Pyrenophora teres f. teres (Ptt), causing net blotch in barley, is an important and frequently isolated leaf pathogen across the globe. The virulence spectrum of Ptt from North Africa including Morocco is poorly understood. Sixteen barley genotypes were challenged, at seedling stage, with 15 Ptt isolates that were collected from different agroecological zones of Morocco. The experiment was conducted in a factorial arrangement of treatments in a randomized complete block design with three replicates. The ANOVA revealed highly significant (P < 0.001) effects of genotype (G), isolate (I) and G×I interaction explaining 23.2, 62.5, and 13.9% of the variation, respectively. Therefore, the current study revealed highly diverse virulence pattern of Moroccan isolates. Furthermore, the results indicated that minor virulence of Ptt isolates dominated over virulence interaction. In addition, Taffa (6-rowed) and Aglou (2 rowed), had the highest level of resistance to Ptt, while Coast and Rabat071 were the most susceptible genotypes. Pt2, Pt7, Pt8 and Pt4 were being the most virulent isolates, while Pt10 and Pt11 were the least virulent isolates. The emergence of the new Ptt pathotypes, which were highly virulent to durable resistance in Rabat071 posed a risk of breaking down the currently deployed resistance to net blotch in Morocco. A careful evaluation and selection of Ptt isolates based on minor virulence pattern to barley genotypes is essential for successful barley breeding program for resistance to net blotch in Morocco.