Fine mapping of a FHB resistance QTL using genome-wide association study of a durum breeding population derived from DT696 source of resistance

Commercial durum cultivars have a low level of resistance to Fusarium head blight (FHB) with devastating consequences in favourable disease environments. Triticum turgidum ssp. durumline DT696 is an adapted source of FHB resistance in Canada. Previous analysis using a bi-parental population developed from a cross of experimental lines DT707 with DT696 returned a stable FHB QTL on chromosome 5AL spanning a 16.3 cM interval. A Genome-Wide Association Study (GWAS), which benefits from the recombination events in diverse genotypes, was used for genetic dissection of the 5AL QTL. A set of 223 lines that represented all the recombination events at the 5A locus was selected from 401 lines derived from multiple populations with DT696 in their pedigree. The set of 223 lines was genotyped with the 90K iSelect high density wheat array. The GWAS was conducted using 8782 Single Nucleotide Polymorphism (SNP) markers and multi-locational time-course phenotypic data that included FHB incidence, severity, index and Area Under Disease Progress Curve (AUDPC). The 5A QTL was confirmed in the population of derivatives, suggesting the QTL is stable in various genetic backgrounds. Only three SNP markers, spanning 0.7 cM within the previously detected interval, retained the association with FHB traits and 12% of phenotypic variation was explained by this QTL. These SNP markers have been converted to Kompetetive Allele Specific PCR (KASP) markers and we are further validating them in the durum breeding program as candidates for marker assisted selection.