Effect of Leaf-Fruits Ratio on Sugar Accumulation of Japanese Pear ‘Gold Nijisseiki’ Fruits

Abstract

We estimated Brix values of Japanese pear ‘Gold Nijisseiki’ fruit on the tree using a portable non-destructive near infrared spectrometer to compare net Brix value of the fruit during the 30-day period before harvest at different fruit load. Although the bias (mean of difference between actual Brix value and non-destructively derived value) differed on each measurement day, the correlation between estimated and measured values was high. Therefore, estimated Brix value of tree fruit could be used to adapt a bias correction for each measurement time. The increase in Brix value during 30 days before harvest for 5 seasons ranged from 1.4% to 2.3%. Thus, we could predict Brix value of mature fruit using an estimated Brix value of the tree fruit 30 days before harvest. Fruit load was regulated to 4, 6, 8, and 10 fruit per one meter length of lateral branch 30 days before harvest, and then the changes in fruit Brix value were estimated using the described method until harvest. The lower fruit load resulted in the higher increase in Brix value from 2 weeks after treatment. Defoliated branches showed a lower increase in Brix value than control branches, even if they had the same fruit load. Therefore, we concluded that the leaf-fruit ratio affects sugar accumulation during maturation in Japanese pear fruit and that an appropriate ratio to produce fruit having adequate Brix value (greater than 11) was 35/50.