Determination of Number of Resistance Genes to Stem Rust Disease (Puccinia graminis f.sp. tritici), Race Ug99 in Two Wheat Cultivars

Wheat Stem (Black) rust, caused by the Puccinia graminis f. sp. tritici, is an important disease in the world. Crop losses due to stem rust reported between 70-100 percent. The use of resistant cultivars is the most effective, economic and environmentally safe method to control the disease. Extensive research on stem rust resistance in wheat has been carried out over many years and has been successful in providing farmers with rust resistant cultivars. The main objective of this study was to gain a better genetic understanding of resistance to stem rust (Ug99) in two Iranian wheat cultivars included: Parsi and Sivand, which were crossed with the susceptible parent Morocco. Race TTKST (Ug99) used for this study, which especially has virulence on Sr31 and Sr24 genes. F₃ families were studied in field (adult plant) in Najoro- Kenta in 2011, where they were exposed to artificial inoculation of stem rust. F₃ families were classified into three classes: homozygous resistant, segregating and homozygous susceptible. The number of genes involved was then estimated from the frequencies of families classified in each class. The results of F₃ from the cross Sivand/Morocco and Parsi/Morocco segregated for 2 dominant genes for each Cv. On the base of present of Pseudo-Black Chaff (PBC) on Parent of Parsi Cv. and segregating F₃ family, one of resistance gene in Parsi expected to be Sr2 gene and second unknown gene. The ultimate objective of the work reported in this study would be to catalogue the different unknown genes for APR by locating them on chromosomes using aneuploid analysis or suitable molecular marker systems.