Genetic diversity of pathogenic and nonpathogenic populations of Fusarium oxysporum isolated from carnation fields in Argentina

In order to elucidate the origin of Fusarium oxysporum f. sp. dianthi in Argentina, the genetic diversity among pathogenic isolates together with co-occurring nonpathogenic isolates on carnation was investigated. In all, 151 isolates of F. oxysporum were obtained from soils and carnation plants from several horticultural farms in Argentina. The isolates were characterized using vegetative compatibility group (VCG), intergenic spacer (IGS) typing, and pathogenicity tests on carnation. Seven reference strains of F. oxysporum f. sp. dianthi also were analyzed and assigned to six different IGS types and six VCGs. Twenty-two Argentinean isolates were pathogenic on carnation, had the same IGS type (50), and belonged to a single VCG (0021). The 129 remaining isolates were nonpathogenic on carnation and sorted into 23 IGS types and 97 VCGs. The same VCG never occurred in different IGS types. Our results suggest that the pathogen did not originate in the local populations of F. oxysporum but, rather, that it was introduced into Argentina. Given the genetic homogeneity within Argentinean isolates of F. oxysporum f. sp. dianthi, either IGS type or VCG can be used for the identification of the forma specialis dianthi currently in Argentina.Centro de Investigaciones de Fitopatologí

Metatranscriptomic Comparison of Endophytic and Pathogenic \u3cem\u3eFusarium\u3c/em\u3e-Arabidopsis Interactions Reveals Plant Transcriptional Plasticity

Plants are continuously exposed to beneficial and pathogenic microbes, but how plants recognize and respond to friends versus foes remains poorly understood. Here, we compared the molecular response of Arabidopsis thaliana independently challenged with a Fusarium oxysporum endophyte Fo47 versus a pathogen Fo5176. These two F. oxysporum strains share a core genome of about 46 Mb, in addition to 1,229 and 5,415 unique accessory genes. Metatranscriptomic data reveal a shared pattern of expression for most plant genes (about 80%) in responding to both fungal inoculums at all timepoints from 12 to 96 h postinoculation (HPI). However, the distinct responding genes depict transcriptional plasticity, as the pathogenic interaction activates plant stress responses and suppresses functions related to plant growth and development, while the endophytic interaction attenuates host immunity but activates plant nitrogen assimilation. The differences in reprogramming of the plant transcriptome are most obvious in 12 HPI, the earliest timepoint sampled, and are linked to accessory genes in both fungal genomes. Collectively, our results indicate that the A. thaliana and F. oxysporum interaction displays both transcriptome conservation and plasticity in the early stages of infection, providing insights into the fine-tuning of gene regulation underlying plant differential responses to fungal endophytes and pathogens

A biological method to control pathogenic strains of Fusarium oxysporum in soil

International audienceFusarium oxysporum is a very common fungus found in soils throughout the world, some strains of which are pathogenic. The only method available at present to control these strains is the use of methyl bromide. INRA scientists in Dijon have developed a biological method to control pathogenic strains of Fusarium oxysporum by clarifying the conditions for the introduction in soil of a strain known for its lack of pathogenicity

Genetic diversity of Pythium oligandrum in Iran

National audiencePythium oligandrumis an important potential biological control agent of plant pathogens. The objective of this study was to evaluate the genetic diversity and population structure of 45 isolates from various provinces in Iran. Genetic diversity was characterized based on inter-simple sequence repeat (ISSR) markers. Cluster analysis of ISSR data categorized the isolates into three main clusters. A high level of variability was revealed withinP. oligandrumisolates, however, no significant diversity among geographical regions was observed and isolates from different regions were grouped into the same cluster. Genetic diversity was moderate within populations (i.e. Bushehr, Fars and Kermanshah) with high average gene flow and low genetic distances between populations. The observed and effective numbers of alleles were higher in the Fars population than in other studied populations. This is the first report on the genetic diversity ofP. oligandrumusing ISSR markers. This study paves the way for the selection of isolates to be assessed for their antagonistic efficacy

Genetic diversity of pathogenic and nonpathogenic populations of Fusarium oxysporum isolated from carnation fields in Argentina

International audienc

Complexity of the tripartite interaction in the rhizosphere: case of soil-borne pathogenic fungi with the holoparasitic plant Phelipanche ramosa and its host plant

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Terminal restriction fragment length polymorphism analysis of ribosomal RNA genes to assess changes in fungal community structure in soils

International audienceMonitoring the structure and dynamics of fungal communities in soils under agricultural and environmental disturbances is currently a challenge. In this study, a terminal restriction fragment length polymorphism (T-RFLP) fingerprinting method was developed for the rapid comparison of fungal community structures. The terminal restriction fragment polymorphism of different regions of the small-subunit (SSU) ribosomal RNA (rRNA) gene was simulated by sequence comparison using 10 restriction enzymes, and analyzed among three different soils using fungal-specific primers. Polymerase chain reaction amplification of the 3' end of the SSU rRNA gene with the primer nu-SSU-0817-5' and with the fluorescently labelled primer nu-SSU-1536-3', and digestion of the amplicons with AluI and MboI were found to be optimal and were used in a standardized T-RFLP procedure. Both the number and the intensity of terminal restriction fragments detected by capillary gel electrophoresis were integrated in correspondence analyses. Three soils with contrasting physicochemical properties were differentiated according to the structure of their fungal communities. Assessment of the impact on the fungal community structure of the amendment of two soils with compost or manure confirmed the reproducibility and the sensitivity of the method. Shifts in the community structure were detected between non-amended and amended soil samples. In both soils, the shift differed with the organic amendment applied. In addition, the fungal community structures of the two soils were affected in a different way by the same organic amendment. The fingerprinting method provides a rapid tool to investigate the effect of various perturbations on the fungal communities in soils

Characterization of Fusarium oxysporum populations by growth parameter evaluation in microtiter plates

International audienc

Recovery of strains impaired in their antagonist activity after transposition of the Fot1 element in Fusarium oxysporum

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Perspectives : projets de recherche en cours et à développer

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