チコリ（Ｃｉｃｈｏｒｉｕｍ ｉｎｔｙｂｕｓ Ｌ．）軟白葉の工場生産を前提とした根株養成適期

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In order to establish a hydroponic blanching system for culturing Witloof chicory in Japan, seeds of five F1 hybrids were sown in different months to determine the optimum time of sowing. In 1991, seeds were sown in a cell tray and transplanted one month later. In 1992, seeds were sown directly in an open field.The minimum temperature in the greenhouse in March 1991 was 10°C. In the days following planting in the field in mid April, the average minimum temperature was 10°C, although for several days the minimum temperature fell to 2.4°C. In 1992, from mid April to May, minimum temperatures of less than 10°C were maintained for 6consecutive days.The bolting ratio 5 to 6 months after sowing was lowest for seeds sown in March and highest for seeds sown in April. Sowing after July resulted in only a small amount of bolting. The late season cultivars had a tendency to be late in flowering. In the transplanted culture in 1991, enlargement growth of the underground part of the plant was suppressed for plants sown in March and August compared with those sown in June. However, in 1992, there was no difference in root enlargement growth between plants sown in June and August. In 1991, enlarged roots of plants that were sown in June and that were cultured for 5 or 6 months were used for hydroponic blanching culture. The enlarged roots that were cultured for 5 months produced small (20-30g) blanched leaves (chicons), but those cultured for 6 months produced rather bigger chicons (50-80g). In 1992, enlarged roots of plants that were sown in June or August and cultured for 5 months were used for blanching culture. For three of the five cultivars, the plants sown in August produced bigger chicons (ca. 120g). For the other two cultivars, the chicon productivity was not affected by the sowing month.