AUTHOR=Lozano-González José María , Lucena Juan José , López-Rayo Sandra 

TITLE=A pyoverdine-based iron biochelate from bacterial secretions as an effective fertilizer under alkaline conditions

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 16 - 2025

YEAR=2025

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2025.1675837

DOI=10.3389/fpls.2025.1675837

ISSN=1664-462X

ABSTRACT=IntroductionIron (Fe) deficiency in crops grown on calcareous soils seriously limits their productivity. The most common practice to address this issue is the application of Fe-chelates. However, more environmentally friendly methods are now being adopted. This study evaluated a pyoverdine-based siderophore extract from Pseudomonas RMC4 (Pvd) as an Fe biofertilizer.MethodsStability batch tests and plant assays were conducted, including ferric chelate reductase (FCR) activity, ⁵⁷Fe-labeled uptake, phytotoxicity, and a hydroponic test with cucumber plants at two Fe levels (5 and 10 µM).Results and discussionThe Pvd/Fe³⁺ biofertilizer showed high stability at alkaline pH and resistance to Ca²⁺ interference. Although only a limited reduction of Pvd/Fe³⁺ by FCR was observed, Fe showed efficient translocation to shoots. Pvd/Fe³⁺ improved root morphology and biomass, and decreased reactive oxygen species, demonstrating biostimulant effects. At 10 µM, Pvd/Fe³⁺ provided Fe supply efficiency comparable to commercial HBED/Fe³⁺, and improved Fe/Mn ratio. These findings support the potential of Pvd/Fe³⁺-based formulations as dual-function biofertilizers and biostimulants.