Changes in cold hardiness and carbohydrate content in peach (Prunus persica) trunk bark and wood tissues during cold acclimation and deacclimation

- Cold hardiness of peach trunk tissues can be estimated by TTC reduction analysis.
- 'Janghowonhwangdo' had more cold-hardy trunk tissues than 'Hikawa Hakuho'.
- Sucrose was the predominant sugar in trunk tissues of both peach cultivars.
- Sucrose contents were closely related to cold hardiness of peach trunk tissues.
- Correlations of cold hardiness with sugar contents were dependent on tissue types.

Freezing injury in trunk tissues of peach (Prunus persica) trees can compromise their survival. We therefore exposed the trunk tissues of 10-year-old 'Janghowonhwangdo' and 'Hikawa Hakuho' peach trees to various freezing temperatures during cold acclimation and deacclimation and assessed the extent of freezing injury by analyzing low-temperature freezing exotherms (LTEs), electrolyte leakage (EL), and triphenyl tetrazolium chloride (TTC) reduction. Since LTEs, which indicate intracellular ice formation, were not detected, exotherm analysis was not useful for estimating cold hardiness in peach tree trunk tissues. However, EL and TTC reduction analyses provided reproducible results, allowing the level of cold hardiness to be expressed as the temperature at which 50% injury occurred (LT50). Based on the LT50 values, the trunk bark and wood tissues of 'Janghowonhwangdo' were more cold hardy than those of 'Hikawa Hakuho', except that the bark tissues of the two cultivars showed similar cold hardiness when estimated by TTC reduction analysis. We investigated the levels of sucrose, glucose, fructose, sorbitol, raffinose, and stachyose in the trunk tissues of both cultivars. Of the soluble sugars detected, sucrose was predominant. The contents of sucrose, and to some extent total soluble sugars, were closely correlated to cold hardiness in trunk tissues of both 'Janghowonhwangdo' and 'Hikawa Hakuho' peach trees during cold acclimation and deacclimation. The correlations between soluble sugar contents and cold hardiness were different depending on the tissue types.