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Abstract:
Wheat, a strategic crop in Iranian agriculture, plays a vital role in ensuring food security and national self-sufficiency. Increasing its production is a primary economic priority for the country, as improved wheat yield not only boosts farmers' income but also enhances the livelihoods of rural families. The production and application of plant growth regulators (PGRs) have significantly increased in recent years, and these compounds have become important in enhancing wheat yield and quality. As signaling molecules, plant hormones regulate essential physiological processes such as cell division, cell elongation, tissue differentiation, and responses to environmental stresses, even at very low concentrations. In this context, a two-year field study was conducted at the Research Farm of the Seed and Plant Improvement Institute (SPII) in Karaj, Iran, to evaluate the effects of PGRs on the physiological, morphological, and yield-related traits of BSead and durum wheat. The study was carried out using a randomized complete block design (RCBD) with a split-plot arrangement and three replications. In the first year, four treatments—including two types of gibberellic acid (GA₃) (commercial: Megafil, and laboratory-grade), 24-epiBSassinolide (BS), and a control (distilled water)—were applied at the end of the tillering stage to four wheat cultivars: Mehrgan and Torabi (BSead wheat), and Taban and Sana (durum wheat). Results showed that GA₃ (in both forms) had no significant effect on grain yield. In contrast, BS treatment led to a 16% average increase in grain yield across all cultivars, with no significant differences observed among them. In the second year, in addition to BS and cytokinins (CK), GA₃ and Megafil were also evaluated. Among the genotypes, Hana exhibited the highest yield (7115 kg/ha), significantly outperforming the others, while Sirvan showed the lowest yield (6296 kg/ha). Hormonal treatments revealed that BS and CK significantly increased grain yield, with mean values of 7191 and 7155 kg/ha, respectively. However, GA₃ and Megafil not only lacked positive effects but, in some cases, even reduced yield. The results of this two-year study indicate that utilizing high-yielding genotypes like Hana, along with the targeted application of PGRs—especially BSassinosteroids and cytokinins—can effectively enhance wheat yield under field conditions. Conversely, gibberellins, whether in commercial (Megafil) or laboratory form, tend to reduce yield in various wheat genotypes. These findings underscore the importance of proper and scientific management of PGRs to maximize the production of this strategic crop.
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