Grafts of Woody Plants and the Problem of Incompatibility Between Scion and Rootstock (a review)

Abstract

Grafting can occur naturally between branches or more often roots of the same species, or artificially via asexual propagation where the tissues of two plants are encouraged to fuse with one another. Artificial grafting is commonly used for propagation to improve qualities of trees grown commercially via selecting for its roots (called the rootstock) and for stem, leaves, flowers or fruits (called the scion). It is often used to reduce the time to flowering and shorten the breeding program, improve quality and yield of fruits and seeds, improve hardiness in response to environmental conditions and pathogens resistance, and change cultivars. Incompatibility between rootstock and scion has been more often observed for inter-specific than intraspecific grafts, and might result in a dieback of a graft. The objective of this paper was to review the recent literature related to graft applications and incompatibility between scion and rootstock. Anatomical studies of incompatible grafts demonstrated a poor vascular connection, vascular discontinuity and phloem degeneration at the union area, which might be detected as early as few weeks after a graft establishment. These vascular fusion problems can disturb water, nutrient and assimilate flows in the plant and might result in a further breakdown of a union area. Incompatibility might be also a result of insufficient plasmodesmatal coupling at an early stage of development within one of the graft partners. Differences in abundance of phenol compounds and starch below and above the graft union, as well as peroxidase amount at the union might serve as biochemical markers of the rootstock/scion incompatibility. Genetically and biochemically similar scions and rootstocks could improve graft compatibility.

Keywords

• scion
• rootstock
• graft
• compatibility