Abstract
‘Suioh’ is a sweetpotato (Ipomoea batatas (L.) Lam.) cultivar developed for utilizing the tops as a green vegetable The leaves are rich in lutein and polyphenol, which increases the economic value of the cultivar a functional food. An hydroponic method suitable for tops production from ‘Suioh’ exam ined by comparing a deep flow technique (DFT) system with pumice sand culture (was ) (PSC) system in the phytotron glass room of the Biotron Institute of Kyushu University located in Fukuoka city, Japan. The air temperature and humidity of the were controlled at 25°C and 70% RH, respectively. In early summer, the DFT system showed 2 times higher yield than the PSC system, while the lutein concentration in the leaves in DFT-grown plants was 30% lower than that of those grown in the PSC system In winter, the yield in DFT was 1.2 times higher than that in the PSC system, and both lutein and polyphenol concentrations were almost the same between these two hydroponic systems. Thus, the DFT system is considered appropriate for ‘Suioh’ production, although it requires the development of a cultivation technique to increase the lutein concentration in leaves. The effects of cultural conditions on the concentrations of functional food factors were also investigated. Concentration of the nutrient solution scarcely affected the concentrations of lutein and polyphenol in the leaves, whereas increased light intensity appeared to increase both the lutein and polyphenol concentrations.
