Assessing the Interplay between Weather and Septoria Leaf Blotch Severity on Lower Leaves on the Disease Risk on Upper Leaves in Winter Wheat.

Septoria leaf blotch (SLB) is among the most damaging foliar diseases of wheat worldwide. In this study, data for seven cropping seasons (2003−2009) at four representative wheat-growing sites in the Grand-Duchy of Luxembourg (GDL) were used to assess SLB risk on the three upper leaves (L3 to L1, L1 being the flag leaf) based on the combination of conducive weather conditions, simulated potential daily infection events by Zymoseptoria tritici, and SLB severity on lower leaves between stem elongation and mid-flowering. Results indicated that the variability in SLB severity on L3 to L1 at soft dough was significantly (p < 0.

A Threshold-Based Weather Model for Predicting Stripe Rust Infection in Winter Wheat.

Wheat stripe rust (caused by Puccinia striiformis f. sp. tritici) is a major threat in most wheat growing regions worldwide, which potentially causes substantial yield losses when environmental conditions are favorable.

Draft genome sequence of Pseudomonas fuscovaginae, a broad-host-range pathogen of plants.

Pseudomonas fuscovaginae was first reported as a pathogen of rice causing sheath rot in plants grown at high altitudes. P. fuscovaginae is now considered a broad-host-range plant pathogen causing disease in several economically important plants.

Site-Specific Septoria Leaf Blotch Risk Assessment in Winter Wheat Using Weather-Radar Rainfall Estimates.

The Septoria leaf blotch prediction model PROCULTURE was used to assess the impact on simulated infection rates when using rainfall estimated by radar instead of rain gauge measurements. When comparing infection events simulated by PROCULTURE using radar- and gauge-derived data, the simulated probability of detection (POD) of infection events was high (0.83 on average), and the simulated false alarm ratio (FAR) of infection events was not negligible (0.

The plant pathogen Pseudomonas fuscovaginae contains two conserved quorum sensing systems involved in virulence and negatively regulated by RsaL and the novel regulator RsaM.

Pseudomonas fuscovaginae is a Gram-negative fluorescent pseudomonad pathogenic towards several plant species. Despite its importance as a plant pathogen, no molecular studies of virulence have thus far been reported. In this study we show that P.

Genetic diversity of the mating type and toxin production genes in Pyrenophora tritici-repentis.

Pyrenophora tritici-repentis, the causal agent of tan spot on wheat, is a homothallic loculoascomycete with a complex race structure. The objectives of this study were to confirm the homothallic nature of the pathogen, characterize mating type diversity and toxin production genes in a global collection of strains, and analyze how these traits are associated between each other and with existing races. The pseudothecia production capacity, race identification, mating type locus (MAT), internal transcribed spacer, and glyceraldehyde-3-phosphate dehydrogenase regions were analyzed in a selection of 88 strains originating from Europe, North and South America, North Africa, and Central and South Asia.

Assessing the Accuracy of Simulation Model for Septoria Leaf Blotch Disease Progress on Winter Wheat.

A mechanistic model, PROCULTURE, for assessing the development of each of the last five leaf layers and the progress of Septoria leaf blotch, caused by Septoria tritici (teleomorph Mycosphaerella graminicola), has been applied on susceptible and weakly susceptible winter wheat (Triticum aestivum) cultivars in two locations (Everlange and Reuland) in Luxembourg over a 3-year period (2000 to 2002). A double performance assessment of PROCULTURE was conducted in this study. First, the capability of PROCULTURE to correctly simulate S.

Ophiostomatoid fungi (Ascomycota) associated with Pinus tabuliformis infested by Dendroctonus valens (Coleoptera) in northern China and an assessment of their pathogenicity on mature trees.

Dendroctonus valens is an invasive pest in coniferous forests of northern China. It was suspected of being responsible for the death of more than three million Pinus tabuliformis trees. The present study sought to identify the ophiostomatoid fungi associated with D.

Xanthomonas translucens from Small Grains: Diversity and Phytopathological Relevance.

ABSTRACT Sixty-eight presumptive Xanthomonas translucens strains isolated from 15 small grains or grass species were studied by pathogenicity tests on barley, bread wheat, oat, and bromegrass species, and also by AFLP, analysis of fatty acid methyl esters (FAME), and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of protein extracts. The X. translucens strains were divided into three pathogenicity types based on differences observed on barley and bread wheat.

Serological Methods for Detection of Polymyxa graminis, an Obligate Root Parasite and Vector of Plant Viruses.

A purification procedure was developed to separate Polymyxa graminisresting spores from sorghum root materials. The spores were used as im-munogen to produce a polyclonal antiserum. In a direct antigen coating enzyme-linked immunosorbent assay (DAC ELISA), the antiserum could detect one sporosorus per well of the ELISA plate.

Leptographium sinoprocerum sp. nov., an undescribed species associated with Pinus tabuliformis-Dendroctonus valens in northern China.

During a study of ophiostomatoid fungi associated with the invasive pest Dendroctonus valens in the Pinus tabuliformis ecosystem in northern China, a multigenic (ITS2-LSU, beta-tubulin and EF1-alpha) phylogenetic analysis and examination of morphological features revealed in addition to Leptographium procerum the occurrence of an undescribed species. The new species, Leptographium sinoprocerum, belongs to the L. procerum-L.

Barley yellow mosaic virus is overcoming RYM4 resistance in Belgium.

Barley yellow mosaic virus (BaYMV) is the causal agent of a soil-borne systemic mosaic disease on barley. It has been reported in Belgium since the 1980s. The control of this disease is managed almost exclusively through the use of resistant varieties.

A certain but non-exclusive association between Polymyxa graminis special forms and cereals.

Polymyxo graminis, a ubiquitous plasmodiophorid obligate root endoparasite, is recognized as the vector of about 15 viruses on cereals and groundnut in temperate and tropical areas. Within the species, five special forms have been distinguished on the basis of specific ribotypes. Three of them occur in tropical areas: P.

Identification and Quantification of Polymyxa graminis f. sp. temperata and P. graminis f. sp. tepida on Barley and Wheat.

Polymyxa graminis f. sp. temperata and P.

Ophiostoma arduennense sp. nov. (Ophiostomatales, Ascomycota) from Fagus sylvatica in southern Belgium.

Ophiostoma arduennense sp. nov. is described from several cultures isolated from Fagus sylvatica in southern Belgium.

Widespread Occurrence of Wheat spindle streak mosaic virus in Belgium.

In order to assess the occurrence of Wheat spindle streak mosaic virus (WSSMV) in Belgium, a reverse-transcription polymerase chain reaction (RT-PCR) was developed, targeting WSSMV isolates from Canada, France, Germany, Italy, and the United States. The primers also were designed for virus quantification by real-time RT-PCR with SYBR-Green. No cross-reaction with soilborne cereal viruses such as Barley mild mosaic virus, Barley yellow mosaic virus, Soilborne cereal mosaic virus, and Soil-borne wheat mosaic virus was observed.

Individual and combined effects of dosages of azoxystrobin and epoxiconazole in wheat.

The effects of single fungicide applications on Mycosphaerella graminicola (septoria leaf blotch) control and winter wheat yield were evaluated in field trials conducted in central Belgium between 2000 and 2004. Individual applications of 25, 50, 75 and 100% of the manufacturer's recommended dose rates of azoxystrobin and epoxiconazole, and all the combinations of these treatments, were made at GS 39 in 2001 to 2004 and at GS 59 in 2000. Disease assessments were made at growth stage 75, some 7-8 weeks after the last applications.

Gibberella xylarioides sensu lato from Coffea canephora: a new mating population in the Gibberella fujikuroi species complex.

Gibberella xylarioides Heim & Saccas (presumed anamorph, Fusarium xylarioides Steyaert) is the causal agent of coffee wilt disease, an economically important tracheomycosis in Africa. In vitro crosses carried out with Congolese, Ugandan, and Tanzanian single-ascospore/conidial isolates originating from diseased Coffea canephora/excelsa demonstrated a heterothallic mating system, controlled by a single locus with two alleles, MAT-1 and MAT-2. Compatible isolates produced fertile perithecia within 2 to 8 weeks after mating.

First detection of resistance to QoI fungicides in Mycosphaerella graminicola on winter wheat in Belgium.

A total of 740 Mycosphaerella graminicola strains were isolated between 2000 and 2002 from winter wheat F1 or F2 leaves showing Septoria leaf blotch lesions (SLB) collected mainly at the soft dough stage in fungicide trials, analysing at 12 locations in Belgium the possibilities and risks associated with the use of epoxiconazole and azoxystrobin at various doses, mixtures and application dates. Fungicide sensitivity tests were performed in microtitre plates on potato dextrose broth amended with various concentrations of azoxystrobin. A wide range of sensitivity to azoxystrobin was observed, with EC50 values ranging for 735 strains between 0.

Understanding Puccinia striiformis West. epidemics on winter wheat.

Yellow rust epidemics, caused by Puccinia striiformis West., often arise in wheat field as infection focus of a few decimetres of diameter, including some sporulating lesions on a few plants. Under appropriate environmental conditions such as high relative humidity and temperatures between 2 and 20 degrees C, those initial foci may grow rapidly and initiate new foci elsewhere in the field.

Lessons from the year 2001 Mycosphaerella graminicola epidemic on winter wheat in Belgium.

Infection by Mycosphaerella graminicola (anamorph Septoria tritici) was monitored between April and July 2001 on F6 to flag leaf in 11 farmers' fields or fungicide trials. Data were analysed by mean of the decision support system "Proculture" which links an automatic weather station of the PAMESEB network to a particular field, simulates plant development with adjustment by one phenological observation during the stem elongation and analyses superposition of emerged leaves and infection events (http://www.fymy.

High-performance liquid chromatography analyses of pyoverdin siderophores differentiate among phytopathogenic fluorescent Pseudomonas Species.

The relationship of pyoverdins produced by 41 pathovars of Pseudomonas syringae and by phytopathogenic Pseudomonas species was investigated. A high-performance liquid chromatography method for analyzing the culture medium proved to be superior to isoelectric focusing for detecting pyoverdin production, for differentiating slightly different pyoverdins, and for differentiating atypical from typical Fe(III)-chelated pyoverdins. Nonfluorescent strains were found in Pseudomonas amygdali, Pseudomonas meliae, Pseudomonas fuscovaginae, and P.

Characterization of fluorescent and nonfluorescent peptide siderophores produced by Pseudomonas syringae strains and their potential use in strain identification.

Nonfluorescent highly virulent strains of Pseudomonas syringae pv. aptata isolated in different European countries and in Uruguay produce a nonfluorescent peptide siderophore, the production of which is iron repressed and specific to these strains. The amino acid composition of this siderophore is identical to that of the dominant fluorescent peptide siderophore produced by fluorescent P.

Modulation of plant plasma membrane H+-ATPase by phytotoxic lipodepsipeptides produced by the plant pathogen Pseudomonas fuscovaginae.

Pseudomonas fuscovaginae produces the lipodepsipeptides syringotoxin, fuscopeptin A and fuscopeptin B concurrently. These phytotoxins inhibit acidification of the external medium by fusicoccin-treated rice leaf sheath discs. When tested in vitro on H+-ATPase of rice shoot plasma membranes, syringotoxin and its structural analogue syringomycin, produced by P.

Structure of fuscopeptins, phytotoxic metabolites of Pseudomonas fuscovaginae.

The structure of the fuscopeptins, bioactive lipodepsipeptides produced in culture by the gramineae pathogen Pseudomonas fuscovaginae, has been determined. The combined use of FAB mass spectroscopy NMR spectroscopy and chemical and enzymatic procedures allowed one to define a peptide moiety corresponding to Z-Dhb-D-Pro-L-Leu-D-Ala-D-Ala-D-Ala-D-Ala-D-Val-Gly-D-Ala-D-Val-D-Ala-D- Val-Z-Dhb-Da-Thr-L-Ala-L-Dab-D-Dab-L-Phe with the terminal carboxyl group closing a macrocyclic ring on the hydroxyl group of the allothreonine residue. The N-terminus is in turn acylated by 3-hydroxyoctanoate in fuscopeptin A and 3-hydroxydecanoate in fuscopeptin B.