Effects of repeated 1-methylcyclopropene (1-MCP) treatments on ripening and superficial scald of 'Cortland' and 'Delicious' apples

Postharvest 1-MCP can maintain fruit quality and inhibit development of superficial scald, a physiological storage disorder found in apple fruit, but the extent of the inhibition can vary by cultivar. In this study, we investigated whether multiple applications of 1-MCP, which are now permitted by a label modification of the commercial 1-MCP product, SmartFresh (TM), might improve scald control. 'Cortland' and 'Delicious' apples were untreated, treated on the day of harvest with the antioxidant inhibitor of scald, diphenylamine (DPA), or with 1 mu L L-1 1-MCP at different intervals after harvest. Treatment times (days) were 1, 4, 7, 1 + 4,4 + 7, 1 + 4 + 7, 7 + 14, 7 + 28, 7 + 42, and 7 + 84. Internal ethylene concentrations (IECs), flesh firmness, and accumulations of alpha-farnesene and conjugated trienols (CTols) were measured at harvest, at the time of treatment, and at intervals during air storage at 0.5 degrees C for up to 36 weeks. Scald was completely inhibited by DPA and all 1-MCP treatments in 'Delicious'. However, effective control of scald in 'Cortland' was obtained with 1-MCP treatments within the first 4 days of harvest, either alone or in combination. Scald control with delayed 1-MCP treatments resulted in poorer scald control that was comparable to that obtained with DPA. IECs and alpha-farnesene accumulation were similar in untreated and DPA treated fruit, but inhibited by 1-MCP. However, differences among 1-MCP treatments became more evident with increasing storage periods. Inhibition of IECs and alpha-farnesene accumulation was greater in fruit treated on days 1, 4, 1 + 4, 4 + 7, 1 + 4 + 7, than on day 7 alone. A second application of 1-MCP on day 14 to fruit treated on day 7 increased inhibition of IECs, alpha-farnesene and CTol accumulations, but increasing delays before the second 1-MCP treatment resulted in progressively less inhibition of these factors. Similar effects of treatment on IECs, alpha-farnesene and CTol accumulations were found for both cultivars, even though no scald was detected in treated 'Delicious' apples. The results indicate that initial 1-MCP treatments should be applied to faster ripening cultivars such as 'Cortland' within a few days of harvest. (c) 2012 Elsevier B.V. All rights reserved.