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'

The effects of dipping fruit in solutions made from factorial combinations of 0 and 10 ppm thidiazuron (TDZ), 0 and 50 ppm gibberellic acid (GA(3)), 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 x GA3 and TDZ x GA3 x 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.