Preharvest VDAL treatment enhances ROS scavenging and activates phenylpropanoid metabolism to improve postharvest storability of prune (Prunus domestica) fruit

• VDAL, a novel plant-derived immune-activating protein, offers an eco-friendly and residue-free preharvest treatment. This study is the first to demonstrate that its preharvest application effectively reduces postharvest losses and preserves quality in prune. • Research indicates that pre-harvest spraying with 10 mg/L VDAL can Maintain storage quality of prune and extend their storage period. • Preharvest VDAL priming sustains postharvest quality of prune by potentiating the enzymatic antioxidant machinery (SOD, CAT, APX, GR, POD) and activating the core phenylpropanoid pathway (PAL, C4H, 4CL, PPO), thereby driving the biosynthesis of phenolics, flavonoids and lignin and fortifying disease resistance. • We propose a simple, effective, and sustainable preharvest VDAL strategy that enhances prune storability, reducing postharvest food waste. VDAL is a novel plant immune-activating protein that acts as an elicitor to promote growth and stress resistance by modulating multiple hormone signaling pathways. Here, we evaluated the effects of preharvest VDAL application on defense responses and storage quality of prune fruit. Fruit were sprayed with 10 mg L⁻¹ VDAL 5 days before harvest and stored at 1–2 °C for 63 days. Quality attributes, antioxidant enzyme activities, phenylpropanoid metabolism, and oxidative stress indicators were assessed at regular intervals during storage. VDAL treatment significantly maintained postharvest quality by inhibiting softening, delaying declines in total soluble solids (TSS) and titratable acidity (TA), and preserving higher levels of ascorbic acid (AsA) and glutathione (GSH). Activities of key antioxidant enzymes, including superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR), and peroxidase (POD), were also markedly increased. In parallel, VDAL upregulated core enzymes in the phenylpropanoid pathway, including polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), and 4-coumarate-CoA ligase (4CL), which increased lignin and total phenolics and flavonoids. Consistent with these changes, VDAL-treated fruit showed significantly lower superoxide anion (O₂•⁻) production, reduced hydrogen peroxide (H₂O₂) accumulation, and decreased malondialdehyde (MDA) levels. Collectively, preharvest VDAL treatment improves prune storability by strengthening enzymatic and non-enzymatic antioxidant defenses, activating phenylpropanoid metabolism via upregulation of PAL, C4H, 4CL, and PPO, and suppressing oxidative stress. These findings support preharvest VDAL application as a novel, eco-friendly strategy to enhance fruit storability.