1,721,008 research outputs found
Caratteri patogenetici, microbiologici, sierologici ed elettroforetici di alcuni isolati di Pseudomonas corrugata.
No full textCARATTERI PATOGENETICI, MICROBIOLOGICI, SIEROLOGICI ED ELETTROFORETICI DI ALCUNI ISOLATI DI PSEUDOMONAS CORRUGATA. Pseudomonas corrugata Roberts et Scarlett, segnalato per la prima volta in Inghilterra nel 1978 quale agente della "necrosi del midollo" del Pomodoro, è ormai presente nei principali paesi ove viene coltivata la solanacea. Oltre che su radici asintomatiche di erba medica il batterio è stato re¬centemente rinvenuto su Crisantemo, ove provoca il "marciume del fusto", e su Peperone nel quale è responsabile della "necrosi del midollo".
Esso presenta adattabilità patogenetica e mostra variabilità in alcuni caratteri microbiologici e sierologici degni di maggiore considerazione e approfondimento.
La "necrosi del midollo" del Pomodoro è presente anche in Sardegna e in Sicilia ove P. corrugata è stato ripetutamente isolato ed identificato.
Nel presente lavoro sono stati presi in considerazione tredici isolati (11 da pomodoro e 2 da crisantemo); di questi è stata saggiata la patogenicità in diverse specie e varietà ortive e floricole; sono stati studiati i carat¬teri morfologici, biochimici, fisiologici e sierologici ed è stata eseguita l'ana¬lisi elettroforetica (CHEF) dei frammenti di restrizione del DNA cromosomale. Gli isolati hanno indotto caratteristici sintomi di necrosi del midollo su pomodoro e reazioni variabili (imbrunimenti e/o necrosi del midollo) su lattuga, peperone, garofano e crisantemo; cavolfiore e cavolo rapa hanno mostrato iperplasie e accrescimenti definiti a carico del midollo con conseguente fessurazione del fusto.
Gli stessi isolati hanno mostrato variabilità nella morfologia delle colonie, nella produzione di pigmenti diffusibili e nella risposta ai più importanti tests.
I saggi di agglutinazione su piastra (ODD), immunofluorescenza ed ELISA, hanno rivelato, nei confronti dell'antisiero usato, risposte variabili.
L'analisi CHEF ha evidenziato un certo polimorfismo dei frammenti di restrizione ottenuti dopo taglio con enzimi di restrizione a bassa frequenza di taglio (xbai e DraI). I profili ottenuti sono risultati caratteristici e differenti da quelli di altre Pseudomonadi (P. syringae e P. fluorescens)
A polyphasic approach to the identification of ochratoxin A-producing black Aspergillus isolates from vineyards in Sicily
No full textAspergillus strains belonging to section Nigri isolated during a two year survey in eight Sicilian vineyards located on the slopes of Mount Etna (Sicily, Italy) were analysed analyzed in order to characterize species responsible for ochratoxin A (OTA) contamination of grapes. The polyphasic approach permitted analysis of
biodiversity of Aspergillus isolates in relation to their morphology, ochratoxigenicity and genetic variability.
We assessed OTA production by A. carbonarius, A. niger, A. tubingensis and A. japonicus using an enzymelinked immunosorbent assay. A. carbonarius isolates were the strongest OTA producers. A subset of 66 representative strains was selected for further DNA-based characterization. PCR assays using species-specific primers discriminated between A. niger, A. carbonarius and A. japonicus on the basis of the target sequences for each species. The PCR-based methods matched morphological characterization in identifying all the black aspergilli (BA) isolates tested, whereas RFLP analysis with RsaI of isolates positive to PCRs with A. niger
specific primers identified three A. tubingensis isolates. The identification of thirteen isolates was further confirmed by ITS analysis. By this method, each of the isolates was identified and assigned to an Aspergillus species. The fAFLP analysis of 40 isolates highlighted the power of this technique to discriminate different
species and single strains, to verify the presence of mixed populations in the same vineyard, through homogeneous species clusters. No correlation was observed between the clusters and OTA production level or origi
Quantitative detection of pseudomonas corrugata and pseudomonas mediterranea in tomato plants by duplex real-time PCR
No full textPseudomonas corrugata and P. mediterranea are two closely related bacterial species both causal agents of tomato pith necrosis. To screen tomato planting material reliably, a quantitative real-time PCR assay was developed, to detect and/or discriminate both bacterial pathogens in a single tube. So, two species-specific primer/probe sets were designed on the sequences of two DNA fragments amplified by a previously reported specific PCR protocol. TaqMan real-time PCR assays were developed for individual (simplex PCR) and simultaneous (duplex PCR) amplifications. The assays were performed with the SmartCycler TD II System (Cepheid) and the fluorescence from both FAM and Texas Red channels were recorded at the annealing step. Specificity was tested with an extended range of P. corrugata and P. mediterranea strains, with other Pseudomonas spp. And with a number of tomato bacterial pathogens. The detection limit was approximately 10 cells per reaction for both bacteria, and quantification was linear over a six-log range. The duplex real-time PCR assay was validated on tomato plants artificially inoculated by pricking the stem with a strain of each species either separately or together
First report of leaf spot and blight caused by Ralstonia pickettii on Bird of Paradise tree in Italy
No full textEU-COST ACTION CA16107 - EUROXANTH: INTEGRATING SCIENCE ON XANTHOMONADACEAE FOR INTEGRATED PLANT DISEASE MANAGEMENT IN EUROPE.
No full textBacteria of the family Xanthomonadaceae, including species of
Xanthomonas and Xylella fastidiosa, are devastating plant pathogens.
Many are quarantine organisms in the EU and their study
is of uttermost importance. These pathogens infect all kinds of
crop plants. The COST Action CA16107 “EuroXanth” aims at creating
an interdisciplinary network in order to develop strategies
for sustainably protecting plants and prevent yield losses. COST
(European Cooperation in Science and Technology) is a funding
agency for research and innovation networks. COST Actions help
connect research initiatives and enable scientists to grow and share
ideas with their peers. Specifically, this COST Action addresses
key aspects of the pathogen-vector-host interactions, from the cellular
to the population level. A better insight into population structures
and virulence mechanisms of the pathogens, together with
the exploration of the molecular mechanisms underlying disease
resistance, will enable development of durably resistant plant cultivars
and exploitation of bio-control schemes tailored to population and pathogen. This COST Action has duration of 4 years (March
2017-March 2021) and will generate a platform that gathers experts
from different disciplines, such as molecular diagnostics, molecular
host-microbe interactions, plant resistance breeding, etc. The
network includes 43 working groups from 21 different countries.
Joining their efforts will help to develop and implement effective
plant protection schemes, be it via resistant crop cultivars or via
other control mechanisms. This goal will be achieved by mobilizing
and training scientists from major European institutions, regulatory
bodies and commercial companies working on the various aspects
of this complex of problems
Evaluation of oleander accessions for resistance to Pseudomonas savastanoi pv. nerii
No full textNine oleander accessions were evaluated for resistance to Pseudomonas savastanoi pv. nerii, causal agent of the oleander knot disease. None of the accessions was resistant when tested with three bacterial strains of different virulence, but they varied significantly in the severity of symptoms induced by these strains. The most susceptible accessions "Dark Salmon" (dark salmon flower) showed deformation of stems, leaves and seed pods and secondary knots on aerial parts, whereas the least susceptible one "White" (white flower), inoculated with the least virulent strain, showed neither localized knots at the inoculation point nor secondary symptoms. In this study an in vitro test, based on prick inoculation of leaf segments, was optimised for use in pathogenicity tests or as an in vitro resistance screening test
Characterization of Alternaria alternata Isolates from Tangerine Hybrids Affected by Brown Spot in Italy
No full textAlternaria brown spot, caused by Alternaria alternata, is the most important disease of tangerines and their hybrids worldwide, including Italy. The disease represents, for some susceptible citrus cultivar, a limiting factor in profitable cultivation. The results of the characterization of A. alternata isolates obtained from lesions on leaves and fruits of Fortune, Nova and Winola hybrids and Valencia sweet orange, collected in two groves located in Calabria and Sicily, is reported. An endopolygalacturonase gene (endoPG) was sequenced from five representative strains and a phylogenetic tree based on endoPG sequence data of Italian isolates and those of citrus associated Alternaria species deposited in Genbank was constructed. Italian brown spot isolates were grouped both in clusters with brown spot isolates from different countries and in clusters with A. alternata isolates associated with other diseases of citrus. Intra-population variability was demonstrated by a fAFLP protocol. A primer pair combination was selected amongst four primer combinations and tested on 18 A. alternata isolates. Mixed populations of A. alternata were recovered in a single citrus grove in Calabria. No correlation was found among geographical origin, host, and year of isolation
Mixed infection of Pectobacterium carotovorum subsp. Carotovorum and P. carotovorum subsp. Brasiliensis in tomato stem rot in Italy
No full textGrafted tomato plants grown in a soilless culture system in heated greenhouses in Sicily were affected by stem rot disease. Symptoms consisted of dark brown longitudinal discoloration of the basal part of the stem and petioles. Longitudinal sections of the stem revealed brown watersoaked or soft-rotted pith tissue and internal vascular discoloration. Bacterial isolates with two different colony morphologies were obtained from symptomatic tissues. Isolates were identified as Pectobacterium spp. on the basis of biochemical and molecular analyses. The analysis of the 16S rRNA gene sequence and of the concatenated sequences of the housekeeping genes rpoS and pgi revealed that the isolates of the two morphotypes belong to P. carotovorum subsp. carotovorum and P. c. subsp. brasiliensis, respectively. Isolates from both taxa reproduced disease symptoms on artificially inoculated tomato plants. This is the first report of P. carotovorum subsp. brasiliensis in Italy
Defense-related gene expression in two olive cultivars inoculated with Pseudomonas savastanoi pv. savastanoi
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