A modelling approach for prediction of chilling injury risk in kiwifruit from softening early in storage

Chilling injury (CI) is a significant risk for the kiwifruit industry. However, despite CI being associated with maturity, predictability of the risk of CI based on commonly used at-harvest maturity indicators is limited. Kiwifruit softening early in storage is strongly indicative of harvest maturity and integrates biological maturity and postharvest temperature management. This paper proposes a prediction model for CI risk based on the biology of kiwifruit softening and employs a Bayesian framework with Monte Carlo integration to account for the uncertainty associated with the destructive firmness measures and CI observed in the empirical data. The model was tested for 10 lines (orchards) each of 'Zesy002' and 'Hayward' kiwifruit. Firmness was measured after up to 6 weeks of storage and CI quantified after 12 and 16 weeks of storage. The risk of CI for a line of 'Zesy002' was predicted reasonably by fruit firmness after 4-6 weeks of storage, with a greater risk in firmer fruit. In addition, the within-line proportion of risk of CI for 'Zesy002' fruit may be quantified from individual fruit firmness, with a greater risk in fruit >40 N. Similarly, the 'Hayward' data also fitted well to the model, as all lines of fruit softened rapidly and had a low CI incidence. However, a lack of 'Hayward' fruit that retained firmness and/or had a high CI incidence limited the strength of the interpretation for 'Hayward'. It is concluded that the line risk of CI may be indicated by the firmness of fruit after 4-6 weeks of storage and the size of the risk from the individual fruit firmness variability.