1,720,985 research outputs found
Differential transcripts in Pyrenophora graminea and Pyrenophora teres putatively related to pathogenicity
No full textNon radioactive Differential Display Reverse Transcription- PCR (DDRT-PCR) was used to screen molecular variants at expression level in Pyrenophora graminea and Pyrenophora teres, grown in vitro with glucose or plant cell walls as carbon sources. Several differential transcripts from both species were identified, either constitutive or induced by barley leaf cell walls. Three cloned species-specific transcripts were sequenced: one was constitutively expressed in P. graminea and absent in P. teres, two were specifically induced by host leaf cell walls either in P. graminea or in P. teres. For all three, sequence analysis showed significant homology with known pathogenicity-related genes available in databases, coding for toxic metabolites, cell wall degrading enzymes and regulative factors as kinases. These data are discussed in relation to the biology of the two pathogens under study
Selection of Trichoderma spp. isolates beneficial to crop plants
No full textFungi belonging to the genus Trichoderma are known as potential biocontrol agents for plant pathogens and as promoters of plant growth. In order to check a Trichoderma spp. collection (48 isolates) for beneficial effects on plants, growth stimulation of tomato plants and resistance induction in tomato vs Botrytis cinerea were screened. All investigations were performed in a greenhouse. For growth promotion tests, height and dry weight were measured in plants developed in soil inoculated by a Trichoderma conidial suspension. 12 strains affected positively both parameters assayed. Variance analysis pointed out one strain significantly improving both height and dry weight of plants and five strains significantly enhancing the height. The ability to induce disease resistance in plants was assayed in the same conditions, but plants were infected by Botrytis cinerea after Trichoderma inoculation. Leaves were then checked for typical symptoms (necrotic areas) and lesions size was measured. 9 Trichoderma isolates were able, in our experimental conditions, to protect tomato plants from Botrytis cinerea infection: no disease symptoms were detectable in plants pre-treated with such isolates
Plasmid distribution in European Diaporthe helianthi isolates
No full textA collection of twenty-six Diaporthe helianthi isolates deriving from different geographic origin was analysed in order to determine the presence of extra-chromosomal genetic determinants and their molecular diversity. Extra-chromosomal bands in total genomic DNAs were identified in all the French and the Yugoslavian isolates and in only one Italian isolate, while no Romanian and Argentinean isolates resulted to host any plasmids. When tested for their chemical-physical nature by Rnase A and DNA exonucleases (III-exo and λ-exo) digestions, they were recognised as linear plasmids sized about 2.3 Kb. More detailed analysis was then performed on a plasmid purified from a French isolate (plasmid F). Its intracellular localisation resulted to be mitochondrial. Plasmid F was also exploited as a probe in Southern hybridisation experiments and it recognised only plasmids present in genomes of French and Yugoslavian isolates (countries were the disease has a heavy incidence) suggesting some specificity in relation to the geographic origin. An RFLP hybridisation analysis performed on genomic DNAs revealed a homogeneous restriction pattern in all French and Yugoslavian isolates, strongly supporting the hypothesis of a molecular relationship among plasmids present in those isolates
An endopolygalacturonese gene of Diaporthe helianthi
No full textIn the attempt of defining virulence determinants of Diaporthe helianthi, the causative agent of sunflower stem canker, the gene named Dhpg, coding for an endopolygalacturonase, was investigated in the highly virulent strain 8/96 isolated from a diseased plant in France. The 1624 bp coding sequence, in addition to 1343 bp from the upstream region, were cloned, sequenced and analyzed. Dhpg was most closely related to polygalacturonase genes from phytopathogenic fungi, such as Ophiostoma ulmi, O. novo-ulmi, and Gibberella zeae. A Southern blot RFLP analysis proved that Dhpg was represented in single-copy in the genome of the isolate 8/96. Analyses carried out both in vitro on liquid cultures and in vivo on host infected tissues provided evidence of the constitutive expression of the Dhpg transcript under all tested conditions. Moreover, an European collection of D. helianthi isolates was screened for the presence of Dhpg homologues by PCR, revealing the same single band in all French and Yugoslavian isolates, while one Romanian and all Italian isolates displayed a variable pattern. This genetic variability related to the different D. helianthi geographic origin is consistent with data previously reported for different loci on the same set of isolates. This is the first report concerning a polygalacturonase gene in D. helianthi
A coding region in Diaporthe helianthi reveals genetic variability among isolates of different geographic origin
No full textA set of Diaporthe helianthi isolates collected in different geographic areas was studied in order to examine
whether different genetic biotypes could be responsible for epidemiological differences shown by sunflower
stem canker. D. helianthi causes serious losses in France and in former Yugoslavia, while the pathogen
is only sporadically recorded in Italy in spite of conducive pedoclimatic conditions. Variability of a
D. helianthi coding genomic region, evaluated by means of polymerase chain reaction (PCR), Southern blot
hybridisation and restriction fragments length polymorphism (RFLP), showed a conserved homogeneous
pattern shared by French and Yugoslavian isolates compared with the heterogeneous pattern of Italian
isolates. These results are consistent with other investigations (IGS and ITS region variability) performed
on the same set of isolates, allowing a correlation between D. helianthi biotypes, their geographic origin and
sunflower stem canker epidemiology
Variability in Diaporthe helianthi isolates of different geographic origin at coding sequences level
No full textDiaporthe helianthi (Phomopsis helianthi), agente del cancro dello stelo, è uno dei più importanti patogeni del girasole in Europa, ma non risulta particolarmente aggressivo in Italia. I funghi fitopatogeni producono uno spettro di enzimi che degradano la parete cellulare vegetale, tra i quali le pectinasi svolgono un ruolo importante, poiché degradano uno dei principali componenti della parete cellulare e della lamella mediana. Al momento in letteratura non è disponibile alcuna informazione circa la produzione di specifici enzimi pectinolitici in D.helianthi.
In questo studio abbiamo confrontato 12 isolati di D.helianthi di origine geografica diversa, per i quali sono note anche differenze di virulenza sul girasole, al fine di individuare la presenza di geni per l’endo-poligalatturonasi (endo-PG) e di valutarne la variabilità. A questo scopo sono stati condotti esperimenti di PCR, utilizzando una coppia di oligonucleotidi degenerati costruiti sulla sequenza del gene endo-PG (pgA) di Fusarium moniliforme. I profili di amplificazione ottenuti sono risultati interessanti in quanto diversi tra gli isolati, in relazione all’origine geografica. In particolare i pattern degli amplificati derivati da DNA genomico di isolati francesi ed yugoslavi risultano simili, mentre quelli ottenuti con DNA di isolati italiani, rumeni o argentini sono molto variabili.
Sono stati quindi effettuati esperimenti di Southern blot per confermare l’identità dei prodotti di amplificazione, utilizzando come sonda il gene clonato per l’endo-PG (pgA) di F.moniliforme. La sonda ha ibridato con la maggior parte dei prodotti di amplificazione, anche se con livelli di riconoscimento diversi.
Il prodotto di amplificazione principale degli isolati francesi ed yugoslavi è stato selezionato come rappresentativo delle sequenze conservate in questo gruppo di isolati. Uno degli isolati francesi è stato scelto per avviare l’analisi di sequenza. Dal confronto del prodotto di amplificazione di D.helianthi con le sequenze note di endo-PG in letteratura emerge un allineamento variabile, in accordo con la divergenza riscontrata tra questi geni nelle varie specie fungine. Inoltre una ricerca in banca dati evidenzia una omologia significativa tra la sequenza di D.helianthi e un gene di Aspergillus terreus per una polichetide sintasi, come già descritto in letteratura per un gene endo-PG di Botrytis cinerea (BcPGA2).
Lavoro svolto nell’ambito del Programma di Ricerca di Interesse Nazionale (MURST, finanziamento 1999) “Diaporte helianthi – girasole: studio di un patosistema”
Identification of plasmids in Diaporthe helianthi isolates from different geographic origin
No full textDiaporthe helianthi is the causal agent of sunflower stem canker and it is threatening in Europe, although sporadically recorded in Italy. In a program aimed to investigate molecular variability among D.helianthi isolates from several countries, our approach was focused on the identification of extrachromosomal genetic determinants.
Twenty-six isolates from different geographic origin, 14 deriving from France, 3 from ex-Yugoslavia, 3 from Argentina, 1 from Romania, 5 from Italy, have been studied.
Extrachromosomal bands have been detected in most isolates. Rnase A and DNA exo-nucleases (exo-III and exo-λ) digestions suggested they were DNA plasmid-like elements apparently with a circular conformation.
More detailed analysis was then performed on a selected plasmid derived from a French isolate presumably present, as inferred by molecular weight, in all French and Yugoslavian isolates (countries were the disease has a heavy incidence). Its intracellular localisation resulted to be mitochondrial. In order to check its specificity, it was used in Southern blot experiments as a probe against DNAs derived from all twenty-six D.helianthi isolates.
Further investigations are needed to characterise that plasmid (cloning and sequence analysis) and to make a comparison (e.g. RFLP) with plasmids from the other D.helianthi isolates
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