Protein Hydrolyzate-Based Biostimulants in Fruit Crops: Mechanisms, Agronomic Effects, and Practical Applications

This review summarizes current scientific knowledge on the use of protein hydrolyzate-based biostimulants in fruit production through evidence mapping, cross-species comparison, and evaluation of protocol-dependent responses within an agronomic framework, centered on foliar applications and their role in sustainable production systems. Research across a broad range of fruit species reports that protein hydrolyzates can significantly enhance yield, improve fruit quality, and mitigate the adverse effects of abiotic stresses such as drought and high temperatures. Treated plants often exhibit improved nutrient uptake, increased photosynthetic efficiency, and enhanced morphological traits, including better root development and vegetative growth. However, the effectiveness of these biostimulants varies depending on the fruit species, developmental stage, and application frequency, indicating the need for more tailored and crop-specific protocols. In conclusion, the literature confirms the functional role of protein hydrolyzates in enhancing resilience and productivity in fruit crops, while highlighting the need for further research to optimize their use under diverse agroecological conditions. Protocol harmonization and robust field validation will be essential for improving the reliability, interpretability, and practical relevance of future research on protein hydrolyzates in fruit production.