Recovery of mutants impaired in pathogenicity after transposition of Impala in Fusarium oxysporum f.sp. melonis

The ability of transposon impala to inactivate genes involved in pathogenicity was tested in Fusarium oxysporum f. sp. melonis. Somatic excision of an impala copy inserted in the nitrate reductase-encoding niaD gene was positively selected through a phenotypic assay based on the restoration of nitrate reductase activity. Independent excision events were analyzed molecularly and shown to carry reinsertedimpala in more than 70% of the cases. Mapping of reinserted impala elements on large NotI-restriction fragments showed that impala transposes randomly. By screening 746 revertants on plants, a high proportion (3.5%) of mutants impaired in their pathogenic potential was recovered. According t…

Determinism of the biocontrol capacity of a strain of Fusarium oxysporum: identification of genes expressed during interactions with tomato

Expression de quelques PR protéines dans des cultures cellulaires et des plantes de tomate inoculées avec une souche pathogène ou une souche protectrice de Fusarium oxysporum

Maîtrise de communautés microbiennes pour lutter contre les maladies d'origine tellurique

Fusarium oxysporum and its biocontrol

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Diversity and interactions among strains of Fusarium oxysporum : application to biological control.

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Enhancing biological control by combining microorganisms

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Colonization of flax roots and early physiological responses of flax cells inoculated with pathogenic and nonpathogenic strains of Fusarium oxysporum

ABSTRACT Fusarium oxysporum includes nonpathogenic strains and pathogenic strains that can induce necrosis or tracheomycosis in plants. The objective of this study was to compare the abilities of a pathogenic strain (Foln3) and a nonpathogenic strain (Fo47) to colonize flax roots and to induce early physiological responses in flax cell culture suspensions. Both strains colonized the outer cortex of the root; however, plant defense reactions, i.e., the presence of wall appositions, osmiophilic material, and collapsed cells, were less frequent and less intense in a root colonized by Foln3 than by Fo47. Early physiological responses were measured in flax cell suspensions confronted with germin…

Potentialités de croissance et de fertilité du bourgeon latent chez la vigne (<em>Vitis vinifera</em> L.), étude réalisée de l'initiation à l'entrée en dormance

<p style="text-align: justify;">Les potentialites de croissance et de fertilité du bourgeon latent de rang 6 (<em>Vitis vinifera</em> L, cépage Pinot noir) sont étudiées grâce à des techniques de forçage pratiquées au vignoble. Ces techniques sont appliquées au bourgeon latent depuis l'état méristématique jusqu'à son entrée en dormance.</p><p style="text-align: justify;">Les potentialités de croissance importantes diminuent en même temps que la dormance s'installe.</p><p style="text-align: justify;">Nous avons montré qu'il est possible d'obtenir une certaine fertilité à partir de bourgeons qui n'ont pas encore formé d'inflorescences au moment des fo…

Microbiological control of soil-borne phytopathogenic fungi with special emphasis on wilt-inducing Fusarium oxysporum

Contents   Summary  529 I. Biological control of plant diseases: state of the art  530 II. Main modes of action of biological control agents  530 III. The protective strains of F. oxysporum: an unexplored model  532 IV. Future directions for the study of the protective capacity of strains of F. oxysporum  539 V. How to make biological control successful in the field?  540   References  541 Summary Plant diseases induced by soil-borne plant pathogens are among the most difficult to control. In the absence of effective chemical control methods, there is renewed interest in biological control based on application of populations of antagonistic micro-organisms. In addition to Pseudomonas spp. a…

Recovery of Fusarium oxysporum Fo47 mutants affected in their biocontrol activity after transposition of the Fot1 element

Trouvelot, S., Olivain, C., Recorbet, G., Migheli, Q., and Alabouvette, C. 2002. Recovery of Fusarium oxysporum Fo47 mutants affected in their biocontrol activity after transposition of the Fot1 element. Phytopathology 92:936-945. To investigate the biocontrol mechanisms by which the antagonistic Fusarium oxysporum strain Fo47 is active against Fusarium wilt, a Fot1 transposon-mediated insertional mutagenesis approach was adopted to generate mutants affected in their antagonistic activity. Ninety strains in which an active Fot1 copy had transposed were identified with a phenotypic assay for excision and tested for their biocontrol activity against F. oxysporum f. sp. lini on flax in greenho…

Production and characterization of pathogenicy-deficient mutants of Fusarium oxysporum f. sp. melonis

Degradation of aromatic compounds through the β-ketoadipate pathway is required for pathogenicity of the tomato wilt pathogenFusarium oxysporumf. sp.lycopersici

Plant roots react to pathogen attack by the activation of general and systemic resistance, including the lignification of cell walls and increased release of phenolic compounds in root exudate. Some fungi have the capacity to degrade lignin using ligninolytic extracellular peroxidases and laccases. Aromatic lignin breakdown products are further catabolized via the β-ketoadipate pathway. In this study, we investigated the role of 3-carboxy-cis,cis-muconate lactonizing enzyme (CMLE), an enzyme of the β-ketoadipate pathway, in the pathogenicity of Fusarium oxysporum f. sp. lycopersici towards its host, tomato. As expected, the cmle deletion mutant cannot catabolize phenolic compounds known to …

Divers aspects de la fertilité de la vigne après une grêle

<p style="text-align: justify;">Following a hail storm, the question normally posed is first to what extent a repruning is beneficial, and then to evaluate the hail's effect on the following year's fertility. A careful study of the influence of hail, using numerous measurements of fertility taken during winter has allowed to determine the parameters that should be taken into account in choosing the course of action to follow.</p>

Use of protective strains of Fusarium oxysporum to control fusarium wilts

Méthodes alternatives de lutte contre les maladies des plantes

Production of a mixed inoculum of Fusarium oxysporum Fo47 and Pseudomonas fluorescens C7 to control Fusarium diseases

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Wanted : pathogenesis-related marker molecules for Fusarium oxysporum

Summary Although Fusarium oxysporum pathogens cause severe wilts in about 80 botanical species, the mechanisms of pathogenicity and symptom induction are poorly understood. Knowledge about the genetic and biochemical pathways involved in the pathogenesis of F. oxysporum would be invaluable in getting targets for both fungicide development and search for biocontrol agents. In this respect, we described the main approaches that have been developed to identify some mechanisms underlying the pathogenesis of F. oxysporum . During the last decades, the potential functions triggering of F. oysporum pathogenicity have mainly been investigated by comparing soilborne pathogenic strains with nonpathog…

Colonization of tomato root by pathogenic and nonpathogenic Fusarium oxysporum strains inoculated together and separately into the soil.

ABSTRACT In soil, fungal colonization of plant roots has been traditionally studied by indirect methods such as microbial isolation that do not enable direct observation of infection sites or of interactions between fungal pathogens and their antagonists. Confocal laser scanning microscopy was used to visualize the colonization of tomato roots in heat-treated soil and to observe the interactions between a nonpathogenic strain, Fo47, and a pathogenic strain, Fol8, inoculated onto tomato roots in soil. When inoculated separately, both fungi colonized the entire root surface, with the exception of the apical zone. When both strains were introduced together, they both colonized the root surface…

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

Déterminisme du pouvoir protecteur d’une souche de Fusarium oxysporum : recherches de gènes impliqués lors de l’interaction avec la tomate

Comparative analysis of PR gene expression in tomato inoculated with virulent Fusarium oxysporum f. sp. lycopersici and the biocontrol strain F. oxysporum Fo47

Non-pathogenic strains of Fusarium oxysporum have the capacity to protect plants against wilt induced by pathogenic strains of F. oxysporum. Among the mechanisms involved in this protection, induced systemic resistance has been demonstrated by using a split-root method. The aim of this study was to follow the accumulation kinetics of transcripts encoding 5 PR proteins in roots and leaves of tomato inoculated with a pathogenic or a protective strain in comparison to non-inoculated control. Moreover quantification of transcripts was assessed by real-time RT-PCR in cell cultures inoculated with the pathogenic or the protective strain. Results showed a lower expression of PR encoding genes in t…

Use of marked strains of pathogenic (FOL8) and protective (FO47) Fusarium oxysporum to visualize their interactions with the tomato root in soil

Several modes of action have been proposed to explain the biocontrol capacity of the Fusarium oxysporum protective strain Fo47, especially competition with the pathogen for root colonization. Confocal microscopy has been used to visualize the interactions between the ransformed strains and the tomato root in soil. A disinfested soil was infested by Fo47 GFP, Fol8 DsRed2, or both fungi together at several concentrations before transplanting tomato seedlings. The general pattern of soil and root colonization was similar for the two fungi, but the saprophytic development of Fo47 was faster than that of the pathogenic strain. Conidia, at the surface of soil particles, germinated as early as 18 …

The nuclear protein Sge1 of Fusarium oxysporum is required for parasitic growth

Dimorphism or morphogenic conversion is exploited by several pathogenic fungi and is required for tissue invasion and/or survival in the host. We have identified a homolog of a master regulator of this morphological switch in the plant pathogenic fungus Fusarium oxysporum f. sp. lycopersici. This non-dimorphic fungus causes vascular wilt disease in tomato by penetrating the plant roots and colonizing the vascular tissue. Gene knock-out and complementation studies established that the gene for this putative regulator, SGE1 (SIX Gene Expression 1), is essential for pathogenicity. In addition, microscopic analysis using fluorescent proteins revealed that Sge1 is localized in the nucleus, is no…

Phenotype characterization of Fo47 mutants affected in their biocontrol activity

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