Seleniferous soils as a source for production of selenium-enriched foods and potential of bacteria to enhance plant selenium uptake

Selenium (Se) is an essential micronutrient for animals and humans but toxic at high levels. Soil Se concentration is highly variable. Selenium toxicity occurs in areas with seleniferous soils, while Se deficiency is prevalent in low-Se areas. Selenium-accumulating crop plants may be used to extract Se from seleniferous soils and provide dietary Se in low-Se areas. In this study, Se accumulator, Brassica juncea (Indian mustard), was tested for its capacity to extract Se from naturally seleniferous soil (similar to 8 mg Se kg(-1) of soil) collected from west Fort Collins, CO, USA. Two Se-tolerant bacterial consortia (G1 and G2, 4-5 bacterial strains in each) were tested for their effects on plant growth and Se accumulation. B. juncea accumulated Se to 711 mg kg(-1) dry weight (DW) in leaves, 276 mg kg(-1) DW in pod husk and 358 mg kg(-1) DW in seeds. Plants inoculated with consortium G1 showed significantly increased growth (dry biomass, seed weight) compared to control plants and G2-inoculated plants. G2-Inoculated plants showed reduced photosynthesis and stomatal conductance compared to control plants and G1-inoculated plants, as well as reduced Se accumulation in leaf and seed tissues. Sulfur levels were not affected by inoculation. Non-protein thiol levels were significantly elevated in G2-inoculated plants. In conclusion, B. juncea may be used to extract Se from seleniferous soil for the production of Se-enriched plant material, and inoculation with bacterial consortium G1 further enhances the efficiency of this process by stimulating plant growth.