Browsing by Author "Kunter, B."

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Effects of Crown Gall (Rhizobium Vitis) Disease on Physical and Biochemical Characteristics of ‘narince’ (Vitis Vinifera L.) Grape Berries
(International Society for Horticultural Science, 2020) Yagci, A.; Keskin, N.; Sucu, S.; Kunter, B.; Cangi, R.; Altinci, N.
Crown gall (Rhizobium vitis) is an economically important disease affecting growth of grapevine (Vitis vinifera L.). But the effects of the disease are generally focus on the lack of vine vigour rather than chemistry of berry content. In this study, impacts of crown gall disease on fruit yield and berry quality were investigated in the white wine grape cultivar ‘Narince’ planted in a commercial vineyard. ‘Narince’ vines showing symptoms and non-symptoms were compared. An equal number of 15 vines were evaluated in each group. Juice from grapes were collected at five stages of berry ripening after the onset of veraison. Number and total weight of clusters and berries were collected at the time of commercial harvest. Data on berry quality attributes (total soluble solids measured as °Brix, pH, titratable acidity, and some phytochemical characters) were investigated in grape samples of symptomatic and non-symptomatic vines. Descriptive analysis was realised by variance analysis and the test of Duncan. © 2020 International Society for Horticultural Science. All rights reserved.
Melatonin Enhances Antioxidant Defense and Physiological Stability in Grapevine (Vitis Vinifera L.) Cultivars ‘Merlot’ and ‘Erciş’ Under UV-B Stress
(Tech Science Press, 2025) Yıldız, S.; Keskin, N.; Kunter, B.; Hatterman-Valenti, H.; Kaya, O.
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. © © 2025 The Authors.
Production of Trans-Resveratrol in 'cabernet Sauvignon' (Vitis Vinifera L.) Callus Culture in Response To Ultraviolet-C Irradiation
(Jki-institut Rebenzuchtung, 2008) Keskin, N.; Kunter, B.
In this study, the effects of ultraviolet (UV) irradiation time, incubation time and callus age were investigated for the induction of trans-resveratrol production in callus cultures of Vitis vinifera L. 'Cabernet Sauvignon'. Callus tissues were exposed to 254 nm UV light at 10 cm distance from the source for 10 and 15 min by opening covers of the petri dishes in sterile cabin. High Pressure Liquid Chromatography (HPLC) was used for the determination of trans-resveratrol production and concentrations were recorded at 0, 24, 48 and 72 hours after beginning of incubation. Separation by HPLC was achieved using a C18 column and a gradient elution with acetonitrile and water (from 10 to 85% acetonitrile). The peak of trans-resveratrol was detected at 330 nm and identified from the retention time (12.5 min) trans-resveratrol standard. Determination coefficient for linearity (R-2), Limit of Detections (LOD), Limit of Quantification (LOQ) and relative standard deviation (RSD) values of the method were found as 0.9994, 0.12, 0.35 and 1.9, respectively. The highest trans-resveratrol concentration (62.66 mu g.g(-1) callus fresh weight) was determined in 48 hours of 12 days-old callus cultures irradiated for 10 minutes. Both 10 min and 15 min UV irradiation periods were found to be effective for the induction of trans-resveratrol production and thus callus cultures could be convenient for trans-resveratrol production.
Production of Trans-Resveratrol in Callus Tissue of Okuzgozu (Vitis Vinifera L.) in Response To Ultraviolet-C Irradiation
(Pakistan Agricultural Scientists Forum, 2010) Keskin, N.; Kunter, B.
In this study, the effects of ultraviolet (UV) irradiation time, incubation time and callus age were investigated for trans-resveratrol induction in callus cultures of Vitis vinifera L. cv. Okuzgozu. Callus tissues were exposed to 254 nm UV light at 10 cm distance from the source for 10 and 15 minutes by opening covers of the petri dishes in a sterile cabinet. High Pressure Liquid Chromatography was used for determining trans-resveratrol production and concentrations were recorded at 0, 24, 48 and 72 hours after beginning of incubation. The highest trans-resveratrol concentration (62.23 mu g/g callus fresh weight) was determined at 48 hours of 12-day-old callus cultures irradiated for 15 min. 15 min UV irradiation period was found to be effective for induction of trans-resveratrol production and thus callus cultures could be convenient for trans-resveratrol production.
Stilbenes Profile in Various Tissues of Grapevine (Vitis Vinifera L. Cv. 'ercis
(Scibulcom Ltd, 2017) Keskin, N.; Kunter, B.
This study aims to determine amount of stilbenes production in berry (skin, flesh, seed), and one-year-old cane of grapevine (Vitis vinifera L. cv. 'Ercis') as well as induced leaves and berries. The samples were obtained from potted grapevines grown in controlled conditions. Piceid, transresveratrol, e-viniferin, piceatannol, and pterostilbene were considered as stilbene compounds. In order to determine maximum stilbene production, berries and leaves were exposed to UV irradiation for 10 and 15 min. After this practice, the samples were taken at 24th, 48th, and 72nd h. HPLC (High Pressure Liquid Chromatography) technique was used to determine the amount of stilbene in the grapevine tissues. As conclusion, it was suggested that UV irradiation is one of the most effective application to induce stilbene synthesis in the tissues. In addition, it was also emphasised that the maximum stilbene production was recorded at the 48th hour of UV irradiation. And trans-resveratrol was found the most synthesisable stilbene compound in one-year-old cane. However, it was unable to determine stilbene compounds in the non-irradiated leaves and berries.