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White mould can affect the production of a wide range of economically important crops worldwide. The symptoms may be caused by several species, including Sclerotinia subarctica, a species mostly occurring in northern latitudes in sympatry with S. sclerotiorum. Although the two species are morphologically indistinguishable, S. subarctica was reported to have different climatic requirements for mycelial growth and production of apothecia. These differences may affect the precision of white mould risk prediction models that are based on the production of ascospores by S. sclerotiorum. To assess the presence of S. subarctica in France, we adapted a rapid PCR-based test to distinguish S. subarctica from other commonly found species of Sclerotinia. This test was used to characterize a collection of 969 Sclerotinia sp. isolates originating from various plants (bean, canola, carrot, lettuce, melon and witloof chicory), air and soil samples in different regions of France. One single isolate, collected from witloof chicory in northern France, was identified as S. subarctica. When genotyped with five microsatellite markers designed for S. sclerotiorum, this isolate had a haplotypic profile that was clearly distinct from the other isolates. The ITS sequence of this isolate was identical to those of isolates collected in northern Europe and Alaska. Koch’s postulates were verified. When inoculated on witloof chicory, the isolate identified as S. subarctica induced white mould symptoms. This study is the first to report the presence of S. subarctica south of the 51st parallel north and on witloof chicory., La pourriture blanche affecte la production d’un vaste panel de cultures économiquement importantes partout dans le monde. Les symptômes peuvent être causés par plusieurs espèces, dont S. subarctica, une espèce principalement présente sous les latitudes septentrionales en sympatrie avec S. sclerotiorum. Bien que les deux espèces ne puissent être distinguées sur la base de critères morphologiques, S. subarctica semble avoir besoin de conditions climatiques différentes pour sa croissance mycélienne et sa production d’apothécies. Ces différences peuvent affecter la précision des modèles de prédiction de risque de pourriture blanche qui sont basés sur la production d’ascospores par S. sclerotiorum. Pour évaluer la présence de S. subarctica en France, nous avons adapté un test PCR rapide pour distinguer S. subarctica des autres espèces de Sclerotinia communément rencontrées. Ce test a été utilisé pour caractériser une collection de 969 isolats de Sclerotinia sp. provenant de plantes (haricot, colza, carotte, laitue, melon, endive), d’air et de sol dans différentes régions de France. Un seul isolat, prélevé sur endive au nord de la France, a été identifié comme S. subarctica. Lorsque cet isolat a été genotypé avec 5 marqueurs microsatellites spécifiques de S. sclerotiorum, son profil haplotypique était clairement distinct de celui des autres isolats. La séquence ITS de cet isolat était identique à celle des isolats prélevés en Europe du Nord et en Alaska. Les postulats de Koch ont été vérifiés. L’isolat identifié comme S. subarctica a produit les symptômes de pourriture blanche lorsqu’il a été inoculé sur endive. Cette étude est la première à signaler la présence de S. subarctica au sud du 51e parallèle nord et sur endive.

Epidemiological studies have associated environmental exposure to polychlorinated biphenyls (PCBs) with an increased risk of type 2 diabetes; however, little is known about the underlying mechanisms involved in the metabolic side-effects of PCB. Our study evaluated the transcriptional effects of a subchronic exposure (gavage at Day 0 and Day 15 with 10 or 100 μmol/Kg bw) to PCB118 (dioxin-like PCB), PCB153 (non-dioxin-like PCB), or an equimolar mixture of PCB118 and PCB153 on various tissues (liver, visceral adipose tissue, muscle, and colon) in mice. Our results showed that a short-term exposure to PCB118 and/or PCB153 enhanced circulating triglyceride levels but did not affect glycemia. Among the studied tissues, we did not observe any modification of the expression of inflammation-related genes, such as cytokines or chemokines. The main transcriptional effects were observed in visceral adipose and liver tissues. We found a downregulation of lipin1 and glut4 expression in these two target organs. In adipose tissue, we also showed a downregulation of Agpat2, Slc25a1, and Fasn. All of these genes are involved in lipid metabolism and insulin resistance. In muscles, we observed an induction of CnR1 and Foxo3 expression, which may be partly involved in PCB metabolic effects. In summary, our results suggest that lipin1 and glut4, notably in adipose tissue, are the main targeted genes in PCB-induced metabolic disorders, however, further studies are required to fully elucidate the mechanisms involved.

Bacterial blight of fruit trees caused by Pseudomonas syringae causes significant economic losses worldwide. With the expansion of bacterial canker of kiwi caused by P. syringae pv. actinidiae (Psa) and bacterial canker of apricot caused by P. syringae pv. syringae (Pss), identification of reservoirs of pathogenic strains is required. One potential reservoir is ground covers in orchards. A solution could be the development of ecological engineering practices, particularly ground cover management in order to reduce their impact as a source of inoculum for bacterial diseases of fruit trees caused by P. syringae and increase their role as a reserve for microorganisms that are antagonistic to pathogens of fruit trees. However, with the recent discovery of the complexity of the phylogeny of P. syringae and the existence of phylogroups containing more aggressive strains than others (Psa in phylogroup 1, Pss in phylogroup 2), one of the first goals is the development of a specific molecular detection method, by PCR, allowing rapid and accurate identification of the different phylogroups of P. syringae. This would be much more efficient than the only method currently available - sequencing of specific conserved genes used in phylogenetic identification. The simple implementation of this new method of genotyping makes it possible to screen samples of very large size with little effort. This method can be deployed to develop methods of control of bacterial blight, and can be used as a generic mean of detecting and monitoring orchards and crops. Indeed, the use of a technique targeting a single pathovar may be insufficient, as it is not uncommon for plants to be simultaneously attacked by several different strains of P. syringae. The method of detection and identification of phylogroups will be presented and a concrete example for specific samples (ground cover, buds, twigs) from orchards of apricot and kiwi will be described.

Bacterial cankers of perennial trees caused by Pseudomonas syringae provoke serious economic losses all around the world, and also affect tree species in the genus Prunus. When pedo-climatic conditions are favorable, the disease can severely affect apricot (Prunus armeniaca).The epidemiology of this complex disease is not completely understood. Based on recent work on the presence of P. syringae in very diverse non-agricultural habitats, the complexity of the phylogeny of P. syringae, and the existence of phylogroups containing more aggressive strains than others, the scope of this work was the identification of the potential reservoirs of pathogenic strains of P. syringae in Prunus orchards. We addressed the following questions: What is the structure of the P. syringae population in the ground-cover, in the soil, in the irrigation water, and in the plant (epiphytic and endogenous)? What are the relationships between these populations and the populations in non-agricultural habitats? What are the factors that trigger disease when pathogenic populations are present? To answer these questions, a specific molecular detection method, by PCR, allowing rapid and accurate identification of the different phylogroups of P. syringae was developed. With this method, the different potential reservoirs: plants (buds, leaves, twigs), cover-grass, soil, and water, were investigated in 2014 in 3 different French orchards of apricot, at 3 different periods of the plant’s vegetative development. Leaf litter was collected and analyzed during winter. Preliminary results showed different structuration of the populations according to their origin. For example, in March, the abundance of isolates of phylogroup 1 (including P. syringae morsprunorum race 2) and phylogroup 2 (including P. syringae pv syringae) was different in plant, soil and ground-cover populations.

International audience; Mealybugs (Hemiptera: Pseudococcidae) are pests constraining the international trade of Brazilian table grapes. They damage grapes by transmitting viruses and toxins, causing defoliation, chlorosis, and vigor losses and favoring the development of sooty mold. Difficulties in mealybug identification remain an obstacle to the adequate management of these pests. In this study, our primary aim was to identify the principal mealybug species infesting the major table grape-producing regions in Brazil, by morphological and molecular characterization. Our secondary aim was to develop a rapid identification kit based on species-specific Polymerase Chain Reactions, to facilitate the routine identification of the most common pest species. We surveyed 40 sites infested with mealybugs and identified 17 species: Dysmicoccus brevipes (Cockerell), Dysmicoccus sylvarum Williams and Granara de Willink, Dysmicoccus texensis (Tinsley), Ferrisia cristinae Kaydan and Gullan, Ferrisia meridionalis Williams, Ferrisia terani Williams and Granara de Willink, Phenacoccus baccharidis Williams, Phenacoccus parvus Morrison, Phenacoccus solenopsis Tinsley, Planococcus citri (Risso), Pseudococcus viburni (Signoret), Pseudococcus cryptus Hempel, four taxa closely related each of to Pseudococcus viburni, Pseudococcus sociabilis Hambleton, Pseudococcus maritimus (Ehrhorn) and Pseudococcus meridionalis Prado, and one specimen from the genus Pseudococcus Westwood. The PCR method developed effectively identified five mealybug species of economic interest on grape in Brazil: D. brevipes, Pl. citri, Ps. viburni, Ph. solenopsis and Planococcus ficus (Signoret). Nevertheless, it is not possible to assure that this procedure is reliable for taxa that have not been sampled already and might be very closely related to the target species.

Bacillus cereus group bacteria are able to produce toxins and their various enzymatic activities are also recognized as causing food spoilage, even at refrigerated temperatures, when psychrotolerant strains are involved. The lack of a rapid and accurate detection method, suitable for a simple routine analysis, is currently the main hurdle for the control of these populations in the sector of egg product manufacturing.Rationale : The aim of this study was to evaluate the performances of two PCR methods for the detection of B. cereus group bacteria. Whole liquid egg products (174 samples) provided by different companies were enriched in 5 g/L lithium chloride in peptone water. After DNA extraction, the detection of B. cereus group bacteria was assayed by a classical PCR method targeting a cspF gene sequence, as described by Francis et al. (1998) and by a real-time PCR method targeting a sspE gene sequence, as described by Kim et al. (2005). Results : Our results show good correlation between both methods for 86% of the analyzed samples. Ten percent of positive samples assayed by real-time PCR, targeting the sspE gene sequence, were found negative under classical PCR detection, targeting the cspF gene sequence. Only 4% of the analyzed samples were negative under real-time PCR detection and positive under classical PCR. Conclusion : Our results show good correlation between both the PCR methods described in the literature for the detection of B. cereus group bacteria in liquid whole egg and probably in other food, by targeting two different specific gene sequences. The method using real-time PCR seems to be more sensible and presents the advantage to be faster than the classical PCR method. Depending on the availability of their laboratory material, one of these methods could be proposed to manufacturers in order to detect this food spoilage and putative pathogenic microbiota.

International audience; We present a reliable PCR-based method to avoid the biases related to identification based on the conventional phenotypes currently used in the identification of Pseudomonas syringae sensu lato, a ubiquitous environmental bacterium including plant pathogens. We identified a DNA target suitable for this purpose by applying a comparative genomic pipeline to Pseudomonas genomes. We designed primers and developed PCR conditions that led to a clean and strong PCR product from 97% of the 185 strains of P. syringae strains tested and gave a clear negative result for the 31 non-P. syringae strains tested. The sensitivity of standard PCR was determined with pure strains to be 10(6) bacteria mL(-1) or 0.4 ng of DNA μL(-1). Sensitivity could be improved with the touchdown method. The new PCR-assisted isolation of P. syringae was efficient when deployed on an environmental sample of river water as compared to the isolation based on phenotypes. This innovation eliminates the need for extensive expertise in isolating P. syringae colonies, was simpler, faster and very reliable. It will facilitate discovery of more diversity of P. syringae and research on emergence, dispersion, and evolution to understand the varied functions of this environmental bacterium.

La collaboration, entamée en 1996 avec A. Davison du Medical Research Council de Glasgow, a permis d'aboutir à l'obtention d'informations sur la équence de fragments clonés d'ADN de virus de type herpès infectant les huîtres.

Direct detection of [i]Pseudomonas syringae[/i] pathovar Phaseolicola using the polymeras chain reaction (PCR). 4th International Working Group on Pseudomonas syringae Pathovars