Genome-wide association mapping for field and seedling resistance to the emerging Puccinia graminis f. sp. tritici race TTRTF in wheat

Authors: NEGASH, TAMRAT - Ethiopian Institute Of Agricultural Research; EDAE, ERENA - University Of Minnesota; TILAHUN, LIDIYA - Ethiopian Institute Of Agricultural Research; ANDERSON, JAMES - University Of Minnesota; Rouse, Matthew; BAJGAIN, PRABIN - University Of Minnesota

Submitted to: The Plant Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2022
Publication Date: 10/20/2022
Citation: Negash, T., Edae, E.A., Tilahun, L., Anderson, J.A., Rouse, M.N., Bajgain, P. 2022. Genome-wide association mapping for field and seedling resistance to the emerging Puccinia graminis f. sp. tritici race TTRTF in wheat. The Plant Genome. 15(4). Article e20274. https://doi.org/10.1002/tpg2.20274.
DOI: https://doi.org/10.1002/tpg2.20274

Interpretive Summary: Wheat is grown on over 37 million acres in the United States. The rust diseases of wheat can cause devastating yield losses. Emerging races of the wheat stem rust pathogen such as TTRTF threaten global and United States wheat production. In order to mitigate wheat stem rust, disease-resistant wheat varieties need to be developed. Association analysis for resistance to TTRTF resulted in detection of 20 markers on 11 chromosomes; the marker S1B_175439851 was associated with resistance at both seedling and adult plant stages. Models with 2-4 QTL combinations reduced seedling and field disease severity by 12%-48% and 9%-17%, respectively. Genomic prediction for TTRTF resistance resulted in low to moderately-high predictions (mean correlations of 0.25-0.47). Identification of resistance lines and QTL is expected to assist in selection towards improved resistance to TTRTF. The wheat lines identified with resistance to emerging stem rust race TTRTF can be used in wheat breeding to develop rust-resistant wheat varieties for the United States.

Technical Abstract: Stem rust of wheat, caused by Puccinia graminis f. sp. tritici (Pgt), is one of the most impactful wheat diseases because of its threat to global wheat production. While disease mitigation has primarily been achieved through the deployment of resistant wheat varieties, emerging new virulent races continue to pose risks to the crop. For example, races such as Ug99 (TTKSK), TKTTF, and TTRTF have caused epidemics in different wheat growing regions of the world in recent years. A continual search for new and effective sources of resistance is therefore necessary to safeguard wheat production. This study assessed a breeding panel from the Ethiopian Institute of Agricultural Research (EIAR) wheat breeding program for seedling and field plant resistance to TTRTF, and reports genomic regions conferring resistance to TTRTF. Trait correlations (r) were medium to strong (range of 0.38-0.71) and heritabilities were moderate (0.32-0.56). Association analysis for resistance to TTRTF resulted in detection of 20 markers on 11 chromosomes; the marker S1B_175439851 was associated with resistance at both seedling and adult plant stages. Models with 2-4 QTL combinations reduced seedling and field disease severity by 12%-48% and 9%-17%, respectively. Genomic prediction for TTRTF resistance resulted in low to moderately-high predictions (mean correlations of 0.25-0.47). Identification of resistance lines and QTL in the EIAR population is expected to assist in selection towards improved resistance to TTRTF. Specifically, the application of genomic selection in identifying resistant lines in future related breeding populations will further assist breeding efforts against this new stem rust race.