Accumulation of Reducing Sugar and Resistance of Grapefruit Peel to Chilling Injury as Related to Winter Temperatures1

Resistance of grapefruit ( Citrus paradisi Macf.) to chilling injury (CI) was compared with the concentration of reducing sugars in the peel through 3 harvesting seasons. Accumulation of reducing sugars preceded increased resistance to CI. The increase in reducing sugar concentration at mid-season (December – February) resulted from the hydrolysis of sucrose which is regulated by temperature. Accumulation of reducing sugars may be prerequisite to increased resistance of grapefruit to CI, but the role(s) of reducing sugars in the resistance mechanism has not been determined.