Genome-wide association study for adult plant resistance to yellow rust in spring bread wheat (Triticum aestivum L.)

Yellow rust, caused by Puccinia striiformis f. sp. tritici, is a common and serious fungal disease of wheat (Triticum aestivum L.) all over the world and particularly in the Central and West Asia and North Africa region. To identify effective yellow rust resistance loci, genome-wide association study (GWAS) was performed using 196 bread wheat genotypes based on 10,477 single nucleotide polymorphisms markers. Adult plants were evaluated under field conditions for resistance to yellow rust for 2 years (2014–2015) at ICARDA station, Marchouch, Morocco. Out of the 196 genotypes, 85 genotypes (43.37%) were resistant, 22 genotypes (11.22%) were moderately resistant, 13 genotypes (6.63%) were moderately susceptible, 48 genotypes (24.49%) were moderately susceptible to susceptible and 28 genotypes (14.29%) were susceptible to Puccinia striiformis f. sp. tritici. GWAS using mixed linear model identified 23 markers on chromosomes 2A, 2B, 2D and 7B significantly associated with adult plant resistance at false discovery rate (FDR-adjusted P ≤ 0.05). Of which, three markers were within 10 wheat functional genes involved in several plant disease resistance and defense mechanism. Five of the reported functional genes are annotated as disease resistance proteins with nucleotide-binding site leucine repeat domains. BLAST analysis confirmed that YrR61 and Yr17 were mostly the candidate genes linked to the marker Tdurum_contig29983_490 on chromosome 2A. Moreover, markers identified on chromosome 7B and Kukri_c12648_434 on 2D were not mapped within any of previously reported gene/QTL region hence, representing novel resistance loci for Pst and needs to be confirmed using an allelism test.