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.

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    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.
    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
    Potato Blackleg, remedies for a way out
    Wolf, J.M. van der; Kastelein, P. - \ 2013
    In: EAPR Pathology Section Meeting. - Bet-Dagan, Israel : Agricultural Research Organization - the Volcani Center, Israel - p. 20 - 20.
    Characterization of Dickeya strains isolated from potato grown under hot-climate conditions
    Tsror, L. ; Ben-Daniel, B. ; Chalupowicz, L. ; Wolf, J.M. van der; Lebiush, S. ; Erlich, O. ; Dror, O. ; Barel, V. ; Nijhuis, E.H. ; Manulis-Sasson, S. - \ 2013
    Plant Pathology 62 (2013)5. - ISSN 0032-0862 - p. 1097 - 1105.
    soft-rot erwinias - chrysanthemi - population - israel - crops - pcr
    Dickeya strains isolated in Israel in 2006–2010 were characterized by dnaX sequence analysis, pulsed-field gel electrophoresis (PFGE), biochemical assays and pectolytic activity, and found to be homogeneous: most of them could be classified as ‘Dickeya solani’. Of the 34 strains isolated from imported seed tubers or potato plants grown from imported seed, 32 were typed as ‘D. solani’ and only two were characterized as Dickeya dianthicola. Biovar typing indicated that all ‘D. solani’ strains were biovar 3. ‘Dickeya solani’ strains were most closely related to Dickeya dadantii subsp. dieffenbachiae according to PFGE and dnaX analyses and both species exhibited high pectolytic activity. Expression levels of two putative virulence genes, pelL (encoding a pectic enzyme) and dspE (encoding a type III effector) were significantly induced in ‘D. solani’ strains isolated from potato plants or tubers grown in hot climates such as the Negev region in Israel, compared to those isolated from seed tubers imported from the Netherlands, France or Germany. Results of this study support the hypothesis that ‘D. solani’ strains isolated in Israel are also clonal; however, they appear to be more virulent than strains isolated in Europe
    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
    First report of potato blackleg caused by a biovar 3 Dickeya sp. in Georgia
    Tsror, L. ; Erlich, O. ; Lebiush, S. ; Wolf, J.M. van der; Czajkowski, R.L. - \ 2011
    New Disease Reports 23 (2011). - ISSN 2044-0588 - 1 p.
    In Western and Northern Europe, Dickeya species are causing increasingly severe economic losses in potato (Solanum tuberosum) crops. The costs of seed potato production resulting from Dickeya spp. infection are high due to rejection and declassification of seed tubers (Slawiak et al., 2009). Potato blackleg caused by Dickeya spp. is primarily a seed tuber-borne disease (Tsror et al., 2009). Symptoms including blackening of the stem base, wilting of plants and rotten seed tubers are observed. Recently, outbreaks of potato blackleg were recorded in Georgia on three cultivars, in Samtskhe-Javakheti region, Akhalkalaki district, in an area in excess of 100 hectares
    First report of latent infection of Cyperus rotundus caused by a biovar 3 Dickeya sp. (Syn. Erwinia chrysanthemi) in Israel
    Tsror, L. ; Lebiush, S. ; Erlich, O. ; Ben-Daniel, B. ; Wolf, J.M. van der - \ 2010
    New Disease Reports 22 (2010). - ISSN 2044-0588 - 1 p.
    Recent outbreaks of potato blackleg in Israel, caused by Dickeya spp., on plants grown from seed tubers imported from Northern Europe, are of a great concern. The warm climatic conditions during the growing season favour disease expression, and may result in the establishment of the pathogen in the potato ecosystem and a spread to weeds and other crops (Tsror et al., 2009). Until recently, most of Dickeya spp. strains found in association with potato blackleg in Europe were characterised as D. dianthicola (biovars 1 or 7). These strains have a relatively lowgrowth temperature compared with other Dickeya spp. and seem to be more adapted to cool European climate conditions. However, during the last three years, Dickeya spp. strainsbelonging to a new biovar 3 clade, probably constituting a newspecies, have been isolated from potato tubers inseveral countries in Northern Europe (Slawiak et al., 2009 and references therein). To study dissemination to weeds, surveys were conducted in potato fields where Dickeya-infected potato plants were detected during two consecutive spring seasons (2009 and 2010). Symptomless plants of 12 species of local weeds were randomly collected: Cyperus rotundus,Orobanche aegyptiaca, Amaranthus spinosus, Polygonum equisetiforme, Chenopodium sp., Heliotropium sp., Centaurea iberica, Sorghum haepense, Malva nicaeensis, Cynodon dactylon, Amaranthus blitum and Solanum elaeagnifolium. Roots or tubers (in the case of C. rotundus)of 15 plants of each weed were washed, surface sterilised and then sample homogenates were plated on crystal violet pectate medium (CVP). Cavity forming bacteria were transferred to nutrient agar and analysed. Dickeya spp. were isolated only from the perennial weed C. rotundus.Incidence of infected plants was 6.7 and 14.3% in 2009 and 2010, respectively). DNA extracted from the bacteria isolated from C. rotundus was positive in a PCR amplification procedure using pelADE specific primers which are specific for E. chrysanthemi (Nassar et al., 1996).Isolates were identified by biochemical assays as biovar 3 (Palacio-Bielsa et al., 2006). They were characterised as the new genetic clade, using dnaX sequence (Slawiak et al., 2009) and REP-PCR analyses (Tsror et al.,2009). These isolates caused maceration of potato tubers at 30°C (Laurila et al., 2008) and formed clear haloes on a polygalacturonic acid medium (Collmer et al.,1988). This is the first report of Dickeya spp. latent infection in one of the most prevalent weeds in potato fields in Israel. C. rotundus is difficult to control because of resistance to most herbicides. Therefore, it may serve as an alternative host for Dickeya spp. allowing the pathogen to survive in the absence of a host crop.
    Assessment of recent outbreaks of Dickeya sp (syn. Erwinia chrysanthemi) slow wilt in potato crops in Israel
    Tsror, L. ; Erlich, O. ; Lebiush, S. ; Hazanovsky, M. ; Zig, U. ; Slawiak, M. ; Grabe, G. ; Wolf, J.M. van der; Haar, J.J. van de - \ 2009
    European Journal of Plant Pathology 123 (2009)3. - ISSN 0929-1873 - p. 311 - 320.
    soft-rot erwinias - temperature tolerances - carotovora - bacterial - tubers - pcr - erythromycin - polymorphism - sensitivity - diseases
    Suspected Dickeya sp. strains were obtained from potato plants and tubers collected from commercial plots. The disease was observed on crops of various cultivars grown from seed tubers imported from the Netherlands during the spring seasons of 2004-2006, with disease incidence of 2-30% ( 10% in average). In addition to typical wilting symptoms on the foliage, in cases of severe infection, progeny tubers were rotten in the soil. Six strains were characterised by biochemical, serological and PCR amplification. All tests verified the strains as Dickeya sp. The repPCR and the biochemical assays showed that the strains isolated from blackleg diseased plants in Israel were very similar, if not identical to strains isolated from Dutch seed potatoes, suggesting that the infection in Israel originated from the Dutch seed. The strains were distantly related to D. dianthicola strains, typically found in potatoes in Western Europe, and were similar to biovar 3 D. dadanti or D. zeae. This is the first time that the presence of biovar 3 strains in potato in the Netherlands is described. One of the strains was used for pathogenicity assays on potato cvs Nicola and Mondial. Symptoms appeared 2 to 3 days after stem inoculation, and 7 to 10 days after soil inoculation. The control plants treated with water, or plants inoculated with Pectobacterium carotovorum, did not develop any symptoms with either method of inoculation. The identity of Dickeya sp. and P. carotovorum re- isolated from inoculated plants was confirmed by PCR and ELISA.
    Interlaboratory comparison of methods to quantify microsclerotia of Verticillium dahliae in soil.
    Termorshuizen, A.J. ; Davis, J.R. ; Harris, D.C. ; Huisman, O.C. ; Gort, G. ; Lazarovits, G. ; Locke, T. ; Melero Vara, J.M. ; Mol, L. ; Paplomatas, E.J. ; Platt, H.W. ; Powelson, M. ; Rouse, D.I. ; Rowe, R.C. ; Tsror, L. - \ 1998
    Applied and Environmental Microbiology 64 (1998)10. - ISSN 0099-2240 - p. 3846 - 3853.
    Conclusions on crop management.
    Struik, P.C. - \ 1993
    In: Advanced potato production in hot climates / Tsror, L., - p. 64 - 65.
    Comments on potato seed production in hot climates.
    Struik, P.C. ; Lommen, W.J.M. - \ 1993
    In: Proc. Symp. Advanced potato production in hot climates, L. Tsror et al. (eds.). Nahal-Oz, Israel - p. 21 - 28.
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