Unlocking Zn biofortification: leveraging high-Zn wheat and rhizospheric microbiome interactions in high-pH soils

Abstract

Cereals zinc (Zn) biofortification represents an effective strategy for alleviating human Zn malnutrition. However, understanding how to enhance Zn uptake in shoots by optimizing the soil–root interface, particularly considering Zn availability, microbiome interactions, and plant physiology, remains poorly understood, especially in high-pH soils. In this study, we investigated Zn rhizomobilization, plant Zn uptake, and the composition of bacterial and fungal communities in the rhizosphere and roots of ten high-yielding wheat cultivars with consistently contrasting grain Zn concentrations, within calcareous fields. We found that a range of beneficial bacteria, fungi/mycorrhizas, and their interactions play crucial roles in Zn rhizomobilization and wheat Zn uptake. Zn-solubilizing rhizobacteria demonstrated the ability to enhance Zn rhizomobilization, leading to a 35.4% increase in available Zn concentration and a 0.11 units reduction of soil pH. Increased colonization by arbuscular mycorrhizal fungi, along with reduced the presence of fungal pathogens, significantly promoted Zn uptake, ranging from 22 to 132% per unit of root biomass. Additionally, the enriched bacteria relevant with nitrogen cycle and plant growth-promotion not only optimized soil mineral-N/available-P supply but also potentially suppressed fungal pathogens in root and rhizosphere. Optimizing the microbiome to enhance soil nutrient supply and root health emerges as a promising strategy for improving Zn-efficient wheat cultivars’ ability to uptake Zn in shoots. Combining Zn-efficient cultivars with specific soil bacteria and fungi in the rhizosphere holds potential for realizing Zn biofortification in wheat.