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Fusarium Oxysporum (fusarium + oxysporum)
Selected AbstractsDiagnosis and detection of host-specific forms of Fusarium oxysporum,EPPO BULLETIN, Issue 3-4 2000R. P. Baayen Diagnosis and detection of host-specific forms of Fusarium oxysporum are traditionally based on the combination of diagnostic symptoms on the host with the presence of the fungus in the affected tissues. The classical approach is becoming increasingly problematic because more than one forma specialis may occur on a given host, along with non-pathogenic strains which are common soil and rhizosphere inhabitants. Neither formae speciales nor pathogenic races within formae speciales can be distinguished morphologically. Although united by joint pathogenicity to a given host, strains belonging to the same forma specialis need not be phylogenetically related. Development of diagnostics for host-specific groups in F. oxysporum requires monophyletic target groups. Recent studies on gene-genealogy and AFLP-based phylogenies show that the majority of formae speciales in F. oxysporum are polyphyletic (unnatural) and do not offer any prospects for the development of molecular diagnostics. In contrast, highly specific PCR primers have been developed for formae speciales (or races) that consist of a single clonal lineage, and for monophyletic groups of lineages within a forma specialis. Among others, specific PCR primers have thus been developed for F. oxysporum f. sp. basilici, specific races in F. oxysporum ff. spp. dianthi and gladioli, and for the EPPO A2 (EU II/A1) quarantine fungus F. oxysporum f. sp. albedinis which can reliably replace conventional isolation and pathogenicity testing procedures. [source] Genetic variation among Fusarium oxysporum isolates from cucumberEPPO BULLETIN, Issue 2 2000D. J. Vakalounakis Isolates of Fusarium oxysporum obtained from cucumber worldwide were classified into 3 groups by random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). All isolates of f. sp. radicis-cucumerinum fall into one group. Isolates of races 1 and 2 of f. sp. cucumerinum fall into a second group related to isolates of f. sp. melonis and niveum. Isolates of race 3 fall into a third group, related to f. sp. momordicae. Because f. sp. radicis-cucumerinum has relatively recently been introduced into Greece, where it is actively spreading and very damaging, RAPD-PCR may be valuable in monitoring populations of F. oxysporum. [source] Microbial communities in roots of Pinus sylvestris seedlings with damping-off symptoms in two forest nurseries as determined by ITS1/2 rDNA sequencingFOREST PATHOLOGY, Issue 4 2009H. Kwa Summary A methodological molecular procedure, which included extraction and cloning of the ITS1/2 rDNA of root-associated organisms with subsequent transformation and sequencing of representative clones, was effective for detection, discrimination and determination of the frequency of the main damping-off pathogens in roots of Pinus sylvestris seedlings growing in different forest-tree nursery soils and exhibiting different rates of disease progress. Roots exhibiting slower damping-off progression were colonized by Fusarium oxysporum, Neonectria radicicola (Ascomycota) and Pythium spp. (Oomycota), which comprised 50% of the microbial community. Roots exhibiting faster damping-off progression were dominated by Thanatephorus cucumeris (Basidiomycota), which comprised 80% of the microbial community. The microbial community was more diverse in roots with slower damping-off progression (14 species) than in roots with faster disease progression (seven species). [source] Pathogenicity of Fusarium verticillioides and Fusarium oxysporum on Pinus nigra seedlings in northwest SpainFOREST PATHOLOGY, Issue 2 2008P. Martín-Pinto Summary Fusarium verticillioides may be responsible for causing significant damping-off damage similar to that incited by F. oxysporum on forest seedlings, resulting in considerable losses in nurseries in northwest of Spain. Traditionally, F. oxysporum has been considered the most important agent of this disease in Spanish forest nurseries. However, recent studies have showed that F. verticillioides also has been frequently isolated from diseased plants. This has increased the necessity for a more comprehensive knowledge of the behaviour and pathogenicity of both Fusarium spp. isolated from these sites. The effect of Fusarium spp. on seed germination and on seedling mortality was analysed by inoculating the fungus at seeding. The in vitro growth of the two species was studied and is discussed in relation to in vivo virulence. Both species caused a reduction in seed germination and an increase in seedling mortality. Mortality caused by F. verticillioides treatments occurred sooner than that for F. oxysporum and the growth rate of F. verticillioides was also greater. [source] Pathogenicity of seed-associated fungi to Podocarpus falcatus in vitroFOREST PATHOLOGY, Issue 1 2005A. Gure Summary Twenty-nine fungi that were isolated from seeds and female cones of Podocarpus falcatus from natural forests in Ethiopia, were assessed for their impact on seeds and seedlings of the same host. Based on the results from in vitro seed inoculation tests, we could group the fungi into five categories as: (i) isolates that were pathogenic only to seeds and had no obvious impacts on the germlings; (ii) isolates that were pathogenic only to the germlings; (iii) isolates that were pathogenic both to seeds and the emerging germlings; (iv) isolates that were more or less harmless; and (v) isolates that were germination promoters. Inoculation tests were also performed on 4,7-day-old aseptically grown seedlings. Fusarium oxysporum and Polyporus sp., were strongly pathogenic to both seeds and seedlings, while Nectria gliocladioides, Peniophora cinerea and Pestalotiopsis neglecta also demonstrated pathogenicity but to a lesser extent. Other isolates, e.g. Diaporthe spp. resulted in increased germination of P. falcatus seeds and no pathogenicity to seedlings. However, further investigations are required in order to find out how these fungi behave under nursery or field conditions. Résumé L'étude porte sur l'impact sur les graines et semis de Podocarpus falcatus de vingt-neuf champignons isolés de graines et fruits du même hôte en forêts naturelles en Ethiopie. D'après les résultats des inoculations de semences in vitro, les champignons peuvent être classés en 5 groupes: (i) les isolats pathogènes uniquement sur graines et sans effet apparent sur plantules; (ii) les isolats pathogènes uniquement sur plantules; (iii) les isolats pathogènes à la fois sur graines et sur plantules émergentes; (iv) les isolats non pathogènes; (v) les isolats favorisant la germination. Des inoculations ont également été pratiquées sur des semis de 4,7 jours produits en conditions axéniques. Fusarium oxysporum et Polyporus sp. montrent un fort pouvoir pathogène à la fois sure graines et semis, Nectria gliocladioides, Peniophora cinerea et Pestalotiopsis neglecta sont également pathogènes mais à un moindre degré. D'autres isolats, comme Diaporthe spp., induisent une augmentation de germination des graines de P. falcatus et ne sont pas pathogènes sur plantules. Des études complémentaires sont nécessaires pour déterminer le comportement de ces champignons en pépinières ou en conditions naturelles. Zusammenfassung Von Samen und weiblichen Zapfen von Podocarpus falcatus aus Naturwäldern in Äthiopien wurden 29 Pilze isoliert und auf ihre Pathogenität an Samen und Sämlinge der gleichen Art getestet. Anhand der Inokulationstests an Samen in vitro wurden die Pilze in 5 Klassen eingeteilt: (i) Pilze, die nur den Samen schädigen und keine Auswirkung auf den Keimling haben; (ii) Pilze, die nur den Keimling schädigen; (iii) Pilze, die sowohl den Samen als auch den Keimling schädigen; (iv) nicht pathogene Pilze; und (v) Pilze, welche die Keimung fördern. Zusätzlich wurden Inokulationstests an vier bis sieben Tage alten steril gekeimten Sämlingen durchgeführt. Fusarium oxysporum und Polyporus sp. waren sowohl an Samen als auch an Keimlingen stark pathogen, Nectria gliocladioides, Peniophora cinerea und Pestalotiopsis neglecta waren weniger stark pathogen. Andere Isolate, wie z.B. Diaporthe spp. waren apathogen und förderten die Keimung. Zur Abklärung des Verhaltens dieser Pilze unter Freilandbedingungen sind jedoch weitere Untersuchungen notwendig. [source] Serological detection and immunogold localization of cross-reactive antigens shared by Camellia sinensis and Exobasidium vexansJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2007B.N. Chakraborty Abstract Aims:, Pathogenicity of Exobasidium vexans, causal agent of blister blight of tea, was studied in 30 commercially cultivated tea varieties by analysing the antigenic patterns of host and pathogen using immunological techniques. Methods and Results:, Whole plant inoculation of tea varieties with E. vexans showed that T-78 and T-17/1/54 were most susceptible and most resistant respectively. Antigen preparations from tea varieties, pathogen, nonpathogen (Fusarium oxysporum) and of nonhosts (Glycine max, Leucaena leucocephala and Oryza sativa) were compared by indirect enzyme-linked immunosorbent assay and dot-immunobinding assay using polyclonal antibodies raised against the pathogen, nonpathogen, susceptible and resistant tea varieties. Cross-reactive antigens (CRA) were found among susceptible varieties and E. vexans isolates but not in resistant varieties, nonhosts or nonpathogen. Indirect staining of antibodies using fluorescein isothiocyanate indicated CRA were concentrated mainly around epidermal and mesophyll cells in compatible host (T-78). This was substantiated by ultrastructural studies using gold-labelled antibodies through transmission electron microscopy which showed specific localization in the chloroplasts and host cytoplasm. Conclusion:, Pathogenicity of E. vexans to different tea varieties is therefore related to the level of antigenic similarity between host and pathogen. Significance and Impact of the Study:, Immunological methods proved to be valuable in screening commercially cultivated tea varieties against E. vexans. [source] Plant and fungal identity determines pathogen protection of plant roots by arbuscular mycorrhizasJOURNAL OF ECOLOGY, Issue 6 2009Benjamin A. Sikes Summary 1.,A major benefit of the mycorrhizal symbiosis is that it can protect plants from below-ground enemies, such as pathogens. Previous studies have indicated that plant identity (particularly plants that differ in root system architecture) or fungal identity (fungi from different families within the Glomeromycota) can determine the degree of protection from infection by pathogens. Here, we test the combined effects of plant and fungal identity to assess if there is a strong interaction between these two factors. 2.,We paired one of two plants (Setaria glauca, a plant with a finely branched root system and Allium cepa, which has a simple root system) with one of six different fungal species from two families within the Glomeromycota. We assessed the degree to which plant identity, fungal identity and their interaction determined infection by Fusarium oxysporum, a common plant pathogen. 3.,Our results show that the interaction between plant and fungal identity can be an important determinant of root infection by the pathogen. Infection by Fusarium was less severe in Allium (simple root system) or when Setaria (complex root system) was associated with a fungus from the family Glomeraceae. We also detected significant plant growth responses to the treatments; the fine-rooted Setaria benefited more from associating with a member of the family Glomeraceae, while Allium benefited more from associating with a member of the family Gigasporaceae. 4.,Synthesis. This study supports previous claims that plants with complex root systems are more susceptible to infection by pathogens, and that the arbuscular mycorrhizal symbiosis can reduce infection in such plants , provided that the plant is colonized by a mycorrhizal fungus that can offer protection, such as the isolates of Glomus used here. [source] CHEMICAL CHARACTERIZATION AND ANTIFUNGAL ACTIVITY OF ORIGANUM ONITES L. ESSENTIAL OILS AND EXTRACTSJOURNAL OF FOOD SAFETY, Issue 1 2009MIHRIBAN KORUKLUOGLU ABSTRACT Essential oils (EOs) and extracts (methanol, acetone and diethyl ether) of fresh and dried oregano (Origanum onites L.) were used to determine the antifungal effect on Alternaria alternata, Aspergillus flavus (two strains), Aspergillus niger (two strains), Aspergillus parasiticus, Fusarium semitectum, Fusarium oxysporum, Mucor racemosus and Penicillium roqueforti by disk diffusion methods. Minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of all samples were determined. The antifungal activity of the fresh herb was greater than that of the dried herb. MIC values for fresh and dried methanol extracts were 150,950 µg/mL and 750,950 µg/mL, respectively. MFC values for methanol extracts were determined between 300 and 1200 µg/mL for fresh oregano and between 750 and 1100 µg/mL for dried oregano. The EOs of fresh and dried oregano totally inhibited test fungi. EOs produced the lowest MIC and MFC values: 8.5 µg/mL and 9.0 µg/mL, respectively (P < 0.005). The highest extract activity was exhibited by fresh oregano against A. alternata (24 mm) followed by P. roqueforti (20 mm). The greatest total antifungal effect was observed from methanol extracts. The chemical composition of fresh oregano EO and extracts was examined using gas chromatography-mass spectrometry (GC-MS). Over 80 volatiles were detected, of which 42 were positively identified by matching both MS fragmentation patterns with standardized retention characteristics. p-Cymene, thymol and carvacrol were the most prominent, followed by ,-pinene, camphor and borneol. PRACTICAL APPLICATIONS In the past decade interest in natural antimicrobial plant extracts has been growing. Various plants have historically been used for the purposes of food preservation and flavor enhancement as well as medicinal purposes. An example is oregano, the leafy part of the plant belonging to the Labiatae family. It has been used to improve the flavor and the organoleptic properties of many foods from numerous cultures. It has also been used to prolong the storage life of foods probably because of antifungal properties. The preservative nature of fresh oregano has been employed in many food applications, including meat and fish products, as well as in pharmaceuticals, alternative medicines and natural therapies. [source] Purification of Angularin, A Novel Antifungal Peptide from Adzuki BeansJOURNAL OF PEPTIDE SCIENCE, Issue 3 2002Dr X. Y. Ye Abstract An antifungal peptide was isolated from the adzuki bean with a procedure involving affinity chromatography on Affi-gel blue gel and ion exchange chromatography on CM-Sepharose. The protein designated angularin was adsorbed on both types of chromatographic media and possessed a molecular weight of 8 kDa. Angularin exhibited antifungal activity against a variety of fungal species including Mycospharella arachidiocola and Botrytis cinerea. It inhibited mycelial growth in B. cinerea with an IC50 of 14.3 µM. Fusarium oxysporum and Rhizoctonia solani were not inhibited. Angularin demonstrated inhibitory activity on translation in the rabbit reticulocyte lysate system (IC50 = 8.0 µM) but did not affect proliferation of splenocytes. The activity of HIV-1 reverse transcriptase was inhibited in the presence of angularin. Its N -terminal sequence was GEPGQKE. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd. [source] Gerbera jamesonii, a New Host of Fusarium oxysporum f.sp. tracheiphilumJOURNAL OF PHYTOPATHOLOGY, Issue 1 2010Marco Troisi Abstract The random amplified polymorphic DNA (RAPD) technique was used to analyze the total genomic DNA of pathogenic isolates of Fusarium oxysporum on Gerbera jamesonii by comparing them to representatives of the formae speciales chrysanthemi and tracheiphilum. A close genetic relationship was observed among most of the new isolates from G. jamesonii. They shared RAPD markers with the tested representatives of the forma specialis chrysanthemi. Some isolates of those tested from diseased G. jamesonii were placed in a different cluster, which included representative isolates of forma specialis tracheiphilum. This is the first report of F. oxysporum f.sp. tracheiphilum on G. jamesonii. A rapid protocol for DNA extraction directly from fungal colonies grown on potato dextrose agar allowed complete analysis in less than 4 h. [source] Development of a Sensitive Serological Method for Specific Detection of Latent Infection of Macrophomina phaseolina in CowpeaJOURNAL OF PHYTOPATHOLOGY, Issue 1 2009Leonard Afouda Abstract A double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) was developed for the specific detection and quantification of Macrophomina phaseolina in plant tissue. Both polyclonal antisera produced against immunogens from mycelium and culture filtrate of M. phaseolina detected the fungus in mycelial and plant extracts, although the antibodies raised against mycelium were more sensitive. No cross-reaction occurred with Rhizopus stolonifer, Pythium ultimum, Mucor hiemalis, Fusarium oxysporum, Septoria nodorum, Rhizoctonia solani, Sclerotinia sclerotiorum, Phytophthora infestans and Aspergillus niger. In enzyme assays, activity of the endo-acting hydrolytic enzymes 1,3-,-glucanase and, less, cellulase, but not xylanase was detected in infected plants. DAS-ELISA was more sensitive than the 1,3-,-glucanase assay. In polyacrylamide gel electrophoresis (PAGE) up to 18 protein bands were observed, with four bands occurring in the 12 tested isolates deriving from various geographical origin in Niger and Nigeria. The enzyme assays and protein patterns were considered not suitable for specific M. phaseolina detection. Macrophomina phaseolina was essentially located in the roots and hypocotyls, and less in epicotyls and leaves of infected plants. The antibodies were also useful to detect latent infection and the infection of cowpea seeds. [source] Identification and Regulation of Genes from a Biocontrol Strain of Fusarium oxysporumJOURNAL OF PHYTOPATHOLOGY, Issue 9 2007D. R. Fravel Abstract Differential display with three time points revealed that thiram altered expression of numerous genes in the biocontrol fungus Fusarium oxysporum CS-20. Of the 101 bands purified from the differential display gel, 86 were successfully cloned, and 64 sequenced. Based on nucleic acid sequences, homology to known products was found using BLASTn for 26 sequences and homology to hypothetical proteins was found for six sequences, also from Gibberella zeae. One band (BM1 24-1) showed homology to an ABC transporter from three different fungi. Because of its association with detoxification functions, the ABC transporter was selected for further study. Mycelia of CS-20 were exposed to 25 ,g active ingredient (a.i.) thiram in liquid culture for various times from 0 to 8 h. Quantitative real-time PCR was used to evaluate gene expression. At 30 min after treatment with thiram, the ABC transporter was upregulated 20- to 25-fold relative to the control treatment. The ABC transporter was upregulated 15-fold at 1 h after treatment and 10-fold at 2 h. At 8 h after treatment, there was no difference between treated and non-treated for expression of the ABC transporter. Transcription of the gene encoding EST BM1 24-1 is induced in response to thiram treatment and may function in providing resistance in F. oxysporum isolate CS-20 to fungicides and other toxins. Tolerance to toxins may be critical to the successful inclusion of CS-20 in disease control strategies in cropping systems. [source] Biocontrol and Plant Pathogenic Fusarium oxysporum -Induced Changes in Phenolic Compounds in Tomato Leaves and RootsJOURNAL OF PHYTOPATHOLOGY, Issue 7-8 2007Y. Panina Abstract The biocontrol fungus Fusarium oxysporum strain CS-20 was previously shown to reduce the incidence of Fusarium wilt of tomato through an uncharacterized host-mediated response. As phenolic compounds are involved in the defence response of tomato to pathogens and other stressors, this work was undertaken to determine whether biocontrol strains induced changes in phenolic compounds in leaves and roots of tomato seedlings in the presence and absence of pathogenic F. oxysporum f. sp. lycopersici. Roots of intact tomato seedlings were placed in water or aqueous fungal spore suspensions. Two biocontrol F. oxysporum strains [CS-20 (host-mediated mechanism) and 85SK-1 (control mechanism unknown)] and two plant pathogenic strains of F. oxysporum f. sp. lycopersici Race 1 were used. After 24 or 72 h exposure, phenolic compounds were extracted from leaves and roots before identification by HPLC. There were significant qualitative and quantitative differences between the two sampling times. Compared with the control treatment, strain CS-20 significantly altered (usually increasing) the ferulic, caffeic and vanillic acid contents, and concentrations once unidentified phenolic compounds recovered from leaves and roots. In another experiment, tomato seedlings growing in sterile sand were drenched with spores of strain CS-20 the day before treating them with varying concentrations of spores of the pathogen for 24 or 72 h. The amount of pathogen present did not significantly affect the plant phenolic response to the presence of strain CS-20. This work demonstrates that tomato responds within 24 h to the presence of the biocontrol strain CS-20 by alterations in secondary metabolism that are typical of resistance responses in tomato. [source] Isozyme Analysis and Soluble Mycelial Protein Pattern in Iranian Isolates of Several formae speciales of Fusarium oxysporumJOURNAL OF PHYTOPATHOLOGY, Issue 5 2004M. Mohammadi Abstract A total of 13 representative isolates of Fusarium oxysporum f. sp. melonis (FOM) from Iran, USA and France, eight isolates of seven formae speciales from Iran and one isolate of F. oxysporum f. sp. niveum from the USA were compared based on isozyme analysis and soluble mycelial protein pattern. Isozyme analyses of alkaline phosphatase (ALP), catalase (CAT), esterase (EST), malate dehydrogenase (MDH), superoxide dismutase (SOD) and xanthine dehydrogenase (XDH) revealed polymorphism among the F. oxysporum isolates in which 22 electrophoretic phenotypes (EP) were determined. At least 10 putative loci for these six enzymes were detected and they were all polymorphic. Maximum genetic diversity was observed in CAT, EST and XDH loci. Using UPGMA, the 22 isolates were separated into three main groups with one of the groups divided into two subgroups. Group I included isolates belonging to five formae speciales from Iran, whereas group II that included FOM isolates from both Iran and the USA was divided into two subgroups each containing the vast majority of the respective isolates from either country. Group III constituted FOM isolates from France and one pathogenic isolate on pepper from Iran. FOM isolates representing five different geographical regions from Iran belonged to two different races of 1 and 1,2Y and one vegetative compatibility group (VCG)0134 and thus were genetically homologous. Isozyme polymorphism in these isolates was highly correlated with VCG and geographical origins and to a lesser extent with races. Variations in soluble protein profile in FOM isolates were correlated with genetic distances determined in isozyme analysis. This study suggests that isozyme analysis could be a useful tool for identifying genetic diversity not only in FOM but also several formae speciales of F. oxysporum. [source] Pathogenicity and Vegetative Compatibility of Fusarium oxysporum f. sp. phaseoli in GreeceJOURNAL OF PHYTOPATHOLOGY, Issue 8-9 2002K. Elena Abstract Twenty-seven isolates of Fusarium oxysporum (Fo) obtained from diseased beans from Greece were characterized for pathogenicity to bean cultivars and vegetative compatibility (VCG). Twenty-three isolates were intermediate to highly virulent to five local bean cultivars and characterized as F. oxysporum f. sp. phaseoli (Fop). Zarganes, Gigantes (two selections) and Chondra were the most susceptible cultivars, while Psila was resistant to 10 of the isolates. Four Fo isolates were not pathogenic against tested cultivars. By demonstrating complementation assay, with nitrate non-utilizing (nit) mutants, 15 pathogenic isolates were grouped into one VCG, two isolates into a previously identified VCG 0165 and six into unique unclassified VCGs. The four non-pathogenic Fo isolates failed to anastomose with any tested pathogenic Fop strain. Our results suggest that most of Fop isolates in Greece belong to one VCG. [source] Micro-scale Systematic Sampling of Soil: Heterogeneity in Populations of Fusarium oxysporum, F. solani, F. roseum and F. moniliformeJOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2000M. C. Rodríguez-Molina Abstract The variability of Fusarium spp. density in soil was studied in a field located in Badajoz (south-western Spain). The upper 40 cm of each side of a 1 m × 1 m × 1 m pit were sampled intensively, taking soil samples from points 10 cm apart. The species isolated were F. oxysporum, F. solani, F. roseum and F. moniliforme. For all four sides of the pit population densities of F. oxysporum, F. solani and F. roseum significantly decreased with increasing soil depth and for all the four layers significant differences were detected between sides of the pit. Horizontal variability also occurred on a smaller sampling scale: when a layer of a side was sampled, densities might be significantly different between points in the layer. However, no clear trend in horizontal variability was observed for any species. These findings demonstrate that Fusarium spp. populations were heterogeneously distributed in this reduced soil volume. Zusammenfassung Die Variabilität der Dichte von Fusarium spp. im Boden wurde in einem Feld in Badajoz (Südwestspanien) untersucht. Die oberen 40 cm jeder Seite einer 1 m × 1 m × 1 m großen Grube wurden intensiv beprobt, wobei im Abstand von jeweils 10 cm Bodenproben entnommen wurden. Aus den Proben wurden F. oxysporum, F. solani, F. roseum und F. moniliforme isoliert. An allen vier Seiten der Grube nahmen die Populationsdichten von F. oxysporum, F. solani und F. roseum mit zunehmender Bodentiefe signifikant ab. Bei allen vier Schichten wurden signifikante Unterschiede zwischen den Seiten der Grube festgestellt. Bei kleinerem Beprobungsmaßstab wurde auch horizontale Variabilität festgestellt: Wenn eine Schicht einer Seite beprobt wurde, unterschieden sich die Dichten zwischen den einzelnen Punkten der Schicht teilweise signifikant. Für keine Art war jedoch eine deutliche Tendenz bei der horizontalen Variabilität feststellbar. Die Ergebnisse zeigten, daß die Populationen von Fusarium spp. in diesem kleinen Bodenvolumen heterogen verteilt waren. [source] In vitro fungitoxic activity of Larrea divaricata cav. extractsLETTERS IN APPLIED MICROBIOLOGY, Issue 1 2004E.N. Quiroga Abstract Aims:, To evaluate the fungitoxic activity of Larrea divaricata Cav. extract and one of its components against yeasts and fungi. This activity was compared with the action of ketoconazole, a known synthetic antimycotic. Methods and Results:, Antifungal activity of Larrea divaricata extract and of a fraction (Fr. B) purified by thin layer chromatography, was investigated using different methodologies. Both exhibited strong activity against the majority of the assayed fungi. Only Fusarium oxysporum and Schizophyllum commune growth was not affected with the assayed conditions. The fungitoxic and cytotoxic activity of the ethanolic extract and ketoconazole were compared. Conclusions:, Ethanolic extracts of L. divaricata Cav. produce growth inhibition of several fungi. One of its constituents with the same activity was purified and identified as a glycoside of a flavanone. A comparison with the action of ketoconazole, which is currently used as antimycotic and can cause adverse health effects was made. Significance and Impact of the Study:, Our data suggest that L. divaricata extract contains, at least, one compound of phenolic nature, with fungitoxic potency against yeasts and fungi. [source] Isolation and characterization of phorate degrading soil bacteria of environmental and agronomic significanceLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2003N. Bano Abstract Phorate [O,O -diethyl- S -(ethylthio)methyl phosphoradiothioate] degrading bacteria were isolated from agricultural soil and characterized based on their morphological and biochemical characteristics. The selected isolates PS-1, PS-2 and PS-3 were presumptively identified as Rhizobium, Pseudomonas and Proteous species, respectively. The HPLC analysis of phorate in bioaugmented soil revealed its complete disappearance within 40 days. The degradation isotherms of the isolates PS-1, PS-2 and PS-3 suggested time-dependent disappearance of phorate following the first order rate kinetics at the corresponding rate constants of 0·04, 0·05 and 0·04 days,1. Besides, the isolates concurrently exhibited substantial phosphate solubilization, indole acetic acid, and siderophore production. The isolate PS-3 also showed anti-fungal activity against a phytopathogen Fusarium oxysporum. As a result of the multifarious biological properties, the isolates have been suggested to be important bioresource for efficient bioinoculant development. [source] Pathogenesis of Streptoverticillium albireticuli on Caenorhabditis elegans and its antagonism to soil-borne fungal pathogensLETTERS IN APPLIED MICROBIOLOGY, Issue 5 2002J.-O. Park Aims: To examine the biological activity of Streptoverticillium albireticuli. Methods: Isolation of S. albireticuli was carried out using the dry-heat technique. Nematicidal and pathogenic activity on Caenorhabditis elegans was measured by mortality in metabolites and colonization rate on fishmeal extract agar. Antifungal and enzymatic activities of S. albireticuli were measured by the agar plate method and the semidefined solid media method, respectively. Results:S. albireticuli showed strong nematicidal activity against C. elegans . Pathogenic activity was also evident with the colonized nematode by the isolate on fishmeal extract agar. It also showed antifungal activity against certain fungal pathogens such as Rhizoctonia solani , Phytophthora cinnamomi and Fusarium oxysporum . Significance and Impact of the Study: The discovery of an actinomycete showing pathogenic activity against the nematode may indicate the potential for it to be used as a biocontrol agent of parasitic nematodes, in addition to its ability to suppress fungal pathogens. [source] Scanning electron microscopy applied to seed-borne fungi examinationMICROSCOPY RESEARCH AND TECHNIQUE, Issue 7 2009Marcelo De Carvalho Alves Abstract The aim of this study was to test the standard scanning electron microscopy (SEM) as a potential alternative to study seed-borne fungi in seeds, by two different conditions of blotter test and water restriction treatment. In the blotter test, seeds were subjected to conditions that enabled pathogen growth and expression, whereas the water restriction method consisted in preventing seed germination during the incubation period, resulting in the artificial inoculation of fungi. In the first condition, seeds of common bean (Phaseolus vulgaris L.), maize (Zea mays L.), and cotton (Gossypium hirsutum L.) were submitted to the standard blotter test and then prepared and observed with SEM. In the second condition, seeds of cotton (G. hirsutum), soybean (Glycine max L.), and common bean (P. vulgaris L.) were, respectively, inoculated with Colletotrichum gossypii var. cephalosporioides, Colletotrichum truncatum, and Colletotrichum lindemuthianum by the water restriction technique, followed by preparation and observation with SEM. The standard SEM methodology was adopted to prepare the specimens. Considering the seeds submitted to the blotter test, it was possible to identify Fusarium sp. on maize, C. gossypii var. cephalosporioides, and Fusarium oxysporum on cotton, Aspergillus flavus, Penicillium sp., Rhizopus sp., and Mucor sp. on common bean. Structures of C. gossypii var. cephalosporioides, C. truncatum, and C. lindemuthianum were observed in the surface of inoculated seeds. Microsc. Res. Tech., 2009. © 2009 Wiley-Liss, Inc. [source] Fusarium oxysporum: exploring the molecular arsenal of a vascular wilt fungusMOLECULAR PLANT PATHOLOGY, Issue 5 2003Antonio Di Pietro SUMMARY Taxonomy: Vascular wilt fungus; Ascomycete although sexual stage is yet to be found. The most closely related teleomorphic group, Gibberella, is classified within the Pyrenomycetes. Host range: Very broad at the species level. More than 120 different formae speciales have been identified based on specificity to host species belonging to a wide range of plant families. Disease symptoms: Initial symptoms of vascular wilt include vein clearing and leaf epinasty, followed by stunting, yellowing of the lower leafs, progressive wilting of leaves and stem, defoliation and finally death of the plant. In cross-sections of the stem, a brown ring is evident in the area of the vascular bundles. Some formae speciales are not primarily vascular pathogens but cause foot- and rootrot or bulbrot. Economic importance: Causes severe losses on most vegetables and flowers, several field crops such as cotton and tobacco, plantation crops such as banana, plantain, coffee and sugarcane, and a few shade trees. Control: Use of resistant varieties is the only practical measure for controlling the disease in the field. Under greenhouse conditions, soil sterilization can be performed. Alternative control methods with potential for the future include soil solarization and biological control with antagonistic bacteria or fungi. Useful websites: http://www.fgsc.net/fus.htm, http://www-genome.wi.mit.edu/annotation/fungi/fusarium/, http://www.cbs.knaw.nl/fusarium/database.html [source] Antifungal effects of aminosulphoxide and disulphide derivativesMYCOSES, Issue 3 2006Veerle Wittebolle Summary 2-Benzenesulphinyl-(1,4)-naphtoquinone and 14 derivatives were synthesised and were used to evaluate their cytotoxicity against a human myelomonocyte cell line and their antifungal activity against two yeast, i.e. Candida albicans and C. tropicalis and against two filamentous fungi such as Aspergillus niger and Fusarium oxysporum and against one dermatophyte, namely Trichophyton tonsurans. The cytotoxicity and antifungal activities were investigated in comparison with amphotericin B as reference drug. No compound was significantly more toxic than amphotericin B at 0.2 ,g ml,1. The best results of antifungal activity were obtained with GFL 10, GFL 13 and GFL 30 on C. tropicalis, F. oxysporum and T. tonsurans. For C. albicans and A. niger, there was no difference between amphotericin B and the other molecules. The sterol quantitation, the time-kill curves were carried out for these three compounds in order to confirm their action in ergosterol synthesis. Time-kill curves showed a fungistatic activity. For C. tropicalis GFL 10, GFL 13 and GFL 30 increased the growth delay better than amphotericin B, in contrast to F. oxysporum. As for T. tonsurans, GFL10 and GFL13 gave a delay, but the effect of GFL 30 was a bit less marked. [source] Onychomycosis in children: a survey of 46 casesMYCOSES, Issue 6 2005C. Romano Summary This is a retrospective study of the agents, clinical aspects, sources of infection and therapy of onychomycosis in children. In the period 1989,2000, we observed 46 consecutive children, until 16 years of age with onychomycosis (29 boys, 17 girls, mean age 10.8 years). Dermatophytes were isolated in 30 cases (Trichophyton rubrum in 22 cases, Trichophyton mentagrophytes in five, Epidermophyton floccosum in two and Trichophyton violaceum in one) and Candida spp. in 16, associated with Trichophyton rubrum in two. Moulds were isolated in three children (Fusarium oxysporum in one, Scopulariopsis brevicaulis in another and Aspergillus fumigatus associated with Trichophyton rubrum in a third). The commonest features were distal and distolateral subungual hyperkeratosis in dermatophyte infections (93%) and onychodystrophy and paronychia in Candida infections (56% and 50% respectively). Forty patients achieved clinical and mycological recovery. It is appropriate to suspect onychomycosis in children, perform microbiological diagnosis and undertake early treatment. An approach of this kind may help to prevent nail dystrophy and the spread of infection. [source] Recent developments in the molecular discrimination of formae speciales of Fusarium oxysporumPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 8 2008Bart Lievens Abstract Rapid and reliable detection and identification of potential plant pathogens is required for taking appropriate and timely disease management measures. For many microbial species of which all strains generally are plant pathogens on a known host range, this has become quite straightforward. However, for some fungal species this is quite a challenge. One of these is Fusarium oxysporum Schlechtend:Fr., which, as a species, has a very broad host range, while individual strains are usually highly host-specific. Moreover, many strains of this fungus are non-pathogenic soil inhabitants. Thus, with regard to effective disease management, identification below the species level is highly desirable. So far, the genetic basis of host specificity in F. oxysporum is poorly understood. Furthermore, strains that infect a particular plant species are not necessarily more closely related to each other than to strains that infect other hosts. Despite these difficulties, recently an increasing number of studies have reported the successful development of molecular markers to discriminate F. oxysporum strains below the species level. Copyright © 2008 Society of Chemical Industry [source] The potential efficiency of irrigation management and propargyl bromide in controlling three soil pests: Tylenchulus semipenetrans, Fusarium oxysporum and Echinochloa crus-galliPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 8 2005Suzanne E Allaire Abstract Propargyl bromide (3-bromopropyne, 3BP) is a potential alternative for methyl bromide. Little information is available about its efficiency in controlling pests. The purpose of this paper is to estimate the 3BP dose required for killing three pests and to compare the efficiency of water management approaches to that of fumigation. The pests, Fusarium oxysporum Schlecht (fungus), Echinochloa crus-galli (L) Beauv (grass) and Tylenchulus semipenetrans Cobb (nematode) were exposed to different 3BP concentrations in a sandy loam at 30 °C in a closed system. The lethal dose for killing 90% of the population (LD90) was calculated from the total applied mass, and varied from 0.3 µg g,1 soil for the nematode, 3 µg g,1 for the grass, and 9 µg g,1 for the fungus. The concentration,time index for killing 90% of the population (CT90) was 11 µg g,1 h for the nematode, 112 µg g,1 h for the grass and 345 µg g,1 h for the fungus. 3BP seems as efficient as other fumigant alternatives in controlling these pests. Using an open system, it was shown that the volume of soil in which the pests were controlled varied for different irrigation managements. Even 96 h after fumigation (with a concentration 10 times higher than would potentially be applied in the field), more than 20% of the soil volume had not reached the fungus and grass CT90 of the non-irrigated soil. The soil underneath the furrow and the bed reached CT90 only slowly in all irrigated treatments even though techniques for increasing efficiency were used (tarping, surface sealing with water and high application rate). Copyright © 2005 Society of Chemical Industry [source] Fusarium oxysporum -causal agent of wilt on crops of Phoenix canariensis in ArgentinaPLANT PATHOLOGY, Issue 2 2006H. E. Palmucci No abstract is available for this article. [source] Disease complex in coffee involving Meloidogyne arabicida and Fusarium oxysporumPLANT PATHOLOGY, Issue 3 2000B. Bertrand Coffee corky-root disease, also called corchosis, was first detected in 1974 in a small area of Costa Rica where the root-knot nematode Meloidogyne arabicida is the dominant species. An epidemiological study revealed a constant association between Meloidogyne spp. and Fusarium sp. in cases of corky root. No corky root appears to have been reported in association with Meloidogyne exigua, which is the prevalent root-knot nematode on coffee in Costa Rica. Fusarium spp. are often cited as components of disease complexes in association with nematodes. Combined inoculations using M. arabicida or M. exigua with Fusarium oxysporum under controlled conditions showed that only the combination with M. arabicida produced corky-root symptoms on Coffea arabica cvs Caturra or Catuai. Fusarium oxysporum alone was nonpathogenic. Meloidogyne exigua or M. arabicida alone caused galls and reduction in shoot height, but no corky-root symptoms. When cultivars susceptible and resistant to M. arabicida were studied under field conditions for 5 years, all the susceptible cultivars exhibited corky-root symptoms on 40,80% of their root systems. Cultivars that were resistant to M. arabicida but not to M. exigua showed no corky root. These observations lead to the conclusion that corky-root disease has a complex etiology, and emphasize the dominant role of M. arabicida as a predisposing agent to subsequent invasion by F. oxysporum. Consequently, genetic resistance to M. arabicida appears to provide an effective strategy against the disease. [source] Chemical modification of chitosan: synthesis and biological activity of new heterocyclic chitosan derivativesPOLYMER INTERNATIONAL, Issue 2 2008Mohamed EI Badawy Abstract BACKGROUND: Numerous works have been published on the chemical modification of chitosan; this polymer is still being modified, leading to various derivatives with improved properties. In the present study, heterocyclic aldehydes including furan-2-carbaldehyde, 5-methylfuran-2-carbaldehyde, 3-pyridine carboxyaldehyde, benzo[d][1,3]dioxole-5-carbaldehyde and 4-oxo-4H -chromene-3-carbaldehyde were reacted with chitosan by a reductive alkylation reaction to produce for the first time five new N -heterocyclic chitosan derivatives to improve the biological activity of chitosan against the most important economic plant pests including fungi and insects, in particular the cotton leafworm Spodoptera littoralis. RESULTS: The chemical structures of the synthesized compounds were confirmed by 1H NMR spectroscopy and the degree of substitution ranged from 0.30 to 0.43. The fungicidal assessment was investigated in vitro using a mycelia radial growth inhibition technique against soil-borne pathogenic fungi Fusarium oxysporum and Pythium debaryanum and the rice leaf blast Pyricularia grisea. The results showed that N -[(5-methylfuran-2-yl)methyl] chitosan was the most active against P. grisea with an EC50 value of 0.919 mg mL,1 while N -(benzo[d][1,3]dioxol-5-ylmethyl) chitosan and N -(methyl-4H -chromen-4-one) chitosan exhibited the most potent fungicidal activity against P. debaryanum and F. oxysporum. An insecticidal bioassay against the larvae of S. littoralis showed that N -(methyl-4H -chromen-4-one) chitosan exhibited a significant growth inhibition and antifeedant activity among the synthesized compounds. CONCLUSION: The chemical modification of chitosan molecule with a heterocyclic moiety led to an enhancement in the biological activity against the plant pathogenic fungi F. oxysporum, P. debaryanum and P. grisea and the cotton leafworm insect S. littoralis. Copyright © 2007 Society of Chemical Industry [source] Isotopologue fractionation during N2O production by fungal denitrificationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2008Robin L. Sutka Identifying the importance of fungi to nitrous oxide (N2O) production requires a non-intrusive method for differentiating between fungal and bacterial N2O production such as natural abundance stable isotopes. We compare the isotopologue composition of N2O produced during nitrite reduction by the fungal denitrifiers Fusarium oxysporum and Cylindrocarpon tonkinense with published data for N2O production during bacterial nitrification and denitrification. The fractionation factors for bulk nitrogen isotope values for fungal denitrification were in the range ,74.7 to ,6.6,. There was an inverse relationship between the absolute value of the fractionation factors and the reaction rate constant. We interpret this in terms of variation in the relative importance of the rate constants for diffusion and enzymatic reduction in controlling the net isotope effect for N2O production during fungal denitrification. Over the course of nitrite reduction, the ,18O values for N2O remained constant and did not exhibit a relationship with the concentration characteristic of an isotope effect. This probably reflects isotopic exchange with water. Similar to the ,18O data, the site preference (SP; the difference in ,15N between the central and outer N atoms in N2O) was unrelated to concentration during nitrite reduction and, therefore, has the potential to act as a conservative tracer of production from fungal denitrification. The SP values of N2O produced by F. oxysporum and C. tonkinense were 37.1,±,2.5, and 36.9,±,2.8,, respectively. These SP values are similar to those obtained in pure culture studies of bacterial nitrification but quite distinct from SP values for bacterial denitrification. The large magnitude of the bulk nitrogen isotope fractionation and the ,18O values associated with fungal denitrification are distinct from bacterial production pathways; thus multiple isotopologue data holds much promise for resolving bacterial and fungal production. Our work further provides insight into the role that fungal and bacterial nitric oxide reductases have in determining site preference during N2O production. Copyright © 2008 John Wiley & Sons, Ltd. [source] Fungal community diversity and soil health in intensive potato cropping systems of the east Po valley, northern ItalyANNALS OF APPLIED BIOLOGY, Issue 2 2009L.M. Manici Abstract An ecological approach was used to investigate the relationship between diversity of soil fungal communities and soil-borne pathogen inoculum in a potato growing area of northern Italy affected by yield decline. The study was performed in 14 sites with the same tillage management practices: 10 named ,potato sites', that for many years had been intensely cultivated with potatoes, and 4 named ,rotation sites', subject to a 4-year rotation without potatoes or any recurrent crop for many years. Fungal communities were recorded using conventional (soil fungi by plate count and endophytic fungi as infection frequency on pot-grown potato plant roots in soil samples) and molecular approaches [Basidiomycetes and Ascomycetes with specific and denaturing gradient gel electrophoresis (DGGE) analysis]. Diversity of fungal communities in potato sites was significantly lower than that in rotation sites. In addition, fungal communities in rotation sites showed lower Berger,Parker dominance than those in the potato sites, suggesting that rotation sites had a higher diversity as well as a better fungal community balance than potato sites. The ANalysis Of SIMilarity test of soil fungi and root endophytic fungi revealed that the two cropping systems differed significantly for species composition. Root endophytic fungal communities showed a greater ability to colonise potato roots in soil samples from potato sites than those from rotation sites. Moreover, the majority of endophytic root fungal community species in potato sites belonged to the potato root rot complex and storage disease (Colletotrichum coccodes, Fusarium solani and Fusarium oxysporum), while those in rotation sites were mainly ubiquitous or saprobic fungi. Soil rDNA analyses showed that Ascomycetes were much more frequent than Basidiomycetes in all the soils examined. DGGE analysis, with the Ascomycete-specific primer (ITS1F/ITS4A), did not reveal distinctions between the communities found at the potato and rotation sites, although the same analysis showed differences between the communities of Basidiomycetes (specific primer ITS1F/ITS4B). These findings showed that recurrent potato cropping affected diversity and composition of soil fungal communities and induced a shift in specialisation of the endophytic fungi towards potato. [source] | |||||||||||||||||||||||||||||||