Downy mildew, caused by the Oomycete Plasmopara viticola (Berk. et Curt.) Berl. and De Toni is one of the most destructive and widespread diseases affecting the Eurasian grapevine (Vitis vinifera L.). P. viticola was accidentally introduced into Europe, from North America, in 1878 and was signaled in Italy one year later. In this study were used species-specific microsatellite markers for 106 Italian P. viticola strains belonging to 12 different regions, in order to get insight on genetic variability of pathogen population almost 140 years after its first appearance in Italy. Therefore, the genetic structure of the Italian P. viticola population was put in relation with abiotic (geography, climatic conditions and disease management strategy) and biotic factors (host cultivar), to investigate if they are involved in substructuring the pathogen population. The analysis highlighted the existence of two distinct subpopulations that are dividing on a longitudinal gradient and in presence of different precipitation rates. This indicates that the pathogen population could be evolving according to different forces acting simultaneously, among which are geographic isolation and climatic conditions.

Figure: Localization of the samples at regional level; the isolates belonging to subpopulation 1 are represented in blue, instead the red ones belong to subpopulation 2.

REFERENCE. Maddalena G., Delmotte F., Bianco P.B., De Lorenzis G., Toffolatti S.L., (2020). Genetic structure of Italian population of the grapevine downy mildew agent, Plasmopara viticola. Annals of applied biology, 1–11 [ Doi:10.1111/aab.12567].