Identification of a major dominant gene for race nonspecific tan spot resistance in wild emmer wheat
Key message A single dominant gene found in tetraploid and hexaploid wheat controls broad spectrum race nonspecific resistance to the foliar disease tan spot caused by Pyrenophora tritici repentis Abstract Tan spot is an important foliar disease of durum and common wheat caused by the necrotrophic fungal pathogen Pyrenophora tritici repentis Genetic studies in common wheat have shown that pathogen produced necrotrophic effectors interact with host genes in an inverse gene for gene manner to cause disease, but quantitative trait loci (QTLs) with broad race nonspecific resistance also exist. Less work has been done to understand the genetics of tan spot interactions in durum wheat. Here, we evaluated a set of Langdon durum wild emmer Triticum turgidum ssp. dicoccoides disomic chromosome substitution lines for reaction to four P. tritici repentis isolates representing races 1, 2, 3, and 5 to identify wild emmer chromosomes potentially containing tan spot resistance genes. Chromosome 3B from the wild emmer accession IsraelA rendered the tan spot susceptible durum cultivar Langdon resistant to all four fungal isolates. Genetic analysis indicated that a single dominant gene, designated Tsr7 governed resistance. Detailed mapping experiments showed that the Tsr7 locus is likely the same as the race nonspecific QTL previously identified in the hexaploid wheat cultivars BR34 and Penawawa. Four user friendly SNP based semi thermal asymmetric reverse PCR (STARP) markers cosegregated with Tsr7 and should be useful for marker assisted selection of resistance. In addition to 3B, other wild emmer chromosomes contributed moderate levels of tan spot resistance, and, as has been shown previously for tetraploid wheat, the Tsn1 Ptr ToxA interaction was not associated with susceptibility. This is the first report of a major dominant gene governing resistance to tan spot in tetraploid wheat.
Theoretical and Applied Genetics