Effects of soil pH and aluminum saturation on leaf mineral nutrition and incidence of translucent fruit flesh disorder of mangosteen in east Thailand.

摘要

Mangosteen translucent fruit flesh disorder reduces the quality of the fruit and causes much concern among growers. Excess moisture, Ca deficiencies, and other factors may cause this disorder, although the details have not been elucidated. In east Thailand, low-pH soils prevail. In these soils, the absorption of nutrients such as Ca may be inhibited under excess Al, as is often observed in the tropics. Calcium deficiency has been reported to cause water-core disorder in apple and Japanese pear and soft-nose disorder in mango. The symptoms of translucent fruit flesh disorder are similar to those disorders. In the present study, 19 commercial orchards in Rayong, Chanthaburi, and Trat provinces were examined for plant Ca and for soil Al. The incidence of disorder, soil Al and pH, Ca, Mg, K, Na, and H contents at each orchard were recorded and the Al saturation was calculated. The amounts of leaf mineral components such as Al, Ca, Mg, and K were measured, as well as the SPAD value and the root length density. The Al saturation was generally high, likely inhibiting nutrient uptake and root growth. Soils with higher Al saturation produced plants with higher leaf Al and lower Ca contents, indicating that the excess Al limited the absorption of Ca. The disorder incidence among orchards varied from 0-44%. Orchards with higher leaf Ca contents showed lower incidences of the disorder. Ca content might be related to the mechanism of flesh disorder development. Low-pH soils produced plants with decreased root length density and decreased leaf Ca content, but increased leaf Al content. However, the Al saturation was not strongly correlated with the incidence of the disorder. Instead, the flesh of fruit with the disorder had higher Ca concentration than normal fruit.