INFLUENCE OF GIBBERELLIN TREATMENT ON FLOWERING AND FRUITING PATTERNSIN MANGO

The potential for using gibberellins (GAs) to modify time of flowering and fruit maturity in mango was investigated. Winter spraying of mang o trees grown in the coastal subtropics of Queensland (latitude 27 deg rees S) with gibberellin A(3) (GA(3)) or GA(4) solutions caused a dela y in flowering time of up to 4 weeks, depending on cultivar (Kensingto n Pride, Glenn, Early Gold) and concentration (50-200 mg/L). There was also a general reduction in number of panicles, particularly at highe r GA concentrations. Similar experiments with GA(3) on cvv. Kensington Pride and Keitt in tropical North Queensland (latitude 17 degrees S) did not show any effect either on time or extent of flowering. Fruit y ield was highly correlated with the proportion of terminal buds that f lowered. Consequently, GA treatments caused significant yield reductio ns in cv. Kensington Pride, especially at 200 mg/L where only 23% of t erminal buds flowered. Fruit size was inversely related to yield, and yield was influenced by tree size. Delayed flowering also resulted in later fruit maturation, by up to 2 weeks. With Early Gold, late-flower ing panicles retained 3 times more fruit than those which flowered ear ly, which was possibly related to differences in night temperatures be fore or at anthesis. Delays in flowering time, which lead to somewhat lesser delays in fruit maturation, can be achieved with suitable GA tr eatments, but concentration and timing of application are critical if flowering and, hence, yields are not to be reduced. The potential use of this treatment in commercial mango orchards is discussed in relatio n to extending the fruit production season.