Mediterranean durum wheat: A genetically diverse panel harboring valuable sources of resistance to tan spot disease
The production of durum wheat is threatened by biotic stresses including tan spot (TS), a foliar disease caused by Pyrenophora tritici-repentis. Little is known regarding TS resistance in durum compared with common wheat. In this study, we evaluated the population structure, genetic diversity, and resistance to TS at the adult plant and seedling stages of a collection of durum landraces, elite cultivars and breeding material from 11 countries in the Mediterranean Rim. Two-hundred fifty-eight accessions were genotyped using DArTseq technology and genome-wide association analysis (GWAS) was conducted to identify markers associated with TS resistance. Discriminant analysis of principal components (DAPC) using single nucleotide polymorphism (SNP) markers indicated seven populations, while STRUCTURE analysis identified two populations. The variation observed among populations was 26.0% of the total, whereas 61.3% and 12.8% of the variation was attributed to individuals within populations and differences between individuals, respectively. The broad sense heritability estimate for TS resistance was equal to 0.60. GWAS identified 29 SNPs associated with TS resistance that explained 4.4% to 13.1% of the phenotypic variation, and which were located on all chromosomes with the exceptions of 4A, 5A and 5B. The results indicate that chromosomes 2B, 7A and 7B play an important role in TS resistance, and that the identified resistant genotypes could be incorporated in breeding efforts.