Combined Effects of Cytokinin and UV-C Light on Phenolic Pattern in Ceratonia siliqua Shoot Cultures

Carob (Ceratonia siliqua L.) is an underutilized traditional crop in the Mediterranean regions that has gained much interest due to its high nutritional traits and resilience to drought and salinity. However, conventional methods of carob propagation are not enough to meet its increasing market demands. The present study analyzes to what extent benzyl adenine (BA) treatments (0.1, 0.5 and 1.0 mg L-1) alone or in combination with UV-C irradiation (3.34 and 10.01 kJ m(-2)) affect the antioxidant capacity and the levels of phenolic compounds in in vitro carob shoot cultures as well as their performance in terms of the content of photosynthetic pigments and sugars. Results showed that the combination of both treatments resulted in an increased content of chlorophylls, carotenoids, and sugars, particularly at 0.5 mg L-1 BA and the highest UV-C dose. Antioxidant capacity, assessed by the DPPH method, and the levels of soluble flavonoids, flavones and flavonols, and hydroxycinnamic acids were highly influenced by the interaction between BA and UV-C in the combined treatments. This indicates a clear dependence on BA concentration in the response of carob in vitro shoots to UV-C. This could be the basis for the implementation of more efficient carob micropropagation processes.