Global warming is contributing to extreme weather events such as abnormally colder weather, but there is lack of information on the freezing tolerance of citrus grown in Korea. Therefore, it is necessary to prevent damage from the cold in advance, by acquiring information on the critical temperature at which 50% injury (LT 50 ) occurs for citrus varieties grown in Korea. Electrolyte leakage (EL) and tetrazolium chloride (TTC) analyses were performed to determine LT 50 values and estimate the freezing tolerance for citrus varieties cultivated in Korea. We also investigated which factors such as genotype, environmental condition (e.g., in vitro , in vivo ), cultivation condition, and wind speed affect the LT 50 value in citrus. The LT 50 value measured in the EL and TTC analyses of the ‘Haryejosaeng’ mandarin indicated it had better resistance to the cold than the citrus hybrids. The LT 50 value in the in vitro experiments was lower than for the in vivo experiments, but there was little difference among the genotypes. Some factors, such as cultivation condition and wind speed, affected the LT 50 values. The flavonoid levels, total polyphenol content, and antioxidant activity were affected by exposure to freezing temperatures, which was not related to the change in freezing tolerance level.

中文翻译：

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柑橘对冷冻耐受性的反应因基因型和生长条件而异

全球变暖正在导致极端天气事件，例如异常寒冷的天气，但缺乏关于在韩国种植的柑橘的抗冻性的信息。因此，有必要通过获取有关韩国种植的柑橘品种发生 50% 伤害 (LT 50 ) 的临界温度的信息，提前防止寒冷造成的伤害。进行电解液泄漏 (EL) 和氯化四唑 (TTC) 分析以确定 LT 50 值并估计韩国栽培的柑橘品种的抗冻性。我们还研究了基因型、环境条件（例如，体外、体内）、栽培条件和风速等哪些因素会影响柑橘的 LT 50 值。在 'Haryejosaeng' 柑橘的 EL 和 TTC 分析中测得的 LT 50 值表明它比柑橘杂种具有更好的抗寒性。体外实验中LT 50 值低于体内实验，但基因型间差异不大。一些因素，如栽培条件和风速，会影响 LT 50 值。类黄酮水平、总多酚含量和抗氧化活性受冷冻温度的影响，与冷冻耐受水平的变化无关。