Induction of secondary metabolite production by UV-C radiation in Vitis vinifera L. Öküzgözü callus cultures
BACKGROUND: The aim of the present work was to examine the role of UV-C irradiation on the production of secondary metabolites (total phenolic, total flavanols, total flavonols, catechin, ferulic acid and trans-resveratrol in phenolic compounds and α-, β-, γ- δ-tocopherols) in callus cultures. Studies on the effects of UV-C treatment on callus culture are seldom and generally focused on UV-B. However UV-C radiation play an important role in accumule secondary metabolites. RESULTS: In this study, callus cultures from Öküzgözü grape cultivar were initiated from leaf petiole explants. Calli formed after 6 weeks on the medium supplemented with 0.5 mg L-1 benzylaminopurine (BA), 0.5 mg L-1 indole acetic acid (IAA) on B5 media. Callus tissues were exposed to UV-C irradiation at 10, 20 and 30 cm distances from the UV source for 5 and 10 minutes and samples were collected at hours 0, 24 and 48. CONCLUSIONS: The greatest total phenolic content (155.14 mg 100 g-1) was detected in calli exposed to UV-C for 5 min from 30 cm distance and sampled after 24 h. 24 h and 48 h incubation times, 30 cm and 5 min were the most appropriate combination of UV-C application in total flavanol content. Maximum total flavonol content (7.12 mg 100 g-1) was obtained on 0 h, 5 min and 20 cm combination. The highest (+)- catechin accumulation (8.89 mg g-1) was found in calli with 10 min UV-C application from 30 cm distance and sampled after 48 h. Ferulic acid content increased 6 fold in Öküzgözü callus cultures (31.37 µg g-1) compared to the control group. The greatest trans-resveratrol content (8.43 µg g-1) was detected in calli exposed to UV-C for 5 min from 30 cm distance and sampled after 24 h. The highest α-tocopherol concentration was found in calli exposed to UV-C for 10 min from 30 cm distance and sampled after 24 h. As a conclusion, it was showed that UV-C radiation had remarkable promoting effects on the accumulation of secondary metabolites in the calli of Öküzgözü grape cultivar.