Evaluation of a barley core collection for spot form net blotch reaction reveals distinct genotype-specific pathogen virulence and host susceptibility.

Spot form net blotch (SFNB) caused by Pyrenophora teres f. maculata is a major foliar disease of barley (Hordeum vulgare) worldwide. SFNB epidemics have recently been observed in major barley producing countries, suggesting that the local barley cultivars are not resistant and that virulence of the local pathogen populations may have changed. Here we attempt to identify sources of resistance effective against four diverse isolates of P. teres f. maculata collected from around the world. A total of 2,062 world barley core collection accessions were phenotyped using isolates of the pathogen collected in the United States (FGO), Australia (SG1), New Zealand (NZKF2), and Denmark (DEN 2.6). Isolate-specific susceptibility was identified in several of the barley accessions tested, indicating variability in both pathogen virulence and host resistance/susceptibility. Collectively, only 15 barley accessions were resistant across all isolates tested. These resistant accessions will be used to generate mapping populations and for germplasm development. Future research will involve the characterization of host resistance, pathogen virulence, and the host-pathogen interaction associated with SFNB of barley.