Correlation of reduced chilling injury with Increased spermine and spermidine levels in zucchini squash

Abstract

The development of chilling injury symptoms in zucchini squash (Cucurbita pepo L. cv. Ambassador) was reduced by preconditioning the fruit for 2 days at 10°C. In the control group, held continuously at 2.5°C, increasing chilling injury correlated with an increase in putrescine and decreases in spermidine and spermine. Preconditioning led to a significant increase in spermidine arid spermine levels, beginning after the initiation of storage at 2.5°C and lasting for 5 days, after which the levels decreased but remained elevated relative to the control. The elevation of polyamine levels by direct treatment of the fruit with spermine prior to storage resulted in reduced chilling injury, indicating that polyamines may be involved in the protective mechanism of preconditioning. We have also examined the extent of lipid peroxidation by determining the levels of chloroform‐soluble fluorescent products in the skin of the fruit subjected to chilling. The chilling injury in the control group resulted in an increase in the fluorescent products. The levels of fluorescent products were significantly reduced by the preconditioning treatment. These results may indicate that polyamines can act to prevent chilling injury in squash by a mechanism which involves protecting membrane lipids from peroxidation.