Tyrosol, a phenolic compound from Phomopsis sp., is a potential biostimulant in soybean seed treatment

Abstract Studies have revealed the antioxidant and antifungal activities of the metabolite tyrosol, a phenolic compound from olive oil and several endophytic fungi. The substance was isolated from the ethyl acetate extract of the endophytic fungus Phomopsis sp. and was described as a natural product (NP) with a potential biostimulant effect in soybean seed treatment. In this study, the application of an oil-based solution of tyrosol (10 mg/L) to soybean seeds showed no significant difference from soybean seeds without tyrosol in terms of germination percentage, number of nodules, number of seeds per plant, and number of pods per plant. Metabolomic analysis of the soybean leaves using GC–MS showed differences in the chemical composition between the treatments, with significant differences in the abundance of 11 metabolites. Among them, aspartic acid, which is a precursor to several essential amino acids, presented a positive effect under tyrosol application, and the analysis of the metabolic routes (MetaboAnalyst 4.0) indicated a significant improvement in the nitrogen metabolism pathway. The substances related to nitrogen translocation also behaved differently with the tyrosol treatment of seeds, with a negative effect on the concentrations of allantoin and urea, but a positive effect on aspartate. These results show that tyrosol changes soybean plant metabolism without significant effects on crop yield.