Venturia inaequalis is the causal pathogen of apple scab, one of the most economically important fungal diseases of apples. Understanding how this devastating pathogen evolves over time and space can help plant pathologists predict new pathogen populations and their effective management. In this thesis, I describe my study of the Malus-Venturia pathosystem and the genetics of pathogen evolution and host resistance to apple scab. I present an overview of the pathosystem, including modern apple production, V. inaequalis disease cycle, and previous genetic diversity studies within the species. I describe my analysis of the population genetic study of Venturia spp. and its evolutionary patterns as it coevolved with its Malus spp. hosts. Sequence data was compiled from publicly available sources and locally collected Venturia spp. isolates, and SNPs were identified and filtered within these sequences. These polymorphisms identified population differentiation and genetic diversity differences between Venturia isolates collected on various Malus spp. hosts. I also present the experiments for the identification of genetic recombinants amongst the F1 progeny of two mapping populations for the eventual fine mapping of scab resistance in the apple cultivar ‘Honeycrisp’. The common resistant parent in both populations, MN1980, contains the major scab resistance genes Rvi6 and Vhc1 on linkage group 1 in repulsion. The identification of recombinant progeny with these two genes in the coupling phase will allow development of markers tightly linked with Vhc1 for marker assisted selection to pyramid these loci for apple breeding.