Graft Union Development of the ‘Golden Delicious’ Apple when Combined with Varied Dwarfing Rootstocks

Abstract

Morphological and anatomical characteristics of the graft unions were significant during formative stages of development in that abnormal vascular tissues occurred on the scion side of the union. Dwarfing rootstocks had larger rays than the less dwarfing ones, and the vessels tended to be smaller. Bark thickness increased as the degree of dwarfing increased. Regenerative growth of callus within the graft union was often necrotic or accompanied by growth that was horizontal to the main axis of the plant. Persistent swirling of vascular tissues in the immediate graft union area was associated with the reduction of scion growth.