Salt Stress Mitigation and Field-Relevant Biostimulant Activity of Prosystemin Protein Fragments: Novel Tools for Cutting-Edge Solutions in Agriculture

In an increasingly challenging agricultural environment, the identification of novel tools for protecting crops from stress agents while securing marketable production is a key objective. Here we investigated the effects of three previously characterized Prosystemin-derived functional peptide fragments as protective agents against salt stress and as biostimulants modulating tomato yield and quality traits. The treatments of tomato plants with femtomolar amounts of the peptides alleviated salt stress symptoms, likely due to an increase in root biomass up to 18% and the upregulation of key antioxidant genes such as APX2 and HSP90. In addition, the peptides exhibited biostimulant activity, significantly improving root area (up to 10%) and shoot growth (up to 9%). We validated such activities through two-year field trials carried out on industrial tomato crops. Peptide treatments confirmed their biostimulant effects, leading to a nearly 50% increase in marketable production compared to a commonly used commercial product and consistently enhancing fruit °Brix values.