Abstract
Stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most disturbing diseases of wheat worldwide. Resistant cultivars are the best strategy to control the disease. Importantly, the mechanisms of susceptibility and resistance are required urgently. As a result of wheat inoculation, disease severity, disease symptoms and electrolyte leakage were decreased significantly in resistant cultivars compared with susceptible ones, however, chlorophyll a and b concentrations were increased significantly in the resistant cultivars. Yr18 resistant gene, over accumulated in resistant cultivars, resulted in a much greater of reactive oxygen species (ROS), mainly superoxide (O2) and hydrogen peroxide (H2O2) accumulation and lower catalase (CAT), peroxidase (POX) and polyphenol oxidase (PPO) activities together. Susceptible wheat cultivar inoculated with P. striiformis was colonized extensively, produced large amount of spores, intercellular hyphae and haustoria, compared with the resistant cultivar in which the haustoria and hyphae were restricted and abnormally developed.