Dissecting the influence of the orchard location and the maturity at harvest on apple quality, physiology and susceptibility to major postharvest pathogens

Environmentally driven transcriptomic and metabolic changes leading to color differences in “Golden Reinders” apples

“…The starch index was assigned to each fruit using the starch scale from 1 to 10 developed by the Centre Technique Interprofessionnel des Fruits et Légumes (CTIFL, Paris, France). Further quality measurements were earlier reported by Fernández-Cancelo et al (2021) .…”

“…Notably, fruit from mountain orchards, and especially those from Gotarta, showed enhanced yellow color, as desired by consumers, but also higher antioxidant capacity and elevated levels of MDA, a marker of lipid peroxidation ( Hodges et al, 1999 ). Since the apples were harvested at a similar maturity stage ( Fernández-Cancelo et al, 2021 ), climatic differences between orchards may have influenced peel metabolism ( McTavish et al, 2020 ) leading to different color phenotypes. Indeed, in our previous study, we demonstrated that optimal fruit color in “‘Golden Reinders” apples was not associated to the fruit maturity stage and that fruit grown in the Ebro valley never attain the optimal yellow color desired by the consumer, even if left to ripen on-tree far beyond the CHD ( Fernández-Cancelo et al, 2021 ).…”

“…Since the apples were harvested at a similar maturity stage ( Fernández-Cancelo et al, 2021 ), climatic differences between orchards may have influenced peel metabolism ( McTavish et al, 2020 ) leading to different color phenotypes. Indeed, in our previous study, we demonstrated that optimal fruit color in “‘Golden Reinders” apples was not associated to the fruit maturity stage and that fruit grown in the Ebro valley never attain the optimal yellow color desired by the consumer, even if left to ripen on-tree far beyond the CHD ( Fernández-Cancelo et al, 2021 ). Among the wide variety of environmental factors that can influence fruit color (temperature, solar radiation, hours of sun, precipitations, and relative humidity), the low temperatures and solar radiation reached days before harvest in Gotarta ( Supplementary Figures S8 , S9 ) in combination with a probable higher accumulation of UV radiation due to the high altitude (data not measured; Blumthaler et al, 1997 ) may have favored chlorophyll degradation ( León-Chan et al, 2017 ) and color changes in Gotarta apples.…”

“…“Golden Reinders” apples were harvested at the CHD based on flesh firmness (71 ± 2.5 N) and starch index values (6 ± 0.8) from trees of similar age and grown under the same rootstock (M9) as well as similar agronomical practices. Further characterization of the fruit maturity at the time of harvest (focused on ethylene biosynthesis) is available from Fernández-Cancelo et al (2021) . A set of 45 fruit were harvested at the same canopy height from 10 random trees in each location at CHD.…”

“…Based on previous protocols ( Rassam and Laing, 2005 ), the extraction of ascorbic acid was carried out mixing 2.5 g of frozen peel tissue with 5 ml of metaphosphoric acid suspension (3% metaphosphoric acid, 8% acetic acid) and centrifuging at 24,000 × g for 22 min at 4°C. Quantification of ascorbic acid (AsA) and total ascorbic acid was performed as previously described ( Fernández-Cancelo et al, 2021 ). Dehydroascorbic acid (DHA) was calculated by subtracting the ascorbic acid content from that of total ascorbic acid.…”