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Le Touquet – Paris-Plage, France

Crepin A.,CNRS Laboratory of Microbiology Signals and Microenvironment | Beury-Cirou A.,S.I.P.R.E Comite Nord | Beury-Cirou A.,French National Center for Scientific Research | Barbey C.,CNRS Laboratory of Microbiology Signals and Microenvironment | And 6 more authors.
Sensors | Year: 2012

Soft-rot bacteria Pectobacterium and Dickeya use N-acyl homoserine lactones (NAHSLs) as diffusible signals for coordinating quorum sensing communication. The production of NAHSLs was investigated in a set of reference strains and recently-collected isolates, which belong to six species and share the ability to infect the potato host plant. All the pathogens produced different NAHSLs, among which the 3-oxo-hexanoyl- and the 3-oxo-octanoyl-L-homoserine lactones represent at least 90% of total produced NAHSL-amounts. The level of NAHSLs varied from 0.6 to 2 pg/cfu. The involvement of NAHSLs in tuber maceration was investigated by electroporating a quorum quenching vector in each of the bacterial pathogen strains. All the NAHSL-lactonase expressing strains produced a lower amount of NAHSLs as compared to those harboring the empty vector. Moreover, all except Dickeya dadantii 3937 induced a lower level of symptoms in potato tuber assay. Noticeably, aggressiveness appeared to be independent of both nature and amount of produced signals. This work highlights that quorum sensing similarly contributed to virulence in most of the tested Pectobacterium and Dickeya, even the strains had been isolated recently or during the past decades. Thus, these key regulatory-molecules appear as credible targets for developing anti-virulence strategies against these plant pathogens. © 2012 by the authors. Source


Marhadour S.,FN3PT | Marhadour S.,French National Institute for Agricultural Research | Pelle R.,French National Institute for Agricultural Research | Abiven J.-M.,Station de Creation Varietale | And 4 more authors.
Potato Research | Year: 2013

To decrease the environmental impact of treatments against late blight caused by Phytophthora infestans on potato, plant genetic resistance is a keystone in developing new culture strategies. Nonspecific resistance to late blight is a complex trait which is difficult to evaluate, while selection is both difficult and time consuming. However, we consider it is important to select for this type of resistance as it is a promising way to achieve durable resistance. In this study, parameters derived from disease progress curves (DPCs) were used to characterise the types of resistance among individuals of three tetraploid full-sib families named G1, B2, and K2. These families were composed of 280 (G1), 280 (B2), and 150 (K2) genotypes. Our aim was to avoid visual inspection of 5,710 DPCs and to identify genotypes exhibiting stable resistance. We used three parameters: the slope of the DPC, the date of appearance of the first symptoms in the tested genotypes compared with a susceptible standard, and the relative area under the disease progress curve (rAUDPC). Using an appropriate threshold for each parameter, we demonstrated that it is possible to classify the response of each genotype in one of the following categories: susceptible, non-specific resistance, specific resistance, non-specific resistance plus specific resistance (or specific resistance not overcome). Data were obtained each year from 2005 to 2007 under conditions of natural infection. According to the parameters analysed, non-specific resistance and specific resistance segregated in the families. The year effect was more than double the family effect for rAUDPC. Empirical adjustment of threshold values in a subsample of the tested genotypes led to an increase in the effectiveness of our classification method. Calculated classification enabled detection of stable genotypes in each family. The impact of the year effect differed with the family. In the G1 family, the distribution of genotypes in each category was relatively stable over the 3 years, whereas in K2, the proportion of genotypes demonstrating specific resistance alone increased, particularly in 2007. In the B2 family, the proportion of genotypes in the non-specific resistance category decreased from 40% to 15% from 2005 to 2006, and then remained stable in 2007. The heritabilities of the parameters ranged from 61% to 96% depending on the family and on the parameter concerned. © 2013 EAPR. Source


Helias V.,FN3PT | Helias V.,French National Institute for Agricultural Research | Hamon P.,FN3PT | Hamon P.,French National Institute for Agricultural Research | And 4 more authors.
Plant Pathology | Year: 2012

Pectolytic bacteria, including Pectobacterium spp. and Dickeya spp., are best isolated on crystal violet pectate (CVP), a semiselective medium containing pectin. The source of pectin is essential, because pectolytic bacteria are not able to degrade all of them. The aims of this study were to identify a new pectin source and to perfect formulations of semiselective CVP media to isolate the pectolytic bacteria Pectobacterium spp. and Dickeya spp. from different environmental compartments (plants, soil and water). The AG366 pectin, selected after screening six different formulations, was incorporated into single-layer (SL-CVP AG366) and double-layer (DL-CVP AG366) CVP media. Both media were compared with those based on Bulmer, Sigma-Aldrich and Slendid-Burger pectins, using 39 Pectobacterium and Dickeya strains. All strains formed deep cavities on AG366-CVPs, whereas nine did not produce cavities on Bulmer or Sigma-Aldrich media. Recovery rates were similar on DL-CVP AG366, Sigma-Aldrich and Bulmer CVPs for a given taxon, and did not differ significantly between SL- and DL-CVP AG366. Pectolytic bacteria were successfully isolated on both media from field samples of diseased potatoes, carrots, tobacco, onions, radishes and ornamentals. AG366 is thus a high-performance pectin source for the elaboration of CVP media suitable to isolate Dickeya and Pectobacterium. It is also efficient for enrichment purposes in liquid medium. The validation of AG366 as an improved source of pectin to recover the polyphagous Pectobacterium and Dickeya in different environmental compartments is essential given the current worldwide emergence and recrudescence of these bacteria. © 2011 The Authors. Plant Pathology © 2011 BSPP. Source

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