Plasmopara halstedii, is the causal agent of an economically important disease of sunflower worldwide called downy mildew. This pathogen constantly evolves generating races that are more aggressive to the crop than the pre-existing ones. The traditional determination of the races is based on phytopathology tests, but the apparition of novel races with increased virulence makes necessary the use of a complementary molecular approach for such determinations. The objective of this project is to find genomic regions that would allow to discriminate different races of P. halstedii by the use of Next Generation Sequencing technologies and the analysis of Single Nucleotide Polymorphisms of the DNA corresponding to the different races. This work would be done on biological samples of P. halstedii collected across Argentina and United States, which are countries with different backgrounds of sunflower production and consequently different history of downy mildew. The output of this work would help us to follow the pathogen’s evolution in both countries and to design further disease management strategies for downy mildew.