Identification of the Resistance Gene Sr2 in some Egyptian Wheat Hybrids

Seven Egyptian wheat cultivars were crossed with Sr 2 (the stem rust resistant gene), and their parents, F 1 , F 2 crosses were tested to natural stem rust disease in the field of Gemmeiza Agricultural Station, ARC, during the 2019 to 2021 growing seasons. The Sr 2 gene was completely resistant to stem rust, while the Egyptian cultivars showed different responses to the disease. Sakha-95 was completely resistant, Misr-1 and Misr-2 showed high susceptibility. Gemmeiza-12, Giza-171, and Sakha-94 showed moderate resistance (MR), while a trace of moderate susceptibility (Tr-MS) was recorded for the cultivar Misr-3. All the F 1 crosses were resistant, indicating the dominance of resistance to stem rust disease. Chi-square goodness of fit was used to assess the independence of Sr 2 resistance gene in the tested cultivars and F2 crosses. The crosses Sr 2XGemmeiza-12, Sr 2X Sakha-94, Sr 2XSakha-95 and Sr 2XGiza-171 have the expected segregation ratio of 15:1 for a duplicate gene. However, the crosses Sr 2XMisr-1 and Sr 2XMisr-3 fit a 3:1 ratio conditioned by one dominant gene. The resistance of the cross Sr 2XMisr-2 fits complementary gene action (9:7). Three specific SSR markers (xgwm533, stm559tgag, and stm598cac) were used to identify Sr 2 in the Egyptian cultivars and their F1 populations. The three markers confirmed presence of Sr 2 gene in the Egyptian cultivars and their F1 populations. However, the stm598cac marker could differentiate between the tested cultivars and their F1 populations by amplifying an additional band with a molecular weight of 200bp. Molecular analysis confirmed the results of chi-square test and could be serving in developing wheat programs.