Pseudomonas syringae pv. syringae on pepper seedlings in Italy

Pseudomonas syringae pv. syringae causing leaf spot on pepper seedlings grown in a plant bed is reported in Italy for the first time. The pathogen was identified by means of biochemical, physiological and pathogenicity tests as well as by SDS-polyacrylamide gel electrophoresis of whole-cell proteins. The bacterial isolates showed positive for ice nucleation and biocide production.     

Comparison of ethylene-producing Pseudomonas syringae strains isolated from kudzu (Pueraria lobata) with Pseudomonas syringae pv. phaseolicola and Pseudomonas syringae pv. glycinea

The relationships among strains of Pseudomonas syringae pv. glycinea (Psg) and Pseudomonas syringae pv. phaseolicola (Psp) isolated from kudzu ( Pueraria lobata) and bean ( Phaseolus vulgaris) were investigated. All strains tested showed a close phenotypic similarity, with the exception of the utilization of inositol and mannitol as well as the production of toxins. On this basis the strains could be divided into three groups. Group 1 consists of all strains of pathovar glycinea, group 2 includes all Psp strains isolated from kudzu, and all Psp strains isolated from bean belong to group 3. This grouping was also reflected in the genetic fingerprints using the polymerase chain reaction (PCR) with primers that anneal to dispersed repetitive bacterial sequences (rep-PCR). The rep-PCR generated fingerprints were unique for each of the three groups. The strains of group 2, Psp strains isolated from kudzu, possess certain characteristics of group 1 (ethylene production) and group 2 (phaseolotoxin production). The Psp strains from kudzu can be clearly differentiated from Psp strains isolated from bean. They utilize mannitol, produce ethylene, and are strongly pathogenic to kudzu, bean, and soybean. The results obtained show that the Psp strains from kudzu should be separated from the pathovar phaseolicola and should represent their own pathovar.     

Relationships between populations of Pseudomonas syringae pv. persicae determined by restriction fragment analysis

Pseudomonas syringae pv. persicae , the pathogen causing bacterial decline of stone-fruit, was first noted almost simultaneously in France and in New Zealand, together with a closely related pathogen from myrobalan plum in England. The relative similarity of 31 strains from these three countries was examined by comparing DNA restriction endonuclease fragment patterns. Fragment patterns produced from digested DNA samples which were electrophoresed on polyacrylamide gels and visualized by silver-staining, were analysed using the software package Gelcompar. The fragment patterns produced by strains from France and England formed homogeneous but separate groups, while those from New Zealand were relatively heterogeneous. This finding suggests that the New Zealand population of P.s. persicae is older than those found in Europe. Problems in explaining the distribution of the pathogen are discussed.     

Specificity of polyclonal antibodies to different antigenic preparations of Pseudomonas syringae pv. pisi strain UQM551 and Pseudomonas syringae pv. syringae strain L

Polyclonal antibodies were produced against sonicated and heat-killed cells of Pseudomonas syringae pv. pisi strain UQM551 and Pseudomonas syringae pv. syringae strain L, and their specificities were compared. Evidence is presented that the serological specificity between these two pathovars lies in surface antigens. Of the surface antigens purified and tested, only flagella and lipopolysaccharide from the cell wall showed no cross-reactivity with heterologous antisera. Antisera to glutaraldehyde-fixed flagella of the two strains showed a high level of specificity. At a species or genus level, antisera prepared from heat-killed cells of P. syringae distinguished this species from all other bacterial species and genera tested, including strains of Pseudomonas fluorescens, Escherichia coli, Agrobacterium and Rhizobium.     

Occurrence of Pseudomonas syringae pv. actinidiae on kiwifruit in Italy

Pseudomonas syringae pv. actinidiae has been isolated from kiwifruit plants for the first time in Italy. Biochemical tests were consistent with those characterizing the type-strain; pathogenicity tests yielded severe blights in the inoculated kiwifruit plants and no symptoms on lilac, pear and peach. Nutritional tests as well as whole-cell protein profiles revealed slight differences between the strains isolated in Japan and those of the present study. The main symptoms observed in the field are a red-rusty exudation covering the bark of twigs and trunks, blight of young canes and plants, angular leaf spots surrounded by chlorotic haloes and tiny cankers along the twigs.     

Induction of pear blossom blast caused by Pseudomonas syringae pv. syringae

Conditions were established for inducing pear blossom blast caused by Pseudomonas syringae pv. syringae on both attached and detached shoots. The incidence of blossom blast was proportional to the logarithm of the P.s. pv. syringae population under optimal temperature, moisture, and bloom developmental stage. Highest incidence of blossom infection followed occurrence of a major exotherm (an increase in temperature caused by the heat of fusion from ice formation within blossom tissue) in the presence of P. s. pv. syringae. The exotherm was detected inside ovary tissue at temperatures ranging from –1.8 to –3.5 C. Wetness duration following the thawing process was less important than wetness during and immediately after the freeze event. Blossoms inoculated, then air-dried or removed from low-temperature treatment prior to occurrence of an exotherm, had a low incidence of infection, The full bloom stage of blossom development was more susceptible to blossom blast than either the open cluster or tight cluster stages of development.     

Bacterial inflorescence rot of grapevine caused by Pseudomonas syringae pv. syringae

Molecular sequencing (rpoB) and standard pathological and microbiological methods identified Pseudomonas syringae pv. syringae (Pss) as the causal agent of bacterial inflorescence rot of grapevines (Vitis vinifera) in three vineyards in Tumbarumba, NSW, Australia in 2006 and 2007. Pss strains from shrivelled berries and necrotic inflorescences of diseased grapevines were used to inoculate leaves and inflorescences of potted cv. Semillon grapevines. Pss caused disease symptoms similar to those experienced in the field, including angular leaf lesions, longitudinal lesions in shoot tissues and rotting of inflorescences from before flowering until shortly after fruit set. High humidity promoted symptom severity. The necrotic bunch stem and leaf lesions were susceptible to the development of Botrytis cinerea infections. Cryo‐scanning electron microscopy (cryoSEM) indicated that Pss entered leaves and inflorescence tissues via distorted, open, raised stomata surrounded by folds of tissue that appeared as ‘star‐shaped’ callose‐rich complexes when viewed by UV light microscopy. In necrotic tissues, cryoSEM revealed Pss within petiole parenchyma cells and air‐filled rachis xylem vessels. This is the first report of inflorescence and hence fruit loss caused by Pss in grapevines. The disease is described as ‘bacterial inflorescence rot’ and regarded as one that expands the previously reported pathology of grapevines caused by P. syringae. This study also indicated that infection by Pss might promote destructive B. cinerea infections when the fungus is already present but latent, although further experimentation is needed to prove such an interaction.     

Similarity between Copper Resistance Genes from Pseudomonas syringae pv. actinidiae and P. syringae pv. tomato

Twenty-eight strains of Pseudomonas syringae pv. actinidiae isolated in 1984, 1987 and 1988 from kiwifruit orchards in Japan were tested for their resistance to copper sulfate. All strains isolated in 1984 were copper sensitive with a minimum inhibitory concentration (MIC) of cupric sulfate of 0.75 mM. However, some strains isolated in 1987 and 1988 were resistant, with the MIC ranging from 2.25 to 3.0 mM. All copper-resistant strains contained at least one of two plasmids, pPaCul (about 70.5 kb) or pPaCu2 (about 280 kb), or both. In a copper-resistant strain Pa429, the location of the copper-resistance gene(s) was examined by insertional inactivation with Tn5. The MIC of copper sulfate in the copper-sensitive mutant obtained by Tn5 tagging decreased from 2.75 to 0.75 mM. The 14.5 kb BamHI fragment, designated pPaCuB14, containing the same locus mutagenized with Tn5 was cloned from pPaCu1. However, pPaCuB14 did not confer copper resistance in the transformant of copper-sensitive strain Pa21R, suggesting that this clone did not contain a full set of copper-resistance gene(s). Then a cosmid library of pPaCu1 was constructed and six cosmid clones hybridized with pPaCuB14 were selected. One of the six cosmids, designated pPaCuC1, conferred a near wild-type level of copper resistance in the transformant of the copper-sensitive strain. pPaCuC1 had a homologous region that hybridized with all of the PCR-amplifled fragments of copA, copB, copR, and copS genes of P. syringae pv. tomato. DNA sequence analysis of the homologous region revealed the existence of four open reading frames (ORF A, B, R and S) oriented in the same direction. The predicted amino acid sequences of ORF A, B, R and S had 80, 70, 97 and 95% identity with CopA, B, R and S of P. syringae pv. tomato, respectively. Received 5 July 2001/ Accepted in revised form 27 September 2001     

猕猴桃溃疡病菌在中国的适生性分析

通过分析猕猴桃溃疡病菌在中国的适生性,为科学制定有效的检疫监管措施,防范其入侵和扩散,确保猕猴桃产业健康发展提供理论依据。本研究根据前人研究结果,采用模糊数学综合评判的原理和方法,定量分析猕猴桃细菌性溃疡病菌(Pseudomonas syringae pv.actinidiae)在我国各个地区的适生性。猕猴桃溃疡病菌在我国最适宜的省份主要分布在四川、云南、贵州、福建、安徽、湖南、湖北、河南、江西、陕西、浙江、重庆、西藏。鉴于该病具有发生发展迅速,危害性强,防治难度大等特点,应当加强猕猴桃种苗等繁殖材料的检疫,加强对果园的管理和病害监测,积极采取有效的防治措施并加强抗病育种方面的研究。     

Syringopeptins, Pseudomonas syringae pv. syringae phytotoxins, resemble syringomycin in closing stomata

The recent finding that syringomycin (SR) and syringotoxin (ST)-producing isolates of Pseudomonas syringae pv. syringae also synthesize syringopeptins (SPs), another class of phytotoxic lipodepsipeptides, prompted studies of the biological properties and comparisons of the activities of the two groups of metabolites. The present paper reports the effects of two forms of SP on stomatal movement in detached leaves of Xanthium strumarium and in epidermal strips of Vicia faba and shows that these phytotoxins, as does the previously investigated SR, promote stomatal closure. SPs are at least 10-fold more efficient than SR in both tissues. In epidermal strips, the toxin-induced closure was not reversed by fusicoccin, a fungal metabolite that reversed the closing effects of abscisic acid. As reported in previous papers, these amphiphilic toxins affect several functions of biological membranes. A marked decrease in the rate of photosynthesis recorded in X. strumarium leaves treated with SPs is consistent with effects on biological membranes.     

菜豆晕疫病菌的检测技术研究

通过选择性培养基的筛选,利用菜豆萎蔫毒素基因序列扩增引物和菜豆萎蔫毒素基因缺失菌株独有的ORF6序列的扩增引物,采用双重PCR技术实现了菜豆晕疫病菌的快速检测。     

上海地区大豆细菌性疫病发生危害与防治

大豆细菌性疫病又称大豆细菌性斑点病[Pseu-domonas syringaepv.glycinea(Coerper)Young,Dye&Wilkie],是我国和世界大豆产区主要病害,导致大豆产量损失和品质下降。据报道,在适宜发病条件下此病可使大豆减产18%~22%,一般减产20%左右,最高达50%以上。近年来,随着上海地区菜用大豆种植面积的不断扩大,发生了大豆细菌性疫病。为防治该病进行了田间流行调查和发生特点观测。1病害发生情况2002~2004年,对上海郊区的大豆种植地进行了调查,根据大豆细菌性疫病危害程度进行病级标准划分。0级:无症;1级:复叶上有1~5个病斑;2级:复叶上有6~10个病斑;3…     

Effects of para-aminobenzoic acid on bacterial speck symptom development and Pseudomonas syringae pv. tomato populations in tomato leaves

Para-aminobenzoic (PABA) is reported to induce resistance against a range of plant pathogens in different crops in a salicylic acid-dependent manner. However, factors affecting its efficacy are not well understood. Foliar PABA applications on tomato seedlings reduced lesion incidence caused by Pseudomonas syringae pv. tomato (Pst) in a dose-dependent manner in distal leaves up to 18 mM under controlled environment conditions, but only three out of six commercial processing tomato cultivars tested showed a response to PABA. Leaves in direct contact with 9 and 18 mM PABA of both PABA-responsive and PABA-nonresponsive cultivars showed phytotoxicity. In a PABA-responsive cultivar, one, two and three PABA applications were equally effective at reducing lesion incidence in distal leaves, but the duration of control only persisted for approximately 7 days. Although PABA application reduced lesion incidence in distal leaves, the Pst population in leaves was unaffected. Lesions on PABA-treated plants were larger than nontreated plants, and thus the proportion of leaf surface area with lesions was unaffected by PABA treatment. In in vitro assays, 18 and 72 mM PABA produced zones of inhibition against Pst 15 and 50% larger than the ethanol control, demonstrating direct antimicrobial effects of PABA. PABA application did not affect symptom development in a mixed infection of Pst or Xanthomonas spp. in one field experiment with a PABA-responsive cultivar. Further research is needed to understand why PABA was unsuccessful in the field before it is to be used as a practical disease management tool for foliar bacterial diseases of tomato.

     

Highly specific assays to detect isolates of Pseudomonas syringae pv. actinidiae biovar 3 and Pseudomonas syringae pv. actinidifoliorum directly from plant material

Pseudomonas syringae pv. actinidiae (Psa) is responsible for bacterial canker of kiwifruit. Biovar 3 of Psa (Psa3) has been causing widespread damage to yellow‐ and green‐fleshed kiwifruit (Actinidia spp.) cultivars in all the major kiwifruit‐producing countries in the world. In some areas, including New Zealand, P. syringae pv. actinidifoliorum (Pfm), another bacterial pathogen of kiwifruit, was initially classified as a low virulence biovar of Psa. Ability to rapidly distinguish between these pathovars is vital to the management of bacterial canker. Whole genome sequencing (WGS) data were used to develop PCR assays to specifically detect Psa3 and Pfm from field‐collected material without the need to culture bacteria. Genomic data from 36 strains of Psa, Pfm or related isolates enabled identification of areas of genomic variation suitable for primer design. The developed assays were tested on 147 non‐target bacterial species including strains likely to be found in kiwifruit orchards. A number of assays did not proceed because although they were able to discriminate between the different Psa biovars and Pfm, they also produced amplicons from other unrelated bacteria. This could have resulted in false positives from environmental samples, and demonstrates the care that is required when applying assays devised for pure cultures to field‐collected samples. The strategy described here for developing assays for distinguishing strains of closely related pathogens could be applied to other diseases with characteristics similar to Psa.     

Identification of Pseudomonas syringae pv. syringae causing bacterial leaf blight of Miscanthus sinensis

Journal of Plant Diseases and Protection - In the late summer of 2015, severe leaf blight occurred on Miscanthus sinensis grown on natural riverside lands of the Han River in Seoul, South Korea....