Different susceptibility of European grapevine cultivars for downy mildew

Downy mildew, caused by the obligately biotrophic peronosporomycete Plasmopara viticola, is one of the most destructive of grapevine diseases that occurs worldwide. The classical cultivars of Vitis vinifera, up to date utmost important for wine and table grape production, are all susceptible to P. viticola, resulting in severe epidemics under warm and humid conditions. The aim of our present study was to characterize the susceptibility to infection by P. viticola among different grapevine cultivars grown in European vineyards in comparison to resistant Vitis species. For this purpose we inoculated leaf discs, leaves and whole plants of eight V. vinifera cultivars considered to be susceptible ('Albariño' [Clone1, Clone2 and Clone3], 'Tempranillo', 'Touriga Nacional', 'Riesling', 'Pinot Noir', 'Pinot Blanc', 'Müller-Thurgau' and 'Cabernet Sauvignon') with P. viticola under controlled conditions. Four Vitis genotypes with a distinct degree of resistance to P. viticola (V. riparia, V. rupestris, V. amurensis and the hybrid Vitis x vinifera 'Solaris') were used as resistant and partially resistant references. To assess the degree of susceptibility we scored the disease incidence and severity visually and microscopically analyzed the course of host tissue colonization by the pathogen. The microscopical studies indicated even slight differences in the infection rate, the course of host tissue colonization and the parasitation i.e. haustoria formation, among the V. vinifera cultivars. The obtained data were suitable for statistical analysis that showed significant differences in the assessed parameters among the V. vinifera cultivars. The principal component analysis (PCA) of the data revealed three groups of susceptibility:genotypes which are little susceptible, e.g. 'Cabernet Sauvignon', 'Pinot Blanc', 'Pinot Noir', 'Müller-Thurgau' and 'Riesling';a second group formed by those genotypes which are very susceptible, i.e. the two clones of 'Albariño' (the most susceptible of all) and 'Tempranillo'; anda third group comprising the genotypes used as resistant and partially resistant references (V. riparia, V. rupestris, V. amurensis and the hybrid Vitis x vinifera 'Solaris').Within the first group 'Cabernet Sauvignon' formed a subgroup indicating a very low susceptibility to P. viticola. In this work, for the first time the visual assessment of disease incidence and severity with a microscopical analysis of infection intensity, colonization of host tissue and parasitation to discriminate differences in susceptibility of European V. vinifera cultivars for P. viticola was combined.

Evaluation of foliar resistance to downy mildew in different cv. Albariño clones

Resistance to downy mildew was studied in different Vitis vinifera L. cv. Albariño clones belonging to the collection of the Mision Biológica de Galicia, CSIC (Spain). V. riparia, V. vinifera cv. Solaris and V. vinifera cv. Müller-Thurgau were used as controls. Plants were inoculated with Plasmospora viticola in the laboratory using the leaf disc, whole leaf and whole plant techniques. The results were compared with those obtained in the field for the same Albariño clones. The most susceptible group of clones included MBG-2, MBG-14, MBG-12 and MBG-9, while MBG-13, MBG-3 and MBG-6 formed the most resistant group. The remaining clones showed intermediate resistance. These results coincide with observations made in the field. The resistance observed in MBG-12 could have been generated from in vitro culture, because this induces changes in the downy mildew resistance.

Structure of a photosynthetic reaction centre determined by serial femtosecond crystallography

Serial femtosecond crystallography is an X-ray free-electron-laser-based method with considerable potential to have an impact on challenging problems in structural biology. Here we present X-ray diffraction data recorded from microcrystals of the Blastochloris viridis photosynthetic reaction centre to 2.8 angstrom resolution and determine its serial femtosecond crystallography structure to 3.5 angstrom resolution. Although every microcrystal is exposed to a dose of 33MGy, no signs of X-ray-induced radiation damage are visible in this integral membrane protein structure

Femtosecond dark-field imaging with an X-ray free electron laser

The emergence of femtosecond diffractive imaging with X-ray lasers has enabled pioneering structural studies of isolated particles, such as viruses, at nanometer length scales. However, the issue of missing low frequency data significantly limits the potential of X-ray lasers to reveal sub-nanometer details of micrometer-sized samples. We have developed a new technique of dark-field coherent diffractive imaging to simultaneously overcome the missing data issue and enable us to harness the unique contrast mechanisms available in dark-field microscopy. Images of airborne particulate matter (soot) up to two microns in length were obtained using single-shot diffraction patterns obtained at the Linac Coherent Light Source, four times the size of objects previously imaged in similar experiments. This technique opens the door to femtosecond diffractive imaging of a wide range of micrometer-sized materials that exhibit irreproducible complexity down to the nanoscale, including airborne particulate matter, small cells, bacteria and gold-labeled biological samples. (C) 2012 Optical Society of Americ

Single-shot diffraction data from the Mimivirus particle using an X-ray free-electron laser

Citation: Ekeberg, T., Svenda, M., Seibert, M. M., Abergel, C., Maia, F. R. N. C., Seltzer, V., . . . Hajdu, J. (2016). Single-shot diffraction data from the Mimivirus particle using an X-ray free-electron laser. Scientific Data, 3. doi:10.1038/sdata.2016.60Free-electron lasers (FEL) hold the potential to revolutionize structural biology by producing X-ray pules short enough to outrun radiation damage, thus allowing imaging of biological samples without the limitation from radiation damage. Thus, a major part of the scientific case for the first FELs was three-dimensional (3D) reconstruction of non-crystalline biological objects. In a recent publication we demonstrated the first 3D reconstruction of a biological object from an X-ray FEL using this technique. The sample was the giant Mimivirus, which is one of the largest known viruses with a diameter of 450 nm. Here we present the dataset used for this successful reconstruction. Data-analysis methods for single-particle imaging at FELs are undergoing heavy development but data collection relies on very limited time available through a highly competitive proposal process. This dataset provides experimental data to the entire community and could boost algorithm development and provide a benchmark dataset for new algorithms

Noise-robust coherent diffractive imaging with a single diffraction pattern

The resolution of single-shot coherent diffractive imaging at X-ray free-electron laser facilities is limited by the low signal-to-noise level of diffraction data at high scattering angles. The iterative reconstruction methods, which phase a continuous diffraction pattern to produce an image, must be able to extract information from these weak signals to obtain the best quality images. Here we show how to modify iterative reconstruction methods to improve tolerance to noise. The method is demonstrated with the hybrid input-output method on both simulated data and single-shot diffraction patterns taken at the Linac Coherent Light Source. (C) 2012 Optical Society of Americ

Evaluation of foliar resistance to downy mildew in different cv. Albariño clones

Resistance to downy mildew was studied in different Vitis vinifera L. cv. Albariño clones belonging to the collection of the Mision Biológica de Galicia, CSIC (Spain). V. riparia, V. vinifera cv. Solaris and V. vinifera cv. Müller-Thurgau were used as controls. Plants were inoculated with Plasmospora viticola in the laboratory using the leaf disc, whole leaf and whole plant techniques. The results were compared with those obtained in the field for the same Albariño clones. The most susceptible group of clones included MBG-2, MBG-14, MBG-12 and MBG-9, while MBG-13, MBG-3 and MBG-6 formed the most resistant group. The remaining clones showed intermediate resistance. These results coincide with observations made in the field. The resistance observed in MBG-12 could have been generated from in vitro culture, because this induces changes in the downy mildew resistance.Peer reviewe

Optimal mapping of x-ray laser diffraction patterns into three dimensions using routing algorithms

Coherent diffractive imaging with x-ray free-electron lasers (XFEL) promises high-resolution structure determination of noncrystalline objects. Randomly oriented particles are exposed to XFEL pulses for acquisition of two-dimensional (2D) diffraction snapshots. The knowledge of their orientations enables 3D imaging by multiview reconstruction, combining 2D diffraction snapshots in different orientations. Here we introduce a globally optimal algorithm that can infer these orientations. We apply it to experimental XFEL data of nanoparticles and so determine their 3D electron density