Differential accumulation of beta-1,3-glucanase and chitinase isoforms in tomato roots in response to colonization by either pathogenic or non-pathogenic strains of Fusarium oxysporum

International audience

Biological control of plant diseases and the environment

International audience

The impact of arthropods on fungal community structure in Lascaux Cave

Aims: To determine the major components of the fungal population present in Lascaux Cave, France. The ceiling, walls, sediments and soil were colonized by Fusarium solani in 2001 and later, in 2006, black stains appeared. However, the origin of the successive fungal invasions is unknown as well as the ecology of the cave. Methods and Results: The primers nu-SSU-0817F and nu-SSU-1536R were used for the direct amplification of fungal 18S-rDNA sequences from 11 samples. A total of 607 clones were retrieved. Eight out of the ten most abundant phylotypes corresponded to fungi associated with arthropods and represented about 50% of the clones. Conclusions: Entomophilous fungi play an important ro…

Suppressiveness of 18 composts against 7 pathosystems : variability in pathogen response

International audience; Compost is often reported as a substrate that is able to suppress soilborne plant pathogens, but suppression varies according to the type of compost and pathosystem. Reports often deal with a single pathogen while in reality crops are attacked by multiple plant pathogens. The goal of the present study was to evaluate the disease suppression ability of a wide range of composts for a range of plant pathogens. This study was conducted by a consortium of researchers from several European countries. Composts originated from different countries and source materials including green and yard waste, straw, bark, biowaste and municipal sewage. Suppressiveness of compost-amende…

Early dynamic interactions between Fusarium oxysporum f.sp. lini and the roots of Linum usitatissimum as revealed by transgenic GUS-marked hyphae

International audience

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…

Fusariose du cyclamen : travaux sur la lutte biologique. Phytoma-La défense des végétaux

SPEIPM; Fusariose du cyclamen : travaux sur la lutte biologique. Phytoma-La défense des végétaux

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

Review of factors influencing the success or failure of biocontrol: technical, industrial and socio-economic perspectives

Communication orale au 11. IOBC-WPRS Meeting of the working group "Biological control of fungal and bacterial plant pathogens". Climate change: challenge or threat to biocontrol?, 2010/06/07-11 ; Graz (AUT).; International audience; Although their role in plant health management is still quite modest, ever increasing expectations are placed on biocontrol agents for the complementation or replacement of pesticide use. Despite decades of research and more than 12,000 scientific papers on biological control of plant diseases, little more than 14 microbe-based commercial products are presently registered for use against diseases in the European Union. Through a review of published scientific li…

Real-time PCR detection of Ochroconis lascauxensis involved in the formation of black stains in the Lascaux Cave, France

A real-time Polymerase Chain Reaction (PCR) assay was developed to detect and quantify Ochroconis lascauxensis in the Lascaux Cave in France. This fungus is the principal causal agent of the black stains threatening the Paleolithic paintings of this UNESCO World Heritage Site. The black stains outbreak could not be stopped in spite of using intensive biocide treatments. A sensitive and time-saving protocol is needed for determining the extent of the colonization. Sets of primers that target the ITS and RPB2 regions were designed and evaluated for specificity against O. lascauxensis. Genomic DNA extracted from five species of Ochroconis and 13 other fungal species frequently isolated from ca…

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

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

Trophic competition for the C source is the main mechanism involved in the interaction between pathogenic and non-pathogenic populations of Fusarium oxysporum. Therefore, a phenotypical characterization based on the growth characteristics of these populations will provide classical genotypical characterizations with additionnal information of ecological significance.

The soil as a reservoir for antagonists to plant diseases

The soil is often considered the milieu providing support for plant roots, water and nutrients for plant growth. But it is also considered a hostile environment harbouring plant pathogenic nematodes, bacteria and fungi. The most common attitude is to try to eliminate the plant pathogenic organisms by biocidal treatments such as methyl bromide fumigation, which are dangerous for man and the environment. Beside this pathogen eradication strategy, another approach to control soil-borne plant diseases consists in studying the plant-pathogen interactions at the cellular and molecular level to create new resistant cultivars or to develop new plant protection products based on elicitation of plant…

La lutte biologique contre les parasites du sol : possibilités, spécificités...et pour l'instant rareté

National audience

Effects of the introduction of a biocontrol strain of Trichoderma atroviride on non target soil micro-organisms

International audience; The main objective of this study was to assess the impact of the application of an antagonistic strain of Trichoderma atroviride on the native microbial soil communities. The structures of the fungal and bacterial communities were assessed by T-RFLP (terminal restriction fragment length polymorphism) method, based on T-RFLP analysis of 18S and 16S rRNA genes, respectively. Results showed that the introduction of the strain I-1237 into two soils slightly modified the microbial diversity, only for a short period of time. Nine months post-inoculation resilience took place, resulting in similar structures of the fungal and bacterial communities in the inoculated and cont…

Identification of the pathogens responsible for the surface deteriorations on the potato tubers

Fusariose du cyclamen : vers un outil de détection précoce

SPEIPM; Fusariose du cyclamen : vers un outil de détection précoce

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

The nature of black stains in Lascaux Cave, France, as revealed by surface-enhanced Raman spectroscopy

We used surface-enhanced Raman spectroscopy to investigate the chemical composition of the black stains threatening the rock-art paintings of Lascaux Cave, Montignac, France. The stains are mainly composed of melanin from the fungus Ochroconis sp. and the faecal pellets of the collembolan Folsomia candida. Surface-enhanced Raman spectroscopy is a useful technique for revealing the structure of unknown macromolecules in cultural heritage research. Copyright © 2011 John Wiley & Sons, Ltd.

Fusarium oxysporum and its biocontrol

International audience

Typing of anastomosis groups of Rhizoctonia solani by restriction analysis of ribosomal DNA.

A method based on restriction analysis of polymerase chain reaction (PCR)-amplified ribosomal DNA was developed for the rapid characterization of large populations of Rhizoctonia solani at the anastomosis group (AG) level. The restriction maps of the internal transcribed spacers (ITS) sequences were compared for 219 isolates of R. solani belonging to AG-1 to AG-12 and AG-BI, representing diverse geographic and host range origins. Four discriminant restriction enzymes (MseI, AvaII, HincII, and MunI) resolved 40 restriction fragment length polymorphism (RFLP) types among the 219 ITS sequences of R. solani. Each RFLP type could be assigned to a single AG except for two RFLP types, which were c…

Effect of fusaric acid and phytoanticipins on growth of rhizobacteria and Fusarium oxysporum

International audience

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

International audience

Functionnal aspects of biodiversity in relation to plant health

 Texte intégral; The most visible impact of human activities on biodiversity concerns species which are part of our cultural heritage but a huge part of the diversity is still hidden, mainly in the ocean, in extreme environments and of course in the soil. Although some estimations can be proposed, they are all considered as under-evaluations of the putative number of taxa that could be present on (in?) the planet Earth. Despite it is not yet known, this biodiversity contributes to different services through the functioning of ecosystems, and thus influences the sustainability of these ecosystems. This was the case for instance when the unsuspected major roles of the archeabacteria in the bi…

Enhancing biological control by combining microorganisms

International audience

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 typ…

Écologie microbienne de la grotte de Lascaux

National audience

Détermination des causes de l'apparition des altérations superficielles du tubercule de pomme de terre

Comparaison des interactions plante - Fusarium oxysporum pathogènes et plante F. oxysporum non pathogènes par analyse protéique différentielle

National audience

Biological control of plant diseases

The present chapter reviews the question of developing a microbial control method of plant diseases. All problems which may occur, from the initial screening of an efficient biocontrol agent to the final step of integration of the biological control method into the crop management system are briefly examined.

Variabilité quantitative des carboydrates de surface des conidies de Fusarium oxysporum

Use of Biocides for the Control of Fungal Outbreaks in Subterranean Environments: The Case of the Lascaux Cave in France

The Lascaux Cave in France suffered an outbreak of the fungus Fusarium solani in 2001. Biocides were applied for three years to control this outbreak. Four months after the initial biocide application, a new outbreak appeared in the form of black stains that progressively invaded the cave. The black stains on the ceiling and passage banks were so evident by 2007 that they became one of the caves major problems. Therefore, biocides were used again in 2008. The present study investigated the fungal communities associated with the black stains and the effectiveness of the biocides applied, by using cloning, denaturing gradient gel electrophoresis, and culture-dependent methods. A novel species…

Aerobiology: an ecological indicator for early detection and control of fungal outbreaks in caves

5 pages, 1 table, 13 references.

Biopesticides : réalités et perspectives commerciales

Correspondance : silvy@supagro.inra.fr; National audience

Panorama du biocontrôle en ZNA, zones non agricoles

Les politiques phytosanitaires européennes et françaises ont fixé l'objectif de réduire l'usage des pesticides et, pour ce faire, incitent à la promotion et à l'utilisation des techniques de biocontrôle et de protection biologique intégrée. Cela s'applique aussi ZNA (Zones Non Agricoles). De nombreuses techniques et applications sont utilisées pour contrôler les problématiques phytosanitaires en zones non agricoles. Sur la base d'un premier travail bibliographique et d'une expertise collective, nous dressons un inventaire et une analyse critique des techniques de biocontrôle et de protection biologique intégrée effectives pour gérer les problématiques phytosanitaires des zones non agricoles…

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…

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…

Soil suppressiveness to plant diseases

Prod 2018-286 SPE BIOmE IPM INRA; International audience

Defense Responses of Fusarium oxysporum to 2,4-Diacetylphloroglucinol, a Broad-Spectrum Antibiotic Produced by Pseudomonas fluorescens

A collection of 76 plant-pathogenic and 41 saprophytic Fusarium oxysporum strains was screened for sensitivity to 2,4-diacetylphloroglucinol (2,4-DAPG), a broad-spectrum antibiotic produced by multiple strains of antagonistic Pseudomonas fluorescens. Approximately 17% of the F. oxysporum strains were relatively tolerant to high 2,4-DAPG concentrations. Tolerance to 2,4-DAPG did not correlate with the geographic origin of the strains, formae speciales, intergenic spacer (IGS) group, or fusaric acid production levels. Biochemical analysis showed that 18 of 20 tolerant F. oxysporum strains were capable of metabolizing 2,4-DAPG. For two tolerant strains, analysis by mass spectrometry indicated…

Two new species of the genus Ochroconis, O. lascauxensis and O. anomala isolated from black stains in Lascaux Cave, France

In the year 2001, some conspicuous black stains appeared on the walls of Lascaux Cave in France, which progressively disseminated throughout the cave. These black stains were so evident by 2007 that they have become one of the cave's major problems. In a mycological study of the black stains, Ochroconis strains were abundant among the isolates and constituted the major group of melanised fungi. Two new species of the genus Ochroconis, O. lascauxensis and O. anomala, were isolated and described. The description is based on the morphology of the fungi and the phylogenetic relationships of two of its gene regions internal transcribed spacer (ITS) and RNA polymerase II subunit B (RPB2). In addi…

Ecological fitness of the biocontrol agent Fusarium oxysporum Fo47 in soil and its impact on the soil microbial communities

Some nonpathogenic strains of Fusarium oxysporum can control Fusarium diseases responsible for severe damages in many crops. Success of biological control provided by protective strains requires their establishment in the soil. The strain Fo47 has proved its efficacy under experimental conditions, but its ecological fitness has not been carefully studied. In a series of microcosm studies, the ability of a benomyl-resistant mutant Fo47b10 to establish in two different soils was demonstrated. One year after its introduction at two concentrations in the disinfected soils, the biocontrol agent (BCA) established at similar high population densities, whereas in the nondisinfected soils it survive…

Involvement of various anastomosis groups of Rhizoctonia solani in the superficial blemishes on potato tubers

Effect of the host-plant and the soil-type on the diversity of soilborne populations of fluorescent pseudomonds and of Fusarium oxysporum

International audience

Identification des agents pathogènes du sol associés aux altérations superficielles du tubercule de pomme de terre

Microbial inoculation for improving the growth and health of micropropagated strawberry

Multimicrobial inoculation has been proposed as a way of protecting plants against environmental stress and increasing the sustainability of plant production. To study these possibilities in a micropropagation system, microplants of strawberry, Fragaria × ananssa, were inoculated or left uninoculated with five microorganisms ( Glomus mosseae BEG29, Bacillus subtilis M3, Trichoderma harzianumDB11, Pseudomonas fluorescensC7r12 and Gliocladium catenulatumGliomix ® ), used either singly or in dual mixtures in the presence or absence of the strawberry diseases crown rot ( Phytophthora cactorum) and red stele (P. fragariae). Finnish light Sphagnum peat was used as the growth substrate in the expe…

Interest of cultural practices to manage soilborne diseases

Du nouveau sur les fusarioses du concombre : Fusarium oxysporum f.sp. radicis-cucumerinum (FORC) isolé pour la première fois en France

National audience

The nature of black stains in Lascaux Cave, France, as revealed by surface-enhanced Raman spectroscopy

We used surface-enhanced Raman spectroscopy to investigate the chemical composition of the black stains threatening the rock-art paintings of Lascaux Cave, Montignac, France. The stains are mainly composed of melanin from the fungus Ochroconis sp. and the faecal pellets of the collembolan Folsomia candida. Surface-enhanced Raman spectroscopy is a useful technique for revealing the structure of unknown macromolecules in cultural heritage research. Copyright © 2011 John Wiley & Sons, Ltd. The chemical composition of the black stains threatening the rock-art paintings of Lascaux Cave, Montignac, France was studied using surface-enhanced Raman spectroscopy (SERS). The stains are mainly composed…

Identification des agents pathogènes du sol associés responsables des altérations superficielles du tubercule de pomme de terre

Free-living amoebae in sediments from the Lascaux Cave in France

The Lascaux Cave in France is an old karstic channel where the running waters are collected in a pool and pumped to the exterior. It is well-known that water bodies in the vicinity of humans are suspected to be reservoirs of amoebae and associated bacteria. In fact, the free-living amoebae Acanthamoeba astronyxis, Acanthamoeba castellanii, Acanthamoeba sp. and Hartmannella vermiformis were identified in the sediments of the cave using phylogenetic analyses and morphological traits. Lascaux Cave sediments and rock walls are wet due to a relative humidity near saturation and water condensation, and this environment and the presence of abundant bacterial communities constitute an ideal habitat…

Impact of biocide treatments on the bacterial communities of the Lascaux Cave.

The Lascaux Cave contains a remarkable set of paintings from the Upper Palaeolithic. Shortly after discovery in 1940, the cave was modified for public viewing and, in 2001, was invaded by a Fusarium solani species complex. Benzalkonium chloride was used from 2001 to 2004 to eliminate the fungal outbreak. In this study, we carried out a sampling in most of the cave halls and galleries. Sequence analysis and isolation methods detected that the most abundant genera of bacteria were Ralstonia and Pseudomonas. We suggest that, as a result of years of benzalkonium chloride treatments, the indigenous microbial community has been replaced by microbial populations selected by biocide application.

La grotte de Lascaux : un écosystème complexe où bactéries et champignons interagissent

La presse s’est fait l’écho des contaminations fongiques qui ont fait craindre pour la préservation des gravures pariétales de la grotte de Lascaux. Grâce à un financement du ministère de la Culture, plusieurs actions d’envergure ont été lancées, dont un programme de recherche qui vise à déterminer les causes de ce développement fongique préoccupant.

The future of biological control research and application in Europe

Biological control of fusarium wilts: Toward development of commercial products

105 ref., chap. 2; International audience

Impact de pratiques culturales sur les caractéristiques du sol

National audience; Plusieurs caractéristiques d'un sol ont été évaluées dans une parcelle expérimentale du Ctifl, suite à l'apport d'amendements organiques ou une biodésinfection (culture de radis fourrager, broyage et enfouissement, roulage, bâchage avec film plastique puis semis de carottes). Les résultats de la première année montrent que la biodésinfection a un impact marqué sur les communautés de microbes et de nématodes des sols, et que cette pratique réduit significativement la sensibilité des sols à la fonte de semis due à R. solani.

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

Molecular tools to monitor a biocontrol agent and to assess its environmental impacts

The use of non pathogenic strains of Fusarium oxysporum has been proposed to control Fusarium diseases responsible for severe damages in many crops of economical importance. In order to monitor the biocontrol strain Fo47 after application in greenhouse and field, we have developed a specific molecular tool based on a sequence characterized amplified region (SCAR). Primers targeting a 210-bp fragment were designed to set up a real time PCR assay allowing the identification of the biocontrol strain and its quantification in environmental samples. The assay enabled specific detection of the strain in soils without cross detection of autochthonous populations of F. oxysporum. After its introduc…

Fusarium oxysporum f. sp. cyclaminis: Identification of specific molecular markers for improved disease prevention

Fusarium oxysporum is a well-known soil-borne and ubiquitous fungus. The species includes a high diversity of saprophytic and pathogenic populations. The phytopathogenic ones are subdivided into formae speciales according to their host specificity. The forma specialis cyclaminis (FoCy) is causing Fusarium wilt only on cyclamen. It causes damages during the entire production line and can raise more than 50 % losses. FoCy is considered as the more destructive pathogen on cyclamen. To achieve a better understanding of the disease and a more efficient and eco-friendly way of control, we aim at finding a specific molecular marker allowing for early detection and quantification of the pathogen an…

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 …

Functionnal aspects of biodiversity towards biocontrol in agricultural soils

Diversité génétique au sein de la forme spéciale cyclaminis de Fusarium oxysporum et recherche d’un marqueur spécifique

Le cyclamen est la 3e plante fleurie la plus vendue en France. Une des maladies dommageables de cette culture est la fusariose, causée par Fusarium oxysporum f. sp. cyclaminis (FoCy). Cette forme spéciale, inféodée au cyclamen n’est pas différenciable des autres formes spéciales et souches saprophytes. En se développant dans le xylème, FoCy entraîne la mort de la plante. Quand les symptômes externes apparaissent, la plante est condamnée. La lutte chimique est inefficace, la lutte variétale est inexistante, et les mesures prophylactiques sont difficilement applicables. Pour détecter le pathogène précocement et améliorer la lutte, nous nous sommes intéressés à sa diversité génétique. Pour cel…

Use of sewage sludge compost and Trichoderma asperellum isolates to supress Fusarium wilt of tomato

It has been reported that plant growth media amended with composted bark suppress Fusarium wilts whereas media amended with composted municipal sludge aggravate this disease. However, in this study, a compost prepared from vegetable and animal market wastes, sewage sludge and yard wastes showed a high ability to suppress Fusarium wilt of tomato caused by Fusarium oxysporum f. sp. lycopersici race 1. The ability of this compost to suppress Fusarium wilt of tomato was compared with that of a peat mix (peat:vermiculite, 1:1 v/v) and a naturally suppressive soil from Chateaurenard, France. The compost and the soil from Chateaurenard were highly suppressive, whereas the peat mix was highly condu…

Lutte biologique chez le framboisier : résultats prometteurs et intérêt potentiel de lutte contre Phytophthora fragariae var. Rubi

National audience

Mycelial development of Fusarium oxysporum in the vicinity of tomato roots

The patterns of mycelial development (length and branching) of five strains of Fusarium oxysporum were measured in the vicinity of tomato and wheat roots. Two strains were of f. sp. lycopersici, two of f. sp. radicis-lycopersici and the fifth was a non-pathogenic strain currently used as a biocontrol agent. Hyphal extension and branching were measured microscopically using a CCD camera and an image analyser. Furthermore, the role of soluble root exudates, insoluble root materials, glucose supply, and nitrogen supply (casamino acids) on mycelial development was investigated. Each strain had its own pattern of development in the absence of a root. Fungal development of all five strains was st…

Changes in soil suppressiveness to fusarium wilt and side effects resulting from the introduction of a non-pathogenic strain of Fusarium oxysporum into soils

International audience

Use of protective strains of Fusarium oxysporum to control fusarium wilts

Concepts and methods to assess phytosanitary quality of soils

Chapitre 9.4 : Plant-microbe interactions and soil quality; International audience

Transcription of genes in the biosynthetic pathway for fumonisin mycotoxins is epigenetically and differentially regulated in the fungal maize pathogen Fusarium verticillioides

ABSTRACT When the fungal pathogen Gibberella moniliformis (anamorph, Fusarium verticillioides ) colonizes maize and maize-based products, it produces class B fumonisin (FB) mycotoxins, which are a significant threat to human and animal health. FB biosynthetic enzymes and accessory proteins are encoded by a set of clustered and cotranscribed genes collectively named FUM, whose molecular regulation is beginning to be unraveled by researchers. FB accumulation correlates with the amount of transcripts from the key FUM genes, FUM1 , FUM21 , and FUM8 . In fungi in general, gene expression is often partially controlled at the chromatin level in secondary metabolism; when this is the case, the deac…

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

International audience

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…

Eradication of Plasmodiophora brassicae during composting of wastes

Survival of infectious inoculum of the clubroot pathogen Plasmodiophora brassicae was assessed following bench-scale flask composting experiments and large-scale composting procedures. Clubroot-affected material was provided by artificial inoculation of Chinese cabbage or naturally infected Brussels sprout and cabbage roots. Both sets of diseased material were used in flask experiments, and the latter in large-scale windrow and aerated tunnel experiments. Municipal green wastes, onion waste and spent mushroom compost were evaluated in flask experiments with varying temperature, aeration and moisture conditions. Green wastes were used in larger-scale composts. Within the limits of a Chinese …

Sol, biodiversité et pratiques culturales

Bacteria and free-living amoeba in the Lascaux Cave.

3 pages, 1 table, 18 references. The collaboration of the Lascaux restoration team is highly appreciated. We thank Marisa Chelius for valuable comments on the manuscript.

SCAR-based real time PCR to identify a biocontrol strain (T1) of Trichoderma atroviride and study its population dynamics in soils.

Strains of Trichoderma spp. are known for their antagonistic properties against plant pathogens, some are already on the market, others are under development. In order to launch a strain on the market its perfect identification at the species and strain levels is needed. The aim of this study is to (i) design a SCAR marker for specific identification of strain T1 of Trichoderma atroviride and (ii) monitor population dynamics of this strain in soil by real time PCR. A primer pair targeting a 141-bp fragment enabled specific detection of this strain without cross detection of autochthonous populations of Trichoderma in several field soils. In two soils, population dynamics assessed by real ti…

The microbiology of Lascaux Cave.

Lascaux Cave (Montignac, France) contains paintings from the Upper Paleolithic period. Shortly after its discovery in 1940, the cave was seriously disturbed by major destructive interventions. In 1963, the cave was closed due to algal growth on the walls. In 2001, the ceiling, walls and sediments were colonized by the fungus Fusarium solani. Later, black stains, probably of fungal origin, appeared on the walls. Biocide treatments, including quaternary ammonium derivatives, were extensively applied for a few years, and have been in use again since January 2008. The microbial communities in Lascaux Cave were shown to be composed of human-pathogenic bacteria and entomopathogenic fungi, the for…

Biological control of plant diseases: Future reseach goals to make it successful

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…

Soil health through soil disease suppression: Which strategy from descriptors to indicators?

International audience; Soil is a component of primary importance in crop production, even if it is often neglected, or only regarded as a physical support for the growth of plants. However, with the increasing societal concerns for the sustainability of agriculture, soil must be considered as a living system. Its quality results from the multiple interactions among physicochemical and biological components, notably the microbial communities, primordial for soil function. Crops are threatened by soil-borne diseases. These are often difficult to control, because of the “hidden” status of the pathogens and also because of the absence, noxiousness or lack of efficacy of chemical treatments. In…

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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