A genome-wide association study reveals novel Fusarium head blight resistance QTL in the durum breeding lines derived from the 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. A Genome-Wide Association Study (GWAS), which
benefits from the recombination events in diverse genotypes, is well suited for genetic dissection of QTL.
GWAS was conducted on 401 breeding lines derived from the Triticum turgidum ssp. durum line DT696,
an adapted source of FHB resistance in Canada. The analysis was conducted using 9043 Single
Nucleotide Polymorphism (SNP) markers generated using the 90K iSelect high density genotyping array
and phenotypic data collected for these lines since 2004 that included FHB incidence, severity, index and
intensity (visual rating of plots) and developmental traits that modulate resistance including plant height,
maturity and lodging. SUPER compressed mixed linear model (cMLM) controlling for population structure
and relatedness was found to be the most appropriate for marker-trait association. Significant marker-trait
associations were detected on chromosomes 6BS and 6BL for FHB incidence, 2B and 7B for FHB
severity and on 6AL for FHB intensity. The genomic intervals with FHB QTL harboured orthologues of
genes involved in plant defense responses. None of FHB resistance QTL were linked to FHB-modulating
developmental traits. SNPs associated with the resistance QTL could be used for high-throughput and
rapid selection in durum wheat breeding gene pyramiding programs.