Preharvest Plant Growth Regulators and Conditioning Treatment Effects on Flesh Browning on 'Gala' Apples

Development of a flesh browning disorder in ‘Gala’ apples, which develops initially at the stem end of the fruit, has become an increasing problem for storage operators in part because of the need to store larger volumes of fruit for longer periods of time.  We have investigated the effects of the preharvest plant growth regulators (PGRs) ReTain (aminoethoxyvinylglycine; AVG) and Harvista (1-methylcyclopropene; 1-MCP) over two harvest dates.  At each harvest date, fruit were either untreated or treated with SmartFresh (postharvest 1-MCP), and then either kept in air at 0.5 °C or at 10 °C (conditioning) for a week. Conditioned fruit were cooled overnight and then all fruit were stored in controlled atmosphere conditions of 2% oxygen and 2% carbon dioxide at 0.5 °C for four months. The SmartFresh treatment did not affect browning incidence, but was a necessary treatment to avoid loss of texture associated with conditioning.  Browning incidence was not affected by ReTain treatment, but it was reduced by Harvista treatment.  Except for the Harvista treated fruit in which browning incidence was low, conditioning markedly reduced browning.  Overall, the results indicate that preharvest PGRs, especially Harvista, reduce browning incidence by delaying fruit maturity, but that ethylene metabolism is not involved in the ameliorating effects of conditioning on browning after harvest.