Integrative genomic approaches to study the barley-Pyrenophora teres interaction

Pyrenophora teres f. teres (Ptt), the causal agent of net-form net blotch in barley, was studied using a bi-parental mapping population (Pop1) of 305 isolates derived from a cross between two isolates with contrasting virulence on barley cultivars Skiff and Prior. QTL analysis identified virulence loci on chromosomes (Chr) 3 and 10 for Skiff, and on Chr 1, 4, and 5 for Prior. Major QTL on Chr 3 and 5 explained 24% and 40% of phenotypic variation, respectively. A second population (Pop2) was developed by crossing two Pop1 isolates, one carrying major QTL on Chr 3 and 5 and one avirulent. Isolates from Pop2 with single QTL were phenotyped across a Prior/Skiff recombinant inbred line population to identify corresponding host susceptibility/resistance loci. Skiff virulence QTL on Chr 3 corresponded to barley Chr 3H and 6H, while Prior virulence QTL on Chr 5 mapped to Chr 6H. RNA expression analysis of virulent and avirulent Pop2 isolates identified five candidate genes linked to the Chr 5 QTL, including two predicted effectors. These findings suggest both gene-for-gene and inverse gene-for-gene interactions in the Ptt-barley pathosystem and advance the understanding of molecular mechanisms underlying host-pathogen specificity.