Effects of Stem Constriction Using Steel Washer Rings on the Soluble Solids Content of Pepino (Solanum muricatum Ait.) Fruit

抄録

The objective of this study was to determine whether planting pepino (Solanum muricatum Ait.) cuttings (shoots have 5 or 6 true leaves and length is 5–6 cm) through the hole (diameter is 4 mm) of a steel washer (hereinafter referred to as the “washer ring treatment”) would increase the soluble solids content of pepino fruit. Experiments were conducted twice: i.e. from spring to summer (Experiment 1) and from autumn to spring (Experiment 2). The washer ring treatment caused marked increases in stem diameter immediately above the washer compared to the control, but slightly suppressed stem elongation and leaf unfolding. The stem diameter above the washer at the end of culture was smaller in the treated plants compared to the control plants. The fresh weights of both above-ground and root tissues were also smaller in the treated plants compared with control plants. In contrast, no differences were observed between the treated and control plants in the number of flowers, the fruit set ratio, or the disorder fruits ratio. The marketable fruits harvested from treated plants were smaller compared to those from control plants by 28 to 47 g and 66 to 147 g in Experiments 1 and 2, respectively (i.e. reduction in yield); however, the fruits were denser and contained more soluble solids at 1.1 to 2.4°Brix and 1.1 to 2.9°Brix, respectively. This study confirmed that the washer ring treatment is effective for increasing the soluble solids content of pepino fruit.