Vegetative propagation is a form of asexual reproduction in plants. Asexual propagation or reproduction from vegetative parts of the original plant, is possible because every cell of the plant contains the genetic information necessary to regenerate the entire plant. Reproduction can occur through the formation of adventitious roots and shoots or through the uniting of vegetative parts by grafting or budding. Stem cuttings and layers have the ability to form adventitious roots, and root cuttings can regenerate a new shoot system. It is also possible for leaves to regenerate both new roots and new shoots while a stem and a root can be grafted together to form a single plant.
By the end of the article, the readers should be able to:
- Relate the concepts and principles of grafting, budding and cuttings methods of asexual propagation
- Differentiate which species and when to use grafting, budding or cuttings methods.
- Perform post grafting or budding practices in the nursery before field planting.
Practical use of vegetative propagation methods is based on two biological considerations:
- Maintenance of the physiological condition of the parent tree in the propagated part. • Maintenance of genetic constancy. That is, the part propagated is genetically identical to the original individual.
Vegetative propagation has been widely used in breeding for, among other things:
- The establishment of clonal seed orchards The establishment of clone banks, in which controlled pollination is effected, owing to the possibility it affords for obtaining flowers at low height.
- The propagation of special breeding material: exceptional hybrids (e.g., heterotics) that are lost through sexual reproduction and sterile hybrids.
- The propagation of selected plants on a large scale.
Its usefulness depends on, among other factors:
- The ease with which the species can be manipulated. Many species are difficult to propagate vegetatively, while others are extremely easy. This often affects production costs, both for the establishment of orchards and for large-scale production of plantation material.
- The extent to which development of the parts propagated can be controlled. In some cases the phenomenon of topophysis occurs: the development of the propagated part is influenced by the part of the tree from which it comes, e.g., lateral branches sometimes tend to grow in a horizontal direction.
There are five main methods of vegetative propagation: cuttings, layering, budding, grafting and tissue culture. Cuttings are sections taken from the tree and manipulated to root and produce shoot in an appropriate medium. Grafting and budding involve fusing of scion from a tree that has the desired traits with the rootstock.
Some of the benefits that could accrue from the application of vegetative propagation will include among others:
- Multiplying ‘true-to-type’ elite material
- Controlling male to female tree ratios on farms
- Propagation of seedless plants
- Avoidance of long juvenile periods control of growth form
- Combination of clones
- Economics: elimination of the juvenile phase thus shortening the time to reach the reproductive maturity.
Layers are sections of the tree which are induced to root and then separated from the mother tree to grow as new plant. Tissue culture is the manipulation of a small piece of plant part to grow as new plant under aseptic conditions.