Study on the threshold of late frost damage of ‘ Cabernet Sauvignon ’ grape at different developmental stages in Ningxia

[ Objective ] Frost temperature thresholds of grape are the basis for frost monitoring , prediction , assessment , and prevention. The study investigated the low-temperature tolerance of the main wine grape ‘ Cabernet Sauvignon ’ at different development stages in the eastern foothills of the Helan Mountain , and further established a system of frost temperature thresholds for wine grapes. The study aimed to provide the basis for frost prediction and prevention of wine grapes in the eastern foothills of the Helan Mountain. [ Methods ] We used a field frost chamber to treat the pompom , bud , new leaves , and new shoots of the main wine grape variety ‘ Cabernet Sauvignon ’ at different developmental stages under low temperature in the eastern foothills of the Helan Mountain during the period of April to May 2022. The supercooling point , relative electrical conductivity ( R EC ), and semi-lethal temperature ( L T50 ) were measured. Field survey on frozen ratio under low temperature treatment was carried out. A regression model based on the correlation between frozen ratio and low temperature was set up to calculate the critical temperatures for light , moderate , and severe frost at different development stages of the wine grape. The above mentioned indicators at the temperature of frost were analyzed to determine the frost temperature thresholds at differ- ent development stages of ‘ Cabernet Sauvignon ’ . [ Results ] Low temperature had different effects on ‘ Cabernet Sauvignon ’ during the pompom , bud opening , leaf spreading , and new shoot growth stages. The lower the temperature , the higher the frost exposure rate in each development stage. The supercoo- ling point and the semi-lethal temperature ( L T50 ) were gradually increased with the development of the wine grapes. Low temperature tolerance in the pompom stage was the strongest and followed in the bud opening and leaf spreading stages. The tolerance of new shoot growth stage was the weakest. [ Conclusion ] -7.70 ℃ was the turning point for severe frost at the pompom stage , while the critical temperature of bud opening stage was -4.49 ℃. Temperature lower than -2.79 ℃ at the leaf spreading stage caused ir- reversible damage to the wine grape. Furthermore , below -1.62 ℃ in the new shoot growth stage caused severe frost.