1-Methylcylopropene and controlled atmosphere modulate oxidative stress metabolism and reduce senescence-related disorders in stored pear fruit

Abstract

European pears (Pyrus communis L.) are stored under low temperatures to extend postharvest life. Unfortunately, senescent scald and internal breakdown are likely to occur with prolonged exposure to storage. Both disorders can be reduced by controlled atmosphere (CA) and/or the ripening inhibitor, 1-methylcylcopropene (1-MCP). The principal aim of this study was to investigate the effect of 1-MCP and CA on fruit quality, including physiological disorders, and oxidative stress metabolites in stored ‘Cold Snap’ and ‘Swiss Bartlett’ pears. Freshly harvested pears were treated with or without 1-MCP, and then stored at 0°C under refrigerated air or CA (18kPa or 2.5kPa O2, and 2kPa CO2) for at least 167 d. 1-MCP and CA delayed and/or reduced the rates of ethylene production in stored fruit of both cultivars. 1-MCP and CA delayed fruit softening and peel yellowing in ‘Swiss Bartlett’ pears, but had negligible to slight effects with ‘Cold Snap’. In both cultivars, high incidences of senescent scald and internal breakdown occurred in non-1-MCP-treated pears during refrigerated air storage. For the most part these symptoms were reduced by CA and 1-MCP, resulting in minimal to negligible incidence in 1-MCP-treated pears stored at 2.5kPa O2. γ-Aminobutyrate accumulated in stored pears, although 1-MCP and CA slightly reduced the levels in ‘Cold Snap’ fruit and 1-MCP increased levels in ‘Swiss Bartlett’ fruit. Ascorbate (total and reduced) levels were rapidly depleted in ‘Cold Snap’ fruit, regardless of treatment; these levels were better maintained in 1-MCP-treated ‘Swiss Bartlett’ fruit than control fruit across all storage atmospheres. In both cultivars, glutathione (total and reduced) concentrations and redox status fluctuated during storage, although these levels were generally higher in 1-MCP-treated fruit. Moreover, glutathione depletion occurred in advance of the development of senescence disorders in stored pear fruit.