Net Blotch is a damaging barley disease caused by the necrotrophic fungal pathogen Pyrenophora teres. It occurs in two phenotypically distinct forms: Net Form Net Blotch caused by Pyrenophora teres f. teres (Ptt) and Spot Form Net Blotch caused by Pyrenophora teres f. maculata (Ptm). The recent emergence of fungicide-resistant, increasingly virulent pathotypes and the lack of resistant barley germplasm seriously threaten our barley production. To understand the mechanisms of pathogenicity and differences in virulence, we used various WA-collected Ptt isolates that generate a range of disease phenotypes in commercial barley cultivars. We applied a combination of leaf imaging, confocal microscopy, long-read genome assemblies of the pathogen, and gene expression profiling from targeted tissue sampling of infected leaves. We found that the genomes of the virulent pathotypes of Ptt contained a higher percentage of repeat elements and copy number variation. We also discovered novel barley genes using a new in-house pipeline incorporating direct-RNA reads to improve gene annotations. I will present our recent findings on host-driven adaptation of the pathogen.