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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Cereal Crops Improvement Research » Research » Publications at this Location » Publication #410373

Research Project: Improvement of Disease and Pest Resistance in Barley, Durum, Oat, and Wheat Using Genetics and Genomics

Location: Cereal Crops Improvement Research

Title: Molecular mapping of a novel genetic locus governing enhanced susceptibility to tan spot in durum wheat

item PFAFF, TIANA - North Dakota State University
item SINGH, GURMINDER - North Dakota State University
item RUNNING, KATHERINE - North Dakota State University
item SZABO-HEVER, AGNES - North Dakota State University
item Faris, Justin

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/14/2023
Publication Date: 1/12/2024
Citation: Pfaff, T., Singh, G., Running, K., Szabo-Hever, A., Faris, J.D. 2024. Molecular mapping of a novel genetic locus governing enhanced susceptibility to tan spot in durum wheat. Meeting Abstract. Poster No. PO0379.

Interpretive Summary:

Technical Abstract: Tan spot is an important foliar disease in wheat caused by the fungal pathogen Pyrenophora tritici-repentis (Died.) Drechs. (Ptr). The wheat-Ptr pathosystem follows an inverse gene-for-gene model where pathogen-produced necrotrophic effectors (NEs) are recognized by dominant host genes resulting in host-induced programmed cell death, which leads to disease in the plant. The NE Ptr ToxB is recognized by the gene Tsc2, which results in a compatible interaction that leads to induction of chlorosis in both durum and common wheat. In genome wide association studies (GWAS) on the Global Durum Panel, we observed that infiltration of Ptr ToxB into leaves of some wheat lines showed an expansion of chlorosis outside the infiltrated area to the distal end of the leaf, and this expansion was associated with increased disease severity. The locus responsible for chlorosis expansion, which we have designated as Tsc3, was located on chromosome arm 5BL in durum wheat. To precisely map the Tsc3 locus and initiate map-based cloning of the gene, we developed an F2 population derived from durum varieties Kronos and Simeto. Kronos and Simeto are sensitive to Ptr ToxB, but only Simeto expresses expansion of chlorosis outside the infiltration site. Initial low-resolution mapping was completed using 342 F2 plants and 9 KASP markers developed from the polymorphic SNPs identified in the Infinium iSelect 90K SNP array. For saturation mapping, an additional 15 KASP markers were designed from polymorphic SNPs identified by alignment of genes annotated in the Svevo.v1 reference assembly to the Kronos scaffold assemblies and a Simeto assembly. Using 675 F2 plants and the 24 KASP markers, we have delineated the Tsc3 locus to a 1.1 cM interval and identified nine markers that cosegregate with the gene. The Tsc3 locus resides within a 3.2 Mb physical interval on chromosome arm 5BL in the Svevo.v1 reference genome, which contains about 40 high-confidence genes. High-resolution mapping of the locus using approximately 2,300 F2 plants has been initiated to resolve the markers and further narrow the candidate gene interval. In addition, an ethylmethane-sulfonate (EMS)-induced mutant population is currently being developed to identify putative Tsc3-disrupted mutants for gene validation. This work will shed light on the molecular mechanisms operating in the wheat-Ptr pathosystem and aid in the development of new strategies to develop tan spot resistant wheat.