Effects of Rapid Consecutive Postharvest 1-Methylcyclopropene Treatments on Fruit Quality and Storage Disorders in Apples

The objective of this study was to investigate the effects of rapid consecutive 1-methylcyclopropene (1-MCP) treatments on apple quality and disorders in storage. 'McIntosh' and 'Spartan' apples were harvested twice from commercial orchards and 1-MCP (1 mu L.L-1) was applied postharvest either 1 day after harvest or 1 and 2 days after harvest. Similar fruit from both cultivars were also not treated with 1-MCP, plus an additional treatment of 2 mu L.L-1 (double rate) 1-MCP was used on 'McIntosh'. Fruit were held in either air storage at 0.5 degrees C for three or six months or in controlled-atmosphere (CA) storage for six or nine months. Overall, 1-MCP treatment improved firmness and acidity retention and reduced internal ethylene in both cultivars. However, 'Spartan' stored in CA often maintained these attributes without 1-MCP. 'McIntosh' apples treated twice with 1-MCP were often firmer than those treated just once. All 1-MCP treatments substantially reduced superficial scald and there was no difference in scald incidence among the treatments. Core browning was generally reduced by 1-MCP, but fruit treated once with 2 mu L.L-1 or twice with 1 mu L.L-1 1-MCP sometimes had higher incidence than fruit treated only once with 1 mu L.L-1. 'Spartan' treated twice with 1-MCP also had higher incidence of internal browning after nine months. 1-MCP increased the incidence of external CO2 injury in 'McIntosh' from the first harvest, with fruit treated with 2 mu L.L-1 having the highest incidence after six months of CA storage and those treated once with 1 mu L.L-1 having the highest incidence after nine months. Storage rots were greatest after six months of air storage and 1-MCP treatments usually reduced the incidence, regardless of treatment. These results suggest that using more than the traditional single application of 1 mu L.L-1 1-MCP may improve firmness retention, but there is also some risk associated with increased disorders, especially when storing apples long-term, such as for six months in air or nine months in CA storage.