Genetic analysis and detection of new QTL alleles for Septoria tritici blotch resistance using two advanced backcross wheat populations

Septoria tritici blotch (STB) is the most aggressive disease that plagues wheat production across the world. In this study, we utilized two advanced backcross populations designated as B22 and Z86 to quest new genetic resources for STB field resistance. The populations B22 and Z86 were derived by crossing winter wheat cultivars Batis' and Zentos' with unique primary (exotic) hexaploid wheat accessions Syn022L and Syn086L, respectively. QTL analysis revealed ten QTL in the population B22 of which at five loci the introgression of exotic alleles resulted in an increase in STB resistance. The strongest exotic QTL allele was detected on chromosome 2D which decreases disease severity by 20.8%. In population Z86, five QTL were identified of which three resulted in decreasing STB severity due to the introgression of exotic alleles. Here, the strongest QTL QStb.Z86.3A was found on chromosome 3A which decreases disease severity by 19.7%. In both populations, 53% of the exotic alleles were associated to decrease STB severity suggesting the utility of primary wheat gene pool in questing new resistance resources in wheat.