Simulation of frost damage on overwintering fruiting parent branches in Actinidia arguta

【Objective】This study explored low-temperature damage in Actinidia arguta to provide reference for freeze protection.【Methods】The MSX-2F artificial frost simulation chamber system was employed to simulate both historical low-temperature frost damage events and potential winter low-temperature environments for Actinidia arguta. By measuring the freezing point temperatures of fruiting mother branch cells from four Liaoning varieties and utilizing experimental methods including electrical conductivity analysis, growth recovery assessment, and tissue browning evaluation, the frost damage indicators of Actinidia arguta fruiting mother branches were systematically investigated. By observing the freezing point in the cells of the fruiting mother branches of four varieties in Liaoning, as well as measuring membrane leakage, post-frost growth recovery and tissue browning, damage caused by simulated frost was observed in A. arguta fruiting mother branches.【Results】Among the four main cultivars, Binguo (a high-quality kiwifruit cultivar) had the weakest frost resistance; Huanyou No. 1 (a new kiwifruit cultivar) and Haijia No. 1 (a high-yield variety) were in the middle; and Longcheng No. 2 (a strain with strong adaptability) was the strongest in frost resistance. Based on the cell injury rate of the fruiting mother branches as the main parameter together with the other parameters including the cell freezing point temperature, bud retention rate, bud freezing index, branch freezing index, and the cell semi-lethal temperature, the low-temperature frost damage of fruiting mother branches of A. arguta was catego-rized into four grades: Grade 0, the fruiting mother branch cell injury rate was less than 10%; Grade 1, the cell injury rate was between 10% and 30%; Grade 2, the cell injury rate between 30% and 50%; and Grade 3, the cell injury rate greater than 50%. For the bingo varieties with the weakest frost resistance, the thresholds of damaging intensity and duration of low temperatures at different grades were as follows: T ≥ -25 ℃, duration ≤ 4 h fo Grade 0; -25 ℃ lasting 6-12 h for Grade 1; -30 ℃ lasting 4-12 h for Grade 2; and -35 ℃ lasting 4-12 h for Grade 3. The thresholds of damaging daily minimum temperatures at different grades were Tmin ≥ -26 ℃ for Grade 0, -26 to -32 ℃ for Grade 1; -32 to ≥ -34 ℃ for Grade 2 and, ＜-34 ℃ for Grade 3.【Conclusion】There are significant differences in low-temperature tolerance among different Actinidia arguta varieties, which are mainly influenced by a combination of genetic characteristics, physiological status, and environmental adaptations. In addition, the duration of low temperature is one of the key factors affecting the degree of frost damage. Short-term low temperatures may only cause minor damage to plants and have a small impact on yield, while prolonged low temperatures can significantly aggravate frost damage and have a serious impact on yield and quality. Therefore, in the cultivation and management of A. arguta, it is necessary to comprehensively consider the low-temperature tolerance of varieties and the effect of low-temperature duration on the degree of frost damage, so as to ensure the sustainable development of the industry