Dissecting Temperature-Dependent Variations in Cell Wall Metabolism and Firmness Loss During Postharvest Storage of Two Melting-Type Prunus persica Cultivars

Postharvest modifications in cell wall metabolism as affected by storage temperature were assessed in two Prunus persica cultivars (‘Rich Lady’ peach and ‘Big Top’ nectarine). Commercially mature fruit were stored for up to 5 weeks at 20, 12, 4 or −1 °C to induce a wide range of softening dynamics, including near-freezing conditions. All analyses were done in triplicate and data integrated in a partial least squares regression (PLSR) model for postharvest firmness loss, which was delayed significantly in refrigerated fruit. The decline in the content of covalently bound pectins was strongly associated with progressive firmness loss in both cultivars. The results suggest that enzyme activities involved in pectin sidechain removal, particularly α-L-arabinofuranosidase, may be early drivers of cell wall disassembly by enhancing substrate accessibility for enzymes involved in the degradation of the pectin backbone. While the role of pectin sidechain removal was a common feature, the relative contribution of other cell wall-modifying proteins appeared to be cultivar-dependent. These findings provide a biochemical basis that may inform prospective cultivar-specific storage protocols aimed at optimizing postharvest life in peach and nectarine.