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1.
The manner in which the bacterium Pseudomonas savastanoi pv. savastanoi ( Pss ), the causal agent of knot disease, infects olive plants is erratic and has not been fully documented. To investigate the process of Pss invasion, olive explants were inoculated in vitro and examined visually and by light microscopy at 2-weekly intervals for 10 weeks. In all host genotypes tested, interaction with the pathogen resulted in: (i) a progressive collapse of the stem, originating at the inoculation site at the apex of the explant, and proceeding downwards; and (ii), localized outgrowths on the stem located at various distances from the inoculation site. Histological analysis revealed that the anatomy of the outgrowths closely resembled that of knots formed in vivo ; they showed that Ps. savastanoi also diffused within the olive explants through the xylem vessels, and that the olive host reacted to pathogen invasion, possibly by producing substances of polysaccharidic and/or phenolic nature. 相似文献
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G. Marchi A. Sisto A. Cimmino A. Andolfi M. G. Cipriani A. Evidente G. Surico 《Plant pathology》2006,55(5):614-624
Results of a survey of olive knot disease in central Italy in 2002 and 2003 showed that Pantoea agglomerans was found associated with the pathogen Pseudomonas savastanoi pv. savastanoi ( Ps. savastanoi ) in 70% of the olive knots examined. Pathogenicity tests in which these two bacteria were co-inoculated on the stems of 1-year-old olive plants at ratios of 1:1, 1:100 and 100:1 showed that the growth of P. agglomerans was apparently aided by the presence of an actively growing population of Ps. savastanoi . At the same time, however, a dominant population of P. agglomerans at the inoculation site tended to depress the growth of Ps. savastanoi , probably because of competition for space and nutrients between these bacteria and by means of antibiotic production by P. agglomerans. In some cases the association of P. agglomerans, which in culture was found to produce indole-3-acetic acid but not cytokinins, with Ps. savastanoi resulted in an increase in the size of knots. This boosting effect of P. agglomerans on proliferation was probably due to the release of IAA by this bacterium at the inoculation sites. 相似文献
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J. M. Quesada R. Penyalver J. Pérez‐Panadés C. I. Salcedo E. A. Carbonell M. M. López 《Plant pathology》2010,59(2):262-269
Pseudomonas savastanoi pv. savastanoi (Psv) is the causal agent of olive knot disease. The bacterium survives epiphytically and gains ingress through new wounds where infections and colonization result in knot formation. The natural spread of the bacterium and the subsequent appearance of the disease in olive orchards is poorly understood. The aim of this study was to monitor Psv epiphytic populations in inoculated plants with knots versus non‐inoculated healthy trees within the same orchard over four years. Additionally, disease severity was measured in both inoculated and non‐inoculated control trees. Epiphytic Psv populations moved from inoculated to non‐inoculated trees, although average Psv populations were higher in inoculated trees. Olive knot severity increased over the course of the study in all treatments and cultivars, with all plants reaching a high level of disease by the end of the study. However, the delay in the onset of disease was longer in non‐inoculated than in inoculated trees. Molecular typing of Psv isolates recovered from non‐inoculated control trees confirmed that they were similar to the inoculated strain. These data demonstrate that Psv can move over short distances in olive orchards through dissemination of epiphytic bacteria and suggest a relationship between the presence of epiphytic Psv and the number of knots on trees. 相似文献
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A. Sisto M. G. Cipriani S. Tegli M. Cerboneschi G. Stea E. Santilli 《Plant pathology》2007,56(3):366-372
The genetic diversity of 71 Pseudomonas savastanoi pv. savastanoi strains isolated from different host species and from diverse geographical regions was determined by fluorescent amplified fragment length polymorphism (f-AFLP) analysis. The study was carried out using three different selective primer combinations. Strains of P. syringae pv. syringae , P. syringae pv. phaseolicola , P. syringae pv. glycinea , P. syringae pv. tagetis and P. amygdali were also included as outgroups. Based on cluster analysis of f-AFLP data, all P. savastanoi pv. savastanoi strains showed a high degree of similarity, grouping in a cluster and forming a taxon clearly separate from outgroup strains. AFLP analyses failed to support placing strains of P. savastanoi pv. savastanoi , P. syringae pv. phaseolicola and P. syringae pv. glycinea in the same species. Strains of P. savastanoi pv. savastanoi formed subclusters that correlated with the host species. Strains identified within these subclusters were related to the geographical region where the strains were isolated. Strains of P. savastanoi pv. savastanoi from olive were divided into two subclusters. Strains from oleander were differentiated from those from ash and were divided into two additional subclusters, distinct from olive strains. Three strains isolated from jasmine showed a high level of similarity among them but, at a lower Dice similarity coefficient, were linked to a subcluster including olive strains. Finally, two strains isolated from privet were similar to strains from olive and were included in the same subcluster. 相似文献
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Penyalver R García A Ferrer A Bertolini E Quesada JM Salcedo CI Piquer J Pérez-Panadés J Carbonell EA Del Río C Caballero JM López MM 《Phytopathology》2006,96(3):313-319
ABSTRACT Pseudomonas savastanoi pv. savastanoi causes olive knot disease, which is present in most countries where olive trees are grown. Although the use of cultivars with low susceptibility may be one of the most appropriate methods of disease control, little information is available from inoculation assays, and cultivar susceptibility assessments have been limited to few cultivars. We have evaluated the effects of pathogen virulence, plant age, the dose/response relationship, and the induction of secondary tumors in olive inoculation assays. Most P. savastanoi pv. savastanoi strains evaluated were highly virulent to olive plants, but interactions between cultivars and strains were found. The severity of the disease in a given cultivar was strongly dependent of the pathogen dose applied at the wound sites. Secondary tumors developed in noninoculated wounds following inoculation at another position on the stem, suggesting the migration of the pathogen within olive plants. Proportion and weight of primary knots and the presence of secondary knots were evaluated in 29 olive cultivars inoculated with two pathogen strains at two inoculum doses, allowing us to rate most of the cultivars as having either high, medium, or low susceptibility to olive knot disease. None of the cultivars were immune to the disease. 相似文献
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Genetic and phenotypic diversity of Mediterranean populations of the olive knot pathogen,Pseudomonas savastanoi pv. savastanoi
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Pseudomonas savastanoi pv. savastanoi (Psav) is a member of P. syringae sensu lato, and causes olive knot disease, a disease first reported over 2000 years ago. Analysing 124 isolates of Psav from 15 countries by rep‐PCR, the population genetic structure of Psav was investigated. A total of 113 distinct fingerprints were detected. Cluster analysis revealed the existence of two clusters and four subclusters. These clusters were associated with the geographic origin of isolates, which in turn correspond to historic human migration events and trade routes across the Mediterranean Sea. In contrast, multilocus sequence typing (MLST) of 2788 bp of the gapA, gltA, gyrB and rpoD genes found only one variable site among 77 representative isolates. Virulence variation was observed within the Psav population, with the most virulent strains generating knots that had a weight that was 10‐fold greater than those generated by the least virulent strains. Taken together, these data suggest that today's Psav population is the result of clonal expansion of a single strain, that moderate migration of the pathogen occurred between countries, and that changes in virulence arose during its evolution. 相似文献
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This study assessed the use of in vitro olive plants to evaluate the virulence of Pseudomonas savastanoi pv. savastanoi strains isolated from olive and P. savastanoi pv. nerii strains isolated from oleander knots. First, different olive isolates were inoculated into stem wounds and differences in knot formation and weight of overgrowths were observed for the selected strains. Tissue proliferation was clearly visible in all inoculated plants 30 days after inoculation. Virulence of P. savastanoi pv. nerii mutants with defects in regard to biosynthesis of indole-3-acetic acid and/or cytokinins was tested using this system. In agreement with data previously reported, all mutant strains multiplied in olive but induced attenuated symptoms. To analyze the virulence of P. savastanoi pv. savastanoi affected in their ability to grow in olive tissue, a trpE tryptophan auxotroph mutant was generated using a collection of signature tagged mutagenesis transposons. Virulence of this mutant was clearly reduced as evidenced by swelling of the olive tissue that evolved into attenuated knots. Furthermore, mixed infections with its parental strain revealed that the wild-type strain completely out-competed the trpE mutant. Results shown here demonstrate the usefulness of in vitro olive plants for the analysis of P. savastanoi pvs. savastanoi and nerii virulence. In addition, this system offers the possibility of quantifying virulence differences as weight of overgrowths. Moreover, we established the basis for the use of mixed infections in combination with signature tagged mutagenesis for high-throughput functional genomic analysis of this bacterial pathogen. 相似文献
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A total of 360 Pseudomonas savastanoi pv. savastanoi isolates obtained from 11 Italian olive ( Olea europaea ) cultivars grown in different provinces were assessed with repetitive PCR using short interspersed elements of the bacterial genome as primers (ERIC, BOX and REP primer sets). The population structure of the isolates was determined by using three different hierarchical clustering algorithms: UPGMA, single-link and complete-link methods. REP primers were the most discriminatory. The various fingerprints obtained from the same cultivar and locality persisted over 2 years of knot sampling. Repetitive PCR and UPGMA analysis, using the three data sets combined, revealed 20 patterns with an overall similarity of 81%, with no grouping of the isolates. The resulting dendrogram shows a bush-like topology. Similar results were obtained with the other two clustering methods. In contrast, data obtained from the literature showed that the genetic structure of olive is characterized by bifurcated dendrograms and clear grouping of cultivars. Therefore it appears that the host plant and its pathogen did not cospeciate. The strict adaptation of the bacterium to olive would represent a case of association by colonization. 相似文献
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Isolates of Pseudomonas syringae ssp. savastanoi from ash were examined for their ability to produce phytohormones in culture and for pathogenicity, in comparison with isolates from olive and oleander. Nineteen out of 20 ash isolates produced low levels of indole-3-acetic acid and its methyl ester but no cytokinins. In contrast, the remaining isolate, NCPPB3474, accumulated high levels of auxins and cytokinins in culture, comparable to those of olive and oleander strains. Hybridization of DNA preparations with tryptophan mono-oxygenase ( iaaM ) and isopentenyl transferase ( ipt ) gene-containing probes showed sequences of DNA homologous to both probes only in isolate NCPPB3474, and in which the iaaM and ipt genes were located on the chromosome and on a plasmid of about 80 kb, respectively. When assayed for pathogenicity on ash, olive and oleander, 19 of the 20 ash isolates caused disease only on ash but NCPPB3474 caused knots on both ash and olive. Oleander isolates infected all three hosts whereas those from olive caused symptoms only on olive and ash. All the cultures were able to multiply in host plant tissues, but the growth rates and final population densities were correlated to the plant species inoculated and the host origin of the isolates. In particular, the highest population densities were reached by isolates capable of causing symptoms on the inoculated host. The phytohormone production shown by ash, olive and oleander isolates of P. syringae ssp. savastanoi was in accordance with the type of symptoms: cankers accompanied by wart-like excrescences on ash and knots on olive and oleander. Furthermore, the pathogenic features of these isolates and, in particular, their growth patterns in the different host tissues, support previous evidence on the existence of three distinct pathovars in P. syringae ssp. savastanoi . 相似文献
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Twenty-one strains of Pseudomonas syringae subsp. savastanoi , isolated from knots on olive and oleander trees growing in close proximity to or in physical contact with one another, were evaluated for knot induction and for bacteriocin production. In addition, DNA preparations from the bacterial strains were tested for hybridization to probes containing the tryptophan monooxygenase (iaaM) and isopentenyl transferase (ipt) genes, which are involved in indole-3-acetic acid and cytokinin biosynthesis, respectively, in P.s. subsp. savastanoi.
The strains showed features characteristic of strains usually isolated from their respective host plants. For example, all 10 oleander strains were virulent both to oleander and olive, did not produce bacteriocins and harboured the iaaM gene on plasmids. In contrast, all 11 olive strains were virulent only to olive, 10 strains produced bacteriocins, and nine strains carried the iaaM gene on the chromosome. Two olive strains (OAll, OD21) harboured the gene coding for iaaM on plasmids. Furthermore, strain OD21 carried the iaaM gene on the same plasmid as the ipt gene. This is the first report both of a plasmid-borne iaaM in typical olive strains (virulent only to olive and bacteriocin producers), and of the presence of the ipt gene on the same plasmid. In olive and oleander strains the ipt gene was located either on plasmids or on the chromosome. These results suggest that under natural conditions the pathogen does not appear to spread from oleander to olive even when trees are growing in close proximity or in physical contact.
The location of the phytohormone genes on plasmids or on the chromosome is discussed in relationship to bacteriocin-production and knot-induction on the host species. 相似文献
The strains showed features characteristic of strains usually isolated from their respective host plants. For example, all 10 oleander strains were virulent both to oleander and olive, did not produce bacteriocins and harboured the iaaM gene on plasmids. In contrast, all 11 olive strains were virulent only to olive, 10 strains produced bacteriocins, and nine strains carried the iaaM gene on the chromosome. Two olive strains (OAll, OD21) harboured the gene coding for iaaM on plasmids. Furthermore, strain OD21 carried the iaaM gene on the same plasmid as the ipt gene. This is the first report both of a plasmid-borne iaaM in typical olive strains (virulent only to olive and bacteriocin producers), and of the presence of the ipt gene on the same plasmid. In olive and oleander strains the ipt gene was located either on plasmids or on the chromosome. These results suggest that under natural conditions the pathogen does not appear to spread from oleander to olive even when trees are growing in close proximity or in physical contact.
The location of the phytohormone genes on plasmids or on the chromosome is discussed in relationship to bacteriocin-production and knot-induction on the host species. 相似文献
14.
Polymerase chain reaction (PCR) technology was used to identify Pseudomonas savastanoi pv. phaseolicola at the DNA level. Oligonucleotide primers were designed on the basis of the DNA sequence of the phaseolotoxin gene cluster of P. s . phaseolicola . Identification of the pathogen was significantly improved and appearance of unspecific bands was greatly diminished by experimentally selecting the most suitable annealing temperature (Tm) value. We obtained a single, strong DNA band of 1.4 kb length, specific for the identification of P. s . phaseolicola , using a PCR programme based on a Tm value of 80 °C. 相似文献
15.
T. Cinelli G. Marchi A. Cimmino R. Marongiu A. Evidente M. Fiori 《Plant pathology》2014,63(2):277-289
Genetic, phenotypic and host range diversity among Pseudomonas savastanoi isolates from Myrtus communis were investigated. Thirty‐one isolates from six Sardinian commercial myrtle orchards and three isolates from plants growing spontaneously on the island of Rhodes (Greece) were compared with reference strains of P. savastanoi from olive, oleander, ash and myrtle. Multilocus sequence analysis (MLSA) indicated the presence of a monomorphic population with a very low level of variability. Conversely, Biolog phenotypic fingerprinting and phytohormone production analyses showed a considerable metabolic diversity, as bacteria obtained from single infected tissue differed more than bacteria obtained from different orchards. When pathogenicity tests were carried out on myrtle plants, different types of symptoms were induced: knots, canker lesions with or without tissue proliferations and, occasionally, wilting of the inoculated twig, a symptom never reported before for P. savastanoi. Comparable symptoms were also observed in the natural environment both on spontaneous and cultivated plants. Moreover, the host range of the myrtle population was heterogeneous and not well defined. Some isolates showed a wide host range whilst others were pathogenic only to their natural host. Overall these findings suggest that the diversity of the P. savastanoi population from myrtle does not depend so much on the locality or the natural host and does not allow the Sardinian and Greek isolates, together with previously characterized myrtle strains, to be ascribed to a known pathovar of P. savastanoi, nor to propose their belonging, as a whole, to a new pathovar. 相似文献
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ABSTRACT The virulence of Pseudomonas syringae subsp. savastanoi, which causes hyperplastic symptoms (knots) on olive plants, is associated with secreted phytohormones. We identified a Tn5-induced mutant of P. syringae subsp. savastanoi that did not cause disease symptoms on olive plants although it was still able to produce phytohormones. In addition, the mutant failed to elicit a hypersensitive response in a nonhost plant. Molecular characterization of the mutant revealed that a single Tn5 insertion occurred within an open reading frame encoding a protein 92% identical to the HrcC protein of P. syringae pv. syringae. Moreover, sequence analysis revealed that the gene encoding the HrcC protein in P. syringae subsp. savastanoi was part of an operon that included five genes arranged as in other phytopathogenic bacteria. These results imply that hrp/hrc genes are functional in P. syringae subsp. savastanoi and that they play a key role in the pathogenicity of this plant pathogen. 相似文献
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F. Alvarez J.E. García de los Ríos P. Jimenez A. Rojas P. Reche M.T. Troya 《European journal of plant pathology / European Foundation for Plant Pathology》1998,104(6):603-609
One hundred and sixty strains of Pseudomonas syringae subsp. savastanoi from Olea europaea, Olea europaea var. sylvestris, Nerium oleander, Fraxinus angustifolia and Retama sphaerocarpa, and four type strains of other pathovars were studied, investigating 102 phenotypic traits, among which we include biochemical characteristics, assimilation of different carbon sources, sensitivity or resistance to antibiotics and indoleacetic acid (IAA) production. Results were analysed with an affinity dendrogram via the Jaccard coefficient. They indicate an influence of environmental factors on the formation of the 15 phenons obtained, since isolated (knot) strains from the same species but different geographical areas are segregated. Segregation, also detected in strains from different hosts within the same area, added to the pathogenicity test helps to characterise these strains as different pathovars. 相似文献
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Abi S. dos A. Marques Roselyne Corbière Louis Gardan Catherine Tourte Charles Manceau John D. Taylor Régine Samson 《European journal of plant pathology / European Foundation for Plant Pathology》2000,106(8):715-734
The relationships between strains of Pseudomonas savastanoi pv. phaseolicola (P. sav. phaseolicola), P. syringae pv. tabaci (P. syr. tabaci) and P. syr. syringae which all cause disease on bean; the related species P. sav. glycinea and P. syr. actinidiae, and reference bacteria, were evaluated by studying the phenotypic and genetic diversity of a collection of 62 strains. All the P. sav. phaseolicola strains tested produced characteristic watersoaked lesions on bean pods. Other pathovars produced varying combinations of symptoms including necrotic lesions, with or without watersoaked centres and sunken tissue collapse of the lesion (P. syr. tabaci) and necrotic lesions with or without sunken collapse (P. syr. syringae). At the genomospecies level, all the strains of P. sav. phaseolicola, P. sav. glycinea and P. syr. tabaci, belonging to genomospecies 2, could be separated from P. syr. syringae strains (genomospecies 1) and P. syr. actinidiae strains (unknown genomospecies) by BOX-PCR and DNA/DNA hybridisation. To distinguish P. sav. phaseolicola, within genomospecies 2, from P. sav. glycinea and P. syr. tabaci, it was necessary to perform nutritional characterisations myo-inositol negative and p-hydroxy benzoate positive for P. sav. phaseolicola strains), PCR with specific primers designed from the tox region (positive for all of the P. sav. phaseolicola strains) and serotyping, as 71% of the P. sav. phaseolicola strains reacted as O-serogroup PHA1. Important intrapathovar variation was seen by genomic fingerprinting with REP and ERIC primers, as well as with RAPD primers (AE7 and AE10) and esterase profilings. While RAPD fingerprinting detected variability correlated with two race-associated evolutionary lines, REP, ERIC and esterase profiles revealed intrapathovar variation linked to some host origins, that separated the kudzu isolates, and the mungbean isolates, from the other P. sav. phaseolicola strains. 相似文献
20.
Bacteria forming levan colonies and not producing fluorescent pigments have been isolated from olive knots and the olive phylloplane in central Italy. By their pathogenicity to olive and their morphological, biochemical and physiological features, they clearly belong to Pseudomonas syringae subsp. savastanoi. 相似文献