Enhancement of bioactive compounds in Hylocereus polyrhzus callus mediated by plant growth regulators and elicitors

Deep red coloured fruit flesh of red pitaya, which is due to betalains pigment, provides an alternative source of antioxidants and natural food colourant. Hence, red pitaya callus culture was established for the production of betalains. Murashige and Skoog (MS) medium supplemented with 2 mg/L 1- naphthaleneacetic acid (NAA) and 4 mg/L thidiazuron (TDZ) was identified as the best treatment to produce pigmented callus with high betalains content. A total of 15 bioactive compounds were identified from the callus compared to only eight bioactive compounds identified from the fresh fruit using LCMS/MS analysis. The callus culture produced seven more bioactive compounds that exist in betacyanins biosynthetic pathway. The study was also carried out to determine the elicitation effect on the established red pitaya callus and betalains biosynthesis in the callus culture using salicylic acid. Four different concentrations of salicylic acid (25, 50, 100 and 200 uM) were added to MS medium supplemented with 2 mg/L NAA and 4 mg/L TDZ separately. The morphology of callus produced in all different concentrations of salicylic acid tested was friable and red in colour. Spectrophotometer analysis revealed that 100 uM salicylic acid was determined as optimal concentration to enhance betalains biosynthesis in red pitaya callus culture