16 research outputs found
Diaporthe helianthi isolate DCDSL 101/96 (IMI 318861) intergenic spacer region and 18S ribosomal RNA gene, partial sequence. autori Pecchia,S., Mercatelli,E. and Vannacci,G.
No full textSequenza AF51289
Innovazioni nella difesa delle colture con mezzi a basso impatto ambientale: malattie da funghi
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A comparative study of Neogymnomyces virgineus, a new keratinolytic species from dung, and its relationships with the Onygenales
No full textIsolations of onygenalean fungi were made recently from different dung samples from Italy.. A striking snow-white species with gymnothecial ascomata, developed in damp chamber on dormouse dung collected in a cave, was subjected to keratinolytic tests and morphological, cultural, and phylogenetic studies. The keratinolytic ability of this species, associated with a Chrysosporium anamorph and a sexual state of appendiculate reticuloperidia and oblate ascospores, allows it to be accomodated in Onygenaceae. White ascomata, blunt or subcapitate peridial appendages, pitted ascospores, and tuberculate conidia suggest it to be a new Neogymnomyces, and this was confirmed by parsimony analyses of LSU and ITS nrDNA sequences. Following recent phylogenetic analyses, the morphological and physiological features of order Onygenales and its families are re–examined and discussed. After the introduction of a new species, Neogymnomyces is reviewed and compared with all other genera in Onygenaceae. The Chrysosporium imperfect state of Neogymnomyces virgineus is described and compared to the anamorph of N. demonbreunii. It is also compared to the atypical Chrysosporium merdarium and to several other Chrysosporium species with echinulate to verrucose–tuberculate conidia, isolated from guano, dung, and nitrogen–rich soils in caves. The onygenalean fungi isolated from any kind of dung are discussed and their facultative coprophily ascribed to variable faecal contents of keratin or other degradable substances. A key to the families and genera of the Onygenales is provided
Search for DNA methylation in Cryphonectria parasitica, Botrytis cinerea and Pyrenophora graminea.
No full textAlthough methylation levels are quite low in fungi, conspicuous methylation has been reported in several systems: the best examples are found in Neurospora crassa associated with duplicated sequences (repeat-induced point mutation: RIP), in genomic repeated sequences, mainly rDNA, and in some quiescent stages. In order to study DNA methylation in Cryphonectria parasitica, Botrytis cinerea and Pyrenophora graminea, their total genomic DNA has been analysed both by restriction analysis, based on methylation dependent isoschizomers (HpaII and MspI) and by high pressure liquid chromatography (HPLC). DNA methylation of specific genomic sites has been evaluated in Pyrenophora graminea IGS region; preliminary results based on restriction and Southern blot analysis suggest further studies should be carried out with a wider range of restriction enzymes. The possible involvement of methylation in regulation of gene expression in fungi is evaluated by looking for methylated sites in active or inactive promoters of cloned genes for an ABC transporter in Botrytis cinerea and for laccase in Cryphonectria parasitica. Finally a search will be undertaken in the same fungi to identify genes coding for methyltransferases, enzymes involved in transfer of methyl groups to specific cytosine residues in DNA
Isolation and sequencing of an endopolygalacturonase gene in Trichoderma virens
No full textFungi belonging to the genus Trichoderma are ubiquitous organisms commonly present in the soil. They play an important role in biological control thanks to their advantageous ecological and physiological properties: a good environmental fitness and a high antagonistic ability against soil microorganisms. The latter include the ability to exploit competitively many different nutritional sources and mycoparasitism. Trichoderma spp. produce a large array of antibiotics and degrading enzymes allowing them to inhibit or to parasitize other fungi, including plant pathogens.
Recently some new features of these fungi have been described: Trichoderma isolates are able to establish a symbiotic-like association with plants by colonizing their roots, so promoting plant growth and inducing localized and systemic resistance towards several phytopathogenic fungi.
In order to effectively colonize roots and to exploit dead plant material in the rhizosphere, plant cell wall degrading enzymes, such as endopolygalacturonases (endo-PG), are critical.
The aim of this study was to isolate and to sequence a gene coding for endopolygalacturonase in Trichoderma.
A small genic region has been identified by PCR with degenerate primers in a T. virens isolate (I10) and it has been extended on both sides by TAIL-PCR. A genomic region 2647 bp long has been cloned and its sequence has been determined. Sequence analysis by BLAST programs confirmed its endoPG nature. Alignments with all fungal endoPG genes available in databases allowed the identification of the full T. virens coding sequence, with an extra stretch on both sides: 1185 bp in 5’, 84 bp in 3’ flanking the coding region. Endo-PG sequences are not available in databases for species belonging to this genus, therefore this is the first full endoPG gene sequence in a Trichoderma species.
The complete endo-PG sequence from T. virens can be a starting-point for a number of purposes including the study of the nature of the symbiotic relationship between Trichoderma and plants and could open new perspectives for exploiting Trichoderma as an inducer of plant resistance
TOXIGENIC AND NONTOXIGENIC ASPERGILLUS FLAVUS ISOLATES IN MAIZE FIELDS TREATED WITH THE BIOLOGICAL PRODUCT AF-X1: SOIL AND GRAIN COLONIZATION
No full textAflatoxins contamination of maize, used for both human and animal consumption, is a serious constraint for economical crop production. Different strategies have been developed to manage aflatoxins in crops and among them biological control has shown great promise. This strategy is based on the application of nontoxigenic strains in maize fields to competitively exclude naturally toxigenic strains in the same niche and compete for crop substrates. Field trials were conducted in two different Tuscany locations using maize hybrids of maturity class FAO 400 and 600. Geo-referenced plots (1 ha) were treated or not treated with the biological product AF-X1 (25 kg ha−1). Data were collected from five sites of each plot along two corner-to-corner diagonals (X shaped). Aspergillus section Flavi populations were enumerated and isolated from soils using a modified AFPA medium and were plated on YES medium to assess aflatoxin production by the ammonia vapour method. One-hundred maize kernels from each experimental plot were surface sterilized and plated on PDA amended with streptomycin. All the Aspergillus spp. developed colonies were transferred on AFPA, CZ and YES media in order to determine toxigenic and nontoxigenic A. flavus isolates. Soil propagule density of toxigenic isolates was higher in untreated than in AF-X1 treated plots. A. flavus was isolated from about 80% of all kernels tested, regardless of treatment. Greater than 99% of A. flavus isolates recovered from treated plots were nontoxigenic and significant values of toxigenic isolates were observed in untreated plots
Genetic variability in differently conserved genomic regions of Diaporthe helianthi isolates of different geographic origin
No full textDiaporthe helianthi, the causal agent of sunflower stem canker, a serious pathogen of sunflower in Europe, is sporadically recorded in Italy. A comparison of pathogen populations from different countries can be performed in order to detect genetically different biotypes.
Our approach was turned to study molecular variability in genomic coding and non coding regions among D.helianthi isolates from different geographic origin.
A set of isolates from different countries have been used to evaluate genomic variability in endo-polygalacturonase (endo-PG) genic portions and IGS region of rDNA. A PCR analysis with Fusarium moniliforme endo-PG degenerated primers produced variable amplification profiles between isolates in relation to their geographic origin. French and Yugoslavian isolates (countries where the pathogen is most aggressive) showed conserved patterns, while Italian isolates showed highly variable patterns.
Primers for speciation studies in filamentous ascomycetes were used for the amplification of a portion of IGS region of rDNA. Amplification products were purified and sequenced in both directions. Phylogenetic analysis separated the isolates into two main clusters: i) all isolate from France and Yugoslavia; ii) all isolates from Italy.
This investigation pointed out a good correlation between data obtained by the two different molecular approaches in order to detect intraspecific genetic variability in D.helianthi
Reduction of mycotoxigenic Aspergillus flavus infection and aflatoxin contamination in maize treated with the biological product AF-X1: second year of field trials
No full textAflatoxin contamination of maize, used for both human and animal consumption, is a serious constraint for final users health.
Biocontrol is one of the measures that proved to be effective in aflatoxin reduction. This strategy is based on the application of non toxigenic Aspergillus flavus strains in maize fields to displace aflatoxin-producers during crop development. Field trials, for the second year running, in two different Tuscany locations using maize hybrids of maturity class FAO 400 and 600 were conducted. Georeferenced plots (1 ha) were treated or not treated with the biological product AF-X1 (25 kg ha-1) and kerne samples from plants at five sites on the two diagonals of each plot were collected. 100 maize kernels from each plot were surface sterilized and plated on PDA amended with streptomycin. Seeds mycoflora was assessed and all the Aspergillus
spp. colonies were transferred on AFPA, CZ, CAM and YES media in order to determine toxigenic and non toxigenic A. flavus
isolates. Moreover, maize flour samples were analyzed for aflatoxins by HPLC-FLD. The percentage range of non toxigenic
A. flavus was higher in treated plots compared to untreated plots (31.5-91.3% vs 1.7-41%) and the average ratio of non toxigenic/toxigenic isolates was 79 and 6 in seeds from treated and non treated plots, respectively. The overall average aflatoxin B1 concentration in maize from treated plots was 1.8 μg kg-1 and in untreated plots was 9.5 μg kg-1. The percent reduction in aflatoxin B1 concentration ranged from 67.7% to 99.7%
Genetic variability in differently conserved genomic regions of Diaporthe helianthi isolates of different geographic origins
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