Massimo Pilli

Effects of application of thidiazuron (TDZ), gibberellic acid (GA3), and 2,4‐dichlorophenoxyacetic acid (2,4‐D) on fruit size and quality of Actinidia deliciosa ’Hayward’

Abstract The effects of dipping fruit in solutions made from factorial combinations of 0 and 10 ppm thidiazuron (TDZ), 0 and 50 ppm gibberellic acid (GA3), and 0 and 20 ppm 2,4‐dichlorophenoxyacetic acid (2,4‐D) on fruit size and quality characteristics in Actinidia deliciosa ’Hayward’ were evaluated. When the compounds were used together significant interactions, TDZ × GA3 and TDZ × GA3 × 2,4‐D, were recorded for the increase in fruit weight (+42% and +94%, respectively, compared with untreated fruits that had an average weight of 82.7 g). TDZ and 2,4‐D were very effective in increasing fruit weight when used alone (+31% and +32%, respectively, compared with untreated fruits) or in combination with the other compounds. GA3 only showed an appreciable effect when used in combination with TDZ or TDZ + 2,4‐D. Growth regulator treatments did not affect seed weight and number per fruit. TDZ accelerated fruit ripening and caused a change in fruit shape. TDZ and GA3 did not affect the fruit carbohydrate content at harvest, whereas the use of 2,4‐D slightly decreased the fruit total carbohydrate content. The results indicate that the growth potential of kiwifruit is much higher than is normally expressed.