Impact of pre-harvest fruit-bagging with different coloured bags on peel colour and the incidence of insect pests, disease and storage disorders in ‘Royal Delicious’ apple

Abstract

SummaryAn experiment was conducted to observe the effect of pre-harvest fruit bagging on 'Royal Delicious' apple (Malus x domestica Borkh.). On-tree fruit bagging was done using single-layer, non-woven spun-bound fabric bags of four different colours (light-yellow, blue, green, or red) on 15 July for 30 d before the expected date of harvest (15 August). The bags were removed 3 d before harvest (12 August) in each of two seasons (2010-11; 2011-12). All coloured bags had a significant influence on skin colour development and fruit quality attributes in 'Royal Delicious' apple. However, the light-yellow bags were most effective for the development of an attractive red peel colour (Hunter a* value = 52 ± 4.0). They also gave higher mean values for total anthocyanin concentration (TAC; 297.4 ± 21.9 mg cyanidin-3-glucoside kg 1 FW), phenylalanine ammonia lyase (PAL) activity (0.54 ± 0.03 µmol cinnamic acid produced min 1 g 1 FW), fruit firmness (38.6 ± 1.2 N), calcium concentration (5.38 ± 0.5 mg Ca2 100 g 1 DW), total phenolics concentration (TPC; 9.77 ± 0.25 mg gallic acid equivalents, 100 g 1 FW), anti-oxidant (AOX) activity (12.6 ± 0.35 µmol Trolox g 1 FW), soluble solids concentration (SSC; 14.5 ± 0.46 ºBrix), and ascorbic acid concentration (AAC; 29.3 ± 1.52 mg 100 1 g pulp) compared to blue, red, or green bags, or un-bagged apple fruit. Furthermore, light-yellow bags also resulted in the lowest incidence of San Jose scale insects (0.4 ± 0.2%) and diseases such as scab (1.03 ± 0.86%), fly speck (0.3 ± 0.3%), and sooty blotch (0.17 ± 0.15%) at harvest, and in storage disorders such as bitter pit, cork pit, and brown core. We therefore conclude that fruit bagging using single-layer, light-yellow non-woven, spun-bound fabric bags 30 d before harvest is beneficial for 'Royal Delicious' apple fruit colour and quality.