Fruit quality of ‘Braeburn’ apple trees sprayed at post-bloom and preharvest with prohexadione-calcium and GA4+7

The objective of this study was to assess the effects of post-bloom (PB) or preharvest (PH) treatments of Braeburn apple trees with prohexadione-calcium (ProCa; 300 mg L-1), an inhibitor of gibberellins biosynthesis, or GA4+7 (300 mg L-1) on fruit quality at harvest and after storage (four months at 0±0.5 o C, followed by five days of shelf life). PB treatments started 15 days after full bloom, with one application every week and six applications in total. PH treatments started five weeks before anticipated harvest, with one application every week and four applications in total. Control trees were sprayed with water. GA4+7 PB increased length/diameter ratio, and GA4+7 PH increased titratable acidity (TA) and flesh firmness and slightly reduced red color of the fruit at harvest. ProCa PB and PH reduced ethylene production rate, delayed starch degradation and reduced soluble solids content of the fruit at harvest, and ProCa PH maintained firmness at harvest and after storage and TA of the fruit after storage. ProCa PB or PH delayed the loss of skin green background color at harvest, while at both treatment timings reduced the development of skin red color, but with a much stronger effect when sprayed PH than PB. Index terms: anti-gibberellin, ethylene, Malus domestica Borkh, maturity, skin color.