Genome-wide association mapping of resistance to Exserohilum spike blight in wheat

Authors: KORRA, TULASI - Banaras Hindu University; CHANDRA, RAM - Banaras Hindu University; ANGIDI, SRUSHTIDEEP - North Dakota State University; THERA, UDAY - University Of Maryland; THIRUNARAYANAN, PERUMAL - Banaras Hindu University; Underwood, William

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2026
Publication Date: 7/30/2026
Citation: Korra, T., Chandra, R., Angidi, S., Thera, U., Thirunarayanan, P., Underwood, W. 2026. Genome-wide association mapping of resistance to Exserohilum spike blight in wheat. Plants. 15(15). Article 2351. https://doi.org/10.3390/plants15152351.
DOI: https://doi.org/10.3390/plants15152351

Interpretive Summary: Exserohilum spike blight is an emerging disease of wheat, particularly in warmer climates. This disease is caused by the fungus Exserohilum rostratum, a nectrotrophic pathogen that causes disease by killing host tissues. Resistance of wheat to Exserohilum spike blight is quantitative, involving many genes. However, little is currently known about wheat genes or genetic loci involved in resistance to this disease. To identify wheat genomic regions associated with resistance to Exserohilum spike blight, a genome-wide association study was undertaken using a diversity panel of 289 spring wheat lines evaluated for disease response under field conditions over two seasons and across two field locations in India. Significant differences in disease responses of wheat lines within the diversity panel were observed and environmental factors also contributed significantly to disease response. The genome-wide association study identified 23 total significant genetic markers associated with disease response, with one locus detected across both growing seasons. These results provide important information for future breading efforts to reduce the impact of this emerging wheat disease.

Technical Abstract: Exserohilum spike blight caused by Exserohilum rostratum is an emerging constraint in wheat, and improving host resistance is a sustainable strategy because the disease is governed largely by quantitative, environment-responsive responses rather than single major genes. Identifying the genomic regions and biological pathways underlying this quantitative resistance is therefore essential for developing durable resistant varieties. In this study, the Wheat Association Mapping Initiative (WAMI) spring wheat panel (n = 289) was evaluated under field conditions across two contrasting Indian agroclimatic zones, BHU–Varanasi and UAS–Dharwad, over two seasons, 2019 and 2020. Resistance was quantified using two traits: incubation period (IP) and the area under the disease progress curve (AUDPC). Significant genotype, environment, and genotype × environment effects were observed for both traits (P < 0.001), with IP ranging from 3.0 to 5.0 days at BHU and 2.5 to 5.5 days at UAS, and AUDPC ranging from 350.0 to 689.5 at BHU and 315.0 to 549.5 at UAS. IP and AUDPC were weakly correlated (r = -0.18 to 0.16), indicating that these traits represent partially distinct resistance components. Genome-wide association mapping was conducted using 15,737 high-quality SNPs. A total of 23 significant marker–trait associations were detected, 13 for AUDPC and 10 for IP, with most associations showing environment dependence; however, a repeatable AUDPC locus on chromosome 7D was detected across both UAS seasons. Candidate genes included defense-related functions, including an LRR receptor-like kinase TraesCS7B03G0190200 and a WRKY transcription factor TraesCS3B03G0309700 for IP, and an RGA2-like resistance gene TraesCS6B03G0179200 and a PHLOEM UNLOADING MODULATOR-like gene TraesCS7D03G0417800 near the repeatable 7D signal for AUDPC. Together, these findings provide the first GWAS-based framework for E. rostratum resistance in wheat, prioritizing loci for validation and marker deployment in wheat.