Impact of Sulfur on Biofortification and Speciation of Selenium in Wheat Grain Grown in Selenium-Deficient Soils

Abstract

Selenium (Se) is an essential micronutrient in humans that is required for both physical and mental well-being. Low Se content in food crops is linked to Se-deficient soils globally. The aim of this study was examined the influence of sulfur (S) on the speciation and accumulation of selenium (Se) in three wheat cultivars grown in Se-deficient soils. Plants were grown in soil under glasshouse conditions with two doses of S (0 and 14 mg kg−1) as sulfate and three doses of selenium (0, 1, and 2 mg kg−1) as selenate (SeVI) in a randomized factorial design. Selenium speciation was determined using liquid chromatography inductively coupled plasma mass spectroscopy after enzymatic hydrolysis. Selenocysteine (SeCys), seleno-methyl-cysteine (SeMeCys), selenomethionine (SeMet), selenite (SeIV), and selenate (SeVI) were determined. The addition of SeVI increased the Se content in grain in all wheat cultivars compared to the control treatment. Selenium accumulated to the highest extent in leaf tissue while stem accumulated low amounts of Se. Speciation analysis in grain showed that most of the Se accumulated in wheat grain in the organic forms, SeCys and SeMeCys. Inorganic Se was below 10%, primarily as SeVI. Longsword, a multi-tillering variety, accumulated the highest proportion of SeMeCys (67%). Fertilization with S concurrently with Se resulted in decreased production of SeCys and SeMeCys in grain. The findings from this study provide new insights into the Se biofortification and speciation transformation processes in wheat as impacted by S supplementation in Se-deficient soils.