ETHYLENE PRODUCTION AND FRUIT-SOFTENING RATES IN SEVERAL APPLE FRUIT RIPENING VARIANTS

Ethylene production and fruit softening during postharvest storage of several apple (Malus domestica Borkh.) ripening variants were compared with two standard cultivars PA14-238 and D101-110 produced only low levels of ethylene (<10 mul.kg-1.hour-1) at harvest and throughout most of 86 days of storage at 4C, whereas 'Red Chief Delicious' and 'Golden Delicious' fruit produced > 100 mul ethylene/kg per hour during the same time period. PA14-238 and D101-110 flesh disks converted aminocyclopropane-1-carboxylic acid (ACC) but not methionine (MET) to ethylene. 'Red Chief Delicious' readily converted both MET and ACC to ethylene at the end of cold storage. PA14-238 fruit were the firmest and did not soften during postharvest storage; however, D101-110 softened appreciably. NJ55 did not produce ethylene at harvest, but produced a significant amount of ethylene (90 mul.kg-1.hour-1) during storage. Despite its high capacity to produce ethylene, NJ55 remained nearly as firm as PA14-238 at the end of cold storage.