Increasing the sugar concentration in tomato fruit juice by coiling wire around plant stems

Abstract

Sugar concentration is an important aspect of fruit quality in tomato (Solanum lycopersicum) production. Salt and water stresses have been reported to increase the sugar concentration of fruit. Coiling wire around the lower part of the stems to reduce the capacity of xylem to transport water to shoot would result in low shoot moisture condition and increase the sugar concentration of fruit like salt and water stresses. The objective of this study was to determine whether a prototypic method of wire coiling increases the sugar concentration of fruit. Bonsai wire was coiled around the stems of seedlings in February in a greenhouse between the cotyledon node and the first leaf node. Eleven days after treatment (DAT), the stem diameters immediately above the wire coils were markedly greater in treated plants compared with the corresponding stem regions of control plants. The stems of treated plants were less elongated and developed fewer nodes at 39 and 51 DAT than the control plants. Marketable fruit harvested from the first to third trusses of the treated plants in April to May had average weights that were 49% to 89% of the weights of fruit from control plants. The juice of fruit from the first to third trusses in the treated plants had soluble solids concentrations of 116% to 120%, sucrose concentrations of 263% to 483%, and fructose and glucose concentrations of 135% to 155%, compared with juice from corresponding control fruit. At 112 DAT, the shoots and roots of treated plants had weights that were 58% and 32% of those of control plants, respectively. The basal wire coiling treatment increased the sugar and soluble solids concentrations of tomato fruit juice; however, further investigation will be necessary before the technique can be adopted for practical use.