WHEY protein hydrolysates enhance grapevine resilience to abiotic and biotic stresses

Abstract

Context and purpose of the study. The growing need for sustainable solutions in viticulture has led to increased interest in biostimulants that can enhance plant resilience to both abiotic and biotic stresses. This study investigates the effects of whey protein hydrolysates (PHs), derived from dairy industry by-products, as biostimulants in Vitis vinifera. The goal was to assess their potential in improving plant tolerance to heat and drought stress, as well as their role in mitigating pathogen infections.

Material and methods. Heat stress experiments were conducted on potted grapevines subjected to 40°C without irrigation, with plants treated with either water or PHs. Physiological parameters such as photosynthesis, stomatal conductance, sub-stomatal CO₂ concentration and leaf water potential were monitored. In addition, the expression of key stress-related and photosynthesis-related genes was analyzed. For biotic stress, the efficacy of PHs in reducing Plasmopara viticola and Botrytis cinerea infection was assessed via sporulation assays, zoospore germination and growth inhibition assays as well as berry inoculation tests.

Results. PH-treated plants exhibited a faster recovery of photosynthetic activity and maintained normal sub-stomatal CO₂ concentration during heat stress. Expression of heat stress-responsive genes (HSP101, HSFA2) was significantly higher in PHs-treated plants. Also, PHs treatment alleviated decreases in expression of photosynthesis-related genes (LHCA3, RbcS) during heat stress. Moreover, whey PHs significantly improved grapevine drought tolerance, as indicated by higher leaf water potential values and higher expression of drought-responsive genes (NCED1, TIP2;1) compared to water-treated controls. Additionally, PHs demonstrated a direct toxic effect on P. viticola, inhibiting zoospore germination and reducing sporulation on leaf discs. Finally, PHs displayed a curative effect on B. cinerea, significantly reducing mycelial growth in vitro and infection in berries when applied 24 hours after infection. Whey protein hydrolysates serve as effective biostimulants, enhancing grapevine resilience to drought and heat stress while providing protection against fungal pathogens. This dual benefit underscores their potential as sustainable alternatives to chemical inputs in viticulture.