Molecular Mapping of Resistance to Pyrenophora tritici-repentis in Wheat.

Tan spot, caused by Pyrenophora tritici-repentis, (Died.) Drechs. (anamorph Drechslera tritici-repentis) (Died.) Shoem., is an important foliar disease in the major wheat growing areas of the world. Multiple races of the pathogen have been characterized based on their ability to cause necrosis and/or chlorosis in differential wheat lines. Studies on races determination are recent in Argentina. The International Triticeae Mapping initiative (ITMI) population created by crossing the synthetic hexaploid wheat `W7984´ with the spring wheat cultivar `Opata 85´ was used to identify genomic regions harboring QTLs for resistance to fungal inoculations of two isolates (H0019 and H0120) of the pathogen, obtained at the Facultad de Ciencias Agrarias y Forestales, La Plata, Argentina. Experiments were conducted on three environments. One locus, stable through different environments was found on the short arm of chromosome 6A linked to Xksuh4c, conferring resistance in seedlings. The H0019 isolate was assigned as race 1, it produced necrosis on the differential lines ‘Glenlea’ and ‘Katepwa’, and chlorosis on ‘6B365’. Chlorosis on ‘6B365’ can be attributed to the production of Ptr Tox C, however the gene(s) has not been characterized and it is not possible to confirm this result by PCR. Isolate H0120 is not virulent on the set of differential lines (that would indicate that is race 4).However did not amplify for Tox b gene. Races determination and the possibility of the presence of new races in Argentina are also discussed.