Enhancing nutritional value of common wheat: Impact of foliar selenium application on grain yield and quality under rainfed conditions

Context or problem: Selenium (Se) is a micronutrient for human health, but its deficiency is widespread due to low concentrations in staple crops like common wheat (Triticum aestivum L.). Enhancing the Se content of wheat grains through foliar application can help address dietary deficiencies while maintaining crop yield and quality. Objective or research question: This study aimed to investigate the effects of foliar Se application on grain yield and quality in two common wheat varieties (Bologna and Sieve) grown under rainfed conditions. Specifically, the research examined how Se rates and application timings influenced key quality traits such as protein content, starch concentration, free asparagine levels, and phytic acid content. Methods: A split-split-plot design was employed over two growing seasons (2020–2022) at two experimental sites in Italy. Selenium was foliar-applied at five rates (0, 2.57, 5.14, 10.27, 20.54 g ha⁻¹) and at two growth stages (flowering and watery ripe). Agronomic traits including grain yield, protein content, starch concentration, free asparagine, and phytic acid (Phy) were measured. Statistical analysis was conducted using a mixed-effects linear model to assess the interactions between varieties, Se rates, and application timings. Results: Selenium application did not affect grain yield in either variety, but it had notable effects on quality traits in a variety-dependent manner. Free asparagine and phytic acid content decreased with Se application, with the reduction in free asparagine being more pronounced in Sieve. Additionally, Phy-to-cation molar ratios declined in both varieties, suggesting improved mineral bioavailability. Conclusions: While foliar-Se application did not affect grain yield, it improved several quality traits by reducing free asparagine and phytic acid content, which are important for both food safety and nutritional value. However, the results also suggest that high Se rates may negatively impact protein and starch content. Implications or significance: This study demonstrates the potential of foliar-Se application to reduce anti-nutritional factors such as Phy and free asparagine, while lowering the molar Phy:Se ratio, thereby improving Se bioavailability. However, foliar-Se application decreased protein content and had no effect on grain yield. These findings underscore the importance of tailoring foliar-Se application strategies to specific wheat varieties to balance its effects and optimize its role in addressing Se deficiencies in human diets.