<i>Pyrenophora teres</i> f. <i>maculata</i>, Causal Agent of Spot Form Net Blotch of Barley, Is an Emerging Pathogen of Durum Wheat

Emergent plant pathogens threaten global food security, as they evolve to infect new hosts and spread to new geographic regions. <i>Pyrenophora teres</i> f. <i>maculata</i> is a foliar pathogen of barley that is present worldwide and can cause significant yield losses. Recent reports indicated that <i>P. teres</i> f. <i>maculata</i> has made a host jump to wheat, a staple food crop responsible for a significant portion of global caloric intake. In this study, a tetraploid wheat panel comprising local and global <i>Triticum turgidum</i> subspecies was screened with six <i>P. teres</i> f. <i>maculata</i> isolates, and a range of resistant to moderately susceptible reaction types were observed. A recombinant inbred population, developed from a cross between the moderately susceptible durum cultivar Divide and the resistant cultivated emmer accession PI 272527, was inoculated with <i>P. teres</i> f. <i>maculata</i> isolates from the United States, Denmark, New Zealand, and Australia, and quantitative trait loci analysis identified loci associated with resistance. To identify associations with resistance in the broader durum wheat population, the <i>P. teres</i> f. <i>maculata</i> isolate FGOB10Ptm-1 was used to inoculate a representative subset of the Global Durum Panel, and a genome-wide association study was performed. Results of both host mapping studies indicated a major association with response to <i>P. teres</i> f. <i>maculata</i> on the short arm of durum wheat chromosome 2A with additional minor loci also being identified. This work establishes <i>P. teres</i> f. <i>maculata</i> as an emerging pathogen of durum wheat and identifies genomic loci associated with resistance, potentially useful for controlling this disease.