Nanoscale\nIron (Fe<sub>3</sub>O<sub>4</sub>) Surface\nCharge Controls Fusarium Suppression and Nutrient Accumulation in\nTomato (Solanum lycopersicum L.)

With the growing recognition that conventional agriculture\nwill\nnot be able to meet food production demands, innovative strategies\nto reach food security are imperative. Although nanoscale fertilizers\nare attracting increased attention as a sustainable platform for agricultural\napplications, limited data exist on how surface charge influences\noverall efficacy relative to disease suppression and nutrient accumulation.\nThis study investigated the effect of positively and negatively charged\niron oxide nanoparticles (Fe<sub>3</sub>O<sub>4</sub> NPs) on the\ngrowth of tomato (Solanum lycopersicum L.) plants and their disease resistance against the pathogen Fusarium oxysporum f. sp. <i>lycopersici</i> at both the greenhouse and field scale. In addition, a theoretical\nmodel of the biointerface was employed for a mechanistic understanding\nof the interaction and attachment efficiency between NPs and tomato\nleaves after foliar exposure. In the greenhouse, both positively and\nnegatively charged Fe<sub>3</sub>O<sub>4</sub> NPs significantly suppressed\nFusarium wilt by 41.4 and 44.6% and increased plant shoot biomass\nby 327.6 and 455.0%, respectively, compared to the diseased control.\nThe impact of the NP surface charge was apparent; positively charged\nFe<sub>3</sub>O<sub>4</sub> NPs demonstrated superior efficacy compared\nto their negatively charged counterparts in mitigating disease damage\nand regulating nutrient (Na, Si, and Cu) accumulation. Computationally,\npositively charged Fe<sub>3</sub>O<sub>4</sub> NPs consistently migrate\ntoward lipid layers, indicative of a pronounced affinity between these\nentities compared with the negatively charged particles, which aligns\nwith the experimental data. The findings highlight the importance\nand tunability of nanomaterials properties, especially the surface\ncharge, in optimizing the use for disease suppression and nutrient\nmodulation, which offers a great potential for sustainable agriculture.