Septoria leaf blotch is a foliar wheat disease controlled by a combination of plant genetic resistances and fungicides use.R-gene-based qualitative resistance durability is limited due to gene-for-gene interactions with fungal avirulence (Avr) genes. Quantitative resistance is considered more durable but the mechanisms involved are not well documented. We hypothesize that genes involved in quantitative and qualitative plant-pathogen interactions are similar. A bi-parental population ofZymoseptoria triticiwas inoculated on wheat cultivar ‘Renan’ and a linkage analysis performed to map QTL. Three pathogenicity QTL,Qzt-I05-1, Qzt-I05-6andQzt-I07-13, were mapped on chromosomes 1, 6 and 13 inZ. tritici, and a candidate pathogenicity gene on chromosome 6 was selected based on its effector-like characteristics. The candidate gene was cloned byAgrobacterium tumefaciens-mediated transformation, and a pathology test assessed the effect of the mutant strains on ‘Renan’. This gene was demonstrated to be involved in quantitative pathogenicity. By cloning a newly annotated quantitative-effect gene inZ. triticithat is effector-like, we demonstrated that genes underlying pathogenicity QTL can be similar toAvrgenes. This opens up the previously probed possibility that ‘gene-for-gene’ underlies not only qualitative but also quantitative plant-pathogen interactions in this pathosystem.