Carbohydrate Changes in Peach Shoot Tissues and Their Relationship to Cold Acclimation and Deacclimation

This study was performed to examine differences in cold hardiness, carbohydrate content, and beta-amylase gene expression during cold acclimation and deacclimation in shoots of two peach cultivars (Prunus persica 'Daewor and 'Kiraranokiwami') During cold acclimation (from September to November 2011), cold hardiness of the cultivars as determined by electrolyte leakage analysis increased dramatically. Maximum cold hardiness was reached at the end of December 2011 in both cultivars. During deacclimation (late January to April 2012), the cold hardiness of both cultivars decreased gradually. According to the temperatures at which 50% injury occurred (LT50), there was a noticeable difference in cold hardiness between 'Daewor and 'Kiraranokiwami' during the deacclimation period from the end of January 2012. Cold hardiness was significantly associated with total soluble sugar, sucrose, and beta-amylase gene expression in both cultivars. Sorbitol, the most abundant soluble sugar, was not associated with cold hardiness in either cultivar. Glucose and fructose contents in 'Daewol', which was more freezing-tolerant, were approximately double those in 'Kiraranokiwamr from January to February 2012. These results suggest that the conversion of sucrose to glucose and fructose might be correlated with the difference of cold hardiness during deacclimation in these peach cultivars.