Effect Of Berry Density In Cluster On Sugar Content In Grapes

The sugar content in grapes of Vitis viniferal L. Cabernet Sauvignon of different berry density in cluster were investigated by HPLC and qPCR. This study analyzed the quantity index in the mature period and the ingredient content of leaf, the fruit diameter, acid content, sugar content, mass of 100 berries activities and relative expression of acid invertase in berry of Cabernet Sauvignon during fruit ripening of different berry density. The results indicated that:1) When the temperature of atmosphere changed large, the temperature and humidity of low-density berry in cluster was more various than the control. With the decreasing of berry density in cluster, sugar content in grape berries increased and acid content decreased. The sugar content of berry-thinning-50% grapes was the highest, followed by the berry-thinning-25%; while acid content of fruit and soluble sugar content of leaf decreased. The mass of 100 berries, soluble solid content, total phenols content, tannin content increased.2) The soluble sugar content in grapes increased gradually while the soluble sugar content in the leaf decrased gradually in the berry ripening. At the same time, the activity of soluble acid invertase decreased firstly, and then reached a stable tendency while cell wall invertase enhanced obviously. In the same mature period, the soluble sugar content in leaves of low-density was under the control, while the sugar content in grapes was opposite. The activity of soluble acid invertase and cell wall-bound acid invertase of low-density berry was higher than the control. The berry density in cluster did not affect the chlorophyll content and the area of the leaves. The soluble sugar content of leaves decreased gradually with the decreasing of berry density in cluster. Correlation analysis showed the activity of cell wall-bound acid invertase was negative correlation with the soluble sugar content of leaves and was positive correlation with the sugar content of grape berries. Moreover, the correlation coefficient was higher with the decreasing berry density in cluster. In addition, the higher transcript levels of cell wall-bound acid invertase and soluble invertase was detected in low-density berries, in agreement with higher activities of the two invertases in low-density berries than control. Hence, it could be concluded that low-density treatment of berry in cluster improved the activities of acid invertase of fruit, especially cell wall-bound acid invertase at the berry ripening stage which might be related with accumulation of more sugar in low-density berries.