Relationship between production of ethylene and a-farnesene in apples, and how it is influenced by the timing of diphenylamine treatment

The relationship between ethylene and peel α-farnesene concentrations was examined by applying diphenylamine (DPA) and the ethylene analogue, propylene at varying times after harvest to superficial scald (scald) susceptible ‘Granny Smith’ apples (Malus domestica Borkh.) stored at 10°C. Delaying DPA application after harvest had no large effect on ethylene or on peel α-farnesene production. Propylene advanced fruit ripening and promoted an increase in peel α-farnesene concentration before endogenous internal ethylene production, suggesting that ethylene has an important regulatory role in α-farnesene production, but their biosynthetic pathways are controlled independently. The effect of delayed DPA application (4 and 7 days after harvest) on the relationship between ethylene and peel α-farnesene was further examined at both a scald-inducing temperature (0°C) and a non-scald-inducing temperature (10°C) with ‘Granny Smith’ and the scald resistant ‘Crofton’ cultivar. Similarly a delayed DPA application had only minor effects on internal ethylene and peel α-farnesene concentrations. The relationship between internal ethylene and peel α-farnesene concentration was dependent on storage temperature, and the type of relationship was independent of cultivar. However, the magnitude of the relationship between cultivars was significantly different (‘Granny Smith’ produced significantly more α-farnesene than ‘Crofton’) and may be related to scald development