*corresponding & presenting author’s email: sushan04@yahoo.com

Due to freezing temperatures, wheat production is seriously affected. Wheat acquires freezing tolerance through exposure to low, non-freezing temperatures (cold acclimation, CA). Under CA, many plants respond to extracellular freezing and dehydration by accumulating soluble sugars and modifying cell wall properties, in addition to altering membrane lipids.

However, changes in soluble and cell wall sugars during CA and their role in the freezing tolerance of wheat are still unclear. We investigated the growth, freezing tolerance, changes in soluble sugar, and cell wall composition, followed by the activity and gene expression of key enzymes associated with sugar metabolism in two winter cultivars (Yumechikara and Norin-61) and one spring cultivar (Haruyokoi) during CA. Under CA for 4 weeks, Yumechikara showed higher freezing tolerance and accumulated more soluble sugars, including fructan, than other cultivars.

Changes in cell wall composition during CA were not obvious among the cultivars. Moreover, invertase and α-amylase activity showed no difference between Yumechikara and Haruyokoi during CA, consistent with the results of gene expression. Conversely, the expression of fructan exohydrolase at CA for 4 weeks in Yumechikara was also linked to changes in fructan content. We assume that the varying degrees of freezing tolerance in wheat cultivars are mostly caused by differences in soluble sugars rather than polysaccharides in the cell wall.