Changes in enzyme activities in abscission zone and berry drop of ‘Kyoho’ grapes under high O2 or CO2 atmospheric storage

To investigate the effects of high atmospheric O2 on berry drop in ‘Kyoho’ grapes (Vitis vinifera X V. labrusca), changes in fruit detachment force (FDF), berry abscission and enzyme activities in the abscission zone (AZ) were examined during 60 days of storage in air (control), 40% O2+30% CO2 or 80% O2 at 0 °C and 95% relative humidity. There was a high negative correlation between FDF and berry drop. Cellulase activity increased over time and correlated strongly with berry abscission. Polygalacturonase (PG) activity increased markedly for the first 30 days and then decreased slightly. Pectinesterase (PE) maintained a basal level of activity at low temperatures. Cellulase, PG and PE activities were the lowest in fruits in 80% O2, followed by 40% O2+30% CO2 and air storage. Peroxidase (POD) activity dropped firstly and subsequently rose sharply, which promoted by 80% O2 and inhibited by 40% O2+30% CO2 compared with control. High O2 suppressed the activities of cellulase, PG and PE, maintained higher FDF, and reduced berry abscission during storage.