Univrsity of Tehran Press Iranian Journal of Field Crop Science 2008-4811 57 1 2026 03 21 The Effects of Melatonin and Zinc Sulfate on Agronomic Traits and Grain Yield of Quinoa Cultivars Under Salinity Stress Conditions The Effects of Melatonin and Zinc Sulfate on Agronomic Traits and Grain Yield of Quinoa Cultivars Under Salinity Stress Conditions 31 49 105734 10.22059/ijfcs.2025.396913.655147 FA Mahdi Fathi Moghadam Department of Agronomy, Faculty of Agriculture, Shahrood University of Technology, Shahrood, Iran Hamidreza Asghari Department of Agronomy, Faculty of Agriculture, Shahrood University of Technology, Shahrood, Iran Mahdi BaradaranFirozAbadi Department of Agronomy, Faculty of Agriculture, Shahrood University of Technology, Shahrood, Iran Ahmad Gholami Department of Agronomy, Faculty of Agriculture, Shahrood University of Technology, Shahrood, Iran Journal Article 2025 08 20 Introduction. The increasing salinity of soils and water resources in various regions of Iran, particularly in the central and southern parts of Khorasan Razavi Province, has restricted agricultural expansion and reduced the economic performance of crops. Quinoa (Chenopodium quinoa Willd.), a pseudo-cereal with remarkable salt tolerance, has recently attracted considerable attention in breeding and crop development programs due to its high protein content, essential amino acids, and exceptional nutritional value. Previous studies have demonstrated that salinity stress can significantly reduce water and nutrient uptake, photosynthetic efficiency, chlorophyll synthesis, and grain yield. Therefore, identifying physiological compounds that enhance stress resistance, such as melatonin and crucial micronutrients like zinc, can offer effective strategies for improving plant responses under salinity stress conditions. Melatonin, beyond its regulatory function in plant growth under normal conditions, plays a critical role in activating plant defense systems and scavenging reactive oxygen species (ROS). This compound mitigates oxidative damage and improves photosynthetic efficiency in plants exposed to salinity stress. On the other hand, zinc is one of the most important micronutrients involved in over 300 enzymatic processes, playing a vital role in stabilizing chlorophyll structure, promoting protein synthesis, and reducing the uptake of Na⁺ and Cl⁻ ions. Hence, the simultaneous use of melatonin and zinc sulfate could physiologically and biochemically alleviate the adverse effects of salinity stress and ultimately enhance crop performance. Materials and Methods. Given the growing need to expand crop cultivation in saline lands, the present study was conducted to evaluate the effects of seed priming and foliar application of melatonin and zinc sulfate on agronomic, physiological, and yield traits of two quinoa (Chenopodium quinoa Willd.) cultivars under contrasting ecological conditions (saline and non-saline). The experiment was carried out during the 2023–2024 cropping season in two locations—Kashmar (non-saline) and Bardaskan (saline)—as a factorial arrangement based on a randomized complete block design (RCBD) with three replications. Experimental treatments consisted of two quinoa cultivars (Red Carina and Titicaca), three levels of seed priming (control, 100 µM melatonin, and 40 mM zinc sulfate), and three levels of foliar application (control, 0.2 mM melatonin, and 0.5% zinc sulfate). Seed priming was performed by soaking the seeds in the respective solutions for six hours, while foliar spraying was applied at the beginning of the flowering stage under favorable environmental conditions. Soil and water analyses revealed that Bardaskan had a considerably higher electrical conductivity (EC ≈ 16,880 µS cm⁻¹) compared with Kashmar (EC ≈ 538 µS cm⁻¹), confirming the saline nature of the former site. Following the application of treatments, various traits were measured, including final field emergence percentage, stem height, panicle length, collar diameter, shoot dry weight, forage index (percentage of digestible dry matter), concentrations of chlorophyll a and b, protein yield, and grain yield. Data were analyzed using SAS statistical software. Bartlett’s test was applied to examine error homogeneity, and based on its significance, either separate or combined analyses of variance were performed accordingly. Results and Discussion. The results revealed that in the Bardaskan region, salinity stress caused a significant reduction in seed protein yield in the Red Carina cultivar (by approximately 30.02%) and in the Titicaca cultivar (by about 35.39%) compared with the same cultivars grown in the Kashmar non-saline area. Furthermore, grain yield of the Titicaca cultivar was 23.25% higher in Bardaskan and 25.81% higher in Kashmar than that of Red Carina, indicating the relatively greater salt tolerance of Titicaca. In the non-saline condition (Kashmar), combined seed priming and foliar spraying with melatonin increased grain yield by 17.85%, and zinc sulfate by 18.04%. Under saline conditions (Bardaskan), simultaneous application of melatonin and zinc sulfate resulted in even greater yield improvements of 36.91% and 35.70%, respectively. These findings demonstrate that the regulatory role of melatonin and zinc is strengthened under salt stress conditions, and their synergistic effects are more pronounced compared with non-stress environments. Evaluation of physiological traits showed that salt resistance in melatonin and zinc treatments was associated with increased concentrations of chlorophyll a and b, higher stem height, and an improved forage index. Analysis of variance (ANOVA) indicated that all main factors (cultivar, seed priming, and foliar application), as well as their two-way and three-way interactions, had significant effects (p < 0.01) on most measured traits. In saline conditions, the greatest responses were observed for shoot dry weight and chlorophyll content, which were directly related to enhanced photosynthetic activity and accumulation of energetic compounds. Protein determination using the Kjeldahl method indicated that quinoa plants under saline stress could maintain acceptable seed protein levels when micronutrients were supplied, highlighting the nutritional and economic importance of these treatments. According to the results, combined seed priming and foliar application of melatonin and zinc sulfate were more effective in the Titicaca cultivar than in Red Carina. This superiority is likely attributed to the genetic characteristics of Titicaca, including a shorter growth cycle and better adaptation to ionic and osmotic stresses. The primary mechanism of action for these compounds involves activation of the antioxidative defense system, maintenance of ionic balance, enhancement of chlorophyll efficiency, and mitigation of oxidative cellular damage. Conclusion. From an agronomic perspective, this study confirmed that the simultaneous application of melatonin and zinc sulfate not only improves plant growth and yield attributes but also enhances physiological stability under saline conditions. Thus, this integrated approach can be regarded as a cost-effective biotechnological strategy for improving the productivity of saline and semi-saline lands in Iran. In conclusion, the combined use of two bio-regulatory compounds—melatonin and zinc—exhibited synergistic effects in improving salinity tolerance, resulting in significant increases in grain yield and protein yield. The Titicaca cultivar showed overall better responses compared with Red Carina across both experimental sites, with the highest mean yield obtained under concurrent seed priming and foliar application of these two compounds. Accordingly, within the scope of this study, cultivation of the Titicaca cultivar together with simultaneous melatonin and zinc sulfate application is recommended as an effective salinity management strategy to enhance grain yield and protein productivity in quinoa. Introduction. The increasing salinity of soils and water resources in various regions of Iran, particularly in the central and southern parts of Khorasan Razavi Province, has restricted agricultural expansion and reduced the economic performance of crops. Quinoa (Chenopodium quinoa Willd.), a pseudo-cereal with remarkable salt tolerance, has recently attracted considerable attention in breeding and crop development programs due to its high protein content, essential amino acids, and exceptional nutritional value. Previous studies have demonstrated that salinity stress can significantly reduce water and nutrient uptake, photosynthetic efficiency, chlorophyll synthesis, and grain yield. Therefore, identifying physiological compounds that enhance stress resistance, such as melatonin and crucial micronutrients like zinc, can offer effective strategies for improving plant responses under salinity stress conditions. Melatonin, beyond its regulatory function in plant growth under normal conditions, plays a critical role in activating plant defense systems and scavenging reactive oxygen species (ROS). This compound mitigates oxidative damage and improves photosynthetic efficiency in plants exposed to salinity stress. On the other hand, zinc is one of the most important micronutrients involved in over 300 enzymatic processes, playing a vital role in stabilizing chlorophyll structure, promoting protein synthesis, and reducing the uptake of Na⁺ and Cl⁻ ions. Hence, the simultaneous use of melatonin and zinc sulfate could physiologically and biochemically alleviate the adverse effects of salinity stress and ultimately enhance crop performance. Materials and Methods. Given the growing need to expand crop cultivation in saline lands, the present study was conducted to evaluate the effects of seed priming and foliar application of melatonin and zinc sulfate on agronomic, physiological, and yield traits of two quinoa (Chenopodium quinoa Willd.) cultivars under contrasting ecological conditions (saline and non-saline). The experiment was carried out during the 2023–2024 cropping season in two locations—Kashmar (non-saline) and Bardaskan (saline)—as a factorial arrangement based on a randomized complete block design (RCBD) with three replications. Experimental treatments consisted of two quinoa cultivars (Red Carina and Titicaca), three levels of seed priming (control, 100 µM melatonin, and 40 mM zinc sulfate), and three levels of foliar application (control, 0.2 mM melatonin, and 0.5% zinc sulfate). Seed priming was performed by soaking the seeds in the respective solutions for six hours, while foliar spraying was applied at the beginning of the flowering stage under favorable environmental conditions. Soil and water analyses revealed that Bardaskan had a considerably higher electrical conductivity (EC ≈ 16,880 µS cm⁻¹) compared with Kashmar (EC ≈ 538 µS cm⁻¹), confirming the saline nature of the former site. Following the application of treatments, various traits were measured, including final field emergence percentage, stem height, panicle length, collar diameter, shoot dry weight, forage index (percentage of digestible dry matter), concentrations of chlorophyll a and b, protein yield, and grain yield. Data were analyzed using SAS statistical software. Bartlett’s test was applied to examine error homogeneity, and based on its significance, either separate or combined analyses of variance were performed accordingly. Results and Discussion. The results revealed that in the Bardaskan region, salinity stress caused a significant reduction in seed protein yield in the Red Carina cultivar (by approximately 30.02%) and in the Titicaca cultivar (by about 35.39%) compared with the same cultivars grown in the Kashmar non-saline area. Furthermore, grain yield of the Titicaca cultivar was 23.25% higher in Bardaskan and 25.81% higher in Kashmar than that of Red Carina, indicating the relatively greater salt tolerance of Titicaca. In the non-saline condition (Kashmar), combined seed priming and foliar spraying with melatonin increased grain yield by 17.85%, and zinc sulfate by 18.04%. Under saline conditions (Bardaskan), simultaneous application of melatonin and zinc sulfate resulted in even greater yield improvements of 36.91% and 35.70%, respectively. These findings demonstrate that the regulatory role of melatonin and zinc is strengthened under salt stress conditions, and their synergistic effects are more pronounced compared with non-stress environments. Evaluation of physiological traits showed that salt resistance in melatonin and zinc treatments was associated with increased concentrations of chlorophyll a and b, higher stem height, and an improved forage index. Analysis of variance (ANOVA) indicated that all main factors (cultivar, seed priming, and foliar application), as well as their two-way and three-way interactions, had significant effects (p < 0.01) on most measured traits. In saline conditions, the greatest responses were observed for shoot dry weight and chlorophyll content, which were directly related to enhanced photosynthetic activity and accumulation of energetic compounds. Protein determination using the Kjeldahl method indicated that quinoa plants under saline stress could maintain acceptable seed protein levels when micronutrients were supplied, highlighting the nutritional and economic importance of these treatments. According to the results, combined seed priming and foliar application of melatonin and zinc sulfate were more effective in the Titicaca cultivar than in Red Carina. This superiority is likely attributed to the genetic characteristics of Titicaca, including a shorter growth cycle and better adaptation to ionic and osmotic stresses. The primary mechanism of action for these compounds involves activation of the antioxidative defense system, maintenance of ionic balance, enhancement of chlorophyll efficiency, and mitigation of oxidative cellular damage. Conclusion. From an agronomic perspective, this study confirmed that the simultaneous application of melatonin and zinc sulfate not only improves plant growth and yield attributes but also enhances physiological stability under saline conditions. Thus, this integrated approach can be regarded as a cost-effective biotechnological strategy for improving the productivity of saline and semi-saline lands in Iran. In conclusion, the combined use of two bio-regulatory compounds—melatonin and zinc—exhibited synergistic effects in improving salinity tolerance, resulting in significant increases in grain yield and protein yield. The Titicaca cultivar showed overall better responses compared with Red Carina across both experimental sites, with the highest mean yield obtained under concurrent seed priming and foliar application of these two compounds. Accordingly, within the scope of this study, cultivation of the Titicaca cultivar together with simultaneous melatonin and zinc sulfate application is recommended as an effective salinity management strategy to enhance grain yield and protein productivity in quinoa.

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