1-MCP is an inhibitor of ethylene perception that can delay fruit ripening and extend storage life. 1-MCP is marketed as SmartFresh™ for postharvest treatment and its use has become common practice in many apple-growing regions. 1-MCP reduces ethylene production and respiration rate, improves firmness and acidity retention, and controls senescent-related disorders in apples (DeEll et al., 2007; Fan et al., 1999a, 1999b; Watkins, 2007). 1-MCP has also been shown to increase the risk of stress-related disorders in apples; increased incidence of CO2 injury or flesh browning has been found in 1-MCP-treated ‘McIntosh’ and ‘Empire’ apples (DeEll et al., 2003; Fawbush et al., 2008; Jung and Watkins, 2011). Efficacy of 1-MCP treatment depends on apple cultivar (Bai et al., 2005; Watkins et al., 2000), harvest maturity (DeEll et al., 2008; Toivonen and Lu, 2005), and temperature and timing of application (DeEll et al., 2002; Watkins and Nock, 2005). Effects of 1-MCP on ‘McIntosh’ apples are reduced in later harvests and with longer delays between harvest and treatment (DeEll et al., 2008).
Postharvest treatment of 1-MCP (1 μL·L−1) has traditionally involved a single application soon after harvest. It is recommended that ‘McIntosh’ be treated with 1-MCP within 3 d of harvest for maximum effectiveness (AgroFresh, 2012; DeEll et al., 2008). This has been difficult for small growers with storages that can take 1 week or more to fill.
The SmartFresh™ label in Canada was expanded in 2011 to allow up to four applications of 1-MCP (1 μL·L−1) within 240 d of harvest. Without such restrictions, the label in the United States was modified to include multiple applications in 2009. As a result, many storage operations are treating rooms with 1-MCP more than once during filling. This has provoked interest in the possibility that more than one application of 1-MCP could enhance the fruit quality benefits, but also potentially increase the development of disorders that are aggravated by 1-MCP.
Preliminary studies have shown that a second 1-MCP treatment after four or eight months of CA storage can improve firmness retention and reduce ethylene production and respiration rate in ‘Empire’ apples harvested at optimum maturity (DeEll and Murr, 2005). Response to 1-MCP was better when apples were held in low O2 CA (1.2 kPa O2 + 1.0 kPa CO2) than in standard CA (2.5 kPa O2 + 2.0 kPa CO2) at 2 °C, and the effects diminished with increased time after removal from CA before 1-MCP treatment. This same study found little effect of 1-MCP on ‘Empire’ and ‘Delicious’ apples when the treatment followed air storage instead of CA. DeLong et al. (2004) found no effect of an additional 1-MCP application after 4.5 months on ‘Cortland’ and ‘McIntosh’ apples held in air and CA storage, but the concentration of 1-MCP was less than that used commercially. Mir et al. (2001) found the most effective 1-MCP treatment frequency was once per week in ‘Redchief Delicious’ apples at elevated temperatures (5 to 20 °C). More recently, Watkins et al. (personal communication) showed little advantage of repeated 1-MCP applications at 4 or 7 d after harvest in addition to treatment 1 d after harvest.
There have been no scientific reports on the effects of rapid consecutive 1-MCP treatments on apples at harvest, simulating daily 1-MCP applications as storage rooms are loaded with fruit. The objective of this study was to investigate the effects of rapid consecutive postharvest 1-MCP treatments (1 and 2 d after harvest) on fruit quality and storage disorders in apples. ‘McIntosh’ and ‘Spartan’ apples were studied through long-term storage in air and CA. ‘McIntosh’ was also used to determine if two consecutive treatments of the label rate (1 μL·L−1 1-MCP) were equivalent to one application at double concentration (2 μL·L−1). There have been no scientific reports of 1-MCP treatment on ‘Spartan’ apples.
AgroFresh 2012 SmartFresh™ quality system, apple use recommendations. AgroFresh, Inc., Spring House, PA
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