Amino Acid Seed Priming as a Sustainable Strategy to Mitigate Drought-Induced Growth, Physiological, Biochemical and Yield Losses in Wheat

Drought is a critical environmental stress that limits wheat (Triticum aestivum L.) productivity by impairing growth, physiology, metabolism, and yield formation. A pot experiment was conducted using a completely randomized design (CRD) with three replications per treatment to examine whether seed priming could improve drought tolerance in two contrasting wheat cultivars, FSD-2008 and Anaj-2017. Treatments included unprimed control, hydropriming, glycine betaine priming, and phenylalanine priming. Drought stress markedly reduced shoot and root growth, biomass production, pigment contents, and yield traits, while increasing oxidative damage and membrane injury. However, priming alleviated these adverse effects in both cultivars. Glycine betaine priming was most effective for enhancing shoot biomass, chlorophyll b, carotenoids, osmotic adjustment, proline, soluble proteins, and ionic balance, with stronger effects in FSD-2008. Phenylalanine priming mainly promoted root elongation, chlorophyll a, total chlorophyll and phenolic compounds, being more effective in Anaj-2017. Both amino acid treatments stimulated osmoprotectant accumulation (amino acids, soluble sugars, total soluble proteins), reduced malondialdehyde and electrolyte leakage, and improved potassium and calcium uptake, thereby stabilizing membranes and improving water-use efficiency. Yield-related attributes, especially tiller number per plant and thousand-grain weight, were also improved under priming. Multivariate analyses (ANOVA, PCA, heatmap) further affirmed the superior role of glycine betaine priming (T4) in conferring drought tolerance, with FSD-2008 performing better overall than Anaj-2017. These results demonstrate that amino acid priming, compared with unprimed and hydroprimed seeds, is a cost-effective and eco-friendly approach to strengthening drought resilience in wheat.