The Effects of Calcium and Boron Sprays on the Incidence of Translucent Flesh Disorder and Gamboge Disorder in Mangosteen (Garcinia mangostana L.)

Abstract

Two experimental sites to investigate the effects of Ca and B sprays on the incidence of TFD and GD in mangosteen fruits were established at Nakhon Si Thammarat, southern Thailand. The experiment was designed as factorial design with 2 main factors: 1) fruit positions (outer and inner
canopy) and 2) concentrations of Ca and B sprayed (wt/vol) (control (no spray), 5% CaCl₂, 10% CaCl₂, 5% CaCl₂+0.5 mg kg^-1B and 10% CaCl₂+0.5 mg kg^-1B). Ten treatments with 3 replications were completely randomized under field condition. The mangosteen fruits were sprayed at 6, 7 and 8 weeks after blooming. Soil sampling was taken at 2 depths; 0-15 and 15-30 cm, from soil surface around the middle of the tree canopy at blooming period and analyzed for some important chemical and physical properties. Leaves were sampled at blooming and harvesting periods while fruits were sampled at harvesting period. Ca and B concentrations of the leaf, peel and flesh of all treatments were analyzed. Results indicated that the soil textures varied from sandy loam to clay, and the natural soil in mangosteen orchards were very strongly acid to very extremely acid (pH 3.92-4.92, soil:water = 1:5) with very low essential nutrient levels for plant growth. The applications of CaCl₂ and H₃BO₃ could increase Ca and B
concentrations in peel and flesh of mangosteen fruits. Spraying with 10% CaCl₂ could also increase the percentages of normal fruits (NF), whereas the percentages of defected fruits (TFD and GD) decreased. Spraying 10% CaCl₂+0.5 mg kg^-1B enhanced the efficiency of Ca to increase the ratio of NF:TFD and GD.