OFF-SEASON PRODUCTION OF TROPICAL FRUITS

Even in the tropical area where the temperature is relatively constant year-round, fruits are harvested seasonally. During the harvest season, fruits are available in abundance, but fruit are scarce during the off-season. Extending the fruiting period with an earlier start and delaying the end of the season can solve the problem and improve the balance of long-term supply-demand. The flowering process is the critical point for the fruit production. Several attempts on flowering induction show significant results in regulating off-season production of mango (Mangifera indica L.), mangosteen (Garcinia mangostana L.), durian (Durio zibethinus Murr.) and rambutan (Nephelium lappaceum L.). Flower formation of tropical fruit trees can be inhibited with applications of gibberellins. Plant growth retardants that inhibit gibberellin biosynthesis, such as paclobutrazol, can induce flowering of mango and citrus. The application of paclobutrazol followed by application of a dormancy-breaking substance has forced mango, citrus and mangosteen trees to produce off-season flowers. With this technique, mango trees can be forced to flower practically at any time; while mangosteen trees flowered 3 months earlier than the control trees. However, the same treatment given to durian and rambutan trees has not shown any satisfactory results. It is possible to induce flowering in durian by the application of paclobutrazol in combination with the application of plastic mulching to prevent infiltration of rainfall into the soil. In rambutan, ringing treatments induced the trees to flower and produce fruit off-season. The ringed trees started to flower 4 months earlier than the control trees without any effect on the size and number of inflorescences, and the number of flowers per inflorescence.