Auftreten von Plasmodiophora brassicae als Erreger der Kohlhernie im Winterrapsanbau in Europa sowie Identifizierung, Charakterisierung und molekulare Kartierung neuer Kohlhernieresistenzgene aus genetischen Ressourcen

European monitoring of Plasmodiophora brassicae as the causal agent of clubroot disease in oilseed rape and phenotyping and molecular mapping of new resistance genes derived from genetic resourcesZusammenfassungDer Erreger der Kohlhernie (Plasmodiophora brassicae) gewinnt im europäischen Rapsanbau an Bedeutung und mittlerweile werden stark kontaminierte Flächen v.a. in Nord- und Nordostdeutschland sowie in einigen Regionen Frankreichs und Englands mit zunehmender Tendenz nachgewiesen. Starke Unterschiede in der Virulenz je nach Herkunft sind zwar bekannt, aber bisher kaum untersucht und werden daher in einem Monitoringverfahren anhand von 2 Differentialsortimenten unter kontrollierten Bedingungen detailliert analysiert. Die Kohlhernie ist aufgrund des Fehlens einer Bekämpfungsmöglichkeit mit Fungiziden und der Tatsache, dass für den praktischen Anbau aktuell nur eine einzige rassenspezifische Resistenz in agronomisch anbauwürdigen Rapssorten zur Verfügung steht, besonders problematisch. Ziel ist es daher, bisher weitgehend ungenutzte Resistenzen aus genetischen Ressourcen, z.B. Steckrübensorten, in spaltenden Populationen (RILs & DHs) zu kartieren und eng gekoppelte Marker zu entwickeln, mit deren Hilfe entsprechende Resistenzen effektiv in adaptierte Rapssorten eingelagert werden können. Stichwörter: Kohlhernie, Virulenzanalyse, pflanzengenetische RessourcenAbstractClubroot caused by the obligate biotrophic protist Plasmodiophora brassicae is a serious soilborne disease of cruciferous crops. It causes galls on roots leading to premature death of the plant. Currently, due to the raise of oilseed rape cultivation within the last decades the number of contaminated fields is increasing. The hot spots of clubroot infestation in Europe are mainly located in Northern Germany, France and in the UK. Because numerous populations and races, respectively, are known, differences in pathogenicity are being explored under greenhouse conditions. The main problem is the longevity of resting spores in the soil, the lack of reasonable control measures and that up to now only one race specific resistance is incorporated in adapted cultivars. Therefore, with the aid of segregating populations (RILs and DHs) previously unutilized resistance genes identified in genetic resources like rutabaga cv’s (B. napus ssp. napobrassica) are being mapped as a prerequisite for an efficient breeding for reistance.Keywords: clubroot disease, virulence analysis, plant genetic resource

Incommensurate magnetic ordering in Sr_2Ru_(1-x)Ti_xO_4

In $\rm Sr_2RuO_4$ the spin excitation spectrum is dominated by incommensurate fluctuations at q=(0.3 0.3 q$_z$), which arise from Fermi-surface nesting. We show that upon Ti substitution, known to suppress superconductivity, a short range magnetic order develops with a propagation vector (0.307 0.307 1). This finding confirms that superconducting $\rm Sr_2RuO_4$ is extremely close to an incommensurate spin density wave instability. In addition, the ordered moment in \srton ~ points along the c-direction, which indicates that the incommensurate spin fluctuations exhibit the anisotropy required to explain a p-wave spin triplet pairing.Comment: 4 pages 3 figures revtex-version correcte

A cluster of nucleotide-binding site-leucine-rich repeat genes resides in a barley powdery mildew resistance quantitative trait loci on 7HL

Powdery mildew causes severe yield losses in barley production worldwide. Although many resistance genes have been described, only a few have already been cloned. A strong QTL (quantitative trait locus) conferring resistance to a wide array of powdery mildew isolates was identified in a Spanish barley landrace on the long arm of chromosome 7H. Previous studies narrowed down the QTL position, but were unable to identify candidate genes or physically locate the resistance. In this study, the exome of three recombinant lines from a high-resolution mapping population was sequenced and analyzed, narrowing the position of the resistance down to a single physical contig. Closer inspection of the region revealed a cluster of closely related NBS-LRR (nucleotide-binding site–leucine-rich repeat containing protein) genes. Large differences were found between the resistant lines and the reference genome of cultivar Morex, in the form of PAV (presence-absence variation) in the composition of the NBS-LRR cluster. Finally, a template-guided assembly was performed and subsequent expression analysis revealed that one of the new assembled candidate genes is transcribed. In summary, the results suggest that NBS-LRR genes, absent from the reference and the susceptible genotypes, could be functional and responsible for the powdery mildew resistance. The procedure followed is an example of the use of NGS (next-generation sequencing) tools to tackle the challenges of gene cloning when the target gene is absent from the reference genome

Genetic variation in sorghum germplasm from Sudan, ICRISAT, and USA assessed by simple sequence repeats (SSRs)

Assessment of genetic variability in crops has a strong impact on plant breeding and conservation of genetic resources. It is particularly useful in the characterization of individuals, accessions, and cultivars in determining duplications in germplasm collections and for selecting parents. The objective of this study was to estimate genetic diversity and to obtain information on the genetic relationship among 96 sorghum [Sorghum bicolor (L.) Moench] accessions from Sudan, ICRISAT, and Nebraska, USA, using 16 simple sequence repeats (SSRs). In total, 117 polymorphic bands were detected with a mean of 7.3 alleles per SSR locus. By this approach each accession is uniquely fingerprinted. Genetic similarity estimates ranged from 0 to 0.91, with a mean of 0.30. The polymorphic information content (PIC) for SSRs ranged from 0.46 (SB4-72) to 0.87 (SBAGF06). Diversity index (DI) for all accessions was 0.71. Within subgroups, DI was 0.63 for Sudanese landraces and improved cultivars, 0.49 for PI accessions, 0.42 for Nebraska derivatives, 0.39 for the ICRISAT advanced breeding lines (ABLs), 0.65 for the Feterita group, 0.71 for the Milo group, 0.63 for a Synthetic group (new breeding materials), 0.68 for the Hegiri group, and 0.47 for the Mugud group. Mantel statistics revealed a good fit of the unweighted pair-grouped method with arithmetic average (UPGMA) cluster to the original genetic similarity (GS) data (r = 0.867). UPGMA clustering produced two main clusters comprising mainly nonimproved germplasm (gene bank accessions and Nebraska population derivatives), and improved genotypes (cultivars, Gadarif collections, and ICRISAT advanced lines). Grouping of accessions by UPGMA cluster analysis matched with the geographical origin and/or pedigree information (Sudan, USA, ICRISAT), the adaptation zone (Gadarif area, Sudan), and morphological characters (Feterita, Mugud, and Milo types), indicating the strong differentiation among the sorghum materials

Structural and magnetic aspects of the metal insulator transition in Ca2−x_{2-x}Srx_xRuO4_4

The phase diagram of Ca$_{2-x}$Sr$_x$RuO$_4$ has been studied by neutron diffraction on powder and single-crystalline samples. The experiments reveal antiferromagnetic order and structural distortions characterized by tilts and rotations of the RuO$_6$-octahedra. There is strong evidence that the structural details of the isovalent samples tune the magnetic as well as the electronic behavior. In particular we observe for low Sr-concentration a metal insulator transition associated with a structural change and magnetic ordering

Osmoregulators proline and glycine betaine counteract salinity stress in canola

Salt inundation leads to increased salinization of arable land in many arid and semi-arid regions. Until genetic solutions are found farmers and growers must either abandon salt-affected fields or use agronomic treatments that alleviate salt stress symptoms. Here, field experiments were carried out to study the effect of the osmoregulators proline at 200 mg L-1 and glycine betaine at 400 mg L-1 in counteracting the harmful effect of soil salinity stress on canola plants grown in Egypt. We assessed growth characteristics, yield and biochemical constituents. Results show first that all growth characters decreased with increasing salinity stress but applied osmoregulators alleviated these negative effects. Second, salinity stress decreased photosynthetic pigments, K and P contents, whilst increasing proline, soluble sugars, ascorbic acid, Na and Cl contents. Third, application of osmoregulators without salt stress increased photosynthetic pigments, proline, soluble sugars, N, K and P contents whilst decreasing Na and Cl contents. It is concluded that the exogenously applied osmoregulators glycine betaine and proline can fully or partially counteract the harmful effect of salinity stress on growth and yield of canola.© INRA and Springer-Verlag, France 2012

Optical investigation on the electronic structures of Y_{2}Ru_{2}O_{7}, CaRuO_{3}, SrRuO_{3}, and Bi_{2}Ru_{2}O_{7}

We investigated the electronic structures of the bandwidth-controlled ruthenates, Y$_{2}$Ru$_{2}$O$_{7}$, CaRuO$_{3}$, SrRuO$_{3}$, and Bi$_{2}$Ru$_{2}$O$_{7}$, by optical conductivity analysis in a wide energy region of 5 meV $\sim$ 12 eV. We could assign optical transitions from the systematic changes of the spectra and by comparison with the O 1$s$ x-ray absorption data. We estimated some physical parameters, such as the on-site Coulomb repulsion energy and the crystal-field splitting energy. These parameters show that the 4$d$ orbitals should be more extended than 3$d$ ones. These results are also discussed in terms of the Mott-Hubbard model.Comment: 12 pages (1 table), 3 figure