Delay in ripening of Gala and Pink Lady apples in commercial orchards following pre-harvest applications of aminoethoxyvinylglycine

Abstract

Aminoethoxyvinylglycine (AVG) was applied to Gala and Pink Lady apple trees on commercial orchards at label rates (830 g/ha ReTain with 0.1% v/v organosilicone surfactant) 21–28 days before anticipated first harvest. Fruit from treated and untreated trees in each orchard were sampled weekly during the commercial harvest period (2–6 times) and assessed for starch pattern index, background colour, soluble solids and flesh firmness. Ripening of AVG-treated Gala apples was delayed by 9–12 days based on starch pattern index and background colour whereas fruit softening was delayed by 5 days. Ripening of AVG-treated Pink Lady apples was delayed by 5 days based on SPI and fruit softening was delayed by 7 days. These differential delays for starch pattern index and fruit softening did not adversely affect the fruit quality of either apple variety, as there was no difference between the flesh firmness of treated and untreated fruit when fruit of the same starch pattern index were compared. Regardless of treatment, Gala apples grew an average 1.16 g per day during the harvest period whereas Pink Lady apples grew an average 0.22 g per day. These results suggest AVG has major benefits as a harvest management tool, as it allows growers to regulate fruit ripening.