Impact of plant-derived melanin on in vitro rooting efficiency and biochemical characteristics of grapevines

Background: Grapevine (Vitis vinifera L.) is a globally important crop, and effective in vitro propagation is essential for producing healthy, uniform plants. However, optimizing rooting and growth remains a challenge. Plant-derived melanin, known for its antioxidant and auxin-like properties, has shown potential in promoting plant development. Objectives: This study aimed to assess the impact of plant-derived melanin on in vitro rooting efficiency and key biochemical characteristics—such as chlorophyll content, total soluble sugars, and vitamin C levels—in two grapevine cultivars ('Deghin Yerevani' and 'Parvana'). The study also explored the potential of melanin to enhance the nutritional profile of grapevine leaves, which may contribute to the health-promoting properties of grape-derived products. Materials and Methods: Virus-free grapevine microcuttings were cultured on Murashige and Skoog (MS) medium supplemented with melanin at concentrations of 0.007%, 0.014%, 0.028%, 0.042%, and 0.056%. The control group received no melanin. After 30 days, rooting parameters (root number and root length) were assessed. The regenerated plants were then transferred to an aeroponic system for further growth. Biochemical analyses included measurements of chlorophyll, total soluble sugars, and vitamin C content in the leaves. All experiments were conducted in triplicate, and data were expressed as mean ± standard deviation (SD). Statistical comparisons were made using Student’s t-test (P < 0.05), and a two-way analysis of variance (ANOVA) without replication was performed to assess the effects of cultivar and melanin concentration on rooting efficiency. Results: Melanin enhanced rooting and improved the biochemical profile of grapevine microcuttings in a dose-dependent manner. The 0.028% melanin concentration yielded the highest rooting success and significantly increased chlorophyll, sugar, and vitamin C levels. Higher concentrations (0.042% and 0.056%) did not result in statistically significant improvements (p > 0.05). Conclusion: Plant-derived melanin at an optimal concentration of 0.028% significantly improved rooting efficiency and enhanced essential biochemical traits, including chlorophyll, sugar, and vitamin C content in grapevine microcuttings. These improvements suggest that melanin can serve as a sustainable, natural alternative to synthetic growth regulators in micropropagation systems. Furthermore, the enrichment of bioactive compounds in grapevine leaves indicates a possible link between melanin application and the nutritional quality of grape-derived foods, offering promising implications for both sustainable agriculture and human health. Keywords: melanin, in vitro, virus-free, grapevine, rooting, biochemical composition