Investigation of the effect of seed priming on improving growth, grain yield, and yield components of different wheat (Triticum aestivum L.) cultivars under rainfed conditions

Introduction
Wheat is the third most widely cultivated cereal crop in the world after maize and rice. It is considered a major source of nutrition for the ever-increasing global population as a staple food (Faisal et al., 2023), with an annual global production of 776.7 million tons in 2020/2021. Many strategies have been developed to produce plants capable of withstanding various stresses. Among these approaches, seed priming has been developed as an effective method for enhancing drought tolerance in plants. Selecting an appropriate priming method based on environmental and soil limitations is essential for stress mitigation. Seed priming stimulates physiological processes by soaking seeds in natural or synthetic solutions. This technique is classified into conventional methods (such as hydropriming, osmopriming, and priming with plant growth regulators) and advanced methods such as nano-priming. Based on the above considerations, drought stress represents one of the most significant challenges facing agricultural production, particularly in rainfed cropping systems. Therefore, alongside the development of drought-resistant cultivars, effective agronomic approaches such as seed priming are increasingly required to mitigate drought stress. The objective of this study was to evaluate the effects of seed priming on physiological traits and grain yield of wheat under rainfed conditions.
 
Materials and methods
This study aimed to evaluate the effects of seed priming on yield and yield components of wheat cultivars under rainfed conditions during the 2020–2021 growing season. The experiment was conducted as a factorial arrangement in a randomized complete block design with three replications at the Qamloo Research Station, Agricultural and Natural Resources Research Center of Kurdistan. Various seed priming treatments, including hydropriming, potassium dihydrogen phosphate, zinc sulfate, potassium nitrate, as well as an unprimed control, were applied to four rainfed wheat cultivars (Azar2, Rasad, Ohadi, and Homa). The priming solutions consisted of 20 mM zinc sulfate, 50 mM potassium dihydrogen phosphate, and 1.5% potassium nitrate prepared with distilled water. Then, each solution was added at a volume five times greater than the seed weight. The seeds were treated in aerated containers using an air pump at 20°C for 12 hours. After the specified duration, the seeds were rinsed three to five times with distilled water and then dried on labeled paper at 20 °C for 48 h. The dried seeds were then packaged and transported to the Qamloo station for planting. Data analysis was performed using SAS 9.1 software. Mean comparisons were performed using Duncan’s multiple range test at the 5% probability level.
Results and discussion
The results indicated that seed priming had positive effects on grain yield, germination vigor, and seedling establishment. In this study, potassium nitrate was the most effective priming treatment, resulting in a 45% increase in grain yield compared with the control. This increase in grain yield was attributed to positive effects on several traits, including thousand-grain weight, biological yield, plant height, number of seminal roots, and number of grains per spike. The wheat cultivars exhibited differential responses to priming treatments, with Azar2 producing the highest grain yield (1,293.9 kg ha⁻¹). Additionally, mean comparisons for root length indicated the superiority of Azar2 over the other cultivars. According to the results, potassium nitrate priming of the Azar2 cultivar resulted in a 36% increase in average grain yield compared with unprimed cultivars. Overall, the superiority of seed priming can be attributed to faster germination and improved seedling establishment of wheat seedlings under rainfed conditions.
 
Conclusion
Based on the results of this study, seed priming, in addition to improving seed vigor and seedling establishment, can enhance wheat grain yield and its components under rainfed conditions in cold regions similar to the study area. In this study, potassium nitrate and potassium dihydrogen phosphate priming treatments had positive effects on most measured traits and contributed to increased wheat grain yield. Seed priming with potassium nitrate accelerated seedling emergence, leading to uniform seedling growth and improved grain yield. This advantage becomes particularly important under rainfed conditions, where seedling emergence depends directly on environmental factors such as effective rainfall; otherwise, seedling loss and yield reduction may occur.
Acknowledgements
The authors sincerely thank the laboratory staff of the Faculty of Agriculture, University of Mahabad, for their invaluable support and assistance throughout this research.