Resistance to the oat leaf blotch pathogen (Pyrenophora avenae) is delimited to a region of chromosome 1D that harbors a candidate resistance kinase fusion protein.

key messageAn oat leaf blotch resistance locus effective against different Pyrenophora avenae isolates was identified on chromosome 1D within a narrowly defined region that harbored a kinase fusion protein-encoding candidate resistance gene. Oat leaf blotch, incited by Pyrenophora avenae, can be found globally in all oat-growing regions and has been reported to cause significant yield loss. However, no information exists pertaining to the inheritance, genomic location or class of resistance genes in oat effective against this pathogen. As such, there is no host-pathogen model to describe the pathosystem. Genetic mapping of leaf blotch resistance in two oat populations using three P. avenae isolates identified a common resistance locus situated within a 995-Kb interval on chromosome 1D in the OT3098 genome. Two candidate resistance genes with well-defined roles in plant defense were identified which encoded a serine/threonine-protein kinase and a cysteine-rich receptor-like kinase fusion protein (Cys RLK). Identical and apparently functional proteins encoded by each candidate gene were annotated in susceptible genotypes, while truncated proteins or the absence of a protein was annotated among resistant genotypes. These observations suggest that the candidate genes act as susceptibility genes, consistent with an inverse gene-for-gene system. If the Cys RLK is ultimately proven to be the susceptibility gene, this would provide another example of a kinase fusion protein functioning in plant immunity. It is proposed that this leaf blotch resistance locus on chromosome 1D can be referred to as Spa1