Genome-Wide Association Study Reveals Novel Powdery Mildew Resistance Loci in Bread Wheat

Area of Science:

• Plant Pathology
• Genetics
• Agricultural Science

Background:

• Powdery mildew (PM), caused by *Blumeria graminis* f. sp. *tritici* (*Bgt*), poses a significant threat to global bread wheat production.
• Current wheat cultivars often lack adequate resistance to PM, necessitating the identification of new resistance sources.
• Genome-wide association studies (GWAS) are crucial for dissecting the genetic basis of complex traits like disease resistance.

Purpose of the Study:

• To conduct a genome-wide association study (GWAS) to identify genetic loci associated with powdery mildew resistance in bread wheat.
• To discover novel marker-trait associations (MTAs) and candidate genes for PM resistance.
• To provide genetic resources for breeding programs developing PM-resistant wheat cultivars.

Main Methods:

• A diverse panel of 286 bread wheat genotypes was evaluated for PM severity over three consecutive years under field conditions.
• Genotyping was performed using the Illumina 90K Infinium iSelect assay to generate genome-wide single-nucleotide polymorphism (SNP) data.
• The FarmCPU multilocus mixed model was employed to identify marker-trait associations (MTAs) at a significance level of *p* ≤ 0.001.

Main Results:

• A total of 113 MTAs associated with PM resistance were identified on chromosomes 1A, 1B, 2B, 3A, 3B, 4A, 4B, 5A, 5B, 6B, 7A, and 7B.
• Four novel MTAs on chromosome 6B were consistently detected across two consecutive years (2020-2021 and 2021-2022).
• Ninety-six candidate genes, including those encoding protein kinases, leucine-rich repeats, and zinc finger proteins, were identified within the confidence intervals of the significant SNPs.

Conclusions:

• The identified MTAs and candidate genes provide valuable genetic resources for enhancing powdery mildew resistance in bread wheat.
• The novel loci on chromosome 6B represent promising targets for marker-assisted selection in wheat breeding programs.
• This study contributes to the development of sustainable strategies for managing PM in wheat production through genetic improvement.