Combination of 1-Methylcyclopropene and Ethoxyquin to Control Superficial Scald of ‘Anjou’ Pears

Superficial scald of ‘Anjou’ pears (Pyrus communis) usually develops after cold storage of ≥3 months. Ethoxyquin has been used to control scald commercially. However, only a small amount of fruit can be treated within 7 days after harvest as recommended, and sometimes ethoxyquin causes phytotoxicity. Application of 1-methylcyclopropene (1-MCP) showed excellent scald control potential, with rapid and mass treatment feasible. However, fruit may lose normal ripening ability at a dosage of 1-MCP as low as 30 nL·L−1, whereas a dosage of ≤20 nL·L−1 is not enough to control scald. In this investigation, ‘Anjou’ pears treated with 25 nL·L−1 1-MCP immediately after harvest were stored at −1 °C for up to 5 months. After 1, 7, 30, or 60 days of cold storage, part of the fruit were treated with 1000 μL·L−1 ethoxyquin and the remainder was left untreated as nonethoxyquin controls. The incidence of superficial scald, the concentrations of α-farnesene and its conjugated triene (CT) oxidation products, and the ripening ability of fruit were measured after 3-, 4-, and 5-month storages. All fruit ripened properly within 7 days of shelf life at 20 °C regardless of treatment. 1-MCP treatment at harvest or ethoxyquin alone applied within 7 days adequately controlled scald for only 3 months. By contrast, 1-MCP + ethoxyquin controlled scald for 5 months, regardless of when ethoxyquin was applied from 1 to 60 days after the start of cold storage. Thus, a combination of 25 nL·L−1 1-MCP, which is easily applied and does not influence ripening ability, and a delayed application (up to 60 days) of 1000 μL·L−1 ethoxyquin, which is a low dosage that does not cause phytotoxicity on fruit, controlled scald sufficiently. Scald is linked with accumulation of CT oxidation products of α-farnesene. 1-MCP and ethoxyquin inhibited accumulation of CT in fruit peel by different mechanisms. 1-MCP inhibited the production by reducing α-farnesene synthesis and the oxidation to CT, whereas ethoxyquin worked by inhibiting the latter.