Effects of foliar spraying of selenate at different time points on selenium concentration in wheat grains during grain filling period

Foliar spraying of selenium (Se) during the wheat grain filling period can effectively increase grain Se concentration. However, it is unclear when foliar spraying Se can efficiently increase grain Se concentration. In this study, 0, 18.90, 37.80 and 56.70 g/ha of selenate were sprayed on the leaf blades on the 2nd and 9th day after grain filling, respectively, to investigate the effect of different spraying time points on Se concentration in aerial parts, especially the grains. The results indicated that Se concentrations in aerial parts increased with selenate levels at different time points. On the 7th day after spraying Se, Se concentrations in leaf blades, leaf sheaths, nodes, internodes and cobs sprayed with Se on the 2nd day after grain filling were significantly higher than those in corresponding parts sprayed with Se on the 9th day (p < 0.05). However, the Se concentrations of aerial parts on the 14th day after spraying Se and at grain maturity on the 2nd day after grain filling were significantly lower than those on the 7th day after spraying Se on the 9th day (p < 0.05). Furthermore, on the 7th day and 14th day after spraying Se and at grain maturity, grain Se concentrations sprayed with Se on the 2nd day after grain filling were significantly lower than those sprayed with Se on the 9th day (p < 0.05). These results suggested that spraying Se on the 9th day after grain filling was beneficial for increasing the Se concentration in aerial parts, especially grains. This study provides a theoretical basis for efficiently enhancing grain Se concentration and producing Se-enriched bran and straw, which is of great significance for improving Se intake of livestock, enhancing livestock immunity, and promoting the development of animal husbandry.