Regulating irrigation during pre-harvest to avoid the incidence of translucent flesh disorder and gamboge disorder of mangosteen fruits

In humid tropical areas, excess water during pre-harvest usually causes the occurrence of translucent flesh disorder (TFD) and gamboge disorder (GD) in mangosteen. To evaluate options for avoiding these incidences, an experiment was conducted with different water management regimes during pre-harvest. Twelve 14-year-old trees were grown under transparent plastic cover with three irrigation regimes: 1) Control (rainfed condition), 2) 7-d interval watering, 3) 4-d interval watering and 4) daily watering. A further four trees were arranged as the control (rainfed) treatment, but these were grown without the plastic roof cover. The treatments were started at 9 weeks after bloom. The results showed that diurnal changes of leaf water potential and stomatal conductance were lowest in the control, because intermittent drying occurred during the study period. The highest fruit diameter, fruit weight, flesh firmness and flesh and rind water contents were found in the daily watering treatment. However, all of these values were lowest in the control trees. The amount of TFD was also lowest in the control (3.7%), and it was significantly different from the treatment where trees were watered at 4-d intervals (18.0%) and where trees were watered daily (28.9%). There was no significant difference of TFD between the control and the 7-d interval watering treatments. In contrast, GD was not significantly different among the treatments. It is suggested that the risk of TFD and GD incidence could be avoided by maintaining mild soil water deficit around -70 kPa during pre-harvest.