High Rates of AVG Significantly Delay Ripening and Improve Quality of 'Cortland’ Apples

Aminoethoxyvinylglycine (AVG) is an ethylene inhibitor that has been in commercial use for many years. It is sold as the proprietary product ReTain®. The use has been primarily to retard preharvest drop and to delay ripening of apples thus allowing an orderly sequence of harvest while maintaining overall fruit quality. Initially the amounts used were restricted to relatively low rates due to label limitations and excessive reduction in red color development. The cultivars ‘Gala’ and ‘Honeycrisp’ are being extensively planted and they are harvested in during the same harvest window as older cultivars such as ‘McIntosh’ and ‘Cortland’ making it difficult to harvest high quality fruit in a timely manner. In this study high rates of ReTain® (333 g/acre) were applied to ‘McIntosh’ and ‘Cortland’ at 4 weeks and again at 2 weeks before the anticipated start of harvest. Fruit quality was evaluated periodically during the harvest season. A storage sample was taken and a portion of the ReTain®-treated fruit were also gassed with 1-methylcyclopropene (1-MCP, SmartFresh^SM) prior to storage. After 8 weeks McIntosh apples showed a modest delay in flesh firmness loss but after 12 weeks in storage neither AVG-treated nor 1-MCP-treated fruit was firmer than untreated fruit. Cortland apples received similar treatments as McIntosh. ReTain® applications delayed ripening and firmness loss at harvest. Following storage for 10 weeks both AVG and 1-MCP reduced firmness loss and when both ReTain® and 1-MCP were combined there was a highly significant additive delay in fruit softening. Taste evaluation of fruit treated with both compounds rated significantly higher in several key categories including crispness, flavor and being overall desirable. The large improvement in fruit quality was primarily attributed to a significant delay in fruit ripening which allowed the fruit to ripen and to mature during cooler weather conditions which favored enhanced overall fruit quality.