Limitation to the use of electrolyte leakage for the measurement of chilling injury in tomato fruit

Abstract

Five tomato cultivars were tested for tolerance to chilling. After exposure for varying times to chilling at 3°C, the fruit were returned to ambient temperature (20°C) for development of chilling injury symptoms (uneven ripening and pitting). Ripening was assessed by colorimetry. Chilling injury was determined as electrolyte leakage by measuring electrical conductivity of the leachate from pericarp discs, an indirect measure of membrane damage. During chilling, electrolyte leakage significantly increased in the three sensitive cultivars, but not in the tolerant lines, in correlation with the development of chilling injury symptoms after transfer to ambient temperature. The correlation broke down when the fruit were returned to 20°C. While electrolyte leakage significantly increased at 20°C in slightly injured fruit, it was drastically reduced in extensively injured fruit. We conclude that electrical conductivity of tissue leachate, which is widely used for assessment of chilling injury, is not always a reliable measure of chilling injury or of electrolyte leakage and membrane damage.