The Effect of Deacclimation and Reacclimation on Cold Tolerance, Carbohydrate Levels, and β-Amylase Gene Expression in Prunus persica

To boost our understanding of recent outbreak of freezing injury, distinct factors between relatively cold-tolerant ‘Daewol’ and cold-susceptible ‘Kiraranokiwami’ were confirmed by mimicking unseasonable changes of temperatures that occur in spring through repeated deacclimation and reacclimation treatments. Patterns of cold hardiness declined dramatically during the deacclimation and rose during the reacclimation in both cultivars. Our result indicated that ‘Daewol’ possessed higher capacity in response to repeated deacclimation and reacclimation. Interestingly, in our study both cultivars indicated the distinguished patterns in the contents of different carbohydrates each other. ‘Daewol’ showed more sensitive changes in the carbohydrates in response to warm and low temperatures compared to ‘Kiraranokiwami’. ‘Daewol’ indicated almost similar repeated down- and up- patterns in the contents of soluble sugars in response to repeated deacclimation and reacclimation, whereas indicated repeated up- and down- patterns in the contents of starch. However, ‘Kiraranokiwami’ showed a consistent increase in the contents of soluble sugars and a consistent decrease in the contents of starch. Relative gene expression of β-amylase confirmed by the quantitative real-time RT-PCR during the deacclimation decreased significantly and increased sharply during the reacclimation in both cultivars. Relative expression of β-amylase gene in ‘Daewol’ decreased in approximately half during deacclimation compared to before treatment (BT), whereas during the reacclimation relative expression of β-amylase gene in ‘Daewol’ increased approximately 3- to 4-fold compared to BT. Relative expression of β-amylase gene in ‘Kiraranokiwami’ also showed pattern similar to that in ‘Daewol’. However, the levels of β-amylase gene expression in ‘Kiraranokiwami’ were much lower than in ‘Daewol’ in all the treatments.