Biochelate as an eco-friendly alternative to synthetic chelate for micronutrients supply in tomato grown under alkaline conditions: A multi-omics approach

The increasing incidence of soil alkalinity, which is closely related to drought conditions, seriously affects crop productivity and quality by reducing micronutrient availability for plant uptake. Synthetic-chelates based fertilizers are successfully used for micronutrient supply to crops under alkaline conditions; however, several concerns have been raised on the environmental and human health impacts of synthetic chelates resulting from their accumulation in plant tissues and their ability to mobilize heavy metals in the soil-plant system. Biochelate-based fertilizers could be an eco-friendly alternative to synthetic products for micronutrient supply. This study investigated the effect of two micronutrients-based fertilizers containing different chelating agents [vegetal-derived peptides as biochelate, and Ethylenediaminetetraacetic acid (EDTA) as synthetic chelate] at three rates on morpho-physiological traits, mineral composition and metabolic profile of leaves in tomato plants grown under alkaline conditions. A 3D laser scanner was used to monitor growth and health of plants over the growing cycle. Fresh and dry biomass of shoots and roots were not significantly affected by fertilizer type and rate, despite the presence of leaf chlorosis symptoms at lower fertilizer doses. Similarly, the trend of digital biomass, 3D leaf area, plant height and vegetation indices was not affected by treatments. Leaf mineral composition indicated that EDTA-based fertilizer exhibited higher stability for zinc and copper at higher rates in comparison with biochelate-based fertilizer while leaf concentrations of manganese and boron were increased by fertilizer rate independently from the fertilizer type. Metabolomics analysis revealed that biochelate enhanced mainly phenolic compound pathways, supporting antioxidant defenses and modulating cell responses to mitigate stress. These findings indicate that biochelate-based fertilizer is a sustainable alternative to synthetic-chelate based fertilizer for supporting micronutrients nutrition under alkaline conditions.