Cultivar differences in the influence of a short period of cold storage on ethylene biosynthesis in apples

The effects of exposing three apple (Malus domestica Borkh) cultivars to various periods at 20 degrees C with regard to changes in ACC, MACC, ACC oxidase and ethylene evolution were investigated. The cultivars used were 'Royal Gala', 'Starking Delicious' and 'Granny Smith', representing early, mid-season and late-maturing crops, respectively. The fruit were held at either 20 or 1 degrees C for 32 days, or exposed to 1 degrees C for 10 days and then transferred to 20 degrees C for 22 days. ACC levels rose steadily at 20 degrees C for 'Royal Gala' and 'Starking Delicious', but remained low in 'Granny Smith'. In persistent cold, ACC levels were inhibited except in 'Granny Smith' where they were stimulated. A short period of cold induced intermediate behaviour. MACC values generally followed those of ACC, except in 'Granny Smith' where they remained low, even when cold-induced ACC levels were rising. ACC oxidase activity again rose at 20 degrees C in 'Royal Gala' and 'Starking Delicious', but it was slow to respond in 'Granny Smith'. Activity was always low when cold conditions were imposed. Short cold periods merely postponed activity rises in 'Royal Gala' and 'Starking Delicious', but stimulated activity in 'Granny Smith'. Ethylene output closely followed ACC oxidase activity levels. Thus a short period of cold induced ethylene production in 'Royal Gala' after a few days, was faster in 'Starking Delicious' (almost immediately) and was particularly effective in 'Granny Smith' fruit. This illustrated the differential effect of cold stimulation on the three apple cultivars. Such knowledge could aid more efficient apple storage.