Gibberellin Type and Time of Application Influence Fruit Set and Retention in Mango

Mango industry in a Mediterranean climate of Western Australia is being developed to extend the period of fruit production through April. Low night temperature (<10 degrees C) during flowering in these areas reduces fruit set. To improve mango fruit set, effects of exogenous application of various types of gibberellins and different times of their application were investigated. In the first experiment, GA(3) (0, 10, 25, 50, 75 ppm) was sprayed onto 'Kensington Pride' mango trees at flower bud differentiation (FBD) stage to investigate its effect on delaying flowering and fruit set. GA(3) (75 ppm) at FBD resulted in significantly higher fruit set (84 fruit/panicle) as compared to all other treatments. In the second experiment, GA(3) (0, 1, 10, 25, 50, 100 ppm) was sprayed on the panicles at full bloom (FB) stage to investigate its effects on fruit set. A spray application of GA(3) (10 ppm) at FB resulted in higher fruit set (43 fruit/panicle) as compared to all other treatments. To examine the effects of spray application different types of gibberellins on fruit set and retention, aqueous solutions of GA(3), GA(7), GA(13), or GA(4)/A(7) at different concentrations (0, 1, 5, 10, 25 ppm) were sprayed onto panicles exhibiting fully swollen buds prior to anthesis. Spray application of GA(13) or GA(4)/A(7) resulted in higher mean fruit set as compared to GA(3) or GA(7). GA(13) (10 ppm) was most effective in increasing fruit set as compared to all other treatments of different gibberellins. Exogenous application of GA(4) (10 ppm) onto panicles at fully swollen buds was the most effective in increasing the final fruit retention as compared to all other treatments. Gibberellins seem to play an important role in improving mango fruit set particularly where fruit set is retarded by prevalence of low temperatures during flowering.