Morpho-physiological and Biochemical Responses of Barley Plants (Hordeum vulgare L.) Against Barley Net Blotch Disease with Application of Non-traditional Compounds and Fungicides.

Field experiments were conducted in the experimental farm of the Faculty of Agriculture, Kafrelsheikh University, Kafr El-Sheikh, Egypt, during two growing seasons to study the morpho-physiological and biochemical responses of the susceptible barley plants variety Giza 2000, naturally infected with Pyrenophora teres f. sp. teres (the causal agent of barley net blotch disease). Plants were treated with Premis fungicide as seed treatment however, Bleize fungicide, Na salicylate, Na phosphate, Na carbonate, Tannic acid, Oxalic acid, hydrogen peroxide (H2O2), and benzothiadiazole (BTH) compounds used as foliar application. Dis ease severity (%) was significantly decreased as a result of using all treatments, except oxalic acid, in which exhibited less reduction as compared with the control. Disease symptoms were significantly decreased due to all treatments as compared with control treatment. The endogenous reactive oxygen species (ROS) such as superoxide (O2.-) and H2O2 were significantly accumulated early after the natural infection and in a parallel, activities of antioxidant enzymes catalase (CAT), peroxidase (POX) and polyphenol oxidase (PPO) were not increased or changed compared with the control at early same time. Accordingly, as a result of early accumulation of ROS, later on the activities of antioxidant enzymes were increased significantly compared with the control. High accumulation of ROS levels early after infection could show a central role in killing or inhibiting the fungus as well as perhaps immunizing plants against disease symptoms by increasing the enzyme activities. The tested treatments were effective s o that the chlorophyll a and b concentrations were increased compared with control plants. Consequently, yield character values were increased significantly compared with control treatment. Tested non-traditional treatments seem promising and could be used as an alternate and competitive to fungicides under field conditions. [ABSTRACT FROM AUTHOR]