Gibberellic acid induces parthenocarpy and increases fruit size in the ‘Gefner’ custard apple (Annona cherimola x Annona squamosa)

The biological function of fruiting is to produce and disseminate seeds. However, seedless fruits have some advantages, including the ease of consumption and the increased added value of the final product and fruit quality. The present study aimed to evaluate the combined use of gibberellic acid (GA3) and hand pollination with Annona squamosa pollen grains on fruit set and the physical and chemical parameters of 'Gefner' custard apple fruits. The experiment was performed in a commercial custard apple orchard in a randomized design, with 11 treatments, four replications and five plants per parcel. The treatments applied were as follows: (1) hand pollination with the pollen of sugar apple (HPPSA) (control); (2) HPPSA + 500 ppm GA3 applied on the 1st week after anthesis (WAA); (3) HPPSA + 500 ppm GA3 applied on the 1st and 3rd WAA; (4) HPPSA + 500 ppm GA3 applied on the 1st, 3rd and 5th WAA; (5) HPPSA + 1,000 ppm GA3 applied on the 1st WAA; (6) HPPSA + 1,000 ppm GA3 applied on the 1st and 3rd WAA; (7) HPPSA + 1,000 ppm GA3 applied on the 1st, 3rd and 5th WAA; (8) 1,000 ppm GA3 applied at flowering and on the 1st and 3rd WAA; (9) 1,000 ppm GA3 applied at flowering and on the 1st, 3rd and 5th WAA; (10) 1,500 ppm GA3 applied at flowering and on the 1st and 3rd WAA, and (11) 1,500 ppm GA3 applied at flowering and on the 1st, 3rd and 5th WAA. A total of 20 plants were used. The harvest was performed at the 18th WAA. The fruit set rate, number of seeds per fruit, fruit length, fruit diameter, fruit mass, pulp mass, peel mass and fruit chemical characteristics were evaluated. The results were submitted to an analysis of variance, and the means were compared by the Tukey test (P > 0.05). A significant difference among the treatments was not observed for fruit set, presenting an average of 77% at the 18th WAA. Three applications of 500 ppm GA3 plus hand pollination induced the production of fruits with increased length, diameter and mass. Fruits produced by hand pollination alone or combined with GA3 had a lower percentage of fruit peel. The use of 1,500 ppm of gibberellic acid is efficient for producing seedless fruits in custard apple with high physical and chemical parameters.