# Identification of resistance sources and genomic regions regulating spot blotch resistance in Asian bread wheat (Triticum aestivum L.) via genome‐wide association study

## TL;DR

Researchers identified wheat varieties resistant to spot blotch and found genetic markers linked to resistance, which can help breed more resilient crops.

## Contribution

The study identified stable genetic markers and candidate genes for spot blotch resistance in bread wheat using GWAS.

## Key findings

- Genotypes BGD54, IND56, and BGD55 showed high resistance to spot blotch and are potential donors for breeding.
- Seven stable marker-trait associations were found on chromosomes 3D, 5A, 3B, and 1B, explaining 3.86%–18.17% of phenotypic variance.
- Candidate genes linked to resistance include those encoding leucine-rich repeats, GSTs, zinc fingers, P450s, and kinases.

## Abstract

Spot blotch (SB), caused by Bipolaris sorokiniana, is a major yield‐limiting disease of wheat (Triticum aestivum L.) in the warm, humid agroclimatic zones of South Asia. The development of resistant cultivars through molecular approaches offers a sustainable strategy for managing this disease. This study aimed to identify resistant genotypes and associated single‐nucleotide polymorphism markers in a panel of 187 spring bread wheat lines via field‐based phenotyping and genome‐wide association study (GWAS). The panel was genotyped via the DArTSeq genotyping‐by‐sequencing platform and evaluated for SB resistance under artificially inoculated field conditions across two crop seasons (2019–2020 and 2020–2021) at Agua Fria, Mexico. Significant phenotypic variation was observed, with genotypes BGD54, IND56, and BGD55 showing high levels of resistance, indicating their potential as resistance donors. GWAS identified multiple marker‒trait associations (MTAs) linked to SB resistance, with seven stable MTAs consistently detected across years and models, located on chromosomes 3D, 5A, 3B, and 1B, and explaining 3.86%–18.17% phenotypic variance. Most of these MTAs colocalized with previously reported genomic regions for SB resistance. In silico analysis revealed candidate genes within these regions encoding potassium transporters, zinc finger proteins, glutathione S‐transferases, FBD domain proteins, leucine‐rich repeats, protein kinases, dirigent proteins, and cytochrome P450 enzymes. The identified stable MTAs and associated candidate genes offer valuable resources for marker‐assisted selection and functional validation in wheat breeding programs targeting SB resistance.

Evaluated 187 bread wheat lines for spot blotch resistance across two field seasons.BGD54, IND56, and BGD55 identified as promising donors with high resistance.GWAS identified seven stable marker‒trait associations on chromosomes 3D, 5A, 3B, and 1B.Stable single‐nucleotide polymorphisms explained 3.86%–18.17% of phenotypic variation in disease resistance.Several candidate genes linked to defense: leucine‐rich repeats, GSTs, zinc fingers, P450s, and kinases.

Evaluated 187 bread wheat lines for spot blotch resistance across two field seasons.

BGD54, IND56, and BGD55 identified as promising donors with high resistance.

GWAS identified seven stable marker‒trait associations on chromosomes 3D, 5A, 3B, and 1B.

Stable single‐nucleotide polymorphisms explained 3.86%–18.17% of phenotypic variation in disease resistance.

Several candidate genes linked to defense: leucine‐rich repeats, GSTs, zinc fingers, P450s, and kinases.

Spot blotch, caused by the fungus Bipolaris sorokiniana, is a serious wheat disease that reduces yields, especially in warm and humid regions of South Asia. In this study, 187 wheat varieties from India and Bangladesh were tested for their resistance to the disease under field conditions in Mexico. We identified several wheat lines, such as BGD54, IND56, and BGD55, that showed strong resistance and could be used as parents in breeding programs. Using advanced genetic analysis (genome‐wide association study), we found seven consistent single‐nucleotide polymorphism markers linked to disease resistance, located on four chromosomes. These markers explained up to 18.17% of the variation in resistance and were linked to genes involved in plant defense. These findings provide valuable tools for developing new wheat varieties with durable resistance to spot blotch, helping farmers reduce yield losses and improve food security in regions where the disease is a major problem.