Effects of Five Methods of Bark Inversion and Girdling on the Tree Growth and Fruit Quality of 'Megumi' Apple

Abstract

The effects of five methods of girdling and bark inversion on tree growth and fruit quality in 'Megumi' apple (Malus domestica Borkh.) were compared. Bark inversion treatments were : BI-100 (5 cm bark ring was removed from the trunk and replaced in an inverted position), BI-90 (90% of a 5 cm bark ring was removed from the trunk and replaced in an inverted position, leaving a vertical 10% strip of the bark intact), bark exchange ; B-EX (90% of a 5 cm bark ring was removed from the trunk and exchanged with 'Hokuto' bark, leaving a vertical 10% strip of the bark intact), girdling ; G (90% a 5 cm bark ring was removed from the trunk leaving a vertical 10% strip of the bark intact) and G-N (90% a 5 cm bark ring was removed from the trunk, then that bark was reattached in a normal position, leaving a vertical 10% strip of the bark intact). All treatments, except G-N and B-EX significantly reduced the growth of the trunk's girth below the treatments, but had no effects on trunk growth above the treatments. The shoot length was significantly shorter and the spur/shoots ratio was significantly higher in BI-100 than in those of other treatments. Flowering the following spring was significantly increased by all treatments. Chlorophyll concentration in the leaves of BI-100 was lower than that of the control trees at one month after the treatment ; it decreased after three months in all treatments except B-EX. Soluble solids content in the fruit of BI-100 was the highest, followed by G, BI-90, B-EX, and G-N, and the control in decreasing order. Sugars and sorbitol content on a fresh weight basis were significantly higher in BI-100 than in BI-90, G-N and control fruits. But on a dry weight basis, they were lower in the treated fruits than in the control fruit because in the treated fruits had lower water content than the control fruit. Fruit firmness and fruit size were influenced little by the treatments. All treatments reduced calcium concentration in the fruit flesh. Soluble solids content in the fruits of BI-100 and BI-90 in following year was significantly higher than that of other treatments. These results show that girdling and bark inversion improved the eating quality of the fruit by increasing soluble solids content while lowering water and calcium content.