Abstract
Pectinolytic bacteria from the genus Dickeya (former Erwinia chrysanthemi), belonging to Dickeya dianthicola and Dickeya solani species, are causative agents of blackleg and soft rot diseases in Europe. Recently, D. solani have been isolated most frequently from potato plants with the symptoms of blackleg and soft rot. D. solani strains were shown to cause more severe disease symptoms on potato plants than D. dianthicola especially at the higher temperature. They are also able to develop blackleg disease from lower inoculum levels. In the presented study we not only compared phenotypic features of fifteen D. solani strains isolated in countries having different climatic conditions, Poland, Finland and Israel, but also we examined three D. dianthicola strains. The comparison was performed to determine the influence of the strain origin and the temperature of incubation on the ability of the strains to macerate potato tissue and on their major virulence factors such as: pectinolytic, cellulolytic and proteolytic activities, siderophore production and motility. Polish D. solani strains showed higher activities of cell wall degrading enzymes than the Finnish and Israeli strains at all the tested temperatures: 18, 27, 37 °C. This observation is correlated with the higher ability of Polish D. solani strains to cause soft rot. In addition, D. solani strains exhibited higher activity of the above mentioned enzymes and caused more severe potato tuber maceration in laboratory tests than the tested D. dianthicola strains. The collected results indicate that although D. solani strains from different climatic conditions have identical Pulse Field Gel Electrophoresis (PFGE) profiles in addition to the same fingerprint profiles obtained by the repetitive sequence-based polymerase chain reaction (REP, ERIC and BOX repetitive sequences), they differ in the examined phenotypic features, especially in the activities of pectinolytic, cellulolytic and proteolytic enzymes and their capacity to macerate potato tuber tissue.
Highlights
Dickeya species (Samson et al 2005), formerly named Pectobacterium chrysanthemi (Hauben et al 1998) and Erwinia chrysanthemi (Burkholder et al 1953), are causative agents of soft rot and blackleg in potato
Two molecular profiling techniques: rep-PCR and RFLPPFGE were used to characterize the genomic material of D. solani strains isolated in Poland, Finland and Israel
There are no methods of curing the disease and all protection is based on prevention methods, especially important is planting the pathogen-free potato seeds
Summary
Dickeya species (Samson et al 2005), formerly named Pectobacterium chrysanthemi (Hauben et al 1998) and Erwinia chrysanthemi (Burkholder et al 1953), are causative agents of soft rot and blackleg in potato. The genus Dickeya is a highly diverse group, which according to the present classification contains eight species: D. aquatica, D. chrysanthemi, D. dadantii, D. dianthicola, D. fangzhongdai D. paradisiaca, D. solani and D. zeae (Samson et al 2005; Brady et al 2012; van der Wolf et al 2014; Parkinson et al 2014; Tian et al 2016). Strains isolated from potato plants outside of Europe fell into biovar 3 and 6 and possessed high optimum growth temperature They were classified to D. dadanti, D. chrysanthemi or D. zeae species (Dickey 1981; Samson et al 2005; Toth et al 2011)
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