Virulence of ‘Dickeya solani’ and Dickeya dianthicola biovar‐1 and ‐7 strains on potato (Solanum tuberosum)

Abstract

Studies were conducted to explain the relative success of 'Dickeya solani', a genetic clade of Dickeya biovar 3 and a blackleg-causing organism that, after recent introduction, has spread rapidly in seed potato production in Europe to the extent that it is now more frequently detected than D. dianthicola. In vitro experiments showed that both species were motile, had comparable siderophore production and pectinolytic activity, and that there was no antagonism between them when growing. Both 'D. solani' and biovar 1 and biovar 7 of D. dianthicola rotted tuber tissue when inoculated at a low density of 10 3 CFU mL. In an agar overlay assay, D. dianthicola was susceptible to 80% of saprophytic bacteria isolated from tuber extracts, whereas 'D. solani' was susceptible to only 31%, suggesting that 'D. solani' could be a stronger competitor in the potato ecosystem. In greenhouse experiments at high temperatures (28°C), roots were more rapidly colonized by 'D. solani' than by biovar 1 or 7 of D. dianthicola and at 30 days after inoculation higher densities of 'D. solani' were found in stolons and progeny tubers. In co-inoculated plants, fluorescent protein (GFP or DsRed)-tagged 'D. solani' outcompeted D. dianthicola in plants grown from vacuum-infiltrated tubers. In 3 years of field studies in the Netherlands with D. dianthicola and 'D. solani', disease incidence varied greatly annually and with strain. In summary, 'D. solani' possesses features which allow more efficient plant colonization than D. dianthicola at high temperatures. In temperate climates, however, tuber infections with 'D. solani' will not necessarily result in a higher disease incidence than infections with D. dianthicola, but latent seed infection could be more prevalent.

Genome Sequence of Dickeya solani, a New soft Rot Pathogen of Potato, Suggests its Emergence May Be Related to a Novel Combination of Non-Ribosomal Peptide/Polyketide Synthetase Clusters

“…Among the identified D. solani-specific sequences, ORFs 1369-1388, corresponding to nucleotides 1,546,840-1,602,683 (region 3 in Figure 2), contained several large genes that were annotated as PKS, fatty acid synthases (FAS) and NRPS ( Figure 5). The closest similarity of ORFs 1369-1386 was to Serratia plymuthica strains AS12 and A30, which are antagonists and growth-promoting soil bacteria [12,55]. Within this D. solani genomic region, the ORF 1374 showed similarity to the published 5′ end of zmsA, coding for a novel multidomain polyketide synthase that is essential for the production of zeamine, a novel polyamino-amide antibiotic of Dickeya zeae DZ1 [56,57].…”

“…Furthermore, the bacterium is able to spread from soil into plant roots and vascular tissue very efficiently, which causes a high level of spreading during growing season [11]. In some countries, the new pathogen has replaced other Dickeya strains and Pectobacterium species previously dominant in infected plants, and it appears to be highly aggressive, especially in hot climate conditions, raising implications for the increased importance of this pathogen in response to global warming [12]. Furthermore, D. solani has been proposed to be less susceptible for antagonism by saprophytic bacteria in the potato ecosystem [12].…”

“…In some countries, the new pathogen has replaced other Dickeya strains and Pectobacterium species previously dominant in infected plants, and it appears to be highly aggressive, especially in hot climate conditions, raising implications for the increased importance of this pathogen in response to global warming [12]. Furthermore, D. solani has been proposed to be less susceptible for antagonism by saprophytic bacteria in the potato ecosystem [12]. In addition to D. solani, also a new Pectobacterium species, P. wasabiae, has been recently identified in Europe [13].…”

Salicylic acid can reduce infection symptoms caused by Dickeya solani in tissue culture grown potato (Solanum tuberosum L.) plants

“…The species has become the predominant pathogen responsible for the blackleg incidences in Europe (Toth et al 2011;Tsror et al 2011;van der Wolf et al 2014). D. solani seems to be virulent in potato and possesses features allowing its easy spread and survival under the temperate climate in Europe (Czajkowski et al , 2012a.…”

Fast and reliable screening system to preselect candidate Dickeya solani Tn5 mutants in plant tissue-induced genes

“…Since then the pathogen has been found in association with potato plants and tubers in many European countries and in Israel and Georgia (for review see: Toth et al 2011). It is now generally accepted that D. solani causes severe rotting symptoms in potato in a range of environmental temperatures (Czajkowski et al 2016;Golanowska et al 2016), may survive in surface water for a relatively long time (Laurila et al 2008) and is capable of spreading and systemically infect the host under a wide range of natural conditions (Czajkowski et al 2012). Despite the extensive studies on the ecology of D. solani, still little is known about the regulation of gene expression governing the infection process (Potrykus et al 2014), particularly during the early stages of bacteria-plant interaction leading to efficient colonization of plant tissues.…”