Training systems and pre-harvest ethrel application affect fruit colour development and quality of 'Pink Lady' apple at harvest and in controlled atmosphere storage

Development of poor red blush on the surface of apple (Malus × domestica Borkh.) fruit at commercial harvest is one of the major limiting factors for theirexport. Ethylene has been reported to directly affect accumulation of red pigments and development of red blush in many fruit crops including apple. The efficacy of an ethylene releasing compound – ethrel (ethephon) for the improvement of red blush of ‘Pink Lady’ apple fruit from the trees trained as vase (VS), central leader (CL), spindle bush (SB) and double row (DR) systems, was investigated at harvest in 2005. The influence of ethrel treatment on important quality parameters such as fruit firmness, soluble solids content (SSC) and titratable acidity (TA) was also studied at harvest and following 190 days controlled atmosphere (CA) storage. Pre-harvest ethrel spray significantly increased the concentrations of total anthocyanin and cyanidin 3-galactoside in the fruit skin and improved red blush and chromaticity values a*, C* and h° of the fruit colour at commercial harvest, irrespective of the training systems. Ethrel treatment increased the concentration of total anthocyanin nearly two fold in the skin of the exposed side (ES) of the fruit from the trees trainedas SB, compared to control. There were no significant differences in fruit firmness, SSC or TA of the fruit harvested from ethrel-treated and control trees trained on any of the systems, at commercial harvest. Following 190 days CA storage, ethrel treatment slightly increased SSC and TA of the fruit compared to control, whereas fruit firmness was not consistently influenced by ethrel treatment. In conclusion, preharvest ethrel spray application improves the development of red blush in ‘Pink Lady’ apple fruit at commercial harvest irrespective of training system without adversely affecting fruit quality at harvest or following 190 days CA storage