GRAFTING and Its ADVANTAGES
Grafting or graftage is a horticultural technique where tissues
of plants are joined so as to continue their growth together. The upper part of
the combined plant is called the scion while the lower part is called the
root stock or stock.
It has many
advantages in improving the yield and quality of crops. Following are some
important benefits from grafting as a method of propagation;
Precocity:
The
ability to induce fruitfulness without the need for completing the juvenile
phase is known as precocity. Juvenality is the natural state through which a
seedling plant must pass before it can become reproductive. In most fruiting
trees, juvenality may last between 5 and 9 years, but in some tropical fruits
e.g. Mangosteen,
juvenality may be prolonged for up to 15 years. Grafting of mature scions on to
rootstocks can result in fruiting in as little as two years.
Dwarfing:
Grafting can be used to
induce dwarfing or cold tolerance or other characteristics to the scion. Most apple trees
in modern orchards are
grafted on to dwarf or semi-dwarf trees and planted at high density. They
provide more fruit per unit of land, higher quality fruit, and reduce the danger of
accidents by harvest crews working on ladders. Care must be taken when planting
dwarf or semi-dwarf trees. If such a tree is planted with the graft below the
soil, then the scion portion can also grow roots and the tree will still grow
to its standard size.
Ease of Propagation:
As
the scion in some crops is difficult to propagate vegetatively by other means,
such as cutting grafting can be used as a good alternative.
In this case, cuttings of
an easily rooted plant are used to provide a rootstock. In some cases, the
scion may be easily propagated, but grafting may still be used because it is
commercially the most cost-effective way of raising a particular type of plant.
Hybrid Breeding:
To
speed maturity of hybrids in
fruit tree breeding programs grafting is essential. Hybrid seedlings may take
ten or more years to flower and
fruit on their own roots. Grafting can reduce the time to flowering and shorten
the breeding program.
Hardiness:
Because
the scion has weak roots or the roots of the stock plants have roots tolerant
of difficult conditions. Grafting can combat the problem related to it, for
example Dogridge can be used as a root stock in gape in salinity areas.
Sturdiness:
It can
be used to provide a strong, tall trunk for
certain ornamental shrubs
and trees. In these cases, a graft is made at a desired height on a stock plant
with a strong stem. This is used to raise 'standard' roses, which are rose bushes on
a high stem, and it is also used for some ornamental trees, such as certain
weeping cherries.
Disease
and Pest Resistance:
In
areas where soil-borne pests or pathogens would prevent the successful planting
of the desired cultivar, the use of pest or disease tolerant rootstocks allow
the production from the cultivar that would be otherwise unsuccessful. A major
example is the use of rootstocks in combating Phylloxera.
Pollen Source:
To
provide pollinizers, for example, in tightly planted or badly planned
apple orchards of
a single variety, limbs of crab apple may
be grafted at regularly spaced intervals onto trees down rows, say every fourth
tree. This takes care of pollen needs
at blossom time, yet does not confuse pickers who might otherwise mix varieties
while harvesting, as the mature crab apples are so distinct from other apple
varieties.
Repair:
To
repair damage to the trunk of a tree that would prohibit nutrient flow, such as
stripping of the bark by rodents that
completely girdles the trunk. In this case a bridge grafting may
be used to connect tissues receiving flow from the roots to tissues above the
damage that have been severed from the flow. Where a water shoot, basal
shoot or sapling of the same species is growing nearby, any of these can
be grafted to the area above the damage by a method called inarch grafting.
These alternatives to scions must be of the correct length to span the gap of
the wound.
Changing
cultivars:
To
change the old or less profitable cultivars in
a fruit orchard to a more profitable cultivar, called top working. It may be faster to
graft a new cultivar on to existing limbs of established trees than to replant
an entire orchard.
Maintain
consistency:
Apples
are notorious for their genetic variability, even differing in multiple
characteristics such as, size, color and flavor of fruits located on the same
tree. In the commercial farming industry, consistency is maintained by grafting
a scion with desired fruit traits onto a hardy stock.
Curiosities:
@@ A
practice sometimes carried out by is
to graft related potato and tomato so
that both are produced on the same plant, one above ground and one underground.
@@Cacti
of widely different forms are sometimes grafted on to
each other.
@@ Multiple cultivars of
fruits such as apples are sometimes grafted on a single tree. This so-called family
tree provides more fruit variety from small spaces such as a backyard, and also
takes care of the need for pollenizers. The drawback is that the gardener must
be sufficiently trained to prun them
correctly, or one strong variety will usually "take over."
@@ Ornamental
and functional tree shaping uses grafting techniques to join separate
trees or parts of the same tree to itself.
