Biofortification of wheat in salt-affected soil through seed priming and soil application of zinc

Context: Given the global significance of wheat production and consumption, it is imperative to achieve high yields of nutritious wheat grains. However, the inadequate availability of zinc (Zn) in salt-affected soils can aggravate salt stress, decrease wheat grain yield, and grain Zn concentration. This study compared the effectiveness of soil Zn application and seed Zn priming in increasing Zn biofortification and grain yield of Zn-biofortified wheat grown in alkaline-calcareous soil affected by salts. Methods: Eighteen pots were filled with alkaline-calcareous soil containing elevated levels of soluble salts and exchangeable sodium (Na). The pots were subjected to soil Zn application (0 or 8 mg kg−1) and seed priming (control/non-, hydro-, or Zn-primed seeds) treatments, applied to a Zn-biofortified wheat (cv. Zincol-2016). Plant samples were collected at the heading and maturity stages to measure parameters related to plant growth and grain quality. Findings: Soil Zn application increased grain and straw yields across seed priming treatments by a maximum of 23 %, and seed Zn priming increased grain and straw yields across soil Zn rates by a maximum of 21 %. This yield response was accompanied by significant increases in grain potassium and Zn concentrations at maturity, as well as non-significant to significant increases in photosynthetic parameters (stomatal conductance, photosynthetic rate and transpiration rate) in flag leaves during heading. Additionally, compared to control, the combined treatment of soil Zn application and seed Zn priming decreased grain Na concentration by 14 %. Compared to control, both soil Zn application and seed Zn priming significantly increased grain Zn concentration. With the combined application treatment, the grain Zn concentration reached 27 mg kg−1, but it remained significantly below the desired level of >37 mg kg−1. Seed Zn priming decreased the phytate-to-Zn molar ratio in grains, while the treatments that received soil Zn application exhibited the lowest values of this ratio, potentially increasing Zn bioavailability to humans. Conclusions: The findings suggest that soil Zn application is more effective in enhancing grain yield and Zn concentration, while seed Zn priming remains crucial in low-Zn and high-salt soils. Future research should optimize Zn application strategies for Zn-biofortified wheat cultivated in salt-affected fields.