Selenium speciation in Se-enriched soybean grains from biofortified plants grown under different methods of selenium application

Authors: SILVA, MAILA - Federal University Of Lavras; FERREIRA DE SOUSA, GUSTAVO - Federal University Of Lavras; Banuelos, Gary; AMARAL, DOUGLAS - University Of California; BROWN, PATRICK - University Of California, Davis; GUIMARAES GUILHERME, LUIZ - Federal University Of Lavras

Submitted to: Foods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2023
Publication Date: 3/13/2023
Citation: Silva, M.A., Ferreira De Sousa, G., Banuelos, G.S., Amaral, D., Brown, P., Guimaraes Guilherme, L.R. 2023. Selenium speciation in Se-enriched soybean grains from biofortified plants grown under different methods of selenium application. Foods. 12(6). Article 1214. https://doi.org/10.3390/foods12061214.
DOI: https://doi.org/10.3390/foods12061214

Interpretive Summary: Soil selenium (Se) is potentially a natural source of Se for crops, although its availability is affected by the parent rocks, climate, and soil chemistry (e.g., pH, soil redox potential, and available O2). Edible crops are a major source of Se for humans. The Se soil content, however, is not always adequate to produce crops with sufficient Se that can supply the daily recommended (55 ug Se/day) intake. Since soybean is one of the most widely cultivated protein grains in the world, Se-enriched soybean may be a natural nutritional vehicle for potentially increasing the intake of Se by the world population. The addition of Se fertilizers to soybean production can be carried out via both soil and foliar application. It is, however, not known how either method of Se application affects total Se content and Se speciation in soybean grains. In this biofortification study, we evaluated total Se and Se speciation in Se-enriched soybean grains produced with different forms of Se and with different application methods. Soybean grain samples were collected from three Se application trials conducted under the same field conditions in Capo Bonito (SP), Brazil. Treatments consisted of applying organic or inorganic Se sources at 10 g ha-1 or 80 g ha-1 to two soybean genotypes (Lança and M5917) via soil and foliar application. Results showed overall that foliar application of inorganic Se was most efficient at either rate for increasing the Se content in soybean grains, especially M5917. Additionally, more than 80% of total Se in soybean grains was present in the organic form as selenomethionine with all treatments, which is bioavailable for human intake. We have demonstrated that soybean is a responsive crop to Se fertilizers when used in Se biofortification strategies. Furthermore, it is possible to produce biofortified soybean grains through soil or foliar Se application. However, Se concentration in grains is higher with foliar application of inorganic Se.

Technical Abstract: Disorders related to Se deficiency have been reported in regions worldwide with severe low Se content in soils. In this regard, agronomic biofortification has been an effective strategy for increasing the content of Se in several grain crops, such as wheat, rice, common bean, and sorghum. Additionally, soybean may be an ideal grain crop for Se biofortification strategies to increase Se intake since it is one of the most produced and consumed grains worldwide. In this study, we evaluated the Se content and speciation in Se-enriched soybean grains produced from two genotypes grown in Se biofortification trials using different forms of Se (selenate, acetylselenide, Se/P fertilizers), rates (10, 80 g/ha) and application methods (soil, foliar) under field conditions. Results showed that total Se concentrations in soybean grains ranged from 0.08 to 7.71 mg/kg for all treatments. Inorganic Se applied as selenate via soil or foliar at 80 g/ha increased the Se content the greatest among all treatments, especially in genotype M 5917. Treatment with foliar application of Se as sodium selenate at a rate of 10 g/ha were just as effective for increasing Se content in soybeans as Se soil application via phosphate fertilizer at a rate of 80 g/ha. Speciation analyses showed that organic Se (including SeMet, SeMeCys, and SeCys) accounted for more than 84% of the total Se content in the grains following Se applications. SeMet was the Se species found in the highest percentage and ranged from 54.0% to 94.1%, followed by selenate, SeCys, selenite, and MeSeCys. Our results demonstrate that two common soybean genotypes produced Se biofortified grains after application of inorganic or organic Se to soil and foliarly applied to plant. Foliar application of inorganic Se as selenate appears to be the most effective strategy for increasing both total Se content and percentage of bioavailable Se as SeMet in Se-enriched soybean grains.