Search results for "Imperfect"
showing 10 items of 158 documents
Colonization of tomato root by pathogenic and nonpathogenic Fusarium oxysporum strains inoculated together and separately into the soil.
2006
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…
Characterization ofFusarium verticillioides strains by PCR-RFLP analysis of the intergenic spacer region of the rDNA
2005
Thirty-three Fusarium verticillioides strains from diverse origins and hosts have been analysed for fumonisin production and characterized in order (i) to detect the variability present in this species and (ii) to discriminate among isolates. The method used was a combination of polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) generated by restriction endonucleases applied to the IGS region (intergenic spacer of rDNA). All the F. verticillioides strains associated with crops produced fumonisins B1 and B2 except those isolated from banana. Analysis of the IGS region by PCR-RFLP proved to be useful to detect variability within F. verticillioides and allowed …
Glucose influence on the production of T-2 toxin by Fusarium sporotrichioides
2010
Toxigenic isolate of Fusarium sporotrichioides was tested for the T-2 toxin production on PDA plates during 10 days under various glucose concentrations. T-2 toxin was determined by LC-MS and confirmed with LC-MS/MS. This analytical method has been applied, for the first time, to an extensive study of T-2 accumulation. Results showed that the production of this mycotoxin is directly correlated to the concentration of glucose present in the medium. Concentrations of T-2 toxin produced by the strain of F. sporotrichioides ranged from 0 to 1.45 mg/kg. The better T-2 production was evidenced in the fermentation operated with 20% of glucose.
Fumonisin production by Gibberella fujikuroi strains fromPinus species
2003
Abstract Fumonisins are important mycotoxins basically produced by strains from the Gibberella fujikuroi species complex (with anamorphs in Fusarium genus) which contaminate food and feed products representing a risk to human and animal health. In this work, we report for the first time the fumonisin production of Fusarium moniliforme Sheldon strains associated to edible pine nuts of Pinus pinea. P. pinea is an important and widely distributed Pinus species in the Mediterranean area where their pine nuts are consumed raw or slightly processed in diverse food products. In this work, characterization and further identification of those strains were performed by polymerase chain reaction-restr…
Influence of environmental factors on the biosynthesis of type B trichothecenes by isolates of Fusarium spp. from Spanish crops.
2003
Various species of Fusarium can produce trichothecene mycotoxins that contaminate food commodities and can represent a risk for human and animal health. In this paper, a full factorial design was applied to study the influence of incubation temperature, water activity (a(w)) and type of isolate on the production of deoxynivalenol (DON), nivalenol (NIV) and 3-acetyldeoxynivalenol (3-AcDON) in corn kernel cultures by three isolates of Fusarium graminearum and three isolates of Fusarium culmorum from crops grown in Spain. The tested temperatures were 15, 20, 28 and 32 degrees C. The a(w)-values were 0.960, 0.970 and 0.980. Moisture of cultures (within the studied range) did not affect signific…
Imperfect Batesian mimicry—the effects of the frequency and the distastefulness of the model
1997
Batesian mimicry is the resemblance between unpalatable models and palatable mimics. The widely accepted idea is that the frequency and the unprofitability of the model are crucial for the introduction of a Batesian mimic into the prey population. However, experimental evidence is limited and furthermore, previous studies have considered mainly perfect mimicry (automimicry). We investigated imperfect Batesian mimicry by varying the frequency of an aposematic model at two levels of distastefulness. The predator encountered prey in a random order, one prey item at a time. The prey were thus presented realistically in a sequential way. Great tits (Parus major) were used as predators. This expe…
Presence of nucleosomes inPenicillium chrysogenum
1987
We have studied the chromatin structure ofPenicillium chrysogenum. This fungus presents the typical nucleosomal repeat and the core DNA size characteristic of all the eukaryotes. The repeat length (about 180 base pairs) is in the range of those obtained for most fungi (160–180 base pairs) and shorter than in higher eukaryotes. Knowledge aboutP. chrysogenum chromatin structure opens the way to the study of the mechanisms of genetic regulation in this filamentous fungus.
Molecular characterization of Colletotrichum strains derived from strawberry
1999
Strains of Colletotrichum species derived from diseased strawberry plants from a wide geographical range were studied using mitochondrial and ribosomal DNA RFLPs, and acetyl and propionyl esterase isoenzymes. Two major species aggregates were detected, centred on C. acutatum and C. gloeosporioides respectively, with significant further subdivision. There were apparent discrepancies in the hierarchical nesting of some taxon groups based on the different molecular techniques. Strains assigned to C. acutatum fell into several rDNA RFLP groups, but there was less variation in mtDNA RFLP band patterns. There appears to be at least one probably clonal population in the U.S.A. which is also presen…
Recovery of Fusarium oxysporum Fo47 mutants affected in their biocontrol activity after transposition of the Fot1 element
2002
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…
Recovery of mutants impaired in pathogenicity after transposition of Impala in Fusarium oxysporum f.sp. melonis
2000
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…