Open Access

ARTICLE

Melatonin Enhances Antioxidant Defense and Physiological Stability in Grapevine (Vitis vinifera L.) Cultivars ‘Merlot’ and ‘Erciş’ under UV-B Stress

Sena Yıldız¹, Nurhan Keskin^2,*, Birhan Kunter³, Harlene Hatterman-Valenti⁴, Ozkan Kaya^4,5,*

1 Department of Horticulture, Graduate School of Natural and Applied Sciences, Van Yüzüncü Yıl University, Van, 65080, Türkiye
2 Department of Horticulture, Faculty of Agriculture, Van Yüzüncü Yıl University, Van, 65080, Türkiye
3 Department of Horticulture, Faculty of Agriculture, Ankara University, Ankara, 06110, Türkiye
4 Department of Plant Sciences, North Dakota State University, Fargo, ND 58102, USA
5Republic of Türkiye Ministry of Agriculture and Forestry, General Directorate of Agricultural Research and Policies, Erzincan Horticultural Research Institute, Erzincan, 24060, Türkiye

* Corresponding Authors: Nurhan Keskin. Email: ; Ozkan Kaya. Email:

(This article belongs to the Special Issue: Precision Fertilization and Nutrient Use Efficiency in Crops)

Phyton-International Journal of Experimental Botany 2025, 94(11), 3471-3492. https://doi.org/10.32604/phyton.2025.073180

Received 12 September 2025; Accepted 10 October 2025; Issue published 01 December 2025

Abstract

Climate change-driven environmental stresses, particularly ultraviolet-B (UV-B) radiation, pose severe threats to grapevine (Vitis vinifera L.) productivity and physiological stability. This study investigated the protective role of melatonin in in vitro plantlets of two grapevine cultivars, ‘Merlot’ and ‘Erciş’, subjected to low (≈8.25 μW cm⁻², 16 h) and high (≈33 μW cm⁻², 4 h) UV-B exposure. Significant cultivar-specific responses were observed (p < 0.001). The ‘Erciş’ cultivar exhibited higher oxidative stress, with malondialdehyde (MDA) levels reaching 24.30 mmol g⁻¹ FW in control plants compared with 14.91 ± 0.25 mmol g⁻¹ FW in ‘Merlot’. Melatonin provided dose-dependent mitigation, reducing MDA to 12.68 in ‘Erciş’ and 8.52 ± 0.13 in ‘Merlot’ at 200 μmol L⁻¹. Antioxidant enzyme activities increased significantly: superoxide dismutase rose from 0.02 ± 0.01 to 0.10 EU g⁻¹ in ‘Erciş’ and to 0.13 EU g⁻¹ in ‘Merlot’, catalase increased up to 0.08 in ‘Erciş’ and 0.16 in ‘Merlot’, while ascorbate peroxidase reached 1.06 ± 0.02 and 1.20 ± 0.03, respectively. Pigment traits also improved, with chlorophyll content increasing to 23.70 μg cm⁻² in ‘Merlot’ and 22.66 μg cm⁻² in ‘Erciş’, alongside enhanced nitrogen balance index values. Secondary metabolites were elevated, particularly total phenolic content (8.23 GAE 100 g⁻¹ in ‘Erciş’ and 5.99 in ‘Merlot’) and antioxidant capacity (17.24 and 8.15 μmol TE g⁻¹, respectively). Correlation analyses revealed strong positive associations between melatonin and antioxidant enzymes (r = 0.54–0.85), while principal component analysis explained 64.71% of total variance, separating cultivars and treatments clearly. Clustering patterns showed distinct grouping of enzymatic defenses, phenolic compounds, and pigments, reflecting coordinated protective mechanisms. Overall, melatonin application, especially at 200 μmol L⁻¹, significantly enhanced enzymatic and non-enzymatic antioxidant defenses, stabilized photosynthetic pigments, and reduced oxidative damage, with stronger protective efficiency in ‘Merlot’. The research provided valuable insights for developing biotechnological approaches to enhance grape stress tolerance in the context of climate change challenges.

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