Fruit Bag Removal Timing Influences Fruit Coloration, Quality, and Physiological Disorders in 'Arisoo' Apples

The timing of fruit bag removal is important for achieving optimum fruit quality, coloration, and visual appearance. Therefore, this study investigated the effects of fruit bag removal timing on fruit quality and color and the occurrence of physiological disorders in 'Arisoo' apples. Fruits were bagged in two-layer paper bags, which were removed 30, 20, and 10 days before harvest (DBH). Unbagged fruits served as the control. The incidence of fruit cracking, sunburn, and pathogen infection was highest in the unbagged group, followed by the group with bag removal at 30 DBH, and lowest in those with bag removal at 20 and 10 DBH. However, bag removal at 10 DBH significantly reduced fruit weight and soluble solids content but increased firmness. Additionally, bag removal at 10 DBH resulted in poorly colored fruits with higher chlorophyll and lower anthocyanin and carotenoid pigments and lower expression levels of pigment-related genes, including anthocyanin-, carotenoid-, and chlorophyll degradation-associated genes, compared with those in the other treatment groups. Bag removal at 30 and 20 DBH did not significantly affect fruit quality or coloration, but it did affect fruit size. Overall, this study serves as a reference for determining the optimal timing of fruit bag removal to enhance the quality and coloration of 'Arisoo' apples.