Dickeya dianthicola emerged from a potato culture area exhibiting a wide diversity of pectinolytic pathogens in northern Morocco

Abstract

Abstract Background: Dickeya and Pectobacterium are pectinolytic pathogens that cause damage to many plants including major crops. Emergence of D. solani and re-emergence D. dianthicola were recently observed in potato fields in several continents. The purpose of this work was to describe the species diversity of Dickeya and Pectobacterium collected from potato fields in Northern Morocco, where Dickeya potato pathogens have not been isolated until recently. Results: Along three years, 119 pathogens belonging to Pectobacterium and Dickeya genera were isolated from three potato culture areas and characterized using selective PCR and gapA gene sequencing. Out of them, 19% belonged to P. versatile, 3% to P. carotovorum, 5% to P. polaris, 56% to P. brasiliense, while 17% to D. dianthicola. The taxonomic assignations were confirmed by draft genome analyses of representative isolates belonging to the collected species. D. dianthicola were isolated from a unique area where a wide species diversity of pectinolytic pathogens was also observed. In potato maceration assay, D. dianthicola isolates were more aggressive than Pectobacterium isolates, a feature that should alert stakeholders of a potential threat linked to the emergence of D. dianthicola in this country. By combining Oxford Nanopore Technologies (ONT) and Illumina technologies, the sequence of the complete genome of D. dianthicola LAR.16.03.LID was obtained. A unique circular chromosome of 4,976,211 bp codes for 4,223 predicted proteins. Comparison of the three complete genomes of D. dianthicola strains RNS049, ME23 and LAR.16.03.LID revealed a highly conserved synteny and the occurrence of strain-specific regions associated with the presence of mobile elements. Conclusion: By combining population sampling and genomics, this study highlighted the ecological context from which D. dianthicola emerged in Morocco. Furthermore, the first complete genome of a D. dianthicola strain isolated in Northern Morocco will constitute a reference genome for investigating the dynamics of the emerging D. dianthicola pathogens in this country.