Biostimulants mitigate drought-induced yield losses in tomato and modulate fruit quality traits

Introduction Tomato is one of the most widely consumed vegetable crops worldwide, and both high yield and quality are crucial for the economic success of its production. Biostimulants are emerging as an innovative and sustainable solution to enhance crop productivity and improve fruit quality. Methods A greenhouse experiment was conducted to assess the yield performance and fruit quality attributes of tomato in relation to biostimulant doses and irrigation regimes. Three biostimulant treatments: untreated control, D1 (1.5 g L −1 and 3 g L −1 of Algaren Twin and Drin On) and D2 (2 g L −1 and 4 g L −1 of Algaren Twin and Drin On) and two irrigation regimes (100% of crop water requirement and water-stressed treatment at 50% of crop water requirement) were applied. Results Water stress significantly reduced plant growth, as evidenced by a marked reduction in both total and aboveground dry biomass. Biostimulant application improved plant growth, particularly under water stress conditions. Irrigation regimes and biostimulant application significantly influenced tomato fruit quality and physiological traits. Under optimal water conditions, biostimulant-treated plants exhibited lower levels of total soluble solids, titratable acidity, and total sugar content in their fruits. However, neither lycopene nor total phenolic content was affected by the treatments. In contrast, under water stress (50% of crop water requirement), the application of biostimulants significantly increased lycopene content in the fruits of treated plants compared to the control samples. Moreover, a dose-dependent effect was noted for total sugar, total phenolic content, and antioxidant activity, with lower values observed at the lower biostimulant dose. Conclusion These results suggest that biostimulants can be considered a useful tool for improving fruit quality under optimal irrigation conditions and for alleviating the adverse effects of water stress. Their effectiveness depends on dose, application method, and environmental conditions.