Mapping Resistance to Multiple Leaf Spotting Diseases in Steele-ND/ND 735 Wheat Population.

A recombinant inbred lines (RILs) population (Steele-ND/ND 735) was developed from a cross between the hard red spring wheat (Triticum aestivum L.) (HRSW) leaf spot resistant line ND 735 and the susceptible cultivar Steele-ND. The Steele-ND/ND 735 RILs population has been used extensively to determine the inheritance of resistance to leaf spotting diseases, tan spot (TS) and Stagonospora nodorum blotch (SNB), and to map the resistance gene(s) underlying the traits. Genetic and molecular mapping of the F₁, F₂ generations, and the RILs with spore suspension and culture filtrate of Pyrenophora tritici-repentis race 5 and with DArT and SSR markers indicate the same single recessive gene located on short arm of chromosome 2B, designated Tsr6, controls resistance/insensitivity. The same single recessive gene located on long arm of chromosome 5B, previously designated Tsr1, also controls resistance/insensitivity to necrosis induced by P. tritici-repentis race 2. Resistance to SNB induced by spore suspension and culture filtrate of Phaeosphaeria nodorum Sn2000 was controlled by a single major located on long arm of chromosome 5B. Overall, this study suggests that both TS and SNB follow the toxin model of gene-for-gene hypothesis.