Abstract
The role of six inducing resistance chemicals (IRCs), i.e. ascorbic acid, oxalic acid, sodium salicylate, di-basic potassium phosphate, salicylic acid and benzothiadiazole (BTH) compared to the fungicide (Tilt) was tested against the wheat leaf rust caused by Puccinia triticina in two wheat cultivars Giza 139 and Giza 168 under greenhouse and field conditions in 2011/12 growing season in Sharkia Governorate, Egypt. All treatments and the fungicide significantly decreased disease severity (%), electrolyte leakage and suppressed the disease symptoms as compared to the control treatment in both cultivars. Reactive oxygen species (ROS) such as superoxide (O-2(center dot-)) and hydrogen peroxide (H2O2) levels were decreased significantly as a result of chemical inducers treatments as compared to the control and fungicide treatments. Consequently, antioxidant enzymes, catalase (CAT) and dehydroascorbate reductase (DHAR) activities were significantly increased in the infected wheat leaves treated with IRCs as compared to the control and fungicides treatments. The fungicide was not affecting significantly on ROS levels and antioxidant activities, indicating its direct toxic effect on the pathogen. These results suggest that IRCs up-regulated the antioxidant enzymes, CAT and DHAR which can play an important role in suppressing wheat leaf rust pathogen. This was confirmed by the low levels of ROS such as O center dot- and H2O2.