Induction of callus culture through plant growth regulators supplementation and the effect of elicitors on enhancement of betalain synthesis using Gomphrena globosa

Abstract

Abstract Betalains are water soluble nitrogenous pigments produce by plants under the Caryophyllales order and has been favoured as a natural colourant in food and pharmaceutical industries due to its high stability towards pH and temperature over a wide range of food. There is a constant search for alternative source and technique for betalain production to meet the growing demand as conventional extraction method requires high quantity of plant material. Thus, this study sought to examine the potential of producing betalain through callus culture of a natural betalain bearing plant, Gomphrena globosa using different plant growth regulators (PGR) and to evaluate the effect of elicitation in enhancing betalain production. Callus induction from different explants showed that the percentage of callus induction (84.00-100.00%) from the leaf and hypocotyl explants was significantly higher than seeds (53.33%). A combination of 0.5 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) with 1.0 mg/L 6-benzylaminopurine (BAP) were found to be effective inducing pink callus in full strength MS medium. Elicitation with tyrosine was the most effective in enhancing the betacyanin content (red-violet pigments) followed by salicylic acid. The highest betacyanin content, 0.139 ± 0.035 mg/mg FW callus was obtained when 100 µM of tyrosine was supplied. Copper sulphate was found to be effective in increasing the callus size but not the betalain content. The callus size was about 13-fold bigger in MS medium supplemented with 25 µM copper sulphate compared to medium without elicitors. This is the first study reporting an optimised protocol in the production of pigmented callus containing betalain from G. globosa using a combination of PGRs consisting of 2,4-D and BAP. In addition, tyrosine can be used as a suitable elicitor to enhance betalain production which provides an alternative source of betalain for the commercial production of natural colorants.