Chromosomal location of genes for seedling resistance to tan spot and Stagonospora nodorum blotch in tetraploid wheat

Tan spot and Stagonospora nodorum blotch caused by Pyrenophora tritici-repentis (Died.) Drechs. and Phaeosphaeria nodorum (E. Muller) Hedjarroude, respectively, are the major components of the leaf spotting disease complex of durum wheat (Triticum turgidum L.). These diseases induce significant quality and yield reductions and control through host plant resistance is the most effective and economical method. The objectives of this study were to determine the chromosomal locations of major genes conferring resistance to P. tritici-repentis races 1-3 and 5, toxins Ptr ToxA and Ptr ToxB, and P. nodorum isolate Sn2000 in a set of Langdon- Triticum dicoccoides (Israel A) durum substitution lines. Plants were evaluated for disease reaction at the two-leaf stage under controlled environmental conditions. Based on the reactions of the substitution lines, the chromosomal locations of the resistance genes for P. tritici-repentis races 1 and 2, and 3 and 5, were determined to be chromosomes 5B and 3B, respectively. Resistance to toxin Ptr ToxA was located on chromosome 5B whereas toxin Ptr ToxB failed to induce symptoms in the tetraploid genotypes, including the substitution lines. Resistance to P. nodorum isolate Sn2000 was located on chromosome 5B. This is the first study to reveal the chromosomal locations of major genes for resistance to tan spot and Stagonospora nodorum blotch in tetraploid wheat using the Langdon-T. dicoccoides (Israel A) substitution lines.