Low ethylene controlled atmosphere induces adverse effects on the quality of 'Cox's Orange Pippin' apples treated with aminoethoxyvinylglycine during fruit development

Ethylene scrubbing of stores containing 'Cox's Orange Pippin' ('Cox') apples reduces fruit softening when used in combination with treatments that reduce ethylene production such as orchard sprays with daminozide or pre-storage treatment with high CO2. However, such treatments are injurious to the fruit when stored for long periods. Two experiments were conducted to determine the effects of sprays containing aminoethoxyvinylglycine (AVG) on the ethylene production and quality of 'Cox' apples in low-ethylene controlled atmosphere (CA) storage. In a picking date study ReTain(R) (Valent BioSciences Corp.) sprays (123.5 g AVG ha(-1)) were applied to 'Cox' trees 4 weeks before anticipated harvest. Fruit was harvested on three occasions and stored in static CA conditions of 1.2 kPa O-2 (<1 kPa CO2) at 3.5°C, with and without ethylene removal by catalytic converters. Unsprayed fruit were treated with 5 kPa CO2 prior to low-ethylene storage. After storage until late March/early April (ethylene not removed) ReTain(R)-treated fruits were 5.4 N firmer than the unsprayed (averaged for picks). Ethylene removal improved the firmness of unsprayed fruit by 2.9 N and of ReTain(R)-treated fruits by 8.0 N. The beneficial effect on firmness by ReTain(R)-treatment and ethylene removal (13.4 N) was negated by the development of core flush. After a simulated marketing period 57% of fruits were affected. In a second study ReTain(R) was applied to 'Cox' trees at two rates (123.5 and 185.3 g AVG ha(-1)) on three occasions (2, 4 and 6 weeks before harvest). Fruits were stored for six months at 3.5°C in containers that were flushed continuously with 1.2 kPa O-2 (98.8 kPa N-2) to prevent the accumulation of ethylene. Although fruits from trees treated with either concentration of ReTain(R) at 2 and 4 weeks before harvest were firmer than those from untreated trees after storage, ReTain(R)-treated fruit developed core flush (30-60%) and internal breakdown (10-55%). Increasing the concentration of ReTain(R) applied did not improve firmness but increased the incidence of internal breakdown. Parallels with adverse responses to other methods of suppressing ethylene production are discussed. (C) 2002 Elsevier Science B.V. All rights reserved.