Association mapping of tan spot resistance in the Global Durum Panel

Authors: SZABO-HEVER, AGNES - Oak Ridge Institute For Science And Education (ORISE); SINGH, GURMINDER - North Dakota State University; PETERS HAUGRUD, AMANDA - Oak Ridge Institute For Science And Education (ORISE); RUNNING, KATHERINE - North Dakota State University; SENEVIRATNE, SUDESHI - North Dakota State University; Zhang, Zengcui; SHI, GONGJUN - North Dakota State University; BASSI, FILIPPO - International Center For Agricultural Research(ICARDA); MACCAFERI, MARCO - University Of Bologna; CATTIVELLI, LUIGI - Crea - Research Centre For Genomics And Bioinformatics; TUBEROSA, ROBERTO - University Of Bologna; Friesen, Timothy; LIU, ZHAOHUI - North Dakota State University; Xu, Steven; Faris, Justin

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2023
Publication Date: 10/1/2023
Citation: Szabo-Hever, A., Singh, G., Peters Haugrud, A., Running, K., Seneviratne, S., Zhang, Z., Shi, G., Bassi, F., Maccaferi, M., Cattivelli, L., Tuberosa, R., Friesen, T.L., Liu, Z., Xu, S.S., Faris, J.D. 2023. Association mapping of tan spot resistance in the Global Durum Panel. Phytopathology. 113(10):1967-1978. https://doi.org/10.1094/PHYTO-02-23-0043-R.
DOI: https://doi.org/10.1094/PHYTO-02-23-0043-R

Interpretive Summary: Tan spot is an important fungal disease of durum wheat, which is used to make pasta products. The disease can cause significant losses in yield and quality in most durum wheat-growing regions of the world. In this research, a set of 510 durum wheat lines from various durum-growing regions of the world was tested for reaction to tan spot to identify lines with high levels of resistance. Subsequent genetic analysis was conducted to identify regions of the durum wheat genome that contain genes governing resistance or susceptibility to tan spot. Several durum lines with resistance to all fungal strains tested were identified. Genetic analysis revealed genes identified in previous studies including one major gene that conferred resistance to two fungal strains and three different genes that made durum lines susceptible to specific strains of the tan spot pathogen. In addition to these genes, two new genes associated with resistance to specific fungal strains were identified. The identification of these genes and their locations in the durum wheat genome and the identification of durum lines with high levels of tan spot resistance will allow durum breeders to use conventional breeding techniques to develop tan spot-resistant durum varieties more efficiently.

Technical Abstract: Tan spot, caused by the necrotrophic fungal pathogen Pyrenophora tritici-repentis, is an important disease of durum and common wheat worldwide. Compared to common wheat, less is known about the genetics of tan spot resistance in durum wheat. We evaluated 510 durum lines from the Global Durum wheat Panel (GDP) for sensitivity to the necrotrophic effectors (NEs) Ptr ToxA and Ptr ToxB, and for reaction to P. tritici-repentis isolates representing races 1-5. Overall, susceptible durum lines were most prevalent in South Asia, the Middle East, and North Africa. Genome-wide association analysis showed the race nonspecific resistance gene Tsr7 was significantly associated with tan spot caused by races 2 and 3, but not races 1, 4, or 5. The NE sensitivity genes Tsc1 and Tsc2 were associated with susceptibility to Ptr ToxC- and Ptr ToxB-producing isolates, respectively, but Tsn1 was not associated with tan spot caused by Ptr ToxA-producing isolates, which further validates that the Tsn1-Ptr ToxA interaction does not play a significant role in tan spot development in durum. A unique locus on chromosome arm 2AS was associated with tan spot caused by race 4, a race once considered avirulent. A novel trait characterized by expanding chlorosis leading to increased disease severity caused by the Ptr ToxB-producing race 5 isolate DW5 was identified, and this trait was governed by a locus on chromosome 5B. We recommend that durum breeders select resistance alleles at the Tsr7, Tsc1, Tsc2, and the chromosome 2AS loci to obtain broad resistance to tan spot.