(29) MCP Treatment Makes Delayed Application of Ethoxyquin Effective in Control of Superficial Scald of `d'Anjou' Pears

Superficial scald of `d'Anjou' pears usually develops after storage of 2 months or longer. MCP application controls scald; however, fruit lose their ripening capacity if the dosage is >30 ppb, but lower dosages cannot control scald substantially. In this study, fruit treated with or without 25 ppb MCP within 2 d after harvest were stored at –1 °C for up to 5 months. After 1, 7, 30, or 70 d of storage, part of the fruit were pulled from storage and treated with 1000 ppm ethoxyquin line spray and immediately returned to the storage, left untreated as non-ethoxyquin control. Incidence of superficial scald along with the concentrations of α-farnesene and conjugated trienes (CTs), and the ripening capacity of fruit were investigated after 3, 4, and 5 months storage. All fruit ripened properly within 7 d of conditioning at room temperature regardless of treatments. Both of MCP or ethoxyquin-1d (ethoxyquin was applied after 1 day storage at –1 °C) alone controlled scald for only 3 months; however, MCP + ethoxyquin controlled scald for 5 months, whenever ethoxyquin was applied between 1 to 70 d after storage. Thus, with 25 ppb MCP treatment, which is simple, with rapid and mass treatment available, a delayed application (up to 70 d) of ethoxyquin becomes effective to control scald. Furthermore, the later application of ethoxyquin within 70 d after MCP treatment, the less incidence of scald was observed. Scald is caused by the CTs oxidation products of α-farnesene. MCP and ethoxyquin inhibited accumulation of CTs of fruit peel by different mechanisms. MCP inhibited the production by influencing ethylene production through control of α-farnesene synthesis; however, ethoxyquin worked by inhibiting the oxidation of α-farnesene to the CTs.