance and adult resistance genes (except Lr46 and Lr50) supplied the partial resistance. Lr18 and Lr50 genes transferred from T. timopheevii were ineffective in Western Siberia. Resistance of T. timopheevii to leaf rust was investigated on the example of ten accessions from the VIR collection in seedling stage in laboratory and in ripening stage in the field. Five experiments were performed to investigate the T. timopheevii juvenile resistance. In two experiments the seedlings were inoculated with urediniospores gathered in the field in 2011 and 2012, in three others - with monopustule isolates. In any experiment 100 T. timopheevii plants (10 plants per accession) were exploited. Differences between T. timopheevii accessions as well as the heterogeneity of plants in samples in resistance to rust were determined. The results depended on seasons: in 2011 T. 47 % plants were susceptible or resistant, in 2013 - 24 % had the same symptoms, the others were immune. The racespecific interactions between five T. timopheevii accessions and different P. triticina isolates were revealed at seedling stage. The trend to overcome the nonhost resistance of T. timopheevii at juvenile stage was established. Adult plants of all samples were high resistant to leaf rust. The isolates virulent to T. timopheevii had common alleles pp38, but differed on alleles pp9, pp11 and pp21. It is assumed the emergence of a new virulent genes to T. timopheevii in gene pool of the West Siberian population. Coevolution between P. triticina and T. timopheevii should be taken into account when creating donors of resistance to leaf rust and the introduction of new genes in varieties. Source

Paynel F.,CNRS Polymers, Biopolymer and Surfaces Laboratory | Pavlov A.,Ni Vavilov Research Institute Of Plant Industry | Ancelin G.,CNRS Polymers, Biopolymer and Surfaces Laboratory | Rihouey C.,CNRS Polymers, Biopolymer and Surfaces Laboratory | And 3 more authors.
Plant Physiology and Biochemistry | Year: 2013

Water imbibition of flax seed induces secretion of mucilages whose physico-chemical properties vary according to genotype and environment. The viscosity and composition of mucilage have ecological implications and also affect the utility of the crop. Several types of enzymes are secreted along with the mucilage. Our objective was to study these enzymes in the context of the composition and physical properties of the mucilage. The kinetics of production by flax seeds (variety Eden) of i) mucilages, ii) glycosidases and iii) endo-hydrolases were followed over 48 h under sterile conditions. The impact of enzymatic activities on mucilage was investigated by SEC-MALLS, viscosimetry and sugar composition. The mucilages consisted mainly of rhamnogalacturonan-I (RG-I, 52-62%) and arabinoxylan (AX, 27-36%). RG-I related enzyme activities (rhamnogalacturonase and β,. d-galactosidase) were quantified, together with AX related activity of α,. l-arabinofuranosidase, β,. d-xylosidase and β-xylanase. Maximal xylanase activity was reached after 4 h seed-hydration, when the minimal viscosity of the polysaccharides was observed, and the AX/RG-I ratio was the lowest. At that time, poly and oligosaccharides mainly contained pectic sugars. From 24 to 48 h water-hydration, when mucilages more tightly associated with cell walls were released, the glycosidase activities per g mucilage became maximal; the percentage, average molar-mass and viscosity of the polysaccharides decreased. Glucose, xylose and arabinose were the main sugars in the oligomer fraction. Our data confirmed the presence of β-d xylosidase and α-l-arabinofuranosidase activities and provided evidence for significant pectinase activities in flax mucilages. They also indicate an impact of enzymatic activities on the physicochemical properties of mucilages. © 2012 Elsevier Masson SAS. Source

Paynel F.,CNRS Polymers, Biopolymer and Surfaces Laboratory | Pavlov A.,Ni Vavilov Research Institute Of Plant Industry | Colasse L.,CNRS Polymers, Biopolymer and Surfaces Laboratory | Rihouey C.,CNRS Polymers, Biopolymer and Surfaces Laboratory | And 7 more authors.
Composites Part A: Applied Science and Manufacturing | Year: 2014

Natural biocomposites were prepared from flax fibers and mucilage polysaccharides extracted from flax seeds, as a matrix, in two steps: impregnation and compression molding. The ribbons were preimpregnated with water plasticized mucilage. Solid mucilage (30%, w/w) was added to the ribbon impregnated with 20% mucilage, and the composite was compression molded. The solidified mucilage was homogeneous and rigid (2 GPa) with an elastic deformation of approximately 1%. The mechanical properties of the composites were in the ranges of 7-10 GPa, 300-400 MPa and 4-5% for the modulus, maximal strength and strain, respectively. The two latter parameters were larger than the ones for the fiber. The experimental values of the modulus and strength were in accordance with the values computed using the rule of mixture, which indicated a good interface between the fibers and the matrix. This was confirmed visually with scanning electron microscopy. The water sorption behavior of the composites was intermediate between the mucilage and the fiber alone. © 2014 Elsevier Ltd. All rights reserved. Source

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