Deciphering the mechanism of cyanobacterium‐mediated biofortification of iron and zinc in maize genotypes

BACKGROUND: Iron (Fe) and zinc (Zn) deficiencies in cereals are major nutritional challenges. Cyanobacteria-based biofertilizers have shown potential in micronutrient mobilization, but their role in Fe/Zn uptake, translocation, and accumulation in maize kernels remains less explored. This study evaluated cyanobacterial formulations Anabaena torulosa and two biofilms - A. torulosa with Trichoderma viride (An-Tr) or with Providencia sp. (An-PW5) - for their effect on Fe and Zn biofortification in a maize hybrid and its parental inbreds across two locations following a randomized block design (RBD). RESULTS: Cyanobacterial inoculation improved kernel micronutrient levels significantly. Iron content increased 0.31 to 0.43-fold in An-Tr and 0.18 to 0.28-fold in An-PW5 treatments compared with the control. Zinc content increased 0.46 to 0.66-fold in An-Tr and 0.37 to 0.55-fold in An-PW5 compared with the control. Increased ferric chelate reductase activity in roots supported higher Fe uptake. Gene expression analysis showed significant upregulation of Zn and Fe transporter genes, with ZmZIP6 and ZmZIP8 exhibiting expression levels of 574.12 and 900.04, respectively, relative to the recommended dose of fertilizers (RDF) in kernels. ZmZIP1 expression was strongly positively correlated with kernel Fe and Zn, root Fe, leaf Zn, and soil Fe at the pre-flowering stage. CONCLUSION: Cyanobacterial biofilms, particularly An-Tr and An-PW5, promoted Fe and Zn translocation to maize kernels by enhancing the activity of micronutrient-related enzymes at both physiological and molecular levels. This improved the nutritional quality of maize and allowed a reduction of nitrogen fertilizer inputs by approximately 25%. These findings demonstrate a sustainable approach for micronutrient biofortification in maize. © 2026 Society of Chemical Industry.