Bacillus velezensis stimulated the absorption of iodine to improve antioxidants and delay post-harvest senescence in microgreens

Iodine deficiency is a global public health problem and dietary microgreens represent a possible cost-effective supplement. Bacillus velezensis is a commonly occurring soil bacteria that promotes plant growth. However, little attention has been paid to the effects of B. velezensis on the absorption of iodine by plants. Herein, we demonstrated that B. velezensis accelerates pepper seed germination and growth under 0.01 mmoles/L KI supplement, with an 85.9% increase in fresh biomass. B. velezensis induced approximately 2.0-fold higher iodine absorption. Likewise, colonization by B. velezensis occurred in the microgreens. Consequently, the total thiol, vitamin C, total phenolics, and the antioxidant capacity were increased. This was followed by a marked decrease in the catalase and total superoxide dismutase activities. Furthermore, the combination of B. velezensis and 0.01 mmoles/L KI significantly decreased the relative water content and membrane damage (malondialdehyde and relative electrical conductivity). Intriguingly, the transcripts of ethylene biosynthesis genes CaACS10 and CaACO1 were downregulated, whereas CaACO3 expression was upregulated. Thus, the present study showed that B. velezensis accelerated iodine accumulation; improved seed germination and seedling growth; elicited antioxidant bioactivity; decreased membrane damage; and preserved vegetable microgreen quality during storage.