Study of antioxidant defense genes expression profile pattern of rice (Oryza sativa L.) cultivars in response to drought stress

To study defense genes expression profile pattern of rice in response to abiotic stress, also to evaluate the drought tolerance of cultivars and to investigate the mechanism of drought tolerance, an experiment was conducted based on randomized complete block design in two separate environments (drought stress and non-stress). The rice cultivars used included two commercial cultivars, i.e., Ahlemi-Tarom, Sepidrood, and three promising lines of fourth generation mutants numbered 4, 94 and 95 tested on a research farm at Gonbad Kavous University in the 2018 crop year. When carrying out the drought stress-related experiment, irrigating the farm was completely cut off from the day 40 after the transplantation (a stage with maximum tillering) until the end of the growth period. In seeding stage, each plant’s leaf was separately sampled in each block (under the stress and non-stress conditions). The TBARM, Superoxide and Hydrogen peroxide contents and genes expression of the oxidative stress pathway including Superoxide dismutase, Catalase, Ascorbate peroxidase and Glutathione peroxidase, was measured by extracting from each leaf sample. Results indicated that the drought-tolerant mutant lines had lower TBARM, Superoxide and Hydrogen peroxide contents compared to the studied cultivars. The mutant lines numbered 94, 4 and 95 and the cultivars of Ahlemi-Tarom and Sepidrood had the highest to lowest levels of genes expression and yield content. Accordingly, there was a complete relationship between a decrease in TBARM, Superoxide and Hydrogen peroxide and an increase in levels of genes expression. The mutant No. 94 had the highest yield and genetic potential in terms of drought tolerance; therefore, the mentioned mutant is recommended for carrying out further studies.