The effect of ethylene on transgenic melon ripening and fruit quality

Abstract

Melons are good models used for explaining the physiological and biochemical changes in postharvest ripening. In this study, transgenic melons expressing apple ACC oxidase gene when treated with ethylene (AS3) were evaluated. Cell wall expression (MPG1; MPG2), ethylene synthesis ACC oxidase (ACCO1), flavour synthesis AAT (alcohol acyltransferase) and physiochemical parameters such as pulp firmness, titratable acidity (TA), soluble solid content (SSC), volatile esters, ethylene productions, antioxidant assay capacity and ascorbic acid content were evaluated. In cell wall expression analysis, MPG1 increased when fruits of transgenic melons were exposed to ethylene; showing they are ethylene- dependent. MPG2 decreased gradually when fruits were subjected to ethylene application. Fruit firmness was modified in transgenic fruits when ethylene was applied. There was a great reduction similar to that of non- transgenic fruits. However, TA in transgenic fruits remained lower than in non- transgenic fruit. The ethylene applied in transgenic fruit made the titratable acid to increase during 48 h and after it, a reduction was observed. In relation to soluble solid contents, transgenic fruits treated with or without ethylene did not reduce gradually compared to the wild type melons in all the periods. Ethylene productions in transgenic fruits were reestablished when ethylene was applied, exhibiting the same behavior as transgenic fruits. Antioxidant assay levels were more active in transgenic fruits when ethylene was applied than in control fruits, and it was only in transgenic fruits without ethylene. Ascorbic acid was kept in transgenic fruits with or without the application of ethylene. Results obtained show that the application of ethylene in transgenic ACC oxidase melons is able to change the metabolism of the cell wall, flavors and antioxidant capacity levels in fruit during the ripening process.

Keywords: Esters, antioxidant, solid soluble content, ascorbic acid

African Journal of Biotechnology, Vol 13(31) 3252-3261