Genetic architecture of resistance to Septoria tritici blotch (Mycosphaerella graminicola) in European winter wheat

Genome-wide marker–trait associations (MTA) were established in a population of 358 European winter wheat cultivars and 14 spring wheat cultivars (Triticum aestivum L.) for resistance to Septoria tritici blotch caused by the fungal pathogen Mycosphaerella graminicola. The MTA were based on field data in two consecutive years and genotypic data on 732 microsatellite markers. Best linear unbiased estimations (BLUEs) for resistance were calculated across the trials and ranged from 0.67 (most resistant) to 19.63 (most susceptible) with an average value of 4.93. A total of 115 MTA relating to 68 molecular markers was discovered for the two trials and BLUEs by using a mixed linear model corrected by a kinship matrix. In addition, two candidate genes, Ppd-D1 for photoperiodism and the dwarfing gene Rht-D1, were significantly associated with resistance to Septoria tritici blotch. Several MTA co-located with known resistance genes, e.g. Stb1, 3, 4, 6 and 8, while multiple additional MTA were discovered on several chromosomes, such as 2A, 2D, 3A, 5B, 7A and 7D. The results provide proof of concept for the method of genome-wide association analysis and indicate the presence of further Stb resistance genes in the European winter wheat pool.