Regulation of Physiological and Biochemical Mechanisms Related to Water Stress Tolerance in Barley and Improvement of Growth and Productivity Using Salicylic Acid and Chitosan

The present investigation aimed to assess the impacts of three Salicylic Acid (SA) concentrations (T2=100, T3=200, T4=300ppm), three Chitosan concentrations (T5=150, T6=225, T7=300ppm) and T8= Salicylic Acid (100 ppm) with Chitosan (150 ppm) mixture in comparison to control treatment (T1) on two barley cultivars Giza126 and Giza 134 under rainfed conditions. Some vegetative and yield traits were recorded, plant height, spike length, number of gains spike-1, number of spikes/m2, 1000 grain weight, biological and grain yield. A split plot design was performed with three replications. The field experiment was conducted in the northern west coast region of Egypt (Marsa Matruh government) under the rainfed condi­tions during 2019/2020 and 2020/2021 growing seasons. The results showed a direct relationship between increased foliar application and increased yield attributes. Results indicated that Giza 126 cultivar as affected by T4 showed the most desirable values for grains spikes-1 in first season, spikes/m2, biological yield and grain yield during the first and second seasons respectively. In addition, barley cultivar Giza 126 as affected by T3 showed the highest values for grains spikes-1 in second season. On the other hand, barley cultivar Giza 134 as affected by T4 showed the highest values for plant height, spike length and 1000-grain weight in first and second seasons respectively. From results, it can be concluded that the Salicylic Acid (SA) concentration 300 ppm is recommendable for improving the productivity of barley under rainfed conditions of Egypt. To study the potential role of SA and Chitosan on water stress tolerance mechanisms some biochemical and physiological parameters were recorded. Application of SA and Chitosan decreased significantly Reactive Oxygen Species (ROS) measuring by determined the concentrations of MDA and H2O2 especially SA with concentrations 300 ppm (T4). For osmolytes (proline, SSC and SPC), all treatments using SA and Chitosan induced significant increase in osmolytes content compared with control under water stress only in the two studied barley genotypes, except for treatment with Chitosan 225 and 300 ppm in Giza 126 for proline content. Similar results were recorded for antioxidant enzymes activity (CAT, POX and PPO) which showed up-regulation for all treatments compared with control under water stress for the two studied genotypes. On contrast, APX antioxidant enzyme recorded the highest activity in control treatment under water stress only. In general, for all studied treatments comparing with control, application of SA300 ppm and the mixture between SA100 and Chitosan150 ppm were the best treatment for induction of up and down regulation of biochemical and physiological component in the barley cells which is known as defense system against water stress damage.