Root-zone cooling improves fruit production in high sugar content tomato

Abstract

The high-sugar content tomato is becoming popular because of its sweetness in Japan. However, the production of high-sugar content tomatoes in summer has been unstable especially in number of fruit set. Root-zone cooling is known to have an advantage to increase tomato yield in the summer and the effect of root zone cooling was evaluated in the production of high-sugar content tomato. High-sugar content tomatoes were grown at 2 kinds of plots, 15 and 25°C, in root-zone temperatures (RZT) from December 12, 2015 to February 13, 2016. During the experiment, the average air temperature was 21.8°C. During the daytime (9:00-17:00) the temperature was on average 24.2°C and during the nighttime (17:00-9:00) it was 20.7°C. The number of fruits per cluster was 3.3 in 15°C-RZT and 2.6 in 25°C-RZT. The floret number was larger and the flowering rate (the number of anthesis/floret emerged) was higher in the 25°C-RZT than in the 15°C-RZT. This phenomenon showed the possibility to improve the yield of high-sugar content tomatoes. The present examination was done in winter. It is necessary to perform this kind of examination in summer, over 30°C day temperature.