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The bacterial diseases black leg and soft rot in potatoes cause heavy losses of potatoes worldwide. Bacteria within the genus Pectobacteriaceae are the causative agents of black leg and soft rot. The use of antibiotics in agriculture is heavily regulated and no other effective treatment currently exists, but bacteriophages (phages) have shown promise as potential biocontrol agents. In this study we isolated soft rot bacteria from potato tubers and plant tissue displaying soft rot or black leg symptoms collected in Danish fields. We then used the isolated bacterial strains as hosts for phage isolation. Using organic waste, we isolated phages targeting different species within Pectobacterium. Here we focus on seven of these phages representing a new genus primarily targeting P. brasiliense; phage Ymer, Amona, Sabo, Abuela, Koroua, Taid and Pappous. TEM image of phage Ymer showed siphovirus morphotype, and the proposed Ymer genus belongs to the class Caudoviricetes, with double-stranded DNA genomes varying from 39 kb to 43 kb. In silico host range prediction using a CRISPR-Cas spacer database suggested both P. brasiliense, P. polaris and P. versatile as natural hosts for phages within the proposed Ymer genus. A following host range experiment, using 47 bacterial isolates from Danish tubers and plants symptomatic with soft rot or black leg disease verified the in silico host range prediction, as the genus as a group were able to infect all three Pectobacterium species. Phages did, however, primarily target P. brasiliense isolates and displayed differences in host range even within the species level. Two of the phages were able to infect two or more Pectobacterium species. Despite no nucleotide similarity with any phages in the NCBI database, the proposed Ymer genus did share some similarity at the protein level, as well as gene synteny, with currently known phages. None of the phages encoded integrases or other genes typically associated with lysogeny. Similarly, no virulence factors nor antimicrobial resistance genes were found, and combined with their ability to infect several soft rot-causing Pectobacterium species from Danish fields, demonstrates their potential as biocontrol agents against soft rot and black leg diseases in potatoes.

Soft rot Pectobacteriaceae (SRP) are the causative agents of soft rot and blackleg in potato. In this study, we investigated if potato seed lots of the same cultivar, but originating from different fields, inoculated with the same density of SRP and planted in the same field, showed differences in blackleg disease incidence. We tested if these differences were correlated with the microbial community composition in tuber, and the soil where the mother tubers were grown, as the microbiome is known to play a large role in plant disease resistance. We found that tubers from seed lots with a high disease incidence had a different microbial community composition than tubers from seed lots with a low disease incidence. Several taxa could be identified that were on average more abundant in seed lots with a low disease incidence. However, the taxa that differed in abundance were different between the two growing seasons. Most of the taxa that differed in abundance between seed lots with high and low disease incidence were also present in the soil of the fields from which the tubers originated. However, the taxa did not differ in abundance between the different fields. This raises the question as to how these taxa are recruited by the tuber. [ABSTRACT FROM AUTHOR]

Pectobacterium cacticida (formerly Erwinia cacticida) causes soft rot disease of cactus plants. Its taxonomic status within the genus Pectobacterium remains questionable because no whole genome sequence of this species is available in public databases for reliable taxonomic analyses. Here, we present the complete genome sequence of the P. cacticida type strain CFCC 10813T (=1-12T = ATCC 49481T). P. cacticida can be classified into the genus Pectobacterium because it is on the deepest basal phylogenomic branch of the genus Pectobacterium, and its genome relatedness to other Pectobacterium species is at the border for the genus delimitation boundaries. This complete genome sequence provides the genome resource for elucidating P. cacticida pathogenicity and adaptation to plant hosts and environments. [Figure: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Pectobacterium and Dickeya species belonging to the Soft Rot Pectobacteriaceae (SRP) are one of the most devastating phytopathogens. They degrade plant tissues by producing an arsenal of plant cell wall degrading enzymes. However, SRP-plant interactions are not restricted to the production of these "brute force" weapons. Additionally, these bacteria apply stealth behavior related to (1) manipulation of the host plant via induction of susceptible responses and (2) formation of heterogeneous populations with functionally specialized cells. Our review aims to summarize current knowledge on SRP-induced plant susceptible responses and on the heterogeneity of SRP populations. The review shows that SRP are capable of adjusting the host's hormonal balance, inducing host-mediated plant cell wall modification, promoting iron assimilation by the host, stimulating the accumulation of reactive oxygen species and host cell death, and activating the synthesis of secondary metabolites that are ineffective in limiting disease progression. By this means, SRP facilitate host plant susceptibility. During host colonization, SRP populations produce various functionally specialized cells adapted for enhanced virulence, increased resistance, motility, vegetative growth, or colonization of the vascular system. This enables SRP to perform self-contradictory tasks, which benefits a population's overall fitness in various environments, including host plants. Such stealthy tactical actions facilitate plant-SRP interactions and disease progression. • SRP manipulate the host plants by inducing susceptible responses. • SRP populations produce physiologically and functionally specialized cells. • Susceptible responses and population behavior determine the outcome of interaction. • Induced susceptibility and population behavior are targets for disease control. [ABSTRACT FROM AUTHOR]

The yew tree (Taxus baccata L.) is considered in folklore a symbol of immortality due to its qualities of longevity and regeneration. Despite its poisonous reputation, the yew tree has a long history of medicinal use, particularly in the form of extracts from its leaves and bark. In the work presented herein, gas chromatography–mass spectrometry (GC–MS) chemical profiling was applied to the aqueous ammonia/hydromethanolic extracts of several plant organs of T. baccata, leading to the identification of different bioactive compounds than those previously characterized by high-performance liquid chromatography with tandem mass spectrometry (HPLC–MS/MS) in other extraction media. The leaf aqueous ammonia extract was rich in 2-hexylthiophene and 3-O-methyl-d-fructose; 9-octadecenoic and hexadecanoic acid were the main constituents of the bark aqueous ammonia extract; and the fruit hydromethanolic extract contained methyl 2-O-methyl-α-d-xylofuranoside, 1,3-dioxolane derivatives, and erysimoside. The antimicrobial activity of the extracts was assayed against four bacterial pathogens responsible for the soft rot and blackleg diseases of potatoes, viz. Pectobacterium carotovorum subsp. carotovorum, Pectobacterium atrosepticum, Pectobacterium parmentieri, and Dickeya chrysanthemi, resulting in minimum inhibitory concentration (MIC) values as low as 187 μg·mL−1. Bioassays on potato slices confirmed the efficacy of the leaf extract at this dose when applied as a preventive treatment before artificial inoculation with P. carotovorum subsp. carotovorum. In view of this high activity, these extracts may find application in the integrated pest management of soft rot Pectobacteriaceae (SRP) diseases. [ABSTRACT FROM AUTHOR]

Carrot production in Sri Lanka faces severe post-harvest losses due to bacterial soft rot. The quality deterioration of vegetables owing to typical bacterial soft rot can greatly affect the market value and consumer preference. Although the carrot soft rot causing bacteria occur all over the world, and are well-studied and characterized, the scarcity of data on the precise identification of the causal agents of the disease in Sri Lanka acts as a great barrier in managing such post-harvest losses. In an attempt to bridge this knowledge gap, we have isolated potential causative agents of bacterial soft rot from diseased carrot samples collected from Gampaha district, Sri Lanka. All the seven bacterial isolates were confirmed for their ability to exhibit pectolysis, and vegetable disk assays were used to evaluate the pathogenicity of bacterial isolates. The pathogenicity assays showed that these isolates have the ability to infect not only carrot, but also potato, radish, beetroot and Napa cabbage, suggesting their possible broad host range. The ITS–PCR RELP profiles of the pectobacterial isolates and hierarchical clustering of the resulting profiles have placed the strains isolated in this study into four groups. The 16S rRNA gene sequencing and subsequent analyses aided in identifying isolates as Pectobacterium carotovorum (C1B5, C2B6, C2B7 and C2B8), P. aroidearum (C1B3 and C1B4), and P. polaris (C3B9). The study indicated the possibility of different Pectobacterium spp. being involved in causing carrot soft rot in the area, emphasizing the need to carry out an island-wide, comprehensive analysis to understand the distribution of the pathogen, which could be used in implementing successful disease management strategies. [ABSTRACT FROM AUTHOR]

• Phages present in the Ymer genus represent a new genus. • An in-silico host range prediction indicated phages to infect broadly. • The in-silico host range potential was verified experimentally. • Phages were able to infect several species of soft rot Pectobacteriacea. • The Ymer genus represents important biocontrol agents against soft rot. The bacterial diseases black leg and soft rot in potatoes cause heavy losses of potatoes worldwide. Bacteria within the genus Pectobacteriaceae are the causative agents of black leg and soft rot. The use of antibiotics in agriculture is heavily regulated and no other effective treatment currently exists, but bacteriophages (phages) have shown promise as potential biocontrol agents. In this study we isolated soft rot bacteria from potato tubers and plant tissue displaying soft rot or black leg symptoms collected in Danish fields. We then used the isolated bacterial strains as hosts for phage isolation. Using organic waste, we isolated phages targeting different species within Pectobacterium. Here we focus on seven of these phages representing a new genus primarily targeting P. brasiliense ; phage Ymer, Amona, Sabo, Abuela, Koroua, Taid and Pappous. TEM image of phage Ymer showed siphovirus morphotype, and the proposed Ymer genus belongs to the class Caudoviricetes, with double-stranded DNA genomes varying from 39 kb to 43 kb. In silico host range prediction using a CRISPR-Cas spacer database suggested both P. brasiliense, P. polaris and P. versatile as natural hosts for phages within the proposed Ymer genus. A following host range experiment, using 47 bacterial isolates from Danish tubers and plants symptomatic with soft rot or black leg disease verified the in silico host range prediction, as the genus as a group were able to infect all three Pectobacterium species. Phages did, however, primarily target P. brasiliense isolates and displayed differences in host range even within the species level. Two of the phages were able to infect two or more Pectobacterium species. Despite no nucleotide similarity with any phages in the NCBI database, the proposed Ymer genus did share some similarity at the protein level, as well as gene synteny, with currently known phages. None of the phages encoded integrases or other genes typically associated with lysogeny. Similarly, no virulence factors nor antimicrobial resistance genes were found, and combined with their ability to infect several soft rot-causing Pectobacterium species from Danish fields, demonstrates their potential as biocontrol agents against soft rot and black leg diseases in potatoes. [Display omitted] [ABSTRACT FROM AUTHOR]

The wide host range phytopathogen D. dianthicola, first described in ornamentals in the 1950s, rapidly became a threat for potato production in Europe and, more recently, worldwide. Previous genomic analyses, mainly of strains isolated from potato, revealed little sequence diversity. To further analyse D. dianthicola genomic diversity, we used a larger genome panel of 41 isolates encompassing more strains isolated from potato over a wide time scale and more strains isolated from other hosts. The phylogenetic and pan-genomic trees revealed a large cluster of highly related genomes but also the divergence of two more distant strains, IPO 256 and 67.19, isolated from potato and impatiens, respectively, and the clustering of the three strains isolated from Kalanchoe with one more distinct potato strain. An SNP-based minimal spanning tree highlighted both diverse clusters of (nearly) clonal strains and several strains scattered in the MST, irrespective of country or date of isolation, that differ by several thousand SNPs. This study reveals a higher diversity in D. dianthicola than previously described. It indicates the clonal spread of this pathogen over long distances, as suspected from worldwide seed trading, and possible multiple introductions of D. dianthicola from alternative sources of contaminations. [ABSTRACT FROM AUTHOR]

Abstract Background Bacterial plant pathogens of the Pectobacterium genus are responsible for a wide spectrum of diseases in plants, including important crops such as potato, tomato, lettuce, and banana. Investigation of the genetic diversity underlying virulence and host specificity can be performed at genome level by using a comprehensive comparative approach called pangenomics. A pangenomic approach, using newly developed functionalities in PanTools, was applied to analyze the complex phylogeny of the Pectobacterium genus. We specifically used the pangenome to investigate genetic differences between virulent and avirulent strains of P. brasiliense, a potato blackleg causing species dominantly present in Western Europe. Results Here we generated a multilevel pangenome for Pectobacterium, comprising 197 strains across 19 species, including type strains, with a focus on P. brasiliense. The extensive phylogenetic analysis of the Pectobacterium genus showed robust distinct clades, with most detail provided by 452,388 parsimony-informative single-nucleotide polymorphisms identified in single-copy orthologs. The average Pectobacterium genome consists of 47% core genes, 1% unique genes, and 52% accessory genes. Using the pangenome, we zoomed in on differences between virulent and avirulent P. brasiliense strains and identified 86 genes associated to virulent strains. We found that the organization of genes is highly structured and linked with gene conservation, function, and transcriptional orientation. Conclusion The pangenome analysis demonstrates that evolution in Pectobacteria is a highly dynamic process, including gene acquisitions partly in clusters, genome rearrangements, and loss of genes. Pectobacterium species are typically not characterized by a set of species-specific genes, but instead present themselves using new gene combinations from the shared gene pool. A multilevel pangenomic approach, fusing DNA, protein, biological function, taxonomic group, and phenotypes, facilitates studies in a flexible taxonomic context.

Soft rot Pectobacteriaceae (SRP), typical of Pectobacterium and Dickeya , are a class of Gram-negative bacterial pathogens that cause devastating diseases on a wide range of crops and ornamental plants worldwide. Quorum sensing (QS) is a cell-cell communication mechanism regulating the expression of specific genes by releasing QS signal molecules associated with cell density, in most cases, involving in the vital process of virulence and infection. In recent years, several types of QS systems have been uncovered in Dickeya pathogens to control diverse biological behaviors, especially bacterial pathogenicity and transkingdom interactions. This review depicts an integral QS regulation network of Dickeya , elaborates in detail the regulation of specific QS system on different biological functions of the pathogens and hosts, aiming at providing a systematic overview of Dickeya pathogenicity and interactions with hosts, and, finally, expects the future prospective of effectively controlling the bacterial soft rot disease caused by Dickeya by quenching the key QS signal. [ABSTRACT FROM AUTHOR]

Soft rot Pectobacteriaceae (SRP), typical of Pectobacterium and Dickeya, are a class of Gram-negative bacterial pathogens that cause devastating diseases on a wide range of crops and ornamental plants worldwide. Quorum sensing (QS) is a cell-cell communication mechanism regulating the expression of specific genes by releasing QS signal molecules associated with cell density, in most cases, involving in the vital process of virulence and infection. In recent years, several types of QS systems have been uncovered in Dickeya pathogens to control diverse biological behaviors, especially bacterial pathogenicity and transkingdom interactions. This review depicts an integral QS regulation network of Dickeya, elaborates in detail the regulation of specific QS system on different biological functions of the pathogens and hosts, aiming at providing a systematic overview of Dickeya pathogenicity and interactions with hosts, and, finally, expects the future prospective of effectively controlling the bacterial soft rot disease caused by Dickeya by quenching the key QS signal.

The yew tree (Taxus baccata L.) is considered in folklore a symbol of immortality due to its qualities of longevity and regeneration. Despite its poisonous reputation, the yew tree has a long history of medicinal use, particularly in the form of extracts from its leaves and bark. In the work presented herein, gas chromatography–mass spectrometry (GC–MS) chemical profiling was applied to the aqueous ammonia/hydromethanolic extracts of several plant organs of T. baccata, leading to the identification of different bioactive compounds than those previously characterized by high-performance liquid chromatography with tandem mass spectrometry (HPLC–MS/MS) in other extraction media. The leaf aqueous ammonia extract was rich in 2-hexylthiophene and 3-O-methyl-d-fructose; 9-octadecenoic and hexadecanoic acid were the main constituents of the bark aqueous ammonia extract; and the fruit hydromethanolic extract contained methyl 2-O-methyl-α-d-xylofuranoside, 1,3-dioxolane derivatives, and erysimoside. The antimicrobial activity of the extracts was assayed against four bacterial pathogens responsible for the soft rot and blackleg diseases of potatoes, viz. Pectobacterium carotovorum subsp. carotovorum, Pectobacterium atrosepticum, Pectobacterium parmentieri, and Dickeya chrysanthemi, resulting in minimum inhibitory concentration (MIC) values as low as 187 μg·mL−1. Bioassays on potato slices confirmed the efficacy of the leaf extract at this dose when applied as a preventive treatment before artificial inoculation with P. carotovorum subsp. carotovorum. In view of this high activity, these extracts may find application in the integrated pest management of soft rot Pectobacteriaceae (SRP) diseases.

The wide host range phytopathogen D. dianthicola, first described in ornamentals in the 1950s, rapidly became a threat for potato production in Europe and, more recently, worldwide. Previous genomic analyses, mainly of strains isolated from potato, revealed little sequence diversity. To further analyse D. dianthicola genomic diversity, we used a larger genome panel of 41 isolates encompassing more strains isolated from potato over a wide time scale and more strains isolated from other hosts. The phylogenetic and pan-genomic trees revealed a large cluster of highly related genomes but also the divergence of two more distant strains, IPO 256 and 67.19, isolated from potato and impatiens, respectively, and the clustering of the three strains isolated from Kalanchoe with one more distinct potato strain. An SNP-based minimal spanning tree highlighted both diverse clusters of (nearly) clonal strains and several strains scattered in the MST, irrespective of country or date of isolation, that differ by several thousand SNPs. This study reveals a higher diversity in D. dianthicola than previously described. It indicates the clonal spread of this pathogen over long distances, as suspected from worldwide seed trading, and possible multiple introductions of D. dianthicola from alternative sources of contaminations.

Background: Bacterial plant pathogens of the Pectobacterium genus are responsible for a wide spectrum of diseases in plants, including important crops such as potato, tomato, lettuce, and banana. Investigation of the genetic diversity underlying virulence and host specificity can be performed at genome level by using a comprehensive comparative approach called pangenomics. A pangenomic approach, using newly developed functionalities in PanTools, was applied to analyze the complex phylogeny of the Pectobacterium genus. We specifically used the pangenome to investigate genetic differences between virulent and avirulent strains of P. brasiliense, a potato blackleg causing species dominantly present in Western Europe. Results: Here we generated a multilevel pangenome for Pectobacterium, comprising 197 strains across 19 species, including type strains, with a focus on P. brasiliense. The extensive phylogenetic analysis of the Pectobacterium genus showed robust distinct clades, with most detail provided by 452,388 parsimony-informative single-nucleotide polymorphisms identified in single-copy orthologs. The average Pectobacterium genome consists of 47% core genes, 1% unique genes, and 52% accessory genes. Using the pangenome, we zoomed in on differences between virulent and avirulent P. brasiliense strains and identified 86 genes associated to virulent strains. We found that the organization of genes is highly structured and linked with gene conservation, function, and transcriptional orientation. Conclusion: The pangenome analysis demonstrates that evolution in Pectobacteria is a highly dynamic process, including gene acquisitions partly in clusters, genome rearrangements, and loss of genes. Pectobacterium species are typically not characterized by a set of species-specific genes, but instead present themselves using new gene combinations from the shared gene pool. A multilevel pangenomic approach, fusing DNA, protein, biological function, taxonomic group, and phenotypes, facilitates studies in a flexible taxonomic context. [ABSTRACT FROM AUTHOR]

Pectobacterium and Dickeya species are the causal agents of blackleg and soft rot diseases in potatoes. The main pathogenic species identified so far on potatoes are Dickeya dianthicola, Dickeya solani, Pectobacterium atrosepticum, Pectobacterium brasiliense, Pectobacterium carotovorum, and Pectobacterium parmentieri. Ten years ago, the most prevalent Soft Rot Pectobacteriaceae in Europe were the Dickeya species, P. atrosepticum and P. carotovorum, with some variations among countries. Since then, a drastic increase in the abundance of P. brasiliense has been observed in most European countries. This shift is difficult to explain without comparing the pathogenicity of all Dickeya and Pectobacterium species. The pathogenicity of all the above-mentioned bacterial species was assessed in field trials and in vitro tuber slice trials in Switzerland. Two isolates of each species were inoculated by soaking tubers of cv. Desiree in a suspension of 105 CFU/mL, before planting in the field. For all trials, the Dickeya species were the most virulent ones, but long-term strain surveys performed in Switzerland indicate that P. brasiliense is currently the most frequent species detected. Our results show that the pathogenicity of the species is not the main factor explaining the high prevalence of P. brasiliense and P. parmentieri in the Swiss potato fields.

Blackleg and soft rot in potato caused by Pectobacterium and Dickeya enterobacteral genera are among the most destructive bacterial diseases in this crop worldwide. In Europe, over the last century, Pectobacterium spp. were the predominant causal agents of these diseases. As for Dickeya, before the large outbreak caused by D. solani in the 2000s, only D. dianthicola was isolated in Europe. The population dynamics of potato blackleg causing soft rot Pectobacteriaceae was, however, different in Switzerland as compared to that in other European countries with a high incidence (60 up to 90%) of Dickeya species (at the time called Erwinia chrysanthemi) already in the 1980s. To pinpoint what may underlie this Swiss peculiarity, we analysed the diversity present in the E. chrysanthemi Agroscope collection gathering potato isolates from 1985 to 2000s. Like elsewhere in Europe during this period, the majority of Swiss isolates belonged to D. dianthicola. However, we also identified a few isolates, such as D. chrysanthemi and D. oryzeae, two species that have not yet been reported in potatoes in Europe. Interestingly, this study allowed the characterisation of two “early” D. solani isolated in the 1990s. Genomic comparison between these early D. solani strains and strains isolated later during the large outbreak in the 2000s in Europe revealed only a few SNP and gene content differences, none of them affecting genes known to be important for virulence.

Pectobacterium parmentieri is a pectinolytic plant pathogenic bacterium causing high economic losses of cultivated plants. The highly devastating potential of this phytopathogen results from the efficient production of plant cell wall-degrading enzymes, i.e., pectinases, cellulases and proteases, in addition to the impact of accessory virulence factors such as motility, siderophores, biofilm and lipopolysaccharide (LPS). LPS belongs to pathogen-associated molecular patterns (PAMPs) and plays an important role in plant colonization and interaction with the defense systems of the host. Therefore, we decided to investigate the heterogeneity of O-polysaccharides (OPS) of LPS of different strains of P. parmentieri, in search of an association between the selected genomic and phenotypic features of the strains that share an identical structure of the OPS molecule. In the current study, OPS were isolated from the LPS of two P. parmentieri strains obtained either in Finland in the 1980s (SCC3193) or in Poland in 2013 (IFB5432). The purified polysaccharides were analyzed by utilizing 1D and 2D NMR spectroscopy (1H, DQF-COSY, TOCSY, ROESY, HSQC, HSQC-TOCSY and HMBC) in addition to chemical methods. Sugar and methylation analyses of native polysaccharides, absolute configuration assignment of constituent monosaccharides and NMR spectroscopy data revealed that these two P. parmentieri strains isolated in different countries possess the same structure of OPS with a very rare residue of 5,7-diamino-3,5,7,9-tetradeoxy-l-glycero-l-manno-non-2-ulosonic acid (pseudaminic acid) substituted in the position C-8: →3)-β-d-Galf-(1→3)-α-d-Galp-(1→8)-β-Pse4Ac5Ac7Ac-(2→6)-α-d-Glcp-(1→6)-β-d-Glcp-(1→. The previous study indicated that three other P. parmentieri strains, namely IFB5427, IFB5408 and IFB5443, exhibit a different OPS molecule than SCC3193 and IFB5432. The conducted biodiversity-oriented assays revealed that the P. parmentieri IFB5427 and IFB5408 strains possessing the same OPS structure yielded the highest genome-wide similarity, according to average nucleotide identity analyses, in addition to the greatest ability to macerate chicory tissue among the studied P. parmentieri strains. The current research demonstrated a novel OPS structure, characteristic of at least two P. parmentieri strains (SCC3193 and IFB5432), and discussed the observed heterogenicity in the OPS of P. parmentieri in a broad genomic and phenotype-related context. [ABSTRACT FROM AUTHOR]

Pectobacterium and Dickeya species are the causal agents of blackleg and soft rot diseases in potatoes. The main pathogenic species identified so far on potatoes are Dickeya dianthicola, Dickeya solani, Pectobacterium atrosepticum, Pectobacterium brasiliense, Pectobacterium carotovorum, and Pectobacterium parmentieri. Ten years ago, the most prevalent Soft Rot Pectobacteriaceae in Europe were the Dickeya species, P. atrosepticum and P. carotovorum, with some variations among countries. Since then, a drastic increase in the abundance of P. brasiliense has been observed in most European countries. This shift is difficult to explain without comparing the pathogenicity of all Dickeya and Pectobacterium species. The pathogenicity of all the above-mentioned bacterial species was assessed in field trials and in vitro tuber slice trials in Switzerland. Two isolates of each species were inoculated by soaking tubers of cv. Desiree in a suspension of 105 CFU/mL, before planting in the field. For all trials, the Dickeya species were the most virulent ones, but long-term strain surveys performed in Switzerland indicate that P. brasiliense is currently the most frequent species detected. Our results show that the pathogenicity of the species is not the main factor explaining the high prevalence of P. brasiliense and P. parmentieri in the Swiss potato fields. [ABSTRACT FROM AUTHOR]

Blackleg and soft rot in potato caused by Pectobacterium and Dickeya enterobacteral genera are among the most destructive bacterial diseases in this crop worldwide. In Europe, over the last century, Pectobacterium spp. were the predominant causal agents of these diseases. As for Dickeya, before the large outbreak caused by D. solani in the 2000s, only D. dianthicola was isolated in Europe. The population dynamics of potato blackleg causing soft rot Pectobacteriaceae was, however, different in Switzerland as compared to that in other European countries with a high incidence (60 up to 90%) of Dickeya species (at the time called Erwinia chrysanthemi) already in the 1980s. To pinpoint what may underlie this Swiss peculiarity, we analysed the diversity present in the E. chrysanthemi Agroscope collection gathering potato isolates from 1985 to 2000s. Like elsewhere in Europe during this period, the majority of Swiss isolates belonged to D. dianthicola. However, we also identified a few isolates, such as D. chrysanthemi and D. oryzeae, two species that have not yet been reported in potatoes in Europe. Interestingly, this study allowed the characterisation of two "early" D. solani isolated in the 1990s. Genomic comparison between these early D. solani strains and strains isolated later during the large outbreak in the 2000s in Europe revealed only a few SNP and gene content differences, none of them affecting genes known to be important for virulence. [ABSTRACT FROM AUTHOR]