Food-grade sugar can promote differentiation in melon (Cucumis melo L.) tissue culture

The objective of the present study was to investigate the origin of discrepancy between experimental results in in vitro culture of Turkish melon (Cucumis melo L.) cultivars, conducted by the same individual using the same protocol and same seed batches in two different laboratories. The difference in the sucrose source was found to be the major reason for the deviation in results between the two laboratories. The percentage of regenerating explants and the number of bud-like protuberances and/or shoots were significantly greater when a food-grade Turkish sucrose was used in the medium compared with analytical-grade sucrose. Media formulated with the food-grade sucrose regenerated 37 and 67 % more explants and bud-like protuberances and/or shoots per explant, respectively, than media containing analytical-grade sucrose. No meaningful differences were found in added elements or anions between the sucrose sources or by liquid chromatography/mass spectroscopy. The only significant chemical difference observed between the sucrose samples was the presence of melanoidins (Maillard reaction products) in the food-grade sucrose. The melanoidins were of high molecular weight (> 3,000 Da determined by ultrafiltration), with characteristic ultraviolet-visible spectra and in vitro antioxidant activity. Melanoidin-containing sucrose can be differentiated by color and spectroscopy.