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', repre senting early, mid-season and late-maturing crops, respectively. The f ruit 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 da ys. ACC levels rose steadily at 20 degrees C for 'Royal Gala' and 'Sta rking Delicious', but remained low in 'Granny Smith'. In persistent co ld, ACC levels were inhibited except in 'Granny Smith' where they were stimulated. A short period of cold induced intermediate behaviour. MA CC values generally followed those of ACC, except in 'Granny Smith' wh ere they remained low, even when cold-induced ACC levels were rising. ACC oxidase activity again rose at 20 degrees C in 'Royal Gala' and 'S tarking Delicious', but it was slow to respond in 'Granny Smith'. Acti vity was always low when cold conditions were imposed. Short cold peri ods merely postponed activity rises in 'Royal Gala' and 'Starking Deli cious', but stimulated activity in 'Granny Smith'. Ethylene output clo sely followed ACC oxidase activity levels. Thus a short period of cold induced ethylene production in 'Royal Gala' after a few days, was fas ter in 'Starking Delicious' (almost immediately) and was particularly effective in 'Granny Smith' fruit. This illustrated the differential e ffect of cold stimulation on the three apple cultivars. Such knowledge could aid more efficient apple storage.