Abstract
The growth and graft union strength of apple trees grafted on extremely dwarfing rootstocks, JM5 and M. 27, were investigated. The scion growth of ‘Tsugaru’, ‘Sansa’, ‘New Jonagold’, ‘Hokuto’, ‘Orin’ and ‘Fuji’ apples grafted on the JM5/Marubakaido (Malus prunifolia Borkh. var. ringo Asami) rootstock was less than the scion growth of the same variety of apples on the M. 27/Marubakaido rootstock. Overgrowth of the rootstock JM5 was shown with all scion varieties. However, remarkable enlargement of the graft union was observed on the scions of ‘Tsugaru’, ‘Sansa’, ‘New Jonagold’ or ‘Orin’ grafted on the M. 27 rootstock. When a weight was hung on each scion grafted on the JM5 rootstock, either the scion or the rootstock broke. The amount of weight causing the break varied according to the kind of scion. In the case of the M. 27 rootstock, all scions except for ‘Fuji’ separated from the M. 27 rootstock at the graft union.
