Plant Propogation and Nursery Management

Grafting techniques

Introduction
Before going into the details of different methods of grafting, it becomes very important to know about the basic terminology related to grafting methods.
Grafting: Grafting is a process by which two living parts are joined together in such a manner that they would unite together and subsequently grow into a composite plant. Usually graft has two parts, the scion and rootstock.
Scion: Scion refers to that part of a graft combination that becomes the top of the plant. Scion is the short piece of detached shoot containing 3 or more dormant buds, which when united with the rootstock or inter-stock, comprises the upper portion of the graft and from which will grow the stem or branches or both. It should be of the desired cultivar and free from diseases.



Fig.7.1: Components of a grafted plant

Rootstock: The rootstock is the lower portion of the graft, which develops into the root systems of the grafted plant. It may be seedling, a rooted cutting, or a layered or micro- propagated plant.
Inter-stock: Inter-stock is a piece of stem inserted by means of two graft unions between the scion and rootstock. Inter-stocks are used to avoid an incompatibility between the rootstock and scion, to produce special tree forms, to control diseases or to take advantage of its growth controlling properties.
Vascular cambium: Vascular cambium is a thin tissue located between the bark and the wood. Its cells are meristmatic i.e. they are capable of dividing and forming new cells. For successful graft-union, the cambium of the scion is placed in the close contact with the cambium of the rootstock.
Callus: Callus is a term applied to the mass of parenchymatic cells that develop from and around wounded plant tissues. It occurs at the junction of a graft union, arising from the living cells of both the scion and rootstock. The production and interlocking of these parenchymatic cells (callus) constitute one of the important step in callus bridge formation between the scion and rootstock in a successful graft.
Reasons for grafting and budding

• Perpetuating clones that cannot be readily propagated by cutting, layers, division or other asexual methods
• Obtaining the benefits of certain rootstocks
• Obtaining the benefits of certain plants (double working)
• Changing cultivars of established plants (top working)
• Precocity in bearing
• Reduction in juvenility
• Obtaining special forms of plant growth
• Repairing the damaged parts of trees
• Study and elimination of viral diseases
• Studying the developmental and physiological processes
Elements for successful grafting
There are five important elements for any successful grafting operation. These are:

• The rootstock and scion must be compatible.
• The vascular cambium of the scion must be placed in intimate contact with that of the rootstock.
• The grafting operation must be done at a time when the rootstock and scion are in the proper physiological stage.
• Immediately after completion of grafting, all cut surfaces must be protected from desiccation.
• Proper care must be given to the grafts for some period of time after grafting.