Identification of the Resistance Gene Sr2 in some Egyptian Wheat Hybrids

Abstract

Seven Egyptian wheat cultivars were crossed with Sr2 (the stem rust resistant gene), and their parents, F1, F2 crosses were tested to natural stem rust disease in the field of Gemmeiza Agricultural Station, ARC, during the 2019 to 2021 growing seasons. The Sr2 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 F1 crosses were resistant, indicating the dominance of resistance to stem rust disease. Chi-square goodness of fit was used to assess the independence of Sr2 resistance gene in the tested cultivars and F2 crosses. The crosses Sr2XGemmeiza-12, Sr2X Sakha-94, Sr2XSakha-95 and Sr2XGiza-171 have the expected segregation ratio of 15:1 for a duplicate gene. However, the crosses Sr2XMisr-1 and Sr2XMisr-3 fit a 3:1 ratio conditioned by one dominant gene. The resistance of the cross Sr2XMisr-2 fits complementary gene action (9:7). Three specific SSR markers (xgwm533, stm559tgag, and stm598cac) were used to identify Sr2 in the Egyptian cultivars and their F1 populations. The three markers confirmed presence of Sr2 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.