RIPENING AND SENESCENCE OF TWO SOUR CHERRY (PRUNUS CERASUS L.) CULTIVARS

Abstract

Sour cherry (Prunus cerasus L.) is one of the most important fruit crops in Hungary. However, sour cherry fruits are considered as perishable commodities, which cannot be stored for any length of time. During storage firmness decreases rapidly and fruit becomes sensitive to microbiological damages. The aim of this work was to track the sour cherry cell wall breakdown process by studying pectin decomposition and the role of β-galactosidase in fruit ripening and senescence. The β-galactosidase enzyme is known to be partly responsible for cell wall breakdown. We have monitored changes in size and colour of two well-known Hungarian sour cherry cultivars, 'Kantorjanosi' and 'Pandy 279'. Our results show that the activity of β-galactosidase during ripening was almost always higher in 'Kantorjanosi' than in 'Pandy 279'. In 'Pandy 279' the β-galactosidase activity increased continuously during development, whereas in 'Kantorjanosi' the activity fluctuated, showing a decrease from the green to the pink stage, followed by an increase until fruit reached the red stage and a subsequent decrease. The activity of β-galactosidase increased during senescence by 5- or 3-fold in 'Kantorjanosi' and 'Pandy 279', respectively. For both cultivars, the size of the fruit increased continuously during ripening and did not change during senescence. The results suggest that β-galactosidase plays different roles during ripening and senescence and its different isoenzymes may be responsible for the different activities observed during these two processes.