Biochar derived from grape pomace as a potential antifungal and oomyceticidal sustainable source against soil-borne tomato pathogens: Metabolic effects

Agricultural systems require sustainable alternatives to chemical pesticides for controlling crop pathogens. This study evaluated biochar derived from grape pomace, a major winery byproduct, as an antimicrobial agent against tomato root pathogens (Fusarium oxysporum f. sp. lycopersici, Phytophthora infestans, Verticillium dahliae and Rhizoctonia solani). Under in vitro conditions, pathogens were exposed to biochar, washed biochar, and aqueous extracts in solid and liquid media. Biochar significantly inhibited fungal growth, whereas aqueous extracts showed no antifungal activity. Similar effects of washed and unwashed biochar indicate that inhibition is associated with the solid biochar structure rather than soluble compounds, and pH alone did not explain the effect. F. oxysporum and R. solani were most sensitive at lower concentrations. Metabolomic analysis identified 59 differential metabolites linked to stress responses. These findings highlight grape pomace-derived biochar as a promising sustainable strategy for managing tomato root pathogens.