Document Type : Research Article
Authors
1
Department of Agronomy, Ahv. C., Islamic Azad University, Ahvaz, Iran
2
Department of Water Sciences and Engineering, Ahv.C., Islamic Azad University, Ahvaz, Iran
10.22067/jcesc.2026.97884.1444
Abstract
Introduction
Drought stress is a major constraint limiting maize production and grain quality in arid and semi-arid regions worldwide. It induces oxidative stress, causing damage to cellular structures including DNA. The biomarker 8-hydroxy-2'-deoxyguanosine (8-OHdG) provides a direct quantitative measure of oxidative DNA damage. Grain nutritional quality, particularly iron and protein content, is often compromised under drought conditions. Salicylic acid (SA) enhances antioxidant defense and drought tolerance, while iron (Fe) serves as an essential cofactor for chlorophyll synthesis and antioxidant enzymes. Seed priming with ethephon, an ethylene-releasing compound, can induce systemic stress tolerance. This study hypothesized that seed priming with ethephon combined with foliar application of SA and Fe would reduce oxidative DNA damage, improve plant water status, enhance grain Fe and protein concentrations, and ultimately improve grain yield under water deficit conditions.
Materials and Methods
A two-year field experiment was conducted in a semi-arid region using a split-split plot arrangement based on a randomized complete block design with four replications located in Gotvand County, Khuzestan Province. Treatments included irrigation regimes (full irrigation and irrigation withholding at tasseling stage), SA concentrations (0, 100, 200, and 300 mg lit⁻¹), and Fe rates (0, 2, and 4 kg ha⁻¹ as Fe-EDDHA). All maize seeds were primed with 0.05 mM ethephon. Relative water content (RWC), chlorophyll a and b, grain Fe concentration, grain protein percentage, 8-OHdG concentration, and grain yield were measured. Combined analysis of variance was performed using SAS 9.4 with mean comparisons by Duncan's multiple range test at P ≤ 0.05.
Results and Discussion
Drought stress significantly increased 8-OHdG concentration from 1.64 to 2.07 nmol mg⁻¹ protein, indicating enhanced oxidative DNA damage. Simultaneously, drought decreased RWC from 86.50% to 75.88%, chlorophyll a from 3.69 to 2.80 mg g⁻¹ FW, chlorophyll b from 1.51 to 1.17 mg g⁻¹ FW, grain Fe concentration from 162.15 to 157.51 mg kg⁻¹, and grain yield from 8317 to 6701 kg ha⁻¹. However, grain protein percentage increased from 7.68% to 9.93% under drought stress due to a concentration effect where reduced carbohydrate accumulation leads to relative protein enrichment. Foliar application of SA and Fe, particularly at 300 mg lit⁻¹ SA and 4 kg ha⁻¹ Fe, significantly reduced 8-OHdG concentration to 1.58 and 1.69 nmol mg⁻¹ protein, respectively. The highest RWC values were obtained with 300 mg lit⁻¹ SA (86.92%) and 4 kg ha⁻¹ Fe (88.51%). Under irrigation withholding, applying 4 kg ha⁻¹ Fe increased RWC from 72.02% to 84.11%. Similarly, the highest chlorophyll contents were obtained from 300 mg lit⁻¹ SA and 4 kg ha⁻¹ Fe treatments, with Fe application increasing chlorophyll a and b by 19% and 9% under drought stress. Grain Fe concentration was significantly increased by both SA and Fe application, with 300 mg lit⁻¹ SA and 4 kg ha⁻¹ Fe producing the highest grain Fe contents (166.59 and 165.10 mg kg⁻¹, respectively). Grain protein percentage was also significantly enhanced, with 300 mg lit⁻¹ SA (10.00%) and 4 kg ha⁻¹ Fe (10.62%) producing the highest values. The three-way interaction of irrigation × SA × Fe was significant for grain yield. The highest grain yield (8731.2 kg ha⁻¹) was obtained from normal irrigation with 300 mg lit⁻¹ SA and 4 kg ha⁻¹ Fe. Under irrigation withholding, this same treatment produced the highest yield (7196.0 kg ha⁻¹), demonstrating the synergistic role of SA and Fe in mitigating drought stress damage. This yield improvement resulted from simultaneous enhancement of plant water status, preservation of photosynthetic apparatus, reduction of oxidative damage, and improvement of grain quality.
Conclusion
Seed priming with ethephon combined with foliar application of salicylic acid (300 mg lit⁻¹) and iron (4 kg ha⁻¹) effectively alleviates drought-induced oxidative DNA damage, improves plant water status and photosynthetic efficiency and enhances grain nutritional quality through increased Fe and protein accumulation, thereby increasing grain yield of maize under water deficit conditions.
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