Participation of Reactive Oxygen Species and Nitric Oxide in Defense of Wheat Carrying Sr25 Gene Against Stem Rust

The role of reactive oxygen species (ROS) and nitric oxide (NO) in the defense of Triticum aestivum L. (common wheat) against the rust fungus Puccinia graminis f. sp. tritici Erikss. and Henn. (Pgt) was studied using the example of the interaction between the resistant line of the cultivar Thatcher carrying the Sr25 gene from the tall wheatgrass Thinopyrum ponticum (TcSr25) and the susceptible cultivar Saratovskaya 29 (C29). The seedlings were treated with salicylic acid (SA) as an ROS inducer, verapamil as a Ca²⁺ channel inhibitor, sodium nitroprusside (NP) as a NO donor, and 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (c-PTIO) as NO scavenger. Isolates with reaction 0 (immunity) and 1 (resistance with hypersensitive reaction, HR) were used to infect the seedlings. NO stimulated the growing tube orientation and the formation of the Pgt appressoria on the surface of resistant plants, as well as increased colony growth in susceptible plants if plants were treated one day before or simultaneously with infection. The generation of superoxide anion was the main cause of Pgt appressoria death on the stomata of resistant plants, while NO did not affect tissue penetration. ROS induced HR and accelerated the destruction of the cell cytoplasm, and NO contributed to the expansion of the necrosis zone in resistant plants.