Fine-Mapping of a Novel Leaf Rust Resistance Gene in Swiss Winter Wheat Cultivar ‘Forno’

Leaf rust (Puccinia triticina) is a major fungal wheat disease causing significant yield losses globally. Rapidly evolving pathogen races increase the demand for more durable and race non-specific resistance genes. So far only few durable leaf rust resistance genes have been described in detail. The identification and characterization of new sources of durable leaf rust resistance is important to ensure food security in the future. We earlier identified a leaf rust resistance locus on chromosomes 1BS, QLrP.sfr-1BS in the Swiss winter wheat cultivar ‘Forno’. This locus explained 28-32% of the phenotypic variance in a ‘Arina’ x ‘Forno’ recombinant inbred line population. A genetic linkage map for chromosome 1BS spanning a distance of 193 cM was constructed using publically available SSR and RFLP markers. For the fine mapping of QLrP.sfr-1BS, a high resolution mapping population (BC3F2) consisting of 2500 individuals was generated. For further enrichment of the target region, we used the KASP genotyping technology, which resulted in narrowing the target region to 2.1 cM in the fine mapping population. Further, we screened the four parental lines, Arina, Forno, Arina-Lr34 and Arina-1BS for leaf rust field resistance at adult plant stage using a mixture of 16 Swiss leaf rust isolates. Phenotyping results suggested that QLrP.sfr-1BS is possibly a race non- specific gene which shows partial adult plant leaf rust resistance that is not associated with leaf tip necrosis (LTN). To unfold the physical distance of the target region, detailed analysis of syntenic information of reference genome of Brachypodium and wheat is currently in progress.