Changes in ACC and conjugated ACC levels following controlled atmosphere storage of nectarine

Low temperature disorders of nectarines are thought to be expressions of chilling injury. Chilling injury is a form of stress usually associated with increased synthesis of ethylene and its immediate precursor, aminocyclopropane-1-carboxylic acid (ACC). However, other mechanisms for the development of chilling injury have been proposed. To help determine the nature of the processes leading to chilling injury in nectarines (Prunus persica) and how the gaseous composition of the storage atmosphere effects the development of low temperature disorders, levels of ACC and conjugated ACC were measured in fruit of the cv. Arctic Snow. These compounds were measured in fruit ripened at 20°C immediately after harvest, in fruit on removal from cold storage and in fruit ripened at 20°C following cold storage. During storage, fruit were kept at 0°C in the 4 following atmospheres: air; air + 15% CO2; air + 15 µL/L ethylene; and air + 15% CO2 + 15 µL/L ethylene. Concentrations of ACC remained low in all treatments and no significant changes in ACC levels due to added ethylene or CO2 were observed. Concentrations of conjugated ACC were about 10-times that of ACC and again were not influenced by the composition of the storage atmosphere. No significant changes in either ACC or conjugated ACC were observed until after flesh bleeding, the major symptoms of low temperature disorder expressed in these fruit, had begun to appear. It was concluded that disorders in nectarines stored at low temperatures are not a stress response involving a disruption of ethylene metabolism but may be associated with differential changes in the metabolism of enzymes associated with normal ripening.