Genome wide association mapping for resistance to multiple fungal pathogens in a panel issued from a broad composite cross-population of tetraploid wheat Triticum turgidum

Few resistance genes providing defence against the major fungal diseases septoria tritici blotch (STB), septoria nodorum blotch, leaf rust (LR), and an emerging wheat blast disease have been identified in durum wheat. We identified sixteen fungal disease-associated QTL through genome-wide association mapping of 180 inbred lines sampled from a durum wheat Composite Cross-population. Two STB resistance-associated QTL mapped to chromosome 3A, one of which colocalizes with Stb6 , a known resistance gene previously identified in bread wheat. This partial resistance could be conferred by a new allele of Stb6 or another paralogous gene. The second locus is associated with a reduction in pycnidia density, a recently identified and poorly understood form of resistance. A resistance QTL strongly associated with LR, and colocalizing with Lr61 , was observed in a 3.24 Mbp region on chromosome 6B. QTL mapping of LR resistance following treatment by chitin used in the context of inducer treatment was also investigated. Using a combination of resistance alleles at these loci could confer durable resistance to multiple fungal diseases and aid durum wheat breeders in their fight against these fungal pathogens.