Mapping of quantitative trait loci for resistance to leaf spot diseases in durum wheat

Three leaf spot diseases, tan spot (caused by Pyrenophora tritici-repentis), Septoria/Stagonospora nodorum blotch (SNB, caused by Parastagonospora nodorum) and Septoria tritici blotch (STB, caused by Mycosphaerella graminicola), often occur as a complex in durum wheat. The leaf spotting complex (LSC) is among the most widespread wheat foliar diseases on the Canadian Prairies and significantly reduces both yield and grain quality; therefore the development of LSC resistant cultivars is the most economically effective and environmentally friendly strategy to manage the disease. Consequently, identification and characterization of effective sources of resistance are critical to the development of elite cultivars with more durable LSC resistance. In this study, quantitative trait loci (QTL) mapping for LSC resistance was conducted in a doubled haploid (DH) population, derived from Strongfield/Pelissier. The DH population, parents and checks were grown and evaluated for LSC reaction in multiple environments. The Illumina Infimum wheat 90K SNP chip was used to generate a genotypic data set on this population from which, QTL contributing to LSC resistance were detected on eight of the fourteen chromosomes. A major QTL explaining up to 20% of the phenotypic variance, with the resistant allele derived from Strongfield, was mapped on chromosome 2B across multiple environments. The findings here will facilitate marker assisted selection (MAS) for resistance to LSC in durum and enable more strategic cultivar development.