Pattern and causes of the establishment of the invasive bacterial potato pathogen <i>Dickeya solani</i> and of the maintenance of the resident pathogen <i>D. dianthicola</i>
Pauline Blin, Kévin Robic, Slimane Khayi, Jérémy Cigna, Euphrasie Munier, Pauline Dewaegeneire, Angélique Laurent, Yan Jaszczyszyn, Kar‐Wai Hong, Kok‐Gan Chan, Amélie Beury, Sylvie Reverchon, Tatiana Giraud, Valérie Hélias, Denis Faure
Abstract
Abstract Invasive pathogens can be a threat when they affect human health, food production or ecosystem services, by displacing resident species, and we need to understand the cause of their establishment. We studied the patterns and causes of the establishment of the pathogen Dickeya solani that recently invaded potato agrosystems in Europe by assessing its invasion dynamics and its competitive ability against the closely related resident D. dianthicola species. Epidemiological records over one decade in France revealed the establishment of D. solani and the maintenance of the resident D. dianthicola in potato fields exhibiting blackleg symptoms. Using experimentations, we showed that D. dianthicola caused a higher symptom incidence on aerial parts of potato plants than D. solani , while D. solani was more aggressive on tubers (i.e. with more severe symptoms). In co‐infection assays, D. dianthicola outcompeted D. solani in aerial parts, while the two species co‐existed in tubers. A comparison of 76 D. solani genomes (56 of which have been sequenced here) revealed balanced frequencies of two previously uncharacterized alleles, VfmB Pro and VfmB Ser , at the vfmB virulence gene. Experimental inoculations showed that the VfmB Ser population was more aggressive on tubers, while the VfmB Pro population outcompeted the VfmB Ser population in stem lesions, suggesting an important role of the vfmB virulence gene in the ecology of the pathogens. This study thus brings novel insights allowing a better understanding of the pattern and causes of the D.solani invasion into potato production agrosystems, and the reasons why the endemic D. dianthicola nevertheless persisted.