Foliar application of microbial nano-selenium enhances selenium uptake and alleviates oxidative stress

Selenium (Se) is an essential micronutrient to humans and animals in diet primarily from edible crops. However, limited studies have been conducted on applying microbially synthesized Se nanoparticles (BioSeNPs) to affect plant Se uptake and toxicity. The bacterium Bacillus wiedmannii ES2–45 was able to efficiently produce BioSeNPs by completely reducing 5 mM selenite [Se(IV)] within 24 h. Then, fermented BioSeNPs were sprayed on the leaf surface of Brassica rapa L to investigate their effects on growth and Se accumulation. Total Se and leaf biomass increased significantly by 124 % and 14.3 % respectively in the BioSeNP treatment compared to the Se(IV) treatment. The Se(VI) treatment was found to be toxic to the leaves although Se(VI) had similar effects to BioSeNP treatments. Notably, BioSeNP treatment significantly increased the plant’s ability to alleviate oxidative stress including levels of chlorophyll, malonaldehyde (MDA), and catalase (CAT) (P<0.05). In conclusion, the foliar application of BioSeNPs is a promising strategy to improve the Se content of vegetables and alleviate Se-induced oxidative stress.