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European Journal of Microbiology and Immunology
Authors:
Trudy M. Wassenaar
,
Anke Zschüttig
,
Claudia Beimfohr
,
Thomas Geske
,
Christian Auerbach
,
Helen Cook
,
Kurt Zimmermann
, and
Florian Gunzer

) Wassenaar TM, Gaastra W: Bacterial virulence, where to draw the line? FEMS Microbiol Letters 201, 1–7 (2001) Wassenaar TM, Alter T (2012): Virulence genes in microbial risk assessment of probiotic organisms: what do genome sequences tell us

Open access
European Journal of Microbiology and Immunology
Authors:
Comoé Koffi Donatien Benie
,
Adjéhi Dadié
,
Nathalie Guessennd
,
Nadège Ahou N’gbesso-Kouadio
,
N’zebo Désiré Kouame
,
David Coulibaly N’golo
,
Solange Aka
,
Etienne Dako
,
Koffi Marcellin Dje
, and
Mireille Dosso

, Al-Marzoqi AH , Zahraa MA , Shalan AA : Molecular and phenotypic study of virulence genes in a pathogenic strain of Pseudomonas aeruginosa isolated from various clinical origins by PCR: profiles of genes and toxins . Res J Pharm, Biol Chem Sci 7

Open access

Pyrenophora teres f. teres (Ptt), causing net blotch in barley, is an important and frequently isolated leaf pathogen across the globe. The virulence spectrum of Ptt from North Africa including Morocco is poorly understood. Sixteen barley genotypes were challenged, at seedling stage, with 15 Ptt isolates that were collected from different agroecological zones of Morocco. The experiment was conducted in a factorial arrangement of treatments in a randomized complete block design with three replicates. The ANOVA revealed highly significant (P < 0.001) effects of genotype (G), isolate (I) and G×I interaction explaining 23.2, 62.5, and 13.9% of the variation, respectively. Therefore, the current study revealed highly diverse virulence pattern of Moroccan isolates. Furthermore, the results indicated that minor virulence of Ptt isolates dominated over virulence interaction. In addition, Taffa (6-rowed) and Aglou (2 rowed), had the highest level of resistance to Ptt, while Coast and Rabat071 were the most susceptible genotypes. Pt2, Pt7, Pt8 and Pt4 were being the most virulent isolates, while Pt10 and Pt11 were the least virulent isolates. The emergence of the new Ptt pathotypes, which were highly virulent to durable resistance in Rabat071 posed a risk of breaking down the currently deployed resistance to net blotch in Morocco. A careful evaluation and selection of Ptt isolates based on minor virulence pattern to barley genotypes is essential for successful barley breeding program for resistance to net blotch in Morocco.

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Virulence of the two isolates of Beauveria bassiana, BB2 and AM-118, were evaluated on adults of a predatory hemipteran, Andrallus spinidens Fabricius by conidial bioassay and enzymatic activities. Results of the bioassay revealed LC50 of 37×104 and 15×103 spore/ml for isolates BB2 and AM-118, respectively. Activities of chitinase, lipase and ALP showed the higher activity in the media inoculated by AM-118 while no statistical differences were observed in activity of ACP. Although no statistical differences were found in general protease and Pr1 activities but activity of Pr2 in AM-118 was significantly higher than that of BB2. Activity of general esterases demonstrated no statistical differences when α- and β-naphtyl acetate were used as substrates but activity of glutathione S-transferase in AM-118 was higher than that of BB2 by using CDNB and DCNB as specific reagents. Results of the current study indicated higher virulence of isolate AM-118 against adults of A. spinidens by lower LC50 value and higher activities of the enzymes involved in pathogenicity. Recruiting of these isolates against C. suppressalis must be considered by their adaptability of A. spinidens. Moreover, AM-118 has been isolated from rice fields of northern Iran, so it may somehow indicate a type of host-microorganism interaction.

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The fitness cost associated with virulence was analyzed in a local Plasmopara halstedii (sunflower downy mildew) population. Pathogenic and molecular analyses were carried out on seven pathogen isolates including five progeny isolates of five P. halstedii races arising from two parental ones. P. halstedii isolates showed significant differences for all aggressiveness criteria and important genetic variations. Two cases of relationship (positive and negative) between virulence and aggressiveness for progeny isolates as compared with parental ones were found. Mean virulence cost values varied between 19.9% for positive relationship between the two components of pathogenicity and 50.8% for negative one. For solving the presence of two cases in pathogenicity, the relationship between virulence and aggressiveness among the isolates of three different races localized in the same genetic clade was positive. The hypothesis explaining these cases are discussed.

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European Journal of Microbiology and Immunology
Authors:
Abdelaziz Ed-Dra
,
Fouzia Rhazi Filali
,
Slimane Khayi
,
Said Oulghazi
,
Brahim Bouchrif
,
Abdellah El Allaoui
,
Bouchra Ouhmidou
, and
Mohieddine Moumni

variety of virulence factors that play an important role in a wide range of pathogenic mechanisms, such as adhesion, invasion, intracellular survival, toxin production, and iron acquisition [ 7 ]. However, the presence of virulence genes in multidrug

Open access

Desjardins, A.E., Proctor, R.H., Bai, G., McCormick, S.P., Shaner, G., Buechley, G.., Hohn, T.M. 1996. Reduced virulence of trichothecene nonproducing mutants of Gibberella zeae in wheat field tests. Mol

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Afshari, F. 2008. Identification of virulence factors of Puccinia triticina , the casual agent of wheat leaf rust in Iran. Proc.11 th Int. Wheat Genet. Symp., http://hdl.handle.net/2123

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wheat leaf rust ( Puccinia triticina ) races and virulence changes in Slovakia in 1994–2004 . Biologia 63 : 1 – 4 . Hanzalová , A. , Huszár , J. , Herzová , E. , Bartoš , P

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Phenotypic groups including pathogenic, morphological and genetic characteristics for 50 Plasmopara halstedii (downy mildew) isolates belonging to seven races based on interactions with sunflower plants were revealed. Pathogenicity for pathogen isolates were analysed in sunflower plants showing different levels of resistance. Based on the reaction for the P. halstedii isolates to sunflower hybrids varying only in Pl resistance genes, there were three identified groups based on virulence reaction. Index of aggressiveness was calculated for pathogen isolates and revealed the presence of significant differences between isolates of 100 and 3xx races (more aggressive) and isolates of 710 and 7xx races (less aggressive). Morphological analyses were carried out on zoosporangia and sporangiophores for P. halstedii isolates produced on the surface of cotyledons in sunflower plants infected thought roots. There were no groups based on the morphology of zoosporangia and sporangiophores for pathogen isolates. Genetic relationships were detected between pathogen isolates using 12 EST-derived markers. There was no intra-race genetic variation, but five genetically-identified groups were detected among pathogen isolates of all races. Combining data of pathogen’s variation with variability in sunflower to arrive at durable resistance against P. halstedii was discussed.

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