The total fruit yield was determined separately for each plot. Harvest was performed once at commercial maturity (on 23 and 26 September 2020 and 2021, respectively) when the ethylene concentrations in the core cavity of the control fruit were within the range of 1.5–5.0 μL L-1.
Fruit quality was assessed based on single fruit weight, russeting and skin blushing, flesh firmness (FF), soluble solid concentration (SSC), and titratable acidity (TA). Mean fruit weight, as well as russeting and skin blushing, were determined on an approximately 20 kg bulk sample per plot. Russeting and skin blushing were rated on a scale from 1 (no russeting/blush) to 5 (russeting/blush on > 75% of the skin surface). Flesh firmness, SSC and TA of apples were measured on 30 fruit of similar size taken randomly from each of the 20 kg bulk samples per plot. Firmness was measured on two opposite peeled sides of each fruit using an EPT-1R penetrometer (Lake City Technical Products, Kelowna, BC, Canada) with an 11 mm diameter tip. The SSC was measured with an Atago PR-101 electronic refractometer (Atago Co., Ltd., Tokyo, Japan) using juice squeezed from the fruit homogenate at 20°C. Titratable acidity was determined by titrating the fruit homogenate with 0.1 N sodium hydroxide to pH 8.1 using a Mettler Toledo DL 50 Graphix automatic titrator (Mettler-Toledo AG., Schwerzenbach, Switzerland). The results of the TA represent the malic acid content, expressed as a percentage.
Fruit quality was assessed based on single fruit weight, russeting and skin blushing, flesh firmness (FF), soluble solid concentration (SSC), and titratable acidity (TA). Mean fruit weight, as well as russeting and skin blushing, were determined on an approximately 20 kg bulk sample per plot. Russeting and skin blushing were rated on a scale from 1 (no russeting/blush) to 5 (russeting/blush on > 75% of the skin surface). Flesh firmness, SSC and TA of apples were measured on 30 fruit of similar size taken randomly from each of the 20 kg bulk samples per plot. Firmness was measured on two opposite peeled sides of each fruit using an EPT-1R penetrometer (Lake City Technical Products, Kelowna, BC, Canada) with an 11 mm diameter tip. The SSC was measured with an Atago PR-101 electronic refractometer (Atago Co., Ltd., Tokyo, Japan) using juice squeezed from the fruit homogenate at 20°C. Titratable acidity was determined by titrating the fruit homogenate with 0.1 N sodium hydroxide to pH 8.1 using a Mettler Toledo DL 50 Graphix automatic titrator (Mettler-Toledo AG., Schwerzenbach, Switzerland). The results of the TA represent the malic acid content, expressed as a percentage.
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