Cold Storage and Harvest Date Modifies the Ethylene Requirement for Kiwifruit Ripening.

Abstract

The development of ethylene preconditioning treatments for kiwifruit have made it possible to deliver ripe kiwifruit to consumers early in the season. We report on how maturity and length of storage time affect the ripening responses of kiwifruit [Actinidia deliciosa (A Chev) Liang et Ferguson cv Hayward] preconditioned with 100 ppm ethylene at 0°C for 24 hours and ripened for 10 days at 20°C. Kiwifruit freshly harvested at weekly intervals continued to soften faster in response to ethylene preconditioning compared to air controls for at least 5 weeks following commercial harvest. In contrast, kiwifruit commercially harvested and stored at 0°C for more than 2 weeks no longer responded to low-temperature ethylene preconditioning. However, kiwifruit stored more that 5 weeks were still responsive to exogenous ethylene and softened faster when exposed to continuous ethylene at either 0 or 20°C. Kiwifruit had relatively high respiration rates 1 days after transferring from 0 to 20°C, which quickly dropped to base levels within 1 day. Fruit stored >1 week at 0°C always had higher initial respiration than freshly harvested fruit on transfer to 20°C, and ethylene preconditioning increased initial respiration of freshly harvested fruit but had less of an effect on initial respiration of stored fruit. Plotting firmness against individual fruit's respiration and ethylene production revealed a distinct rise in respiration and ethylene production only after fruit softened to <6.5 N. Preconditioning fruit at 0°C did not significantly alter the timing of the climacteric respiration or ethylene peaks.