Differential responses of wheat genotypes to irrigation regimes through antioxidant defense system, grain yield, gene expression, and grain fatty acid profile

Wheat production under water-limited conditions is lagging due to our restricted understanding of mechanisms involved in drought tolerance. This study was aimed at the assessment of molecular and physio-biochemical responses of three wheat genotypes including Baran (drought-tolerant), Pishtaz (semi-tolerant) and Zarrin (sensitive). The plants were normally irrigated until the four-leaf stage, and then the irrigation was stopped until the soil moisture reached the desired stress at 100% (normal), 70%, and 40% soil field capacity (FC). The results revealed that leaf total protein content decreased under stress, while proline, catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (GPX) increased. Drought stress at 40% FC decreased grain yield by 18, 20, and 39% for Barran, Pishtaz, and Zarrin, respectively. The gene expression of CAT , APX , GPX , pyrroline-5-carboxylate synthase ( P5CS ) , and Pyrroline-5-carboxylate reductase ( P5CR ) significantly increased at drought, and tolerant genotype represented the higher rate of the gene expression compared with other genotypes. The proline level positively and strongly correlated with P5CS and P5CR gene expression. Grain fatty acid profile showed increased polyunsaturated fatty acid and decreased saturated fatty acids in plants experiencing 40% FC over control. Heat map analysis showed that CAT, APX, GPX, and proline with higher variability can be determined as markers to measure drought impacts. Overall, our findings represented the superior genotype for wheat breeding and also showed the physiological and biochemical changes particularly grain fatty acid profile to obtain the better genotype and irrigation regime in terms of human health.