Agriculture Reference
In-Depth Information
Grafting or budding
Grafting is a system where a piece of stem containing two to six buds, called
a scion, is used, while in budding just a single, detached bud is joined with
the stem of a plant that provides the root system (Fig. 4.1c). The plant that
provides the root system is called the rootstock. The bud or stem piece with the
buds (scion) is of the variety that will become the tree canopy.
The most common methods of grafting are cleft, splice (whip), side and
saddle graft, while the main budding methods are 'T' or shield, patch, chip
and veneer. In some cases, branches of dif erent trees are brought in contact to
form a union, and this is called approach grafting. For grafting or budding to
be successful, the cambium layers of both components have to be in intimate
contact to regenerate the union with all needed parts: xylem, phloem and
cambium. Many tropical fruits are, or can be, propagated by this system, and
most of them will do well with dif erent grafting or budding methods. Some
species are more dii cult and a specifi c type of grafting or budding has to be
used. The skill and experience of the grafter plays a very important role as to
which method is best for certain species, while in other species several methods
will produce satisfactory results.
Every grafted or budded plant has two genotypes, that of the root system
(rootstock or stock) and that of the canopy (variety or scion). The orchard
canopies should be genetically identical because the buds are taken from a
tree or trees of the same variety, so they are cloned on dif erent root systems.
The ideal would be for the roots to be from a single clone, which occurs when
they are from vegetatively propagated plants or come from seeds with nucellar
embryos because of their asexual origin (apomixis). In most other fruit trees,
the seedlings used for rootstocks are of sexual origin so they vary among
themselves. Since the rootstock can signifi cantly infl uence the canopy growth
and development, any variation can show up once planted in the fi eld. The
root and canopy maintain their original genetic make-up and do not exchange
genes, except in the few cells around the graft union.
Natural propagative structures
Plants produce organs or structures that are used for its propagation (Table
4.1). Examples of these structures would include runners in strawberry
and suckers in date palms. Some tropical fruits do produce suckers. Banana
or plantain suckers have a solid base called a corm. This corm is the normal
propagation material for these species. The sucker arises from the corm of the
mother plant and can be transplanted whole or with most of the pseudostem
removed, leaving the base and the corm. This piece is buried ~10 cm deep.
Pineapple suckers arise on top of the fruit (crown sucker), at the base of the
fruit (slips) and at the base of the plant (basal sucker) (Fig. 4.1d). The preferred
propagation material is the sucker at the base of the fruit, but they are not
produced all year round by the plants. These suckers are detached from the
