Improving Colour and Size of Apricot Fruit by Means of Exogenous Auxin Application

Techniques that could improve apricot fruit size, colour and precocity would enhance their marketability. Since the 1990's, several synthetic auxins have been tested to increase fruit size. In particular, the synthetic auxin 3,5,6-trichloro-2-pyridyloxyacetic acid (3,5,6-TPA), commercially available as Maxim (R), positively affected fruit size in different species. In the present study, the effect of 3,5,6-TPA was investigated on fruit development of the cv. Portici. The chemical was applied alone and in combination with seaweed extracts at different application time during the pit hardening phase. Biometric parameters, fresh weight of a fruit sample and phytotoxicity were assessed at regular intervals during the fruit growth phase. Yield, fruit number and distribution in the different commercial size classes, percentage of unmarketable fruit were measured at each harvest. The main quality traits were measured by destructive techniques. Maxim (R) alone and in combination with seaweed extracts positively affected fruit size and fresh weight by increasing them especially at the first harvest. Moreover, the synthetic auxin clearly increased peel fruit colour already one week before the first harvest, and thus, at that time, a higher number of fruit was harvested from the treated trees. While flesh firmness and soluble solid content were not affected by the treatments, tritatable acidity was lower in treated fruits as compared to control ones. The positive results obtained in the present study agreed with previous results and confirmed a practical use of the synthetic auxin 3,5,6-TPA (Maxim (R)) for ameliorating apricot morphogenesis and appearance, and for inducing early ripening.