Cultivar-dependent total selenium accumulation and nutrient co-application effects in hydroponically grown rice sprouts supplied with sodium selenite

This study examined cultivar responses to selenium (Se) supplied as sodium selenite and to selected co-applied compounds in rice sprouts. Eight rice (Oryza sativa L.) cultivars received 0, 5, or 10 mg Se L−1, expressed on an elemental-Se basis and supplied as sodium selenite. A separate experiment with Khao Dawk Mali 105 (KDML105) evaluated phosphate, sulfate, urea, and thiourea at 5 mM with 10 mg Se L−1. Shoot total Se concentration was determined after acid digestion by hydride generation atomic absorption spectrometry. The results showed that control sprouts contained 0.23–0.92 mg Se kg−1 dry weight (DW), whereas concentrations increased to 59.33–86.37 and 92.52–125.82 mg Se kg−1 DW at 5 and 10 mg Se L−1, respectively. Selenite supply significantly reduced shoot height and shoot dry biomass. Shoot total Se yield per seed increased from 0.64–1.24 to 0.75–1.81 µg Se seed−1, while calculated shoot total Se accumulation efficiency decreased from 5.11–9.91% to 3.00–7.22%. KDML105 had the highest shoot Se yield and calculated efficiency at both Se supply levels. In KDML105, phosphate co-application significantly increased shoot dry biomass, shoot total Se concentration, Se yield per seed, and calculated efficiency compared with selenite alone. Moreover, sulfate, urea, and thiourea did not significantly alter these responses. The findings support KDML105 selection and phosphate co-application as potential components of hydroponic Se-enrichment strategies under the tested conditions.