1,721,366 research outputs found
Induced Resistance in Bean Leaves Pretreated with Extracellular Polysaccharides from Phytopathogenic Bacteria
No full textBean leaves were infiltrated with bacterial extracellular polysaccharides (= EPS) in order to study their effect on a subsequent (48 h later) inoculation with bacteria during compatible and incompatible interactions. Three different EPS‐preparations from the pathovars pisi and phaseolicola of Pseudomonas syringae were tested: pisi‐EPS (S) contained predominantly levan, phaseolicola‐EVS (Go) predominantly alginate, and phaseolicola‐EPS (S) contained about equal proportions of levan and alginate. Bean leaves showed a distinct chlorosis 48 hours after treatment with phaseolicola‐EPS. The susceptible cultivar ‘Red Kidney’ was more sensitive then the resistant breeding line ‘02’. The latter sometimes developed necrotic reactions after EPS‐treatment. Pisi‐EVS induced only a very weak chlorosis. No chlorosis appeared after treatment with commercial alginate (obtained from seaweed). Other plant species revealed a decreasing sensitivity towards EPS in the following order: ‘Red Kidney’ bean, tobacco, soybean, tomato, cotton. Chlorosis caused by phaseolicola‐EPS was obviously not due to phaseolotoxin, since EPS‐preparations did not inhibit E. coli, and since the concentration of ornithine in affected bean leaves increased only very slightly. EPS‐treatment of ‘Red Kidney’ bean leaves induced a “resistance” towards a subsequent bacterial inoculation in the compatible (P. phaseolicola) as well as in the incompatible (P. pisi) combination. The latter case may more precisely be termed “protection”. A similar effect was observed in the resistant bean ‘02’, that is a protection towards HR (= hypersensitive reaction), which normally develops after inoculation with high bacterial concentrations. Several differences in the reactions of the tested cultivar‐EPS combinations were observed. In general, bacterial EPS in bean leaves induced a more effective protection against P. pisi than against P. phaseolicola. In the cultivar ‘Red Kidney’ the induced resistance against P. phaseolicola was more pronounced with phaseolicola‐EPS than with pisi‐EPS. Induzierte Resistenz in Bohnenblättern, die mit extrazellulären Polysacchariden phytopathogener Bakterien vorbehandelt wurden Bohnenblätter wurden mit bakteriellen, extrazellulären Polysacchariden (EPS) infiltriert, um deren Wirkung auf eine 48 Stunden später erfolgende Bakterieninokulation bei kompatibler und inkompatibler Interaktion zu untersuchen. Drei verschiedene EPS‐Präparate der Pseudomonas syringae Pathovare pisi und phaseolicola wurden eingesetzt: pisi‐EPS (S) enthielt überwiegend Lävan, phaseolicola‐EPS (Go) vornehmlich Alginat und phaseolicola‐EPS (S) bestand zu etwa gleichen Anteilen aus Lävan und Alginat. Auf Bohnenblättern entwickelte sich 48 h nach Behandlung mit phaseolicola‐EPS eine deutliche Chlorose. Die anfällige Sorte ‘Red Kidney’ war empfindlicher als die resistente Zuchtlinie ‘02’. Auf letzterer entstanden manchmal nekrotische Reaktionen nach EPS‐Behandlung. P. pisi‐EPS rief nur eine sehr schwache Chlorose hervor. Nach Behandlung mit einem Handelspräparat von Alginat (aus Meeresalgen gewonnen) erschien keine Chlorose. Andere Pflanzenarten zeigten gegenüber EPS eine abnehmende Empfindlichkeit in folgender Reihenfolge: ‘Red Kidney’ Bohnen, Tabak, Sojabohnen, Tomaten, Baumwolle. Die durch phaseolicola‐E'PS hervorgerufene Chlorose wurde offenbar nicht durch Phaseolotoxin verursacht, da EPS‐Präparationen E. coli nicht hemmten, und da die Konzentration von Ornithin im behandelten Blatt nur sehr schwach anstieg. EPS‐Behandlung von ‘Red Kidney’‐Bohnenblättern induzierte eine Resistenz gegenüber einer 48 Stunden später folgenden Bakterieninokulation, sowohl in der kompatiblen (P. phaseolicola) wie in der inkompatiblen (P. pisi) Kombination. Der zweite Fall müßte zutreffender als “Schutzeffekt” (= protection) bezeichnet werden. Ein ähnlicher Effekt wurde in der resistenten Bohnenlinie ‘02’ beobachtet, d. h. ein Schutz vor der hypersensitiven Reaktion, die normalerweise nach Inokulation mit hohen Bakterienkonzentrationen auftritt. Im allgemeinen induzierten bakterielle EPS in Bohnenblättern einen deutlicheren Schutzeffekt gegenüber P. pisi als gegenüber P. phaseolicola. In der Sorte ‘Red Kidney’ war die induzierte Resistenz gegenüber P. phaseolicola‐bei phaseolicola‐EFS ausgeprägter als bei pisi‐EPS. 1989 Paul Parey Scientific Publishers, Berlin and Hambur
Protein electrophoretograms for the identification of ralstonia solanacearum in potato tubers
No full textDensitometric analysis was performed on the whole cell proteins of 53 strains of Ralstonia solanacearum (Rs) isolated from different host plants and geographical areas. This study also included 18 unidentified, endophytic potato bacteria, non-pathogenic on tomato and eggplant, forming colonies similar to Rs (Rs-like bacteria) on differential or selective media. The comparison of the electrophoretograms was performed by calculating the correlation coefficient (r) and by principal component analysis. Visual comparison generally made it possible to distinguish between the Rs strains and nonpathogenic Rs-like bacteria. Densitometric analysis of the electrophoretograms revealed a main group of strains (r=0.76) including 4 subgroups. Subgroup 1 (r=0.92) included potato and tomato strains attributable to race 3 biovar 2, including all those of Mediterranean origin. Principal component analysis again included the Mediterranean strains in a single group characterised by just one of the two bands identified as differential in the Rs profile. Principal component analysis revealed that one Rs-like bacterium, with a markedly higher correlation coefficient (r=0.83), was clearly distinct from Rs. The results confirmed the reliability of the European diagnostic protocol as a basis for identification at the species level, that must be based on the pathogenicity test combined with whole cell protein profiles when these are used as a single phenotypic fingerprint
I SISTEMI DI MISURAZIONE ECONOMICO-FINANZIARIA NELLE UNIVERSITÀ ITALIANE: PROBLEMI E PROSPETTIVE
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Modification of the Pseudomonas syringae pv. tabaci -tobacco leaf interaction by bacterial oligosaccharides
Full text linkCell-associated oligosaccharides were extracted with trichloroacetic acid treatment from Pseudomonas syringae pv. aptata, purified by column chromatography, analysed by GC-MS and fast atom bombardment-mass spectrometry, and bioassayed on tobacco leaves. The material was shown to be a mixture of neutral oligosaccharides, with a mol. wt of 800-1800, degree of polymerization 5-11, and linear glucose and mannose chains. Local infiltrations of the mixture, in concentrations of 1 mg, 100, 10 and 1 μg ml-1, did not cause tobacco tissue necrosis within 1 week. When the mixture was infiltrated in the interveinal leaf panels, in concentrations of 1 μg, 100, 10 and 1 ng ml-1, 48 h before challenge inoculation, it delayed or prevented normosensitive necrosis by P. syringae pv. tabaci but not hypersensitive necrosis by P. syringae pv. aptata. Five days after inoculation with P. syringae pv. tabaci, inhibition of normosensitive necrosis, as compared with the control tissue, was 80·55, 77·21, 56·36 and 45·46 % for the four concentrations. In the bioassay with P. syringae pv. tabaci the efficacy threshold was assessed at approx. 1 ng ml-1. Pre-treatment with oligosaccharides (1 μg ml-1) significantly inhibited the growth of P. syringae pv. tabaci between 3 and 5 days after inoculation and, between day 6 and 8, it delayed the death of bacteria when the tissue was not subject to necrosis. An interval of 6 h was necessary between the infiltration of oligosaccharides (1 μg ml-1) and inoculation of P, syringae pv. tabaci for a clear inhibition of normosensitive necrosis. These oligosaccharides acted as signal molecules by modifying, at nanomolar concentrations, the P. syringae pv. tabaci-tobacco leaf interaction, but they were not elicitors of the hypersensitive reaction. © 1994 Academic Press, Inc
The economic impact of the bacterial blight of soybean under European agroclimatic conditions
Full text linkThe economic impact of the bacterial blight of soybean caused by Pseudomonas syringae pv. glycinea has been investigated in three countries belonging to the European Union: Italy, France and Spain. Weather and growing conditions have been monitored over three years of field experiments (1992-1994) and the data analysed in order to evaluate possible yield losses and in view of the production of pathogen free seed. In Italy and France, using different cultivars and seed with a contamination level of 0.5-20% no significant yield losses were found. In Italy the initial seed contamination level was positively correlated with the contamination of the harvested seed by the pathogen; both in Italy and in France on some cultivars, it was possible to correlate seed contamination level with the epiphytic population of the pathogen and the intensity of symptoms affecting plants in the field. No epiphytic contamination by the pathogen was observed in Spain, even at the highest seed contamination rate (20%), and there was no disease in the field and no yield reduction. The pathogen seemed not to become systemic since no contamination was observed on seed aseptically taken in the field just before harvest. The experiments highlighted the low impact of soybean bacterial blight under European climatic conditions, but suggested the choice of dry and warm regions for the production of quality seed to prevent the accumulation of effective inoculum on the seed year by year
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