Abstract
This study was carried out to establish suitable screening technique of freezing tolerance in Italian ryegrass (Lolium multiflorum Lam.) with the method modified in terms of freezing treatments of the artificial screening technique for cold hardiness developed by FULLER and EAGLES (1978). Scheme of screening technique of freezing tolerance for Italian ryegrass was as follows : The seedlings were raised in a growth cabinet at day/night temperature of 20/15℃ with 16 h photoperiod for 4 weeks. Raised seedlings at the 3-4 leaf stage were hardened for 14 days in a growth cabinet at 2℃ with 8h photoperiod. Following hardening, the seedlings were subjected to 5 freezing treatments wher,e the temperature was lowered to the fixed temperature of -4 to -12℃ at 2℃ intervals at a cooling rate of 1℃/h followed by 16 h plateaus and thawed at heating rate of 2℃/h, maintained at 2℃ for 24 h. After freezing treatment, seedlings were maintained for 3 weeks under the same condition as the growing condition. Then, plant mortality was recorded and LT50 (Lethal temperature for 50% kill of plants) was estimated by the probit analysis. This technique was applied to assess the change of freezing tolerance during winter.
