Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Pectobacterium parvum sp. nov., having a salmonella SPI-1-like type iii secretion system and low virulence
    Pasanen, Miia ; Waleron, Malgorzata ; Schott, Thomas ; Cleenwerck, Ilse ; Misztak, Agnieszka ; Waleron, Krzysztof ; Pritchard, Leighton ; Bakr, Ramadan ; Degefu, Yeshitila ; Wolf, Jan van der; Vandamme, Peter ; Pirhonen, Minna - \ 2020
    International Journal of Systematic and Evolutionary Microbiology 70 (2020)4. - ISSN 1466-5026 - 1 p.

    There was an error in the Supplementary Material of the published article. Supplementary Table 8 entitled ‘Genome comparisons with GET_HOMOLOGUES. Unique genes identified in P. parvum/P. polaris isolates’ was previously missing from the published Supplementary Material file. Supplementary Table 8 is available with the online version of this article. The author apologizes for any inconvenience caused.

    Pectobacterium parvum sp. nov., having a Salmonella SPI-1-like Type III secretion system and low virulence
    Pasanen, M. ; Waleron, M. ; Schott, Thomas ; Cleenwerck, I. ; Misztak, Agieszka ; Waleron, Krzysztof ; Pritchard, L. ; Bakr, Ramadan ; Degefu, Yeshtila ; Wolf, J.M. van der; Vandamme, Peter ; Pirhonen, M. - \ 2020
    International Journal of Systematic and Evolutionary Microbiology 70 (2020)4. - ISSN 1466-5026 - p. 2440 - 2448.
    Pectobacterium - Pectobacterium parvum - Salmonella SPI-1 T3SS - potato - soft rot - virulence
    Pectobacterium strains isolated from potato stems in Finland, Poland and the Netherlands were subjected to polyphasic analyses to characterize their genomic and phenotypic features. Phylogenetic analysis based on 382 core proteins showed that the isolates clustered closest to Pectobacterium polaris but could be divided into two clades. Average nucleotide identity (ANI) analysis revealed that the isolates in one of the clades included the P. polaris type strain, whereas the second clade was at the border of the species P. polaris with a 96 % ANI value. In silico genome-to-genome comparisons between the isolates revealed values below 70%, patristic distances based on 1294 core proteins were at the level observed between closely related Pectobacterium species, and the two groups of bacteria differed in genome size, G+C content and results of amplified fragment length polymorphism and Biolog analyses. Comparisons between the genomes revealed that the isolates of the atypical group contained SPI-1-type Type III secretion island and genes coding for proteins known for toxic effects on nematodes or insects, and lacked many genes coding for previously characterized virulence determinants affecting rotting of plant tissue by soft rot bacteria. Furthermore, the atypical isolates could be differentiated from P. polaris by their low virulence, production of antibacterial metabolites and a citrate-negative phenotype. Based on the results of a polyphasic approach including genome-to-genome comparisons, biochemical and virulence assays, presented in this report, we propose delineation of the atypical isolates as a novel species Pectobacterium parvum, for which the isolate s0421T (CFBP 8630T=LMG 30828T) is suggested as a type strain.
    Assessment of Dickeya and Pectobacterium spp. on vegetables and ornamentals (Soft rot)
    Wolf, J.M. van der; Bergsma-Vlami, M. ; Saddler, G. ; Hélias, V. ; Tsror, L. ; Yedida, Iris ; Pirhonen, M. ; Degefu, Yeshtila ; Tuomisto, J.T. ; Lojkowska, Ewa ; Li, Sean - \ 2020
    Zenodo - 109 p.
    Euphresco - Plant health - Dickeya - Pectobacterium - soft rot - vegetables - ornamentals - diagnostics - surveys - epidemiology - management
    Dickeya and Pectobacterium belonging to the group of soft rot Pectobacteriaceae (SRP) are causing emerging problems in a wide range of vegetable and ornamental crops in Europe, including potato, carrot, cabbage, Chinese cabbage, celery, leek, pepper, parsley, Zantedeschia, hyacinth, Dahlia, Chrysanthemum, Philodendron, Freesia, Saintpaulia, Iris, Aglaonema, Crocus, Campanula and Phalaenopsis. The phytopathogens in both genera are genetically and phenotypically highly diverse. Disease problems in the different hosts are associated with the introduction of new variants or by spread of groups already present in Europe. Within this Euphresco project we aimed to identify and assess the risks of these new variants, and to develop management strategies, including reliable diagnostic methods to prevent introductions and further spread of SRP. To reach our goals, meetings were organized and collaborations were established with specialists worldwide. All information on meetings, protocols and activities of the Euphresco group are published on the Dickeya/Pectobacterium website, conveyed by the James Hutton Institute in Invergowrie (Scotland) (, contact person Dr I. Toth/Dr J. Fairly).

    During the project, 1.5 days meetings were held in 2015 in Gdansk (Poland), in 2016 in Helsinki (Finland), in 2017 in Edinburgh (Scotland) and in 2018 in Emmeloord (The Netherlands). Meetings were attended by an average of 30 participants from organizations in EU member states, North- and Latin America, Africa, Asia and Australia.

    One project’s objective was to develop methods for the detection and identification of Pectobacterium and Dickeya species in different matrices. For this, a panel of reference strains has been compiled for Dickeya and Pectobacterium species. Most strains have been deposited in international collections. For most strains also whole genome sequence data are available. During the course of this project, several diagnostic tests were developed and evaluated, often based on the TaqMan technology.

    In several countries, surveys in potato and ornamental crops were conducted, but also in other matrices of the potato ecosystem, including water used for irrigation. In addition, new taxonomic groups that have been identified, are now new species including: P. versatile, P. aquaticum, P. fontis and P. polonicum. In potato, P. brasiliense became dominant as blackleg causing organism and has largely outcompeted D. solani in the last five years. In surface water in Europe, D. zeae was found to be the dominant SRP. In other continents, serious outbreaks of potato blackleg with other SRP has been reported, such as D. dianthicola in the USA and Australia. Various new SRP have been described, namely P. punjabense, P. peruviense, P. polaris, D. lacustris and D. zantedeschia. For the first time, D. fangzhongdai was described in Phalaenopsis. Not all species can cause potato blackleg.

    Studies on various virulence factors were conducted for SRP, such as on chemoreceptors, small phenolic plant compounds interacting with signal molecules of Pectobacterium involved in the quorum sensing mechanism of the pathogen. A Tn-seq approach was developed and used to identify new virulence factors.

    Information was exchanged on disease management strategies which include cultivation practices, resistance breeding, hygiene and the use of (bio-) control agents. A strict hygiene and an intensive monitoring of seed lots was found to be associated with a significant reduction of infections with blackleg causing SRP. A phage therapy has been developed to protect (seed) potato tubers against soft rot during storage. Various bacteriophages and bacterial antagonists were characterized and some evaluated for control of potato soft rot and/or blackleg. Steam treatments for seed tubers were found to decrease the blackleg incidence. Cold plasma treatment was found to kill SRP grown in vitro. Similarly, stabilized silver nanostructures killed SRP. It was found that seed potato lots can differ in suppressiveness against D. solani. Indications were found that the microbiome in tuber tissue plays a role in this.
    Biological control of potato soft rot caused by Dickeya solani and the survival of bacterial antagonists under cold storage conditions
    Hadizadeh, I. ; Peivastegan, B. ; Hannukkala, A. ; Wolf, J.M. van der; Nissinen, R. ; Pirhonen, M. - \ 2018
    Plant Pathology 68 (2018)2. - ISSN 0032-0862 - p. 297 - 311.
    Dickeya and Pectobacterium are responsible for causing blackleg of plants and soft rot of tubers in storage and in the field, giving rise to losses in seed potato production. In an attempt to improve potato health, biocontrol activity of known and putative antagonists was screened using in vitro and in planta assays, followed by analysis of their persistence at various storage temperatures. Most antagonists had low survival on potato tuber surfaces at 4 °C. The population dynamics of the best low‐temperature tolerant strain and also the most efficient antagonist, Serratia plymuthica A30, along with Dickeya solani as target pathogen, was studied with TaqMan real‐time PCR throughout the storage period. Tubers of three potato cultivars were treated in the autumn with the antagonist and then inoculated with D. solani. Although the cell densities of both strains decreased during the storage period in inoculated tubers, the pathogen population was always lower in the presence of the antagonist. The treated tubers were planted in the field the following growing season to evaluate the efficiency of the bacterial antagonist for controlling disease incidence. The potato endophyte S. plymuthica A30 protected potato plants by reducing blackleg development on average by 58.5% and transmission to tuber progeny as latent infection by 47–75%. These results suggest that treatment of potato tubers with biocontrol agents after harvest can reduce the severity of soft rot disease during storage and affect the transmission of soft rot bacteria from mother tubers to progeny tubers during field cultivation.
    Dickeya solani sp. nov., a pectinolytic plant pathogenic bacterium isolated from potato (Solanum tuberosum)
    Wolf, J.M. van der; Nijhuis, E.H. ; Kowalewska, M.J. ; Saddler, G.S. ; Parkinson, N. ; Elphinstone, J.G. ; Pritchard, L. ; Toth, I.K. ; Lojkowska, E. ; Potrykus, M. ; Waleron, M. ; Vos, P. de; Cleenwerck, I. ; Pirhonen, M. ; Garlant, L. ; Hélias, V. ; Pothier, J.F. ; Pflüger, V. ; Duffy, B. ; Tsror, L. ; Manulis, S. - \ 2014
    International Journal of Systematic and Evolutionary Microbiology 64 (2014)Pt. 3. - ISSN 1466-5026 - p. 768 - 774.
    strains - identification - pseudomallei - chrysanthemi - relatedness - clonality - mallei - clade - genus
    Pectinolytic bacteria were recently isolated from diseased potato plants exhibiting blackleg and slow wilt symptoms found in a number of European countries and Israel. These Gram-negative, motile, rods were identified as belonging to the genus Dickeya, previously the Pectobacterium chrysanthemi complex (Erwinia chrysanthemi), on the basis of a positive PCR reaction with pelADE primers, 16S rDNA sequence analyis, fatty acid methyl esterase analysis, the production of phosphatases and the ability to produce indole and acids from a-methyl glucoside. Differential physiological assays used previously to differentiate between strains of E. chrysanthemi, showed that these isolates belonged to biovar 3. Eight of the isolates, seven from potato and one from hyacinth, were analysed together with 21 reference strains representing all currently recognised taxa within the genus Dickeya. The new isolates formed a distinct genetic clade in multilocus sequence analysis (MLSA) using concatenated sequences of the intergenic spacer (IGS), as well as genes dnaX, recA, dnaN, fusA, gapA, purA, rplB, rpoS and gyrA. Characterization by whole-cell MALDI-TOF mass spectrometry, pulsed field gel electrophoresis after digestion of whole genome DNA with rare cutting restriction enzymes, average nucleotide identity analysis and DNA-DNA hybridization studies, showed that although related to D. dadantii, these isolates represent a novel species within the genus Dickeya, for which the name Dickeya solani sp. nov. (type strain IPO 2222T =LMG25993T =NCPPB4479T) is proposed
    Characterisation of Pectobacterium wasabiae and Pectobacterium carotovorum subsp. carotovorum isolates from diseased potato plants in Finland
    Pasanen, M. ; Laurila, J. ; Brader, G. ; Palva, E.T. ; Ahola, V. ; Wolf, J.M. van der; Hannukkala, A. ; Pirhonen, M. - \ 2013
    Annals of Applied Biology 163 (2013)3. - ISSN 0003-4746 - p. 403 - 419.
    soft-rot erwiniae - dna-sequences - sp-nov. - strains - virulence - diversity - blackleg - dickeya - identification - chrysanthemi
    To identify bacteria causing soft rot and blackleg in potato in Finland, pectinolytic enterobacteria were isolated from diseased potato stems and tubers. In addition to isolates identified as Pectobacterium atrosepticum and Dickeya sp., many of the isolated strains were identified as Pectobacterium carotovorum subsp. carotovorum. Phylogenetic analysis and biochemical tests indicated that one of the isolates from potato stems resembled Pectobacterium wasabiae. Furthermore, two blackleg-causing P. carotovorum strains recently isolated in Europe clustered with P. wasabiae, suggesting that at least some of these isolates were originally misidentified. All the other Finnish P. carotovorum isolates resembled the subsp. carotovorum type strain in biochemical tests but could be clustered into two distinct groups in the phylogenetic analysis. One of the groups mainly contained strains isolated from diseased tubers, whereas the other mainly included isolates from potato stems. In contrast to the tuber isolates, the stem isolates lacked genes in Type III secretion genes, were not able to elicit a hypersensitive response in tobacco leaves and produced only small amounts of autoinducers in the stationary phase in vitro. P. wasabiae isolate was able to cause similar amount of blackleg-like symptoms as P. atrosepticum in a field experiment with vacuum-infiltrated tubers, whereas both P. atrosepticum and P. carotovorum isolates reduced emergence and delayed growth more than P. wasabiae. Our findings confirm the presence of P. wasabiae in Finland and show that the Finnish P. carotovorum subsp. carotovorum isolates can be divided into two groups with specific characteristics and possibly also different ecologies
    Dickeya species: an emerging problem for potato production in Europe
    Toth, I.K. ; Wolf, J.M. van der; Saddler, G. ; Lojkowska, E. ; Hélias, V. ; Pirhonen, M. ; Tsror, L. ; Elphinstone, J.G. - \ 2011
    Plant Pathology 60 (2011)3. - ISSN 0032-0862 - p. 385 - 399.
    soft-rot erwinias - carotovora subsp atroseptica - polymerase-chain-reaction - biovar 3 - temperature tolerances - rapid identification - chrysanthemi strains - pectate medium - 1st report - pcr
    Dickeya species (formerly Erwinia chrysanthemi) cause diseases on numerous crop and ornamental plants world-wide. Dickeya spp. (probably D. dianthicola) were first reported on potato in the Netherlands in the 1970s and have since been detected in many other European countries. However, since 2004–5 a new pathogen, with the proposed name ‘D. solani’, has been spreading across Europe via trade in seed tubers and is causing increasing economic losses. Although disease symptoms are often indistinguishable from those of the more established blackleg pathogen Pectobacterium spp., Dickeya spp. can initiate disease from lower inoculum levels, have a greater ability to spread through the plant’s vascular tissue, are considerably more aggressive, and have higher optimal temperatures for disease development (the latter potentially leading to increased disease problems as Europe’s climate warms). However, they also appear to be less hardy than Pectobacterium spp. in soil and other environments outside the plant. Scotland is currently the only country in Europe to enforce zero tolerance for Dickeya spp. in its potato crop in an attempt to keep its seed tuber industry free from disease. However, there are a number of other ways to control the disease, including seed tuber certification, on-farm methods and the use of diagnostics. For diagnostics, new genomics-based approaches are now being employed to develop D. dianthicola- and ‘D. solani’-specific PCR-based tests for rapid detection and identification. It is hoped that these diagnostics, together with other aspects of ongoing research, will provide invaluable tools and information for controlling this serious threat to potato production
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