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International audience; Biological control of Phaeomoniella chlamydospora, a pathogen involved in Esca, a grapevine trunk wood disease, was performed using the oomycete, Pythium oligandrum. Three 4-month greenhouse assays showed that necrosis of Vitis vinifera L. cv. Cabernet Sauvignon cuttings caused by P. chlamydospora was significantly reduced (40-50%) when P. oligandrum colonized the plant root systems. The expression of a set of 22 grapevine defense genes was then quantified by real-time polymerase chain reaction to determine plant responses in the interaction between P. oligandrum/. V. vinifera L./. P. chlamydospora. In the trunk, specific grapevine responses to the different treatments (control, P. oligandrum, P. chlamydospora and P. oligandrum+. P. chlamydospora treatments) were significantly differentiated. Expression levels of 6 genes associated with P. chlamydospora infection showed higher induction than when plants were pre-treated with P. oligandrum. These genes are involved in various pathways (PR proteins, phenylpropanoid pathways, oxylipin and oxydo-reduction systems). © 2015 Elsevier Inc.

A method for rapid extraction of both double-stranded RNA (dsRNA) and DNA from an obligate biotrophic phytopathogenic fungus is described. Lyophilised fungal material is incubated in a commercial guanidium thiocyanate reagent. Proteins and cell debris are centrifuged by chloroform precipitation. After precipitation in isopropanol and washing in 75% ethanol, nucleic acids are resuspended in water (10 microl/mg fungal dry weight). DsRNA is directly visualised by agarose gel electrophoresis. DNA contained in 10-fold dilutions of the samples proved to be suitable for PCR-based experiments.

International audience; Strawberry powdery mildew caused by the ascomycota fungus Podosphaera aphanis (Wallr.) U. Braun and S. Takamatsu, reduces fruit production and quality. It is becoming the most damaging disease of strawberry in the soil-less systems which have been recently widely adopted in France. A collaborative project has been developed by several French technical and research institutes to address this issue, with four main objectives: better understanding of the epidemiology of the disease, evaluating the susceptibility of populations of the pathogen towards fungicides, identifying sources of host plant resistance, and assessing new methods for disease management. Several methods were developed and applied to study this obligate parasite. Monoclonal strains were obtained from deposition of single conidia on detached strawberry leaves. Strains were maintained for several months without manipulation on vitro plants at low temperature (7-9C). One- to two-week-old leaves from one- to two-month-old strawberry plants provided the most susceptible material, and were used to produce inoculum. Methods have been developed to measure epidemiological characteristics of the asexual cycle of P. aphanis: conidia germination, infection efficiency, mycelium growth, latent period, and sporulating intensity. Leaf disks and seedlings from strawberry cultivars with varying levels of partial resistance were assessed according to these epidemiological characteristics. Resistance of the fungus towards fungicides was evaluated by inoculating leaf disks previously sprayed with several concentrations of fungicides. Inhibiting concentrations were calculated relative to untreated controls and suggested a range of resistance levels to fungicides.

The biotrophic fungus, Erysiphe necator the causal agent of the grape powdery mildew, has two genetic groups A and B in European and Australian vineyards. A strain of group A was used to isolate a DNA sequence that exhibits high sequence homology to RNaseH of a non-LTR (long tandem repeat) retro-transposon of Glomerella cingulata. PCR primers were designed and tested for their specificity to genetic group A of E. necator. This molecular tool is more efficient and sensitive than nested PCR based on polymorphism in the CYP 51 and β-tubulin genes.

International audience; Cytochromes P-450 (P-450s) constitute a large family of oxygenases catalyzing phase I metabolism of various xenobiotics, including pesticides. In most cases, they mediate reactions resulting in detoxification of the parent molecule. Plant P-450s play an important role in herbicide metabolism, by constituting a key factor of herbicide selectivity, and of herbicide resistance recently observed in some weed biotypes. Definitive proof of P-450-mediated pesticide metabolism in filamentous fungi has not yet been obtained. However, indirect evidence supports such an hypothesis. The detoxification and degradation potential of P-450s from plants or microorganisms could be exploited for bioremediation of water, industrial waste, and soil contaminated with pesticides. A more comprehensive knowledge of these enzymes, including functional characterization of genes and proteins, remains necessary for an efficient management of P-450 potentialities.

International audience; Fenpropimorph (N-[3-(p-t-butylphenyl)-2-methylpropyl]-cis-2,6-dimethylmorpholine), a morpholine fungicide known to be an inhibitor of sterol biosynthesis in fungi and in higher plants, was demonstrated to be an efficient inhibitor of cholesterol biosynthesis in cultured Swiss 3T3 fibroblasts. Treatment of the mammalian cells with fenpropimorph resulted in a dose-dependent inhibition of [14C]acetate incorporation into the C27 sterols [IC50 (concentration causing half-maximal inhibition) = 0.5 microM], which was accompanied by an accumulation of polar sterols and a decrease in cellular hydroxymethylglutaryl-CoA reductase activity. Exposure of the cells to the drug affected cell growth. Analysis of the sterols in the growth-arrested and in the pulse-labelled cells indicate that fenpropimorph has, in the sterol-biosynthetic pathway, target enzymes in mammalian cells different from those in the other phyla. Whereas in plants and fungi fenpropimorph mainly affects sterol isomerases and reductases, in the fibroblasts its main target seems to be the demethylation of lanosterol.