P-135 - A locus on barley chromosome 7H confers susceptibility to the necrotrophic fungal pathogen Pyrenophora teres f. maculata

The fungus Pyrenophora teres f. maculata causes spot form net blotch on barley. Using a biparental fungal mapping population we identified two loci associated with virulence targeting barley susceptibility genes at chromosomes 2H and 7H, respectively, in the barley population Hockett x PI67381, providing evidence of an underlying inverse gene-for-gene interaction. Inoculations on the Hockett x PI67381 population with a set of P. teres f. maculata isolates showed that US isolates harbored both virulence loci targeting barley 2H and 7H. By contrast, Danish and New Zealand isolates targeted only 2H, and the Australian isolate targeted only 7H. To gain deeper understanding of the genetics of susceptibility to spot form net blotch, we developed a second barley population, TR326 x PI67381, segregating for susceptibility to P. teres f. maculata. The TR326 x PI67381 population was inoculated with the same isolates tested on Hockett x PI67381. QTL analysis showed that the US and Australian isolates targeted only the 7H locus, whereas the Danish and New Zealand isolates targeted a novel locus on chromosome 4H. In both populations the same genomic position on 7H was associated with susceptibility to multiple isolates. Therefore, the same susceptibility gene on 7H is likely present in barley lines Hockett and TR326. To verify this hypothesis, we are testing additional isolates from diverse geographical origins as well as a third barley population.