Preharvest 1-methylcyclopropene and aminoethoxyvinylglycine treatment effects on 'NY2' (RubyFrost®) apple fruit quality and postharvest watercore dissipation at different temperatures

Recent studies have found that dissipation of watercore in apple fruit after harvest can be enhanced by preharvest application of 1-methylcyclopropene (1-MCP). In this study, the effects of plant growth regulators (PGRs) on watercore dissipation have been extended to the use of aminoethoxyvinylglycine (AVG) and the effects of storage at 3 degrees C, 10 degrees C, and 20 degrees C over 30 d. Preharvest 1-methylcyclopropene (1-MCP) and aminoethoxyvinylglycine (AVG) treatments were applied one week before harvest to 'NY2' (RubyFrost (R)), a cultivar that is prone to development of a stress-associated type of watercore during fruit maturation. Fruit were harvested twice (H1 and H2), 11 d apart. 1-MCP and AVG treatments had more pronounced effects on maturity at H2, with higher IAD values and flesh firmness, respectively, compared with those of fruit harvested at H1. During storage, 1-MCP and AVG treated fruit had lower ethylene production and respiration rates than untreated fruit at H1, but ethylene production in 1-MCP treated fruit increased on day 17 at H2, reaching levels similar to untreated fruit, while remaining low in AVG-treated fruit. IECs were lower in fruit stored at 3 degrees C than at 10 degrees C or 20 C. Both treatments maintained low IECs, but more persistently in AVG-treated fruit. Flesh firmness and titratable acidity were higher, and greasiness was lower, in AVG and 1-MCP treated fruit compared with untreated fruit. The PGR treatments had no effect on watercore incidence at H1 as incidence was low in all treated fruit. At H2, 1MCP reduced watercore incidence at harvest compared with untreated and AVG-treated fruit, which had similar incidences. Watercore dissipation was enhanced by AVG, being more rapid with higher storage temperature. The mechanism by which PGRs can increase watercore dissipation is unknown, but they might alter sorbitol transporter activity and/or cell membrane stability for sorbitol uptake from the intercellular space into the parenchyma cells. Nevertheless, the use of PGRs may be a useful way to decrease the incidences of flesh browning disorders associated with high watercore incidence in fruit at the time of harvest.