Postharvest physiological characteristics in tuberous roots of three sweetpotato varieties with varying cold tolerance

Abstract

Chilling injury (CI) is a significant factor in postharvest loss in sweetpotato. This study evaluated the cold tolerance of Guangshu 87, Yanshu 25, and Xinxiang sweetpotato varieties stored at 4 °C for 35 days. The assessment was based on reactive oxygen species (ROS) metabolism, antioxidant enzymes activities, ATP level, and alternative oxidase (AOX) expression. Guangshu 87 demonstrated higher cold tolerance than Xinxiang and Yanshu 25, as indicated by the lower CI index. During cold storage, Guangshu 87 had significantly lower ROS accumulation, MDA content, and relative electrolyte leakage (REL), which correlated with its higher catalase (CAT) and ascorbate peroxidase (APX) activities. Moreover, Guangshu 87 exhibited 3–5 times higher transcript levels of IbAOX1a and IbAOX1b than Xinxiang and Yanshu 25 during storage at 4 °C. Guangshu 87 also maintained higher free proline and ATP contents compared to the chilling-sensitive Xinxiang and Yanshu 25. Therefore, antioxidant enzyme activity, ATP content, and the transcript level of AOX may serve as potential markers in screening and breeding cold-tolerant sweetpotato varieties.