Ethylene Inhibition Influences Physiological Disorders in Apples

1-Methylcyclopropene (1-MCP), an inhibitor of ethylene action, delays the ripening and senescence of many climacteric fruits, including apple. As such, 1-MCP reduces respiration and ethylene production, and slows softening and deterioration of apple fruit.

The objective of this work was to examine the effects of 1-MCP on common physiological and storage disorders in apples. 'Empire', 'Honeycrisp', and 'McIntosh' apples were harvested in multiple years and cooled over night to ~3oC. Half of the fruit were then treated with 1-MCP (1 ppm) for 24 hours. All apples were stored in either ambient air (0 or 3oC) for 3-4 months or in controlled atmosphere (CA) for 6-10 months. CA regimes ranged from:

2 to 2.5% O2 + 2% CO2 at 1-3oC for 'Empire'
1.7 to 2.5% O2 + 1-2.5% CO2 at 3oC for 'Honeycrisp'
2.5% O2 + 2.5-4.5% CO2 at 3oC for 'McIntosh.

Senescent-related disorders were substantially reduced in apples treated with 1-MCP, such as senescent breakdown and peel greasiness. Superficial scald and core browning in air-stored 'McIntosh' were also reduced with 1-MCP.

Conversely, disorders related to CA stress tended to be exacerbated by 1-MCP. The incidence of external and/or internal CO2 injury was greatly increased in all cultivars treated with 1-MCP. Flesh browning (i.e. low temperature breakdown, vascular breakdown, and/or internal browning) incidence and severity also increased in 1-MCP-treated 'Empire' stored in CA for 9 or 10 months.

The role of ethylene and 1-MCP in the development of stress-related physiological disorders in apples needs to be investigated further.