Role of Sorbitol in Peach Chilling Tolerance

Low temperatures are beneficial for reducing deterioration and extending the shelf life of peaches; however, they can also lead to higher levels of reactive oxygen species and transformations in lipid metabolism, resulting in compromised fruit quality. The energy state of the product is crucial for maintaining integrity and stress resistance during storage, as depletion of internal energy reserves leads to a decrease in the activities of various enzymes associated with pulp deterioration, such as browning. Sugars protect against chilling damageA high sugar content leads to a higher energy state, thus maintaining a higher ATP content, which is beneficial in preventing cold damage. Sorbitol (a polyol, also called glucitol) is an important photosynthetic product, represents approximately 70% of total carbohydrates, and can accelerate sucrose metabolism. The conversion of sorbitol into fructose and glucose is responsible for the gradual increase in sweetness during fruit development and ripening, and the different types of soluble sugars produced from sorbitol are crucial for influencing its taste. Additionally, sorbitol modulates responses to biotic and abiotic stress, making it essential for post-harvest resistance. Studies have demonstrated the activity of various enzymes related to sorbitol metabolism, as well as phloem-mediated transport systems from the leaf to the fruit, playing a key role in accumulation during fruit growth. Sorbitol maintains better at low temperaturesScientists studied the behavior of a peach variety (yellow peach) when stored at low temperatures (at 1?C and 8?C). The results indicate that treatment at 1?C for 12 days maintains the textural quality of the fruit and delays the onset of chilling damage compared to 8?C. This positive effect is attributed to the fact that storage at 1?C maintains a higher sorbitol content throughout storage, thus maintaining a higher level of adenosine triphosphate (ATP) and, therefore, energy charge. At 1?C, sorbitol synthesis is stimulated by enhancing the activity of the enzyme sorbitol-6-phosphate dehydrogenase (S6PDH), and at the same time, its degradation is suppressed by the decreased activity of the enzyme sorbitol oxidase (SOX). Under these conditions, there is also positive regulation of the enzyme NAD+-sorbitol dehydrogenase (NAD+-SDH), which promotes the conversion of sorbitol into fructose and glucose, providing a broad energy substrate for ATP generation. Furthermore, substantially increased expressions of genes encoding sorbitol transporters (PpeSOT3, PpeSOT5, and PpeSOT7) were observed in fruits stored at 1?C, enhancing their transport and improving cold tolerance in peaches. Collectively, these findings suggest that storage at 1?C delays cold damage by improving sorbitol metabolism and transport, promoting its accumulation, and consequently, raising the energy state in the fruit. ? SourceZhou, H.; ??Su, M.; Du, J.; Zhang, X.; Li, X.; Zhang, M.; Hu, Y.; Huan, C.; Ye, Z. (2023). Crucial roles of sorbitol metabolism and energy status in the chilling tolerance of yellow peach. Plant Physiology and Biochemistry, 204:108092.?https://doi.org/10.1016/j.plaphy.2023.108092 ?