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1.
Bacterial pathogens of onion (Allium cepa) plants and their undetected presence in seed can cause substantial losses to onion producers. In this study, 23 Pseudomonas syringae strains were isolated from five onion plants and 18 onion seeds. The symptoms on leaves and seed stalks were irregular lesions with necrotic centres and water soaked margins. The aim of the study was to characterize these P. syringae strains using Biolog GN III carbon source utilization, multilocus sequence typing (MLST) based on partial sequences of four housekeeping genes (cts, gapA, gyrB and rpoD), and to determine whether or not the strains were pathogenic on onion (cv. Granex 33), chive (Allium schoenoprasum cv. Grasiue), leek (Allium porrum cv. Giant Italian) and spring onion (Allium fistulosum cv. Salotte) plants. Both Biolog analysis and MLST analysis separated onion strains into two clusters, one supporting the existence of a new pathovar of P. syringae, and the other corresponding to P. syringae pv. porri. Pseudomonas syringae strains belonging to the new pathovar we pathogenic only on onion plants of the Allium spp. tested. The results of this study revealed that bacterial blight of onion in South Africa is caused by two pathovars of P. syringae sensu lato, namely, the newly described pathovar, allii, and P. syringae pv. porri. The symptoms caused by these two pathovars in the field were indistinguishable.  相似文献   

2.
Although many Pseudomonas syringae strains have already been determined, only a few genomes of strains belonging to pathovar lachrymans have been sequenced so far. In this study we report the genome sequence of P. syringae pv. lachrymans strain 814/98, which is highly virulent to cucumber. The genome size was estimated to be 6.58 Mb, with 57.97% GC content. In total, 6024 genes encoding proteins and 92 genes encoding RNAs were identified in this genome. Comparisons with the available sequenced genomes of pathovar lachrymans as well as with other P. syringae pathovars were conducted, revealing the presence of three unique plasmids and 24 type III effector proteins (TTEs) in strain 814/98. The phylogenetic analyses of MLST loci and TTEs clearly showed the existence of two distinct clusters of strains within pathovar lachrymans, which were grouped into either phylogroup 1 or 3, supporting non-monophyly within this pathovar.  相似文献   

3.
This study evaluated the role of oxidative stress on the expression of Pht cluster genes involved in phaseolotoxin synthesis in Pseudomonas syringae pv. phaseolicola. Results demonstrate that the expression of Pht cluster genes is regulated by oxidative stress in a manner dependent of the ROS present in the cell. The presence of H2O2 and Paraquat, influences on the expression of the Pht cluster genes in function of the compound and of the concentration evaluated, demonstrating that expression of Pht genes is part of the oxidative stress response in P. syringae pv. phaseolicola NPS3121.  相似文献   

4.
The receptor-like cytoplasmic kinases (RLCK family VII) are required for plant defense against various pathogens. Previously, OsPBL1 (ORYZA SATIVA ARABIDOPSIS PBS1-LIKE 1) was isolated from rice as a potential RSV (rice stripe virus) resistant factor, but its physiological roles in plant defense are yet to be investigated. In this study, we demonstrated that OsPBL1increased defense against P. syringae in transgenic Arabidopsis. To ascertain the role of OsPBL1 gene in plant defense, OsPBL1 tagged with HA (i.e. Hemagglutinin) was overexpressed in Arabidopsis and examined for the resistance against Pseudomonas syringae pv. tomato DC3000 (i.e. Pst DC3000). At 3 dpi of Pst DC3000, transgenic Arabidopsis lines exhibited the reduced chlorotic lesion and propagation of P. syringae, compared to wild type. Elevated pathogen resistance of transgenic lines was correlated with increased H2O2 accumulation and callose deposition on the infected leaves. It was also revealed that expression levels of salicylic acid dependent genes such as PR1, PR2, and PR5, were induced higher in transgenic lines than wild type. Taken together, our data suggested that OsPBL1 exerted the role in defense against pathogen attacks in plant via mainly facilitating salicylic acid dependent pathway.  相似文献   

5.
Olive knot disease in Japan was first reported in Shizuoka Prefecture in 2014, and the causal agent was identified as Pseudomonas savastanoi pv. savastanoi. Subsequently, olive trees having knots were also found in Aichi and Kanagawa Prefectures in 2015, and the isolates from knots were also suspected to be P. savastanoi pv. savastanoi through preliminary examinations. Therefore, the Aichi and Kanagawa isolates were identified through comparison of isolates from three prefectures. Phylogenic analysis based on 16S rDNA and housekeeping genes (gyrB, rpoD, gltA and gap1) revealed that the isolates belonged to the same cluster as the pathotype strain, ICMP4352PT. The iaaM, H and L genes, which are involved in promotion of symptoms, and the ina gene coding the ice nucleation protein, were detected by PCR from all the isolates. In rep-PCR (ERIC and REP) analyses, the isolates yielded DNA fragment-banding patterns that were nearly identical to that of ICMP4352PT, but slight variations in banding patterns were observed among them. In a pathogenicity test, the isolates formed distinct knots on olive and pink jasmine. Phenotypic properties of the isolates were almost identical to those of ICMP4352PT, with the exception of d-sorbitol utilization. Consequently, Aichi and Kanagawa isolates from olive were identified as P. savastanoi pv. savastanoi, and several genetic diversities in terms of rep-PCR were found in the Japanese population of P. savastanoi pv. savastanoi, indicating their heterogeneity.  相似文献   

6.
Bacterial canker caused by Pseudomonas syringae pv. syrinage (Pss) in apricot has widely spread in Turkey, especially in Malatya province, in recent years. The main objective of this study was to determine resistance of apricot cultivars to bacterial canker caused by Pss in apricot cultivars grown in Turkey. During the 2006–2007 growing period, bacterial isolations were taken from diseased apricot trees in Malatya and 53 Pseudomonas syringae isolates were obtained. Forty-two isolates were determined as Pseudomonas syringae pv. syringae and 11 isolates as pv. morsprunorum. In a pathogenicity test, leaves of cv. Hacihalilo?lu were used and five Pss isolates (K24, K25, K43, K47 and K51) were detected to be the most virulent and were used to test for cultivar resistance to Pss. Leaves of fifteen apricot cultivars (Alyanak, Çatalo?lu, Çölo?lu, Erken A?erik, Hacihalilo?lu, Hasanbey, ?smaila?a, Kabaa?i, Karacabey, Sakit 2, So?anci, ?am, ?ekerpare, Tokalo?lu (Erzincan) and Turfanda Eski Malatya) were tested for resistance to Pss. Green shoots were spray-inoculated with a concentration of 108 cfu ml?1 Pss mixed culture. Sprayed shoots were covered with moist plastic bags for 3 days and maintained in the growth chamber and monitored for symptom development. Hasanbey, Çölo?lu, So?anci and ?ekerpare apricot cultivars were resistant and ?am, Tokalo?lu (Erzincan) and Erken A?erik apricot cultivars were susceptible to Pss. This is the first report of a resistance source in apricot cultivars grown in Turkey against Pss.  相似文献   

7.
Bacterial leaf/fruit spot and canker of stone fruits, caused by Xanthomonas arboricola pv. pruni, is a recurrent disease in Italy. A set of 23 strains has been isolated in peach and plum orchards in an intensively stone fruit cultivated area located in north-eastern Italy. They were all identified as X. arboricola pv. pruni by means of phytopathological and serological features: hypersensitive reaction on bean pods, pathogenicity test on immature peach or plum fruitlets, identification by immunofluorescence assay and conventional PCR. Phylogenetic analysis based on sequencing of the gyrB housekeeping gene of the isolates showed that they formed a unique clade, well characterised and separated from other xanthomonads. An insight into the genetic population features was attempted by rep-PCR analysis, using the ERIC, REP and BOX primers. The combined rep-PCR fingerprints showed a slight intra-pathovar variation within our isolates, which grouped in five close clusters. Copper resistance has been assessed in vitro for our whole X. arboricola pv. pruni collection, highlighting that two isolates show a level of resistance in vitro up to 200 ppm of copper. Nonetheless, the copLAB gene cluster, present in many other species of Xanthomonads, was not detected in any isolate, confirming the presence of a still unknown mechanism of copper detoxification in our Xanthomonads arboricola pv. pruni tolerant/resistant strains.  相似文献   

8.
Pseudomonas syringae pv. tomato DC3000 (Pst DC3000), which causes bacterial speck disease of tomato, has been used as a model pathogen to investigate the molecular basis of plant–pathogen interactions. The function of many potential virulence factors encoded in the Pst DC3000 genome and their modes of action are not fully understood. P. syringae is known to produce the exopolysaccharide alginate. Although AlgU, a sigma factor, is known to regulate the expression of genes such as algD related to alginate biosynthesis, the molecular mechanisms of AlgU in the virulence of Pst DC3000 is still unclear. To investigate the function of AlgU and alginate in plant–bacterial pathogen interactions, we generated ΔalgU and ΔalgD mutants. After inoculation with ΔalgU but not ΔalgD, host plants of Pst DC3000 including tomato and Arabidopsis had milder disease symptoms and reduced bacterial populations. Expression profiles of Pst DC3000 genes revealed that AlgU can regulate not only the expression of genes encoding alginate biosynthesis, but also the expression of genes related to type III effectors and the phytotoxin coronatine (COR). We also demonstrated that the ΔalgU mutant showed full virulence in the Arabidopsis fls2 efr1 double mutant, which is compromised in the recognition of PAMPs. Further, the application of COR was able to restore the phenotype of the ΔalgU mutant in the stomatal response. These results suggest that AlgU has an important role in the virulence of Pst DC3000 by regulating COR production.  相似文献   

9.
A repetitive sequence-based (rep)-polymerase chain reaction (PCR) and inter-simple sequence repeat (ISSR)-PCR were used to molecular type Pseudomonas syringae pv. syringae (PSS) strains isolated from barley and wheat plants with bacterial black node symptoms grown in 22 different locations and six different seed-production districts in Japan. Eighteen genomic fingerprinting (GF) genotypes were obtained from the combined results of BOX-, REP-, and GTG5-PCR, indicating that the PSS population in Japan has high genetic diversity. The result based on logistic regression indicated that the population of GF genotype A was significantly related to a seed-producing district and that the epidemic of PSS strains in fields originated mainly from seed infection. This study will be applicable to future studies of the molecular epidemiology of bacterial plant diseases that have multiple infection routes.  相似文献   

10.
We examined the potential for biological control of black rot of broccoli, caused by Xanthomonas campestris pv. campestris (Xcc), using nonpathogenic Xanthomonas sp. strain 11-100-01 (npX) mixed with bacteriophage XcpSFC211 (pXS). Inoculation of intact broccoli plants in greenhouse trials with either npX or pXS did not control black rot. After injured plant inoculation, however, npX alone or npX with pXS significantly controlled black rot. When a mixed suspension of npX with pXS was placed on a membrane filter, then washed with distilled water and air-dried, a substantial amount of pXS adsorbed to the surface of npX. In a field trial, broccoli plants were sprayed with a suspension of npX with pXS, then inoculated with Xcc. A meta-analysis of the results from five field trials showed an integrated risk ratio (IRR, the ratio of disease incidence in inoculated broccoli plants to the incidence in control plants) of 0.69 after treatment with only npX and 0.59 with npX with pXS, indicating that black rot incidence was significantly reduced by each treatment. The difference between these two treatments was also significant. IRR was 1.24 when comparing suppression by npX with pXS and that by basic copper sulfate wettable powder; thus, their control was comparable. The combination of npX with pXS improved the preventive effect against black rot. This is the first report describing that a nonpathogenic Xanthomonas sp. strain mixed with a bacteriophage effectively controlled black rot of broccoli in field trials.  相似文献   

11.
Hydrogen sulfide (H2S) is known to be an important signalling molecule in both animals and plants, despite its toxic nature. In plants it has been seen to control stomatal apertures, so altering the ability of bacteria to invade plant tissues. Bacteria are known to generate H2S as well as being exposed to plant-generated H2S. During their interaction with plants pathogenic bacteria are known to undergo alterations to their genomic complement. For example Pseudomonas syringae pv. phaseolicola (Pph) strain 1302A undergoes loss of a section of DNA known as a genomic island (PPHGI-1) when exposed to the plants resistance response. Loss of PPHGI-1 from Pph 1302A enables the pathogen to overcome the plants resistance response and cause disease. Here, with the use of H2S donor molecules, changes induced in Pph 1302A genome, as demonstrated by excision of PPHGI-1, were investigated. Pph 1302A cells were found to be resistant to low concentrations of H2S. However, at sub-lethal H2S concentrations an increase in the expression of the PPHGI-1 encoded integrase gene (xerC), which is responsible for island excision, and a subsequent increase in the presence of the circular form of PPHGI-1 were detected. This suggests that H2S is able to initiate excision of PPHGI-1 from the Pph genome. Therefore, H2S that may emanate from the plant has an effect on the genome structure of invading bacteria and their ability to cause disease in plants. Modulation of such plant signals may be a way to increase plant defence responses for crops in the future.  相似文献   

12.
Infection by Pyrenophora teres f. teres (Ptt) or P. teres f. maculata (Ptm), the causal agents of the net and spot forms of net blotch of barley, respectively, can result in significant yield losses. The genetic structure of a collection of 128 Ptt and 92 Ptm isolates from the western Canadian provinces of Alberta (55 Ptt, 27 Ptm), Saskatchewan (58 Ptt, 46 Ptm) and Manitoba (15 Ptt, 19 Ptm) were analyzed by simple sequence repeat (SSR) marker analysis. Thirteen SSR loci were examined and found to be polymorphic within both Ptt and Ptm populations. In total, 110 distinct alleles were identified, with 19 of these shared between Ptt and Ptm, 75 specific to Ptt, and 16 specific to Ptm. Genotypic diversity was relatively high, with a clonal fraction of approximately 10 % within Ptt and Ptm populations. Significant genetic differentiation (PhiPT = 0.230, P = 0.001) was found among all populations; 77 % of genetic variation occurred within populations and 23 % between populations. Lower, but still significant genetic differentiation (PhiPT = 0.038, P = 0.001) was detected in Ptt, with 96 % of genetic variation occurring within populations. No significant genetic differentiation (PhiPT = 0.010, P = 0.177) was observed among Ptm populations. Isolates clustered in two distinct groups conforming to Ptt or Ptm, with no intermediate cluster. The high number of haplotypes observed, combined with an equal mating type ratio for both forms of the fungus, suggests that P. teres goes through regular cycles of sexual recombination in western Canada.  相似文献   

13.
In order to provide an alternative for controlling bacterial canker of kiwifruit, caused by Pseudomonas syringae pv. actinidiae, in case of the appearance of copper/antibiotic-resistant strains of the pathogen, the field efficacy of a chitosan-based compound was compared with a copper compound on Actinidia deliciosa cv. Hayward. The 3-year trials were carried out in central Italy, in an area heavily affected by the disease. Both compounds were sprayed on the same day according to the following schedule: every 14 days, from early April to early June (a total of seven treatments), and once a month, from mid November to mid February (a total of four treatments). Chitosan did not incite any phytotoxic effect on plant and fruit and showed an overall higher level of performance than the copper compound in reducing disease symptoms throughout the 3-year trials. Chitosan significantly reduced also the presence of exudates on trunk and leader recorded at the end of winter.  相似文献   

14.
Leaf spots on spinach were found in three greenhouses in Hokkaido and Iwate, Japan, in 2011–2012. Three isolates obtained from the lesions were classified into Stemphylium sp. Subgroups C2 and E3, based on morphology and molecular analyses. We compared the three isolates with two reference isolates belonging to Subgroup C2 from Welsh onion and leek in terms of pathogenicity. All five isolates caused leaf spot symptoms on spinach and leaf blight on Welsh onion in inoculation tests. This is the first report of spinach leaf spot caused by Stemphylium sp. Subgroups C2 and E3.  相似文献   

15.
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16.
Whole genome sequencing of a copper resistant (CuR) black rot strain of Xanthomonas campestris pv. campestris (Xcc) isolated from a broccoli plant in Trinidad revealed a unique operon for copper resistance. The cop genes of strain Xcc-BrA1 were determined to be present on a 160 to 180 kb plasmid shown to be non-conjugative with other xanthomonads. While nucleotide comparison of a putative 8.0 Kbp copLABMGF gene cluster identified in Xcc-BrA1 genome did not reveal any homologous region with other known CuR Xanthomonas strains from diverse origins, the comparison of the translated amino acid sequence indicated similarity with X. citri, X. c. pv. citrumelonis and X. vesicatoria Cop proteins. Cloning of the copLAB gene cluster from Xcc-BrA1 conferred copper resistance to other copper-sensitive xanthomonads. Although Xcc-BrA1 harbors copLAB genes with similar sizes and organization and is able to grow on Cu-amended medium as other CuR xanthomonads, the phylogenetic analysis of nucleotide sequences indicates that the cop cluster in Xcc-BrA1 is unique and distantly related to other copLAB genes from Xanthomonas and Stenotrophomonas. The origin of copper resistance genes in Xcc-BrA1 is likely a result of horizontal gene acquisition from a still unknown phylloplane cohabitant. The findings of this study have implications for the management of crop diseases caused by CuR xanthomonads. Future studies could focus on and determining the distribution, overall importance and appropriate control measures for strains harbouring these unique genes.  相似文献   

17.
The genus Puccinia represents rust infections, which are responsible for great productivity losses in crops of commercial and ornamental plants worldwide. This work is aimed at determining the occurrence of Puccinia spp. spores in Madeira Island in order to infer the exposure risks from a phytopathological point of view. A phytopathological analysis was performed in 203 local plant samples between January 2003 and December 2012. During the same period the airborne concentrations of rust spores were monitored following well-established guidelines. Aerobiological data was compared with meteorological records. Based on macro and microscopic analyses, five species of rusts were identified: P. horiana, P. buxi, P. porri, P. pelargonii-zonalis, and P. sorghi, and they were found mostly in spring and summer. A total of 20 samples out of 203 analysed plants (9.8%), were infected with Puccinia spores, i.e., P. horiana (5.9%), P. buxi (1.47%), P. porri and P. pelargonii-zonalis (0.98%), and P. sorghi (0.5%). During the studied period Puccinia spores attained an annual average concentration of 126 spores m?3 and most of them were recorded between March and October. Meteorological factors were determinant in fluctuations in spore concentration. Relative humidity was the parameter that favoured the biggest release and dispersal of the rust spores, whereas rainfall revealed a significant negative effect. Rusts do not represent an important plant pathogen in Madeira Island, as shown by the low infection frequencies and levels of airborne spore concentrations.  相似文献   

18.
Plant volatile compounds, including terpenes, are known to be involved in the rice defense system. In the present analysis of a terpene synthase, OsTPS18, in rice, we found that OsTPS18 was localized in the cytoplasm and synthesized the sesquiterpenes (E)-nerolidol and (E)-β-farnesene. The amounts of (E)-nerolidol and (E)-β-farnesene increased after jasmonic acid (JA) treatment. (E)-Nerolidol had significant antibacterial activity against Xanthomonas oryzae pv. oryzae (Xoo). These results suggest that (E)-nerolidol plays an important role in JA-induced resistance against Xoo and that it functions as an antibacterial compound in rice.  相似文献   

19.
Bacterial blight (BB) of rice caused by Xanthomonas oryzae pv. oryzae (Xoo), remains a major production constraint in rice cultivation especially in irrigated and rainfed lowland ecosystems in India. The pathogen is highly dynamic in nature and knowledge on pathotype composition among the Xoo population is imperative for designing a scientific resistance breeding program. In this study, four hundred isolates of Xoo collected from diverse rice growing regions of India were analyzed for their virulence and genetic composition. Virulence profiling was carried out on a set of differentials consisting of 22 near isogenic lines (NILs) of IR24 possessing different BB resistance genes and their combinations along with the checks. It was observed that different NILs possessing single BB resistance gene were susceptible to about 59–94% of the Xoo isolates except IRBB 13 (containing BB resistance gene xa13), which showed susceptibility to about 35% of the isolates. Based on the reaction of the Xoo isolates on the differentials, they were categorized into 22 pathotypes. Among the 22 pathotypes, IXoPt-1 and IXoPt-2 were least virulent and IXoPt # 18–22 were highly virulent. Pathotype IXoPt-19 which was virulent on all single BB resistance genes except xa13 constituted the major pathotype (22.5% isolates) and was widely distributed throughout India (16 states). This was followed by pathotype IXoPt-22 (17.25%) which was virulent on all the NILs possessing single BB resistance genes. Molecular analysis was carried out using two outwardly directed primers complementary to sequence of IS1112, a repetitive element of Xoo. A high level of genetic polymorphism was detected among these isolates and the isolates were grouped into 12 major clusters. The data indicated complex nature of evolution of the Xoo pathotypes and there was no strong correlation between pathotypes and genetic clusters as each genetic cluster was composed of Xoo isolates belonging to different pathotypes. The study indicated that none of the single BB resistance genes can provide broad spectrum resistance in India. However, two-gene combinations like xa5 + xa13 and different 3 or 4 genes combination like Xa4 + xa5 + xa13, Xa4 + xa13 + Xa21, xa5 + xa13 + Xa21 and Xa4 + xa5 + xa13 + Xa21 are broadly effective throughout India.  相似文献   

20.
Pinewood nematode (PWN), Bursaphelenchus xylophilus, the causal agent of pine wilt disease (PWD), was detected in Spain in 2008. This gives rise to serious concern, as the disease has caused severe environmental and economic losses in Portugal and in Asian countries. We studied interspecific variation in susceptibility to pine wilt disease and differences in constitutive chemical compounds in the xylem tissue of the seven pine species -P. canariensis, P. halepensis, P. pinaster, P. pinea, P. sylvestris, P. radiata and P. taeda. Two-year-old trees were inoculated with B. xylophilus. Water potential and nematode densities were measured for each species on specific dates; whereas, wilting symptoms were recorded weekly until the end of the assay. Chemical compounds in the xylem were determined prior to inoculation. Three different resistance groups can be established in terms of the pine species susceptibility to PWN: non- to slightly-susceptible (P. canariensis, P. halepensis, P. taeda and P. pinea), susceptible (P. pinaster and P. radiata), and highly-susceptible (P. sylvestris). Nematodes migrated downward to the roots in all seven species. Constitutive xylem nitrogen, total polyphenols, and marginally phosphorus were negatively correlated with mortality caused by PWN. The most susceptible species, Pinus sylvestris, presented high levels of constitutive lipid-soluble substances and low levels of manganese, pointing to a possible relation between these components and PWN susceptibility. The results suggest P. sylvestris, P. pinaster and P. radiata forests could be severely damaged by PWN in Spain and highlight how constitutive chemical compounds such as nitrogen might play a role in resistance mechanisms against PWN.  相似文献   

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