A wheat chromosome 5AL region confers seedling resistance to both tan spot and Septoria nodorum blotch in two mapping populations

Tan spot(TS) and Septoria nodorum blotch(SNB), caused by Pyrenophora tritici-repentis and Parastagonospora nodorum, respectively, are important fungal leaf-spotting diseases of wheat that cause significant losses in grain yield. In this study, two recombinant inbred line populations, ‘Bartai’ בCiano T79’(referred to as B × C) and ‘Cascabel’ בCiano T79’(C × C) were tested for TS and SNB response in order to determine the genetic basis of seedling resistance. Genotyping was performed with the DAr Tseq genotypingby-sequencing(GBS) platform. A chromosome region on 5 AL conferred resistance to TS and SNB in both populations, but the effects were larger in B × C(R2= 11.2%–16.8%) than in C × C(R2= 2.5%–9.7%). Additionally, the chromosome region on 5 BL(presumably Tsn1)was significant for both TS and SNB in B × C but not in C × C. Quantitative trait loci(QTL)with minor effects were identified on chromosomes 1 B, 2 A, 2 B, 3 A, 3 B, 4 D, 5 A, 5 B, 5 D, 6 B,and 6 D. The two CIMMYT breeding lines ‘Bartai’ and ‘Cascabel’ contributed resistance alleles at both 5 AL and 5 BL QTL mentioned above. The QTL on 5 AL showed linkage with the Vrn-A1 locus, whereas the vrn-A1 allele conferring lateness was associated with resistance to TS and SNB.