オリエンタル系ユリ‘カサブランカ’を用い，球根の氷温貯蔵前の予冷方法，長期氷温貯蔵後の解凍あるいは芽伸ばし処理時の温度を変えることにより，シュートおよび葉の障害発生に及ぼす影響を調べ，障害発生の軽減法を検討した。1℃のみで予冷する場合は8～12週間とし，12℃から1℃へと次第に温度を下げて予冷する慣行法では6℃以下の期間を8週間以内とすれば，致死あるいは不開花個体の発生率および葉の障害発生率が低く保たれることが明らかにされた。また，予冷期間中の温度上昇は不開花個体や葉の障害発生率を高める危険性が認められた。長期氷温貯蔵した球根を1℃で解凍すると5，20℃に比べ障害葉の発生を著しく抑制することができた。また，芽伸ばし処理時の温度を変えても切り花品質には差がなく，葉の障害発生率にも差はみられなかった。

Occurrence of black shoots, non-flowering plants, and damaged leaves are often found in retarding culture of Oriental hybrid lilies after long-term storage at a subzero temperature. To reduce their damage, bulbs of ‘Casa Blanca’ produced in Niigata were packed in polyethylene bags with wet peat moss and subjected to pre-chilling at 1℃ for 8 to 20 weeks or conventional method of pre-chilling in which the temperature was gradually lowered from 12℃ to 1℃ at 4-week intervals before storing at －2.0℃. After storage at －2.0℃ for 5 to 7 months, they were planted in a plastic container and grown in a plastic house maintained at min. 14℃. Rates of black shoots, non-flowered plants, and damaged leaves were maintained low when bulbs were pre-chilled at 1℃ for 8 to 12 weeks or at low temperatures below 3℃ within 8 weeks in the conventional method. Temperature rise during the conventional method caused the increase rates of non-flowered plants and damaged leaves. Bulbs produced in Hokkaido and pre-chilled at 1℃ for 14 weeks were stored at －2.0℃ for 7 months and thereafter grown in an artificial growth room controlled at a temperature of 20℃ and a day length of 8 hours (12,000 lux). Occurrence of damaged leaves was reduced remarkably when they were defrosted at 1℃ as compared with defrosting at 5 or 20℃. Treatment by subjecting to temperatures of 5, 8 and 20℃ for 2 weeks to allow rooting and sprouting in a plastic pot filled with wet peat moss before planting resulted in decreased rate of damaged leaves irrespective of treated temperature.

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