The effect of synthetic auxins on fruit development, quality and final fruit size in ‘Canino’ apricot (Prunus armeniaca L.)

Abstract

SummaryThe only commercial apricot cultivar grown in Israel, ‘Canino’, produces relatively small fruit. Over three consecutive years (2003–2005), application of 25 – 50 mg l–1 2,4-dichlorophenoxypropionic acid [2,4-DP; as its butoxyethyl ester (PowerTM)], 15 mg l–1 3,5,6-trichloro-2-pyridyloxyacetic acid [3,5,6-TPA; as the free acid (Maxim®)], or 25 – 40 mg l–1 2,4-dichlorophenoxyacetic acid (2,4-D) plus 30-50 mg l–1 naphthaleneacetic acid (NAA; 0.3% – 0.5% AmigoTM), at the beginning of pit-hardening, when the widest diameter of the fruit was 25 mm, caused appreciable and significant increases in fruit size and total yield. Anatomical studies revealed that the main effect of these synthetic auxins was via direct stimulation of fruit cell enlargement. None of the above auxins had any negative effect on fruit quality, either at harvest or after 1 month of storage at 0°C, or on return yield in the following year. Two other synthetic auxins formulations: 2,4-D (HadranolTM) and 2,4-dichlorophenoxypropionic acid [2,4-DP-P; as its potassium salt (PriganTM)] increased fruit size, but had detrimental effects on fruit quality at harvest and during storage.