Responses of climacteric and suppressed-climacteric plums to treatment with propylene and 1-methylcyclopropene

The aim of this study was to characterise further the ripening behaviour of climacteric ('Gulfruby' and 'Beauty') and suppressed-climacteric ('Shiro' and 'Rubyred') plums by treating preclimacteric fruit with 1-methylcyclopropene (I-MCP) followed by continuous treatment with propylene. Analyses showed that the development of skin colour was an ethylene-independent phenomenon, whilst aroma production was either ethylene-dependent or ethylene-independent, depending on the cultivar. Typical climacteric patterns of ripening were shown by 'Gulfruby' and 'Beauty' fruit, as the application of propylene alone advanced the onset of the respiratory and ethylene climacterics whilst 1-MCP delayed these events. 'Shiro' and 'Rubyred' fruit exhibited suppressed-climacteric patterns or ripening associated with 15-500-fold less ethylene production than the climacteric cultivars. Since 1-aminocyclopropane-1-carboxylic acid (ACC) concentrations were similar in all four cultivars, it is suggested that the suppressed-climacteric phenotype is the result of an impaired ability of the fruit to convert ACC to ethylene. Fruit of these cultivars treated with 1-MCP did not develop an ethylene or respiratory climacteric unless exogenous propylene was applied. We suggest that the inability of 1-MCP treated, suppressed-climacteric fruit to develop a climacteric results from an impaired ability of the fruit to perceive ethylene and to produce new receptors.