Shikonin-induced secondary metabolite modulation in grape berries (Vitis vinifera L. cv. 'Öküzgözü') under salinity stress.

BACKGROUND

Salt stress represents a critical challenge in viticulture, significantly impacting grape berry biochemical profiles and potentially threatening crop productivity and quality. In this study, therefore, we systematically investigated the metabolic responses of grape berries (Vitis vinifera L. cv. 'Öküzgözü') to salinity stress by applying NaCl at four different concentrations (0, 50, 100, and 150 mM) and shikonin at two levels (0 and 25 µM). Our study analyzed changes in organic acids, phenolic compounds, anthocyanins, and sugar contents, employing a standardized foliar spray technique to explore the individual and interactive effects of salt stress and shikonin on grape berry biochemical composition.

RESULTS

Salinity stress induced by NaCl markedly suppressed sugar metabolism in the studied plants, with glucose and fructose contents decreasing by approximately 85% and 82%, respectively, under high salinity conditions (e.g., 150 mM NaCl). This drastic reduction indicates a significant disruption in carbohydrate homeostasis due to ionic and osmotic stress. In contrast, the application of shikonin partially alleviated the deleterious effects of salt stress, particularly by enhancing anthocyanin biosynthesis. Under severe salinity, total anthocyanin accumulation increased by up to 60% with shikonin treatment, suggesting its potential role as a modulator of secondary metabolism and antioxidant defense. Phenolic compound levels exhibited highly variable responses depending on the interaction between NaCl and shikonin, with individual compounds showing changes ranging from a 20% decrease to a 75% increase compared to control conditions. These findings reflect a compound-specific regulation, likely driven by differential activation of phenylpropanoid pathway enzymes under stress and elicitor influence. Furthermore, anthocyanin profiling revealed profound shifts in composition; notably, malvidin-3-O-glucoside levels were elevated by more than 200% under combined high-salinity and shikonin treatment, indicating a strong synergistic effect on flavonoid pathway activation.

CONCLUSIONS

Consequently, the current study provides crucial insights into potential mitigation strategies for salt stress in viticulture, demonstrating that targeted interventions like shikonin treatments can help preserve grape berry metabolic integrity under challenging environmental conditions, potentially offering valuable strategies for sustainable grape production in saline-prone agricultural landscapes.