ruit temperature and ethylene modulate 1-MCP response in ‘ Bartlett ’ pears ax

Introduction 1-Methylcyclopropene (1-MCP) is an ethylene action inhibitor hat delays ripening of many fruit, including European pears (Sisler nd Blankenship, 1996; Bai et al., 2006; Calvo and Sozzi, 2009). 1CP is registered as SmartFreshSM for postharvest gas application n sealed rooms or tents. The use of 1-MCP for ‘Bartlett’ pears has een investigated for several years to improve post-storage quality nd allow ‘Bartlett’ pears to be shipped to distant markets (Calvo nd Sozzi, 2004, 2009; Calvo, 2004; Ekman et al., 2004; Bai et al., 006; Villalobos-Acuña and Mitcham, 2008; Villalobos-Acuña t al., 2011). While results have been promising, a continuing challenge is he balance between storage benefits and eventual ripening of he fruit for marketing (Villalobos-Acuña et al., 2011). Our focus n recent years has been to reduce the fruit’s response to 1-MCP hrough modifications in fruit handling at harvest prior to appliation. However, some commercial trials of 1-MCP conducted in alifornia during 2008 obtained quite variable fruit response, and n many cases no response was seen or a much higher concentraion of 1-MCP was required to see an effect. The reason for these ∗ Corresponding author. E-mail address: ejmitcham@ucdavis.edu (E.J. Mitcham). 925-5214/$ – see front matter © 2010 Elsevier B.V. All rights reserved. oi:10.1016/j.postharvbio. 2010.11. 005 regulating 1-MCP efficacy in ‘Bartlett pears. © 2010 Elsevier B.V. All rights reserved. treatment failures was not at all clear, nor for the widely variable results between the laboratory and the field trials. The rate of fruit cooling and the fruit pulp temperature at the time of 1-MCP application could be a factor, as has been shown in other horticultural commodities (Serek et al., 1995; Ku and Wills, 1999; Mir et al., 2001; DeEll et al., 2002; Jiang et al., 2002; Blankenship and Dole, 2003; Liguori et al., 2004). Recent studies in our laboratory indicate that exposure of fruit to ethylene prior to 1-MCP application results in a moderated effect on fruit ripening, with delayed ripening at harvest, but full ripening after a period of cold storage. Ethylene exposure prior to or during 1-MCP treatment has been shown to induce competition with 1-MCP for binding to the ethylene receptors, reducing the ability of 1-MCP to fully control or reduce ethylene responses (Sisler et al., 2003; Reid and Çelikel, 2008; Apelbaum et al., 2008; Zhang et al., 2009, 2010). Ethylene concentration during 1-MCP treatment in the laboratory or commercial environment in a tent or sealed room can vary from 0.015 to 20 L/L depending on the fruit maturity stage, amount of fruit per volume in the tent or room, and the time fruit have been stored at intermediate or low temperatures prior to treatment (Villalobos-Acuña, unpublished data). Our objectives in this study were to characterize the influence of preand post-treatment temperature exposures and ethylene exposure during 1-MCP treatment on Bartlett pear response to 1-MCP. 18 M.G. Villalobos Acuña et al. / Postharvest Biology and Technology 60 (2011) 17–23 Table 1 Growing region, harvest date, maturity and fruit size of ‘Bartlett’ pears used in each experiment. All the fruit were packed in cardboard boxes and transported to the Postharvest Pilot Plant in a cargo van the same day of packing. Experiment Harvest date Growing region Maturity (N) Fruit size July Aug Aug Aug