Postharvest performance of the yellow-fleshed ‘Hort16A’ kiwifruit in relation to fruit maturation

• Fruit flesh colour is not tightly linked with SSC, firmness or storage performance.
• Fruit at <5% SSC developed a capacity to increase SSC in response to low temperature.
• The capacity for fruit to soften in response to ethylene developed over ∼5 weeks.
• Fruit softening in storage depends on the softening rate at harvest.
• Susceptibility of fruit to chilling injury decreased gradually over 4–6 weeks.

Postharvest performance of fruit is dependent on the maturity or physiological state of the fruit at harvest in conjunction with the postharvest management applied. For yellow-fleshed kiwifruit, the flesh colour is a significant quality attribute, and for ‘Hort16A’, flesh colour has been used for timing harvest. Variability in the postharvest performance of ‘Hort16A’ kiwifruit suggests that flesh colour alone is not as strongly indicative of postharvest performance as soluble solids content (SSC) was found to be for ‘Hayward’ kiwifruit 30 years ago. The postharvest performance of ‘Hort16A’ kiwifruit, assessed as the fruit firmness and chilling injury expression during storage, has been associated with a range of fruit characteristics: flesh colour, SSC, firmness, seed colour, fresh weight, dry matter, starch and soluble carbohydrates measured at harvest throughout maturation. The changing responses of the fruit SSC to temperature, and softening to ethylene, have also been determined. The data illustrate the complex nature of ‘Hort16A’ fruit maturation, even when looking only at simple, easy-to-measure fruit attributes. While a yellow flesh colour is a commercial necessity for ‘Hort16A’ kiwifruit, flesh colour is not a robust indicator of postharvest performance and is not tightly linked to SSC or firmness. Changes in the capacity of fruit to respond to temperature or ethylene are not reflected in on-vine changes. Softening in storage is strongly linked to the softening rate occurring on the vine at the time of harvest. Any association between at-harvest characteristics and chilling susceptibility is less clear, and chilling tolerance appears more associated with the completion of growth and carbohydrate accumulation than with increased soluble solids accumulation rates as in ‘Hayward’. Approaches to extend the understanding of the link between maturation, harvest indices and postharvest performance are discussed.