Effects of 1-methylcyclopropene on activities of ethylene biosynthesis and cell wall degrading enzyme during ripening of papaya ‘Sekaki

Ripening of papaya ‘Sekaki’ at ambient temperature was affected by application of 1-methylcyclopropene (1-MCP). The percentage weight loss of 1-MCP (270 ppb for 12 h) treated fruit was significantly (p 0.05) lower than control fruit. The loss of tissue firmness of 1-MCP treated fruit was significantly (p 0.05) inhibited, whilst the control fruit showed a dramatic loss in tissue firmness up to 50% yellowing-of-skin colour (YR) stage and then gradually until the end of ripening stage. The ethylene production increased significantly (p 0.05) to a maximum at 50% YR in 1-MCP treated and control fruits, and declining sharply thereafter. The 1-MCP treated fruits showed significant (p 0.05) reduction in ethylene production, 1-aminocyclopropane-1-carboxylic oxidase (ACO) and 1-aminocyclopropane-1-carboxylic synthase (ACS) activities but generally maintained the 1-aminocyclopropane-1-carboxylic acid (ACC) level. The activity of α- and β-galactosidase and pectin methylesterase (PME) was significantly (p 0.05) suppressed as compared to control fruit. The capability of 1-MCP to maintain the firmness of ‘Sekaki’ papaya during ripening might be associated with suppression of ethylene dependent cell wall degrading enzyme activities such as α- and β-galactosidases, PME, α-arabinosidase, α-mannosidase and β-glucosidase. This study showed the effectiveness of 1-MCP in delaying fruit ripening, significantly suppressing the cell wall degrading enzyme activity and maintaining the firmness of ‘Sekaki’ papaya fruit during ripening