Introduction:
 |
| http://en.wikipedia.org/wiki/Apple#Production |
Malus
domestica more commonly known as the apple tree is one of the most widely
cultivated fruits by tree today. The trees originated from central Asia from
their ancestors Malus Sieversii. The
apple tree has come a long way through history, from being cultivated all
throughout Europe and brought over to North America by colonists. As well as
being a prominent figure in mythology; from stories like Johnny Apple seed to
Snow White, and even the Bible. Today the genome of the apple tree has been
sequence and we are moving toward understanding and controlling its diseases
and using for the breeding of new resistant cultivars. (1)
Grafting:
The technique of grafting has been
used for thousands of years, dating back to 2000BC in China (2). Propagation by
grafting is the technique where the tissue of one plant is placed on the tissue
of a second plant and allowed to grow together creating a chimera. First, a
rootstock, or the bottom half of the graft which is a plant that is providing
the roots and stability, is chosen for a vigorous root system, drought
tolerance, or disease resistance based upon the needs of the propagator (3).
Second, a scion, or the top half of the plant that is being grafted onto the
root stock, is chosen for desired characteristics such as fruit production,
flower production, attracting pollinators, or simple tree growth. The scion and
rootstock are then cut in a specific way depending on the plants being used in
order to make the most successful graft. The cuts are then matched up so that
the vascular cambium, or outer ring of meristematic tissue within the plant
that can grow new vascular tissue such as xylem and phloem, are matched up
between the two plants (2). This way new vascular tissue that carries nutrients
and water throughout the plant can form between the two plant tissues and allow
them to survive. After the tissues are matched up the graft union should be
wrapped up and kept humid so that the tissues do not lose water while they are
healing. It is important in grafting to
make sure that the two plants being grafted are compatible. If they are not
compatible, no matter how well the vascular cambium tissue is lined up, the
graft will not heal because the rootstock and the scion are too different. Usually
two different trees within the same genus would be compatible. The more related
the two plants are, the more likely the graft will be compatible (2).
Grafting Apples:
The most common way of the
propagation of apple trees is grafting. In order to graft an apple tree the
following steps should be taken:
·
Step
1: Choose the desired scion and rootstock for the apple tree you want to graft.
Keep in mind that they both must be compatible in order for the graft to be
successful.
·
Step
2: Decide which cut you would like to make in order to graft the stock and
scion together. Use a grafting knife and be aware of where your fingers are
when making the cut. Some of the more popular cuts are listed below:
o
Splice
graft – Slanted cuts are made on each piece of wood, the rootstock and the
scion. The cuts are then fitted together on each slant so that vascular cambium
is lined up and the graft is wrapped up. (4)
o
Whip
and Tongue graft – The same slanted cut is made as if it were a splice graft on
each piece. In the middle of the slant, a small straight cut is made into each
piece so that when the cuts are put together the notches fit inside each other
and increase the likelihood that the vascular cambium will be touching. (4)
 |
| Whip and Tongue Graft http://www.extension.umn.edu/distribution /horticulture/components/DG0532c.html |
o
Cleft
graft – The top of the rootstock is cut flat and a cross cut is made to cut the
top in half so the wood looks like two half circles. Two slanted cuts are then
made on the scion so that the bottom comes to a point at one part but still has
a little bit of the wood’s curve at the other end. It will look like a slice of
pizza if done right. Up to two scions can be used in this case and they will be
placed in-between the diagonal cut on top of the rootstock so that the vascular
cambium can match up. (4)
 |
| Cleft Graft http://www.extension.umn.edu/distribution/horticulture/components/DG0532c.html |
o
Side
graft – A diagonal cut is made into the rootstock along the side of it, but not
too close to the roots so that there is enough room for soil. Two cuts are made
into the bottom of the scion so that the bottom comes to a straight point. The point
on the bottom of the scion is then fitted into the diagonal cut on the
rootstock with the vascular cambium lined up. (4)
 |
| Side Graft http://www.extension.umn.edu/distribution/horticulture/components/DG0532c.html |
o
Budding
– Very similar to grafting except a bud is cut from the scion. A matching cut
is made on a bud from the rootstock (there are different ways to make this cut).
The scion bud is then fitted into the rootstock and wrapped up. (4)
 |
| Budding - How the bud is positioned on the rootstock http://www.extension.umn.edu/distribution/horticulture/components/DG0532c.html |
·
Step
3: A strong tie is used to wrap around where the graft union is and it is then
covered with a plastic material in order to keep in the moisture.
·
Step
4: The newly grafted tissue should not be allowed to desiccate and should be
kept humid
·
Step
5: You will be able to tell whether or not the graft has taken if growth is
seen in the scion. If the scion grows too quickly, it may need to be held up
with supports. (3)
Other Propagation Methods:
Depending upon the commercial use of
the apples desired, grafting is the only method of propagation for producing
market ready apples (3). Some advantages to grafting are that the material used
preserves maturity and takes less time to yield fruit than if grown by seed.
Also in certain cases, a plant that would attract pollinators can be grafted
onto the same rootstock as the fruit bearing part. Another advantage is that if
the cultivar of the scion normally has a weak root system or is not sturdy
enough, it can be grafted onto a rootstock that has those characteristics. (3)
The only other way apples are propagated are by seed, however
these apples are not what you would normally consider an apple. These apples
are usually grown to make hard cider due to the fact that they turn out nothing
like the parents that the seed came from. Apples are extreme heterozygotes and
when planted from seed they turn out nothing like their parents. (1)
Works Cited:
(1) - "Apple." Wikipedia.
Wikimedia Foundation, 31 Mar. 2013. Web. 31 Mar. 2013.
<http://en.wikipedia.org/wiki/Apple>.
(2) - "Grafting." Wikipedia.
Wikimedia Foundation, 31 Mar. 2013. Web. 31 Mar. 2013.
<http://en.wikipedia.org/wiki/Grafting#History>.
(3) - "GRAFTING AND BUDDING FRUIT
TREES." Grafting and Budding Fruit Trees. University of
Minnesota, 2009. Web. 31 Mar. 2013.
<http://www.extension.umn.edu/distribution/horticulture/dg0532.html>.
(4)
-
Hartmann, Hudson T., et al. Plant Propagation: Principles and Practices.
New Jersey: Prentice Hall, 1997.
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