MKR1, A DWARFING ROOTSTOCK FOR KAKI, DECREASES EARLY FRUIT DROP

Abstract

We have intensively investigated the field performance of ‘Hiratane-nashi’ and ‘Fuyu’ trees grafted on MKR1 for 10 years. The growth of shoots on MKR1 was inhibited and the shoots hardly showed secondary growth. As a result, the trees were dwarfed. Moreover, early fruit drop of the trees on MKR1 drastically decreased. Trees on D. kaki seedlings and “rootstock a” and own-rooted trees dropped a lot of their young fruit from the middle of May to the beginning of June, but fruit of trees on MKR1 scarcely dropped. The severity of early fruit drop varies with years, but the inhibitory effect of MKR1 on early fruit drop was stable. The fact that the amount of wood of MKR1 trees removed by winter pruning was the smallest in those of all trees seemed to contribute to the inhibitory effect. Fruit yield and yield efficiency of MKR1 trees were the highest, and their fruit-quality, including numbers of seeds, was similar to those of the other trees. Investigation of the field performance of ‘Soshu’, which easily produces secondary shoots and drops young fruit, and ‘Taishuu’ young tree revealed that MKR1 prevented the trees from producing secondary shoots and dropping young fruit, although the effects were smaller than those on the adult trees.